2013 |
Benavente, E; Lozano, H; González, G Fabrication of Copper Nanoparticles: Advances in Synthesis, Morphology Control, and Chemical Stability Artículo de revista Recent Patents on Nanotechnology, 7 (2), pp. 108-132, 2013, ISSN: 1872-2105. Resumen | Enlaces | BibTeX | Etiquetas: assemblies, colloidal copper copper, cu enhanced fabrication irradiation, laser metal micelles, nanocopper, nanoparticle nanoparticles, nanosized particles, polyol process, raman-scattering, reduction, reverse size synthesis, thermal @article{RN133, title = {Fabrication of Copper Nanoparticles: Advances in Synthesis, Morphology Control, and Chemical Stability}, author = { E. Benavente and H. Lozano and G. Gonz\'{a}lez}, url = {/brokenurl#<Go to ISI>://WOS:000327780100002}, doi = {10.2174/1872210511307020002}, issn = {1872-2105}, year = {2013}, date = {2013-01-01}, journal = {Recent Patents on Nanotechnology}, volume = {7}, number = {2}, pages = {108-132}, abstract = {Metal nanoparticles have attracted great interest particularly because of the size dependence of physical and chemical properties and its enormous technological potential. Although most pioneering advancements refers to gold and silver, more recently there is growing interest in nanoparticles of copper, mostly due to its relatively low cost, which could allow the use of these small metal objects in large-scale nanotechnology applications, for example, antiseptics materials and metallic inks. However, the manufacture of copper nanoparticles stable in air with controlled size and shape has been a major challenge because of the relatively high reactivity of this element. Great efforts in getting the basic knowledge and synthesis know-how has gone into finding better ways to produce particles protected against oxidation and self-aggregation under normal conditions. In this review article, we briefly discuss a number of selected papers and recent patents on procedures and other issues related to the fabrication of copper nanoparticles.}, keywords = {assemblies, colloidal copper copper, cu enhanced fabrication irradiation, laser metal micelles, nanocopper, nanoparticle nanoparticles, nanosized particles, polyol process, raman-scattering, reduction, reverse size synthesis, thermal}, pubstate = {published}, tppubtype = {article} } Metal nanoparticles have attracted great interest particularly because of the size dependence of physical and chemical properties and its enormous technological potential. Although most pioneering advancements refers to gold and silver, more recently there is growing interest in nanoparticles of copper, mostly due to its relatively low cost, which could allow the use of these small metal objects in large-scale nanotechnology applications, for example, antiseptics materials and metallic inks. However, the manufacture of copper nanoparticles stable in air with controlled size and shape has been a major challenge because of the relatively high reactivity of this element. Great efforts in getting the basic knowledge and synthesis know-how has gone into finding better ways to produce particles protected against oxidation and self-aggregation under normal conditions. In this review article, we briefly discuss a number of selected papers and recent patents on procedures and other issues related to the fabrication of copper nanoparticles. |
Osorio, E; Pérez, E G; Areche, C; Ruiz, L M; Cassels, B K; Flórez, E; Tiznado, W Why Is Quercetin a Better Antioxidant Than Taxifolin? Theoretical Study of Mechanisms Involving Activated Forms Artículo de revista Journal of Molecular Modeling, 19 (5), pp. 2165-2172, 2013, ISSN: 0948-5023. Resumen | Enlaces | BibTeX | Etiquetas: @article{RN118, title = {Why Is Quercetin a Better Antioxidant Than Taxifolin? Theoretical Study of Mechanisms Involving Activated Forms}, author = { E. Osorio and E.G. P\'{e}rez and C. Areche and L.M. Ruiz and B.K. Cassels and E. Fl\'{o}rez and W. Tiznado}, url = {/brokenurl#10.1007/s00894-012-1732-5}, doi = {10.1007/s00894-012-1732-5}, issn = {0948-5023}, year = {2013}, date = {2013-01-01}, journal = {Journal of Molecular Modeling}, volume = {19}, number = {5}, pages = {2165-2172}, abstract = {The stronger antioxidant capacity of the flavonoid quercetin (Q) compared with taxifolin (dihydroquercetin, T) has been the subject of previous experimental and theoretical studies. Theoretical work has focused on the analysis of hydrogen bond dissociation energies (BDE) of the OH phenolic groups, but consider mechanisms that only involve the transfer of one hydrogen atom. In the present work we consider other mechanisms involving a second hydrogen transfer in reactions with free radicals. The relative stability of the radicals formed after the first hydrogen transfer reaction is considered in discussing the antioxidant activity of Q and T. In terms of global and local theoretical reactivity descriptors, we propose that the radical arising from Q should be more persistent in the environment and with the capability to react with a second radical by hydrogen transfer, proton transfer and electron transfer mechanisms. These mechanisms could be responsible of the stronger antioxidant capacity of Q.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The stronger antioxidant capacity of the flavonoid quercetin (Q) compared with taxifolin (dihydroquercetin, T) has been the subject of previous experimental and theoretical studies. Theoretical work has focused on the analysis of hydrogen bond dissociation energies (BDE) of the OH phenolic groups, but consider mechanisms that only involve the transfer of one hydrogen atom. In the present work we consider other mechanisms involving a second hydrogen transfer in reactions with free radicals. The relative stability of the radicals formed after the first hydrogen transfer reaction is considered in discussing the antioxidant activity of Q and T. In terms of global and local theoretical reactivity descriptors, we propose that the radical arising from Q should be more persistent in the environment and with the capability to react with a second radical by hydrogen transfer, proton transfer and electron transfer mechanisms. These mechanisms could be responsible of the stronger antioxidant capacity of Q. |
Areche, C; Rojas-Alvarez, F; Campos-Briones, C; Lima, C; Perez, E G; Sepulveda, B Further Mulinane Diterpenoids from Azorella Compacta Artículo de revista Journal of Pharmacy and Pharmacology, 65 (8), pp. 1231-1238, 2013, ISSN: 0022-3573. Resumen | Enlaces | BibTeX | Etiquetas: acids activity, azorella carbon compacta, crassifolium, diterpenoid, gastric gastroprotective laretia-acaulis, lesions, llareta, mulinane, natural-products, rats, skeleton, ulcer @article{RN116, title = {Further Mulinane Diterpenoids from Azorella Compacta}, author = { C. Areche and F. Rojas-Alvarez and C. Campos-Briones and C. Lima and E.G. Perez and B. Sepulveda}, url = {/brokenurl#<Go to ISI>://WOS:000321504500014}, doi = {10.1111/jphp.12083}, issn = {0022-3573}, year = {2013}, date = {2013-01-01}, journal = {Journal of Pharmacy and Pharmacology}, volume = {65}, number = {8}, pages = {1231-1238}, abstract = {Objectives The chemical study of a dichloromethane extract from Azorella compacta was directed to the isolation of characteristic mulinane and azorellane diterpenoids in order to determine their gastroprotective activity., Methods Usual chromatographic techniques on the extract led to the isolation of 12 compounds, which were identified by their spectroscopic properties. The HCl/ethanol-induced gastric lesions model in mice was used to determine the gastroprotective activity., keywords findings The new diterpenoids, 13-hydroxymulinane (1), mulin-11,13-dien-20-ol (2), 13-methoxyazorellanol (3) and mulin-11,13-dien-18-acetoxy-16,20-dioic acid (12) were isolated from A.compacta. The known diterpenoids mulin-11,13-dien-20-oic acid (4), 13-hydroxyazorellane (5), 13-hydroxyazorellane (6), mulinic acid (7), mulinolic acid (8) and azorellanol (9), and the aromatic compounds 5,7-dihydroxychromone (10) and isoflavonoid biochanin A (11), were also obtained from the extract. Compounds 6, 9 and 12 at 20mg/kg reduced gastric lesions by 69%, 71% and 73%, respectively, being statistically similar to lansoprazole at the same dose., Conclusions The results corroborate the intraspecific chemical variations detected previously in specimens of A.compacta collected at different Chilean latitudes. A high concentration of azorellanol (9) could account in part for some of the therapeutic properties attributed to this species, in particular in ulcer treatment. Most of the mulinane and azorellane diterpenoids isolated in this study showed relevant gastroprotective activity at a low dose in the bioassay.}, keywords = {acids activity, azorella carbon compacta, crassifolium, diterpenoid, gastric gastroprotective laretia-acaulis, lesions, llareta, mulinane, natural-products, rats, skeleton, ulcer}, pubstate = {published}, tppubtype = {article} } Objectives The chemical study of a dichloromethane extract from Azorella compacta was directed to the isolation of characteristic mulinane and azorellane diterpenoids in order to determine their gastroprotective activity., Methods Usual chromatographic techniques on the extract led to the isolation of 12 compounds, which were identified by their spectroscopic properties. The HCl/ethanol-induced gastric lesions model in mice was used to determine the gastroprotective activity., keywords findings The new diterpenoids, 13-hydroxymulinane (1), mulin-11,13-dien-20-ol (2), 13-methoxyazorellanol (3) and mulin-11,13-dien-18-acetoxy-16,20-dioic acid (12) were isolated from A.compacta. The known diterpenoids mulin-11,13-dien-20-oic acid (4), 13-hydroxyazorellane (5), 13-hydroxyazorellane (6), mulinic acid (7), mulinolic acid (8) and azorellanol (9), and the aromatic compounds 5,7-dihydroxychromone (10) and isoflavonoid biochanin A (11), were also obtained from the extract. Compounds 6, 9 and 12 at 20mg/kg reduced gastric lesions by 69%, 71% and 73%, respectively, being statistically similar to lansoprazole at the same dose., Conclusions The results corroborate the intraspecific chemical variations detected previously in specimens of A.compacta collected at different Chilean latitudes. A high concentration of azorellanol (9) could account in part for some of the therapeutic properties attributed to this species, in particular in ulcer treatment. Most of the mulinane and azorellane diterpenoids isolated in this study showed relevant gastroprotective activity at a low dose in the bioassay. |
Bahamonde-Padilla, V E; Espinoza, J; Weiss-Lopez, B; Cascales, J J L; Montecinos, R; Araya-Maturana, R Effect of Lithium on the Properties of a Liquid Crystal Formed by Sodium Dodecylsulphate and Decanol in Aqueous Solution Artículo de revista Journal of Chemical Physics, 139 (1), 2013, ISSN: 0021-9606. Resumen | Enlaces | BibTeX | Etiquetas: ewald, membrane, mesh micelle, molecular-dynamics number, particle phase, simulation, state systems, water @article{RN155, title = {Effect of Lithium on the Properties of a Liquid Crystal Formed by Sodium Dodecylsulphate and Decanol in Aqueous Solution}, author = { V.E. Bahamonde-Padilla and J. Espinoza and B. Weiss-Lopez and J.J.L. Cascales and R. Montecinos and R. Araya-Maturana}, url = {/brokenurl#<Go to ISI>://WOS:000321716400032}, doi = {10.1063/1.4811678}, issn = {0021-9606}, year = {2013}, date = {2013-01-01}, journal = {Journal of Chemical Physics}, volume = {139}, number = {1}, publisher = {2013 AIP Publishing LLC.}, abstract = {Understanding the molecular interactions that rule the physicochemical properties of molecular assemblies is of particular interest when trying to explain the behavior of much more complicated systems, such as the cell membranes. This work was devoted to study a discotic nematic lyotropic liquid crystal, formed by sodium dodecylsulphate (3% SDS-d(25)) and decanol (20% DeOH-alpha-d(2)), dissolved in aqueous solutions (0.1% D2O) of Na2SO4 or Li2SO4. The average size of the aggregates was estimated using fluorescence quenching experiments, and their dynamics were studied by measuring the H-2-NMR quadrupole splitting (Delta nu(Q)) and the longitudinal relaxation times (T-1) of the deuterated species. To provide an atomic insight into these assemblies, molecular dynamics simulations of the systems were carried out with atomic detail. As a previous step in this study, a reparameterization of the standard GROMOS 87 force field was required to perform the equilibrated simulations and to prevent instabilities emerging during the simulations. Finally, an excellent agreement between simulation and experimental data was obtained. In addition, variations in the long range electrostatic interactions at the aggregate/solution interface, the orientation and the re-orientational relaxation time of the water dipole, the translational diffusion coefficient of sodium ions, and the amphiphile-counterion coordination associated with the presence of Li+ in the solution were other keywords aspects investigated to explain the variation in the quadrupole splittings (Delta nu(Q)) in the presence of lithium in solution.}, keywords = {ewald, membrane, mesh micelle, molecular-dynamics number, particle phase, simulation, state systems, water}, pubstate = {published}, tppubtype = {article} } Understanding the molecular interactions that rule the physicochemical properties of molecular assemblies is of particular interest when trying to explain the behavior of much more complicated systems, such as the cell membranes. This work was devoted to study a discotic nematic lyotropic liquid crystal, formed by sodium dodecylsulphate (3% SDS-d(25)) and decanol (20% DeOH-alpha-d(2)), dissolved in aqueous solutions (0.1% D2O) of Na2SO4 or Li2SO4. The average size of the aggregates was estimated using fluorescence quenching experiments, and their dynamics were studied by measuring the H-2-NMR quadrupole splitting (Delta nu(Q)) and the longitudinal relaxation times (T-1) of the deuterated species. To provide an atomic insight into these assemblies, molecular dynamics simulations of the systems were carried out with atomic detail. As a previous step in this study, a reparameterization of the standard GROMOS 87 force field was required to perform the equilibrated simulations and to prevent instabilities emerging during the simulations. Finally, an excellent agreement between simulation and experimental data was obtained. In addition, variations in the long range electrostatic interactions at the aggregate/solution interface, the orientation and the re-orientational relaxation time of the water dipole, the translational diffusion coefficient of sodium ions, and the amphiphile-counterion coordination associated with the presence of Li+ in the solution were other keywords aspects investigated to explain the variation in the quadrupole splittings (Delta nu(Q)) in the presence of lithium in solution. |
Alcalde-Eon, C; Rivas-Gonzalo, J C; Munoz, O; Escribano-Bailon, M T Schizanthus Grahamii and Schizanthus Hookeri. Is There Any Relationship between Their Anthocyanin Compositions and Their Different Pollination Syndromes? Artículo de revista Phytochemistry, 85 , pp. 62-71, 2013, ISSN: 0031-9422. Resumen | Enlaces | BibTeX | Etiquetas: bee-pollination color, composition, delphinidin, floral flowers, grahamii, hookeri, hplc-dad-msn, hummingbird identification, pigment schizanthus solanaceae, syndromes, tubers @article{RN123, title = {Schizanthus Grahamii and Schizanthus Hookeri. Is There Any Relationship between Their Anthocyanin Compositions and Their Different Pollination Syndromes?}, author = { C. Alcalde-Eon and J.C. Rivas-Gonzalo and O. Munoz and M.T. Escribano-Bailon}, url = {/brokenurl#<Go to ISI>://WOS:000314143100006}, doi = {10.1016/j.phytochem.2012.09.013}, issn = {0031-9422}, year = {2013}, date = {2013-01-01}, journal = {Phytochemistry}, volume = {85}, pages = {62-71}, publisher = {2012 Elsevier Ltd.}, abstract = {Three different pollination syndromes (bee, humming-bird and moth-pollination syndromes) have been described for the different species of the genus Schizanthus Ruiz & Pav. (Solanaceae). Two closely related species from a phylogenetic point of view, Schizanthus grahamii and Schizanthus hookeri, show hummingbird and bee-pollination syndromes, respectively. One of the traits used to assign these pollination syndromes is the colour of the petals, which is red in S. grahamii and bluish-pink in S. hookeri. The objective of this work was to establish the differences in the anthocyanin composition of these two Schizanthus species that contribute to the different pollination syndrome. Identification of the pigments was carried out from the chromatographic and spectral data supplied by the HPLC-DAD-MSn analyses of the samples. Alkaline and acid hydrolyses were also performed in the extracts and in some isolated compounds in order to confirm the identities. First difference between these two species was found in the total anthocyanin content, which was about 13-fold higher in S. grahamii than in S. hookeri. Furthermore, the major peak was also different in both cases, thus explaining quantitative and qualitative colour differences between species. Delphinidin 3-O-rutinoside represented ca. 72% of the total area in S. grahamii and petanin (Petunidin 3-O-p-coumaroylrutinoside-5-O-glucoside) accounted for almost 62% of the total area in S. hookeri. The presence of the p-coumaroylrutinosyl moiety in the petanin makes the intramolecular copigmentation possible, thus conferring the bluish-pink hue to the petals of S. hookeri. Delphinidin 3-O-rutinoside is in turn responsible for the red colour exhibited by the petals of S. grahamii and along with other floral traits, responsible for the attraction of hummingbirds to the plant. Pigments structurally related to petanin, which have been often detected in other genus of Solanaceae, were detected in both species and in similar contents, supporting results from previous studies that pointed to a bee-pollinated common ancestor for both species that further specialised acquiring traits attractive to hummingbirds and among them, red colour of the petals which is mainly supplied by delphinidin 3-O-rutinoside.}, keywords = {bee-pollination color, composition, delphinidin, floral flowers, grahamii, hookeri, hplc-dad-msn, hummingbird identification, pigment schizanthus solanaceae, syndromes, tubers}, pubstate = {published}, tppubtype = {article} } Three different pollination syndromes (bee, humming-bird and moth-pollination syndromes) have been described for the different species of the genus Schizanthus Ruiz & Pav. (Solanaceae). Two closely related species from a phylogenetic point of view, Schizanthus grahamii and Schizanthus hookeri, show hummingbird and bee-pollination syndromes, respectively. One of the traits used to assign these pollination syndromes is the colour of the petals, which is red in S. grahamii and bluish-pink in S. hookeri. The objective of this work was to establish the differences in the anthocyanin composition of these two Schizanthus species that contribute to the different pollination syndrome. Identification of the pigments was carried out from the chromatographic and spectral data supplied by the HPLC-DAD-MSn analyses of the samples. Alkaline and acid hydrolyses were also performed in the extracts and in some isolated compounds in order to confirm the identities. First difference between these two species was found in the total anthocyanin content, which was about 13-fold higher in S. grahamii than in S. hookeri. Furthermore, the major peak was also different in both cases, thus explaining quantitative and qualitative colour differences between species. Delphinidin 3-O-rutinoside represented ca. 72% of the total area in S. grahamii and petanin (Petunidin 3-O-p-coumaroylrutinoside-5-O-glucoside) accounted for almost 62% of the total area in S. hookeri. The presence of the p-coumaroylrutinosyl moiety in the petanin makes the intramolecular copigmentation possible, thus conferring the bluish-pink hue to the petals of S. hookeri. Delphinidin 3-O-rutinoside is in turn responsible for the red colour exhibited by the petals of S. grahamii and along with other floral traits, responsible for the attraction of hummingbirds to the plant. Pigments structurally related to petanin, which have been often detected in other genus of Solanaceae, were detected in both species and in similar contents, supporting results from previous studies that pointed to a bee-pollinated common ancestor for both species that further specialised acquiring traits attractive to hummingbirds and among them, red colour of the petals which is mainly supplied by delphinidin 3-O-rutinoside. |
Morales, M A; Ahumada, F; Castillo, E; Burgos, R; Christen, P; Bustos, V; Munoz, O Inhibition of Cholinergic Contractions of Rat Ileum by Tropane-Type Alkaloids Present in Schizanthus Hookeri Artículo de revista Zeitschrift Fur Naturforschung Section C-a Journal of Biosciences, 68 (5-6), pp. 203-209, 2013, ISSN: 0939-5075. Resumen | Enlaces | BibTeX | Etiquetas: antagonism, cholinergic grahamii hookeri, parts, schizanthus tropane @article{RN121, title = {Inhibition of Cholinergic Contractions of Rat Ileum by Tropane-Type Alkaloids Present in Schizanthus Hookeri}, author = { M.A. Morales and F. Ahumada and E. Castillo and R. Burgos and P. Christen and V. Bustos and O. Munoz}, url = {/brokenurl#<Go to ISI>://WOS:000323864600006}, issn = {0939-5075}, year = {2013}, date = {2013-01-01}, journal = {Zeitschrift Fur Naturforschung Section C-a Journal of Biosciences}, volume = {68}, number = {5-6}, pages = {203-209}, abstract = {The relative lack of specificity of atropine as a competitive antagonist of muscarinic receptors is a frequent cause of undesirable parasympathetic side effects. Consequently, new tropane alkaloids with potentially greater selectivity are usually seen with real interest. The cholinergic antagonistic effects of a purified mixture of tropane alkaloids extracted from Schizanthus hookeri were evaluated in rat ileum. For this purpose, ileal segments were obtained from randomly selected male Sprague-Dawley rats, and the effect of 1 . 10(-4), 1 . 10(-3), and 1 . 10(-2) mg/mL of the purified mixture of alkaloids on the contractile response of the ileum induced with increasing doses of carbachol (5 . 10(-8)-8 . 10(-4) M) was determined. The results were compared with those obtained in the presence of 3.46 . 10(-7), 3.46 . 10(-6), and 3.46 . 10(-5) mg/mL atropine as an agonist. Tropane alkaloids extracted from Schizanthus hookeri competitively antagonized acetylcholine muscarinic receptors.}, keywords = {antagonism, cholinergic grahamii hookeri, parts, schizanthus tropane}, pubstate = {published}, tppubtype = {article} } The relative lack of specificity of atropine as a competitive antagonist of muscarinic receptors is a frequent cause of undesirable parasympathetic side effects. Consequently, new tropane alkaloids with potentially greater selectivity are usually seen with real interest. The cholinergic antagonistic effects of a purified mixture of tropane alkaloids extracted from Schizanthus hookeri were evaluated in rat ileum. For this purpose, ileal segments were obtained from randomly selected male Sprague-Dawley rats, and the effect of 1 . 10(-4), 1 . 10(-3), and 1 . 10(-2) mg/mL of the purified mixture of alkaloids on the contractile response of the ileum induced with increasing doses of carbachol (5 . 10(-8)-8 . 10(-4) M) was determined. The results were compared with those obtained in the presence of 3.46 . 10(-7), 3.46 . 10(-6), and 3.46 . 10(-5) mg/mL atropine as an agonist. Tropane alkaloids extracted from Schizanthus hookeri competitively antagonized acetylcholine muscarinic receptors. |
Cheel, J; Tumova, L; Areche, C; Antwerpen, Van P; Neve, J; Zouaoui-Boudjeltia, K; Martin, A S; Vokral, I; Wsol, V; Neugebauerova, J Variations in the Chemical Profile and Biological Activities of Licorice (Glycyrrhiza Glabra L.), as Influenced by Harvest Times Artículo de revista Acta Physiologiae Plantarum, 35 (4), pp. 1337-1349, 2013, ISSN: 0137-5881. Resumen | Enlaces | BibTeX | Etiquetas: activity, antioxidant constituents, extracts, flavonoids, fruits harvest hplc, ldl licorice, liquid-chromatography, myeloperoxidase, oxidation, performance roots, seasonal-variations, times @article{RN115, title = {Variations in the Chemical Profile and Biological Activities of Licorice (Glycyrrhiza Glabra L.), as Influenced by Harvest Times}, author = { J. Cheel and L. Tumova and C. Areche and P. Van Antwerpen and J. Neve and K. Zouaoui-Boudjeltia and A.S. Martin and I. Vokral and V. Wsol and J. Neugebauerova}, url = {/brokenurl#<Go to ISI>://WOS:000316339400032}, doi = {10.1007/s11738-012-1174-9}, issn = {0137-5881}, year = {2013}, date = {2013-01-01}, journal = {Acta Physiologiae Plantarum}, volume = {35}, number = {4}, pages = {1337-1349}, abstract = {This study investigates the variations in the chemical profile, free radical scavenging, antioxidant and gastroprotective activities of licorice extracts (LE) from plants harvested during the months of February to November. Correlations between biological properties and the chemical composition of LE were also investigated. The results showed that the total contents of phenols, flavonoids and tannins in LE varied at different harvest times. Liquiritin and glycyrrhizin, the major components of LE, varied in the range of 28.65-62.80 and 41.84-114.33 mg g(-1), respectively. The relative proportion of glycyrrhizin derivative (3), glabridin (4), glabrene (5) and liquiritigenin derivative (6), varied in the range of 0.88-11.38 %, 1.86-10.03 %, 1.80-18.40 % and 5.53-16.31 %, respectively. These fluctuations correlated positively with changes in the antioxidant and free radical scavenging activities of licorice. In general, the samples from May and November showed the most favorable free radical scavenging and antioxidant effects, whereas the best gastroprotective effect was in May. Liquiritin and glycyrrhizin, the major constituents in the February and May LE, appeared to contribute to the superoxide radical scavenging and gastroprotective effects. Glabridin and glabrene, the compounds with the highest relative proportion in the November LE, accounted for the antioxidant and DPPH scavenging activities of licorice. It is concluded that the chemical profile of licorice quantitatively varied at different harvest times and these fluctuations determined changes in its bioactivities. These data could pave the way to optimize harvesting protocols for licorice in relation with its health-promoting properties.}, keywords = {activity, antioxidant constituents, extracts, flavonoids, fruits harvest hplc, ldl licorice, liquid-chromatography, myeloperoxidase, oxidation, performance roots, seasonal-variations, times}, pubstate = {published}, tppubtype = {article} } This study investigates the variations in the chemical profile, free radical scavenging, antioxidant and gastroprotective activities of licorice extracts (LE) from plants harvested during the months of February to November. Correlations between biological properties and the chemical composition of LE were also investigated. The results showed that the total contents of phenols, flavonoids and tannins in LE varied at different harvest times. Liquiritin and glycyrrhizin, the major components of LE, varied in the range of 28.65-62.80 and 41.84-114.33 mg g(-1), respectively. The relative proportion of glycyrrhizin derivative (3), glabridin (4), glabrene (5) and liquiritigenin derivative (6), varied in the range of 0.88-11.38 %, 1.86-10.03 %, 1.80-18.40 % and 5.53-16.31 %, respectively. These fluctuations correlated positively with changes in the antioxidant and free radical scavenging activities of licorice. In general, the samples from May and November showed the most favorable free radical scavenging and antioxidant effects, whereas the best gastroprotective effect was in May. Liquiritin and glycyrrhizin, the major constituents in the February and May LE, appeared to contribute to the superoxide radical scavenging and gastroprotective effects. Glabridin and glabrene, the compounds with the highest relative proportion in the November LE, accounted for the antioxidant and DPPH scavenging activities of licorice. It is concluded that the chemical profile of licorice quantitatively varied at different harvest times and these fluctuations determined changes in its bioactivities. These data could pave the way to optimize harvesting protocols for licorice in relation with its health-promoting properties. |
Leiva, M A; Morales, R G E Environmental Assessment of Mercury Pollution in Urban Tailings from Gold Mining Artículo de revista Ecotoxicology and Environmental Safety, 90 , pp. 167-173, 2013, ISSN: 0147-6513. Resumen | Enlaces | BibTeX | Etiquetas: assessment, contamination, environmental chemistry, gold gum health, mercury mining, soil, standard uncertainty @article{RN161, title = {Environmental Assessment of Mercury Pollution in Urban Tailings from Gold Mining}, author = { M.A. Leiva and R.G.E. Morales}, url = {/brokenurl#<Go to ISI>://WOS:000315840000024}, doi = {10.1016/j.ecoenv.2012.12.026}, issn = {0147-6513}, year = {2013}, date = {2013-01-01}, journal = {Ecotoxicology and Environmental Safety}, volume = {90}, pages = {167-173}, publisher = {2013 Elsevier Inc.}, abstract = {It is well-known that small-scale artisanal mining is a source of mercury emissions into the environment, mainly from the use of rudimentary technologies that use mercury amalgamation in the extraction process. Mines near Andacollo, which is located in the Coquimbo region of Chile, use primitive methods to mine gold and copper. In this study, we determined the mercury content of gold mining wastes from Andacollo. At each site, we randomly sampled the soil at the surface and at a depth of 2 m following the ISO 10381 guidelines. Mercury analysis was performed with a direct mercury analyzer. At least one site was contaminated at a mercury concentration of 13.6 +/- 1.4 mg kg(-1), which was above the international recommendations that were set by the Canadian Council of Ministers of the Environment's soil quality guidelines (CA-SQG) and the Dutch guidelines (NL-RIVM). At least four of the fourteen sites in this study were within the control and tolerance levels of these recommendations. Better characterization of these sites is required to establish whether they represent a risk to the local community. Based on the US-EPA recommendations, which have a higher tolerance limit, none of the fourteen sites should pose a risk to humans.}, keywords = {assessment, contamination, environmental chemistry, gold gum health, mercury mining, soil, standard uncertainty}, pubstate = {published}, tppubtype = {article} } It is well-known that small-scale artisanal mining is a source of mercury emissions into the environment, mainly from the use of rudimentary technologies that use mercury amalgamation in the extraction process. Mines near Andacollo, which is located in the Coquimbo region of Chile, use primitive methods to mine gold and copper. In this study, we determined the mercury content of gold mining wastes from Andacollo. At each site, we randomly sampled the soil at the surface and at a depth of 2 m following the ISO 10381 guidelines. Mercury analysis was performed with a direct mercury analyzer. At least one site was contaminated at a mercury concentration of 13.6 +/- 1.4 mg kg(-1), which was above the international recommendations that were set by the Canadian Council of Ministers of the Environment's soil quality guidelines (CA-SQG) and the Dutch guidelines (NL-RIVM). At least four of the fourteen sites in this study were within the control and tolerance levels of these recommendations. Better characterization of these sites is required to establish whether they represent a risk to the local community. Based on the US-EPA recommendations, which have a higher tolerance limit, none of the fourteen sites should pose a risk to humans. |
Contreras, R; Aizman, A; Tapia, R A; Cerda-Monje, A Lewis Molecular Acidity of Ionic Liquids from Empirical Energy-Density Models Artículo de revista Journal of Physical Chemistry B, 117 (6), pp. 1911-1920, 2013, ISSN: 1520-6106. Resumen | Enlaces | BibTeX | Etiquetas: ab-initio, dielectric-constant, diels-alder elimination, kemp polarity, reaction, scale solvents, static @article{RN165, title = {Lewis Molecular Acidity of Ionic Liquids from Empirical Energy-Density Models}, author = { R. Contreras and A. Aizman and R.A. Tapia and A. Cerda-Monje}, url = {/brokenurl#<Go to ISI>://WOS:000315181600051}, doi = {10.1021/jp3114946}, issn = {1520-6106}, year = {2013}, date = {2013-01-01}, journal = {Journal of Physical Chemistry B}, volume = {117}, number = {6}, pages = {1911-1920}, abstract = {Two complementary models of Lewis molecular acidity are introduced and tested in a wide series of 45 room temperature ionic liquids (RTIL). They are defined in the context of the conceptual density functional theory. The first one, which we tentatively call the excess electronic chemical potential, assesses the electron accepting power of the RTIL by relating the H-bond donor acidity with the charge transfer associated to the acidic H-atom migration at the cation of the RTIL considered as a HB-donor species. This global index accounts for the molecular acidity of the cation moiety of the ionic liquid that takes into account the perturbation of the anionic partner. The second index is defined in terms of the local charge capacity modeled through the maximum electronic charge that the cation, in its valence state, may accept from an unspecified environment. Each model is compared with the experimental HB-donor acidity parameter of the Kamlet Taft model. The best comparison is obtained for a combination of both the excess electronic chemical potential and the local charge capacity. As expected, the correlations with the Kamlet Taft alpha parameter do not lead to a universal model of HB-donor acidity. Reduced correlations for limited series of structurally related RTIL are obtained instead. Finally, we illustrate the reliability and usefulness of the proposed model of RTIL molecular acidity to explain the cation-dependent solvent effects on the reactivity trends for cycloaddition, Kemp elimination, and Menschutkin reactions, for which experimental rate coefficients are available from literature.}, keywords = {ab-initio, dielectric-constant, diels-alder elimination, kemp polarity, reaction, scale solvents, static}, pubstate = {published}, tppubtype = {article} } Two complementary models of Lewis molecular acidity are introduced and tested in a wide series of 45 room temperature ionic liquids (RTIL). They are defined in the context of the conceptual density functional theory. The first one, which we tentatively call the excess electronic chemical potential, assesses the electron accepting power of the RTIL by relating the H-bond donor acidity with the charge transfer associated to the acidic H-atom migration at the cation of the RTIL considered as a HB-donor species. This global index accounts for the molecular acidity of the cation moiety of the ionic liquid that takes into account the perturbation of the anionic partner. The second index is defined in terms of the local charge capacity modeled through the maximum electronic charge that the cation, in its valence state, may accept from an unspecified environment. Each model is compared with the experimental HB-donor acidity parameter of the Kamlet Taft model. The best comparison is obtained for a combination of both the excess electronic chemical potential and the local charge capacity. As expected, the correlations with the Kamlet Taft alpha parameter do not lead to a universal model of HB-donor acidity. Reduced correlations for limited series of structurally related RTIL are obtained instead. Finally, we illustrate the reliability and usefulness of the proposed model of RTIL molecular acidity to explain the cation-dependent solvent effects on the reactivity trends for cycloaddition, Kemp elimination, and Menschutkin reactions, for which experimental rate coefficients are available from literature. |
Toral, M I; Nacaratte, F; Nova-Ramirez, F; Otipka, R Parallel Determination of Desogestrel and 17 Alpha-Ethinylestradiol in Pharmaceutical Formulation by Derivative Spectrophotometry Artículo de revista Journal of the Chilean Chemical Society, 58 (2), pp. 1779-1784, 2013, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: desogestrel, estradiol, estrogens, ethinyl ethinylestradiol, formulations, gestodene levonorgestrel, mass-spectrometry, oral-contraceptives, pharmaceutical povidone, spectral study @article{RN111, title = {Parallel Determination of Desogestrel and 17 Alpha-Ethinylestradiol in Pharmaceutical Formulation by Derivative Spectrophotometry}, author = { M.I. Toral and F. Nacaratte and F. Nova-Ramirez and R. Otipka}, url = {/brokenurl#<Go to ISI>://WOS:000331237700031}, issn = {0717-9707}, year = {2013}, date = {2013-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {58}, number = {2}, pages = {1779-1784}, abstract = {This work presents a rapid and simple method for the parallel determination of Desogestrel (DSG) and 17 alpha-Ethinylestradiol (EE2) by second order derivative spectrophotometry and its application in pharmaceutical formulations. Study of the effect of the solvents, excipients and spectral behavior is also included. Acetonitrile was selected as a solvent; subsequently the samples were evaluated by second order derivatives, using a smoothing factor of 8,000 and a scale factor of 10(4). The EE2 determination was carried out using the graphical method at 288 nm and DSG by the zero-crossing method at 220 nm. The determination ranges were found to be between 1.5.10(-6) and 5.10(-4) mol/L and 1.7.10(-7) to 1.0.10(-3) mol/L for DSG and EE2, respectively., The homogenized tablets are divided in two fractions, the first, called sample A, was dissolved in acetonitrile, which contains the absorbents species that is polyvidone, DGS and EE2, the latter is determined directly at 288 nm. Meanwhile, in the second fraction (sample B), after extract with water the polyvidone and partially EE2, it is possible determine DGS at 220 nm. When the pharmaceutical formulation contains Vitamin E (Vit. E) is necessary to use an equations system to be evaluated in sample B.}, keywords = {desogestrel, estradiol, estrogens, ethinyl ethinylestradiol, formulations, gestodene levonorgestrel, mass-spectrometry, oral-contraceptives, pharmaceutical povidone, spectral study}, pubstate = {published}, tppubtype = {article} } This work presents a rapid and simple method for the parallel determination of Desogestrel (DSG) and 17 alpha-Ethinylestradiol (EE2) by second order derivative spectrophotometry and its application in pharmaceutical formulations. Study of the effect of the solvents, excipients and spectral behavior is also included. Acetonitrile was selected as a solvent; subsequently the samples were evaluated by second order derivatives, using a smoothing factor of 8,000 and a scale factor of 10(4). The EE2 determination was carried out using the graphical method at 288 nm and DSG by the zero-crossing method at 220 nm. The determination ranges were found to be between 1.5.10(-6) and 5.10(-4) mol/L and 1.7.10(-7) to 1.0.10(-3) mol/L for DSG and EE2, respectively., The homogenized tablets are divided in two fractions, the first, called sample A, was dissolved in acetonitrile, which contains the absorbents species that is polyvidone, DGS and EE2, the latter is determined directly at 288 nm. Meanwhile, in the second fraction (sample B), after extract with water the polyvidone and partially EE2, it is possible determine DGS at 220 nm. When the pharmaceutical formulation contains Vitamin E (Vit. E) is necessary to use an equations system to be evaluated in sample B. |
Glynn, C; Thompson, D; Paez, J; Collins, G; Benavente, E; Lavayen, V; Yutronic, N; Holmes, J D; González, G; O'dwyer, C Large Directional Conductivity Change in Chemically Stable Layered Thin Films of Vanadium Oxide and a 1d Metal Complex Artículo de revista Journal of Materials Chemistry C, 1 (36), pp. 5675-5684, 2013, ISSN: 2050-7526. Resumen | Enlaces | BibTeX | Etiquetas: charge hybrid intercalation, low-temperature, materials, mechanism, nanocomposites, nanostructures, sol-gel, transport, v2o5 @article{RN136, title = {Large Directional Conductivity Change in Chemically Stable Layered Thin Films of Vanadium Oxide and a 1d Metal Complex}, author = { C. Glynn and D. Thompson and J. Paez and G. Collins and E. Benavente and V. Lavayen and N. Yutronic and J.D. Holmes and G. Gonz\'{a}lez and C. O'dwyer}, url = {/brokenurl#<Go to ISI>://WOS:000323578000011}, doi = {10.1039/c3tc31104j}, issn = {2050-7526}, year = {2013}, date = {2013-01-01}, journal = {Journal of Materials Chemistry C}, volume = {1}, number = {36}, pages = {5675-5684}, abstract = {Electroactive hybrid and layered oxides and related materials where the inorganic phase is the host, offering the conductivity characteristics of semiconductors, have been used in thin film transistors and related electronic devices where the host-guest interaction offered conductivity with improved processability. We describe the synthesis and characterization of a nanocomposite that shows large conductivity anisotropy when deposited as a thin film. We prepared the material by inserting quasi 1-dimensional potassium tetracyanoplatinate metal complexes with insulating electrical properties in between stacked nanosheets of vanadium oxide xerogels. Detailed structural and compositional analysis using transmission electron microscopy and X-ray photoelectron spectroscopy confirms that the hybrid material forms from a topotactic reaction and the framework of the layered host oxide structure is maintained. The hybrid film demonstrates a similar to 1000-fold conductivity change between transport parallel and perpendicular to the film at room temperature. Temperature dependent transport measurements confirm Ohmic conduction perpendicular to the stack and small polaron hopping conduction parallel to the layering direction of the film. The conductivity anisotropy and simple synthesis demonstrate that nanostructured layered hybrids can provide alternative materials for thin film complementary logic and resistive memory.}, keywords = {charge hybrid intercalation, low-temperature, materials, mechanism, nanocomposites, nanostructures, sol-gel, transport, v2o5}, pubstate = {published}, tppubtype = {article} } Electroactive hybrid and layered oxides and related materials where the inorganic phase is the host, offering the conductivity characteristics of semiconductors, have been used in thin film transistors and related electronic devices where the host-guest interaction offered conductivity with improved processability. We describe the synthesis and characterization of a nanocomposite that shows large conductivity anisotropy when deposited as a thin film. We prepared the material by inserting quasi 1-dimensional potassium tetracyanoplatinate metal complexes with insulating electrical properties in between stacked nanosheets of vanadium oxide xerogels. Detailed structural and compositional analysis using transmission electron microscopy and X-ray photoelectron spectroscopy confirms that the hybrid material forms from a topotactic reaction and the framework of the layered host oxide structure is maintained. The hybrid film demonstrates a similar to 1000-fold conductivity change between transport parallel and perpendicular to the film at room temperature. Temperature dependent transport measurements confirm Ohmic conduction perpendicular to the stack and small polaron hopping conduction parallel to the layering direction of the film. The conductivity anisotropy and simple synthesis demonstrate that nanostructured layered hybrids can provide alternative materials for thin film complementary logic and resistive memory. |
Ormazabal-Toledo, R; Contreras, R; Campodonico, P R Reactivity Indices Profile: A Companion Tool of the Potential Energy Surface for the Analysis of Reaction Mechanisms. Nucleophilic Aromatic Substitution Reactions as Test Case Artículo de revista Journal of Organic Chemistry, 78 (3), pp. 1091-1097, 2013, ISSN: 0022-3263. Resumen | Enlaces | BibTeX | Etiquetas: aprotic-solvent, electrophilicity hardness hydrogen-bonds, index, ortho-para ratio, secondary-amines @article{RN166, title = {Reactivity Indices Profile: A Companion Tool of the Potential Energy Surface for the Analysis of Reaction Mechanisms. Nucleophilic Aromatic Substitution Reactions as Test Case}, author = { R. Ormazabal-Toledo and R. Contreras and P.R. Campodonico}, url = {/brokenurl#<Go to ISI>://WOS:000314558300028}, doi = {10.1021/jo3025048}, issn = {0022-3263}, year = {2013}, date = {2013-01-01}, journal = {Journal of Organic Chemistry}, volume = {78}, number = {3}, pages = {1091-1097}, abstract = {We herein report on the usefulness of the reactivity indices profiles along a reaction coordinate. The model is tested to fully describe the reaction mechanism of the title reactions. Group nucleophilicity and electrophilicity profiles help describe the bond-breaking/bond-formation processes and the intramolecular electron density reorganization. The reactivity indices' profile analysis is consistently complemented with hydrogen bonding (HB) effects along the reaction coordinate: the final outcome of the reaction is determined by the stage at which the HB complex can be formed. Transition-state structures located for six reactions studied, including the charged nucleophile thiocyanate, show that the main stabilizing interaction is that formed between the hydrogen atom of the nucleophile and the o-NO2 group. This result discards the role of HB interaction between the nucleophile and the leaving group previously proposed in the literature.}, keywords = {aprotic-solvent, electrophilicity hardness hydrogen-bonds, index, ortho-para ratio, secondary-amines}, pubstate = {published}, tppubtype = {article} } We herein report on the usefulness of the reactivity indices profiles along a reaction coordinate. The model is tested to fully describe the reaction mechanism of the title reactions. Group nucleophilicity and electrophilicity profiles help describe the bond-breaking/bond-formation processes and the intramolecular electron density reorganization. The reactivity indices' profile analysis is consistently complemented with hydrogen bonding (HB) effects along the reaction coordinate: the final outcome of the reaction is determined by the stage at which the HB complex can be formed. Transition-state structures located for six reactions studied, including the charged nucleophile thiocyanate, show that the main stabilizing interaction is that formed between the hydrogen atom of the nucleophile and the o-NO2 group. This result discards the role of HB interaction between the nucleophile and the leaving group previously proposed in the literature. |
Diaz, C; Valenzuela, M L; Bobadilla, D Bimetallic Au/Ag Metal Superstructures from Macromolecular Metal Complexes in Solid-State Artículo de revista Journal of the Chilean Chemical Society, 58 (4), pp. 1994-1997, 2013, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: and au complexes, derivatives, fabrication, gold, macromolecular metallic morphology, nanocrystals, nanoparticles, organometallic polyphosphazenes, precursors, pyrolysis pyrolysis, superstructures, thermolytic transformation @article{RN143, title = {Bimetallic Au/Ag Metal Superstructures from Macromolecular Metal Complexes in Solid-State}, author = { C. Diaz and M.L. Valenzuela and D. Bobadilla}, url = {/brokenurl#<Go to ISI>://WOS:000331238800015}, doi = {10.4067/S0717-97072013000400019}, issn = {0717-9707}, year = {2013}, date = {2013-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {58}, number = {4}, pages = {1994-1997}, abstract = {Novel bimetallic Au/Ag superstructures have been prepared from solid-state pyrolysis of the macromolecular complexes Chitosan( MLn/M'Ln)(n) y PSP-4-PVPx(MLn/M'Ln)(n) with MLn = AuCl3 and M'Ln = Ag(CF3SO3). The characterization was made from XRD (X-ray diffraction of powder), SEM and EDS analysis. Morphologies are influenced by both the nature of the polymer and the metal/polymer, molar ratio of the polymer precursor. EDS analysis suggests a core/shell Au/Ag structure for the materials. A probable mechanism of the formation of these superstructures is discussed. Although separated reports of metallic superstructures of Au or Ag have been recently described, the here reported are the first bimetallic Au/Ag.}, keywords = {and au complexes, derivatives, fabrication, gold, macromolecular metallic morphology, nanocrystals, nanoparticles, organometallic polyphosphazenes, precursors, pyrolysis pyrolysis, superstructures, thermolytic transformation}, pubstate = {published}, tppubtype = {article} } Novel bimetallic Au/Ag superstructures have been prepared from solid-state pyrolysis of the macromolecular complexes Chitosan( MLn/M'Ln)(n) y PSP-4-PVPx(MLn/M'Ln)(n) with MLn = AuCl3 and M'Ln = Ag(CF3SO3). The characterization was made from XRD (X-ray diffraction of powder), SEM and EDS analysis. Morphologies are influenced by both the nature of the polymer and the metal/polymer, molar ratio of the polymer precursor. EDS analysis suggests a core/shell Au/Ag structure for the materials. A probable mechanism of the formation of these superstructures is discussed. Although separated reports of metallic superstructures of Au or Ag have been recently described, the here reported are the first bimetallic Au/Ag. |
Alarcon, D A; Gatica-Díaz, F; Gómez-Jeria, J S Modeling the Relationships between Molecular Structure and Inhibition of Virus-Induced Cytophatic Effects: Anti-Hiv-1 and Anti-H1n1 (Influenza a) Activities as Examples Artículo de revista Journal of the Chilean Chemical Society, 58 , pp. 1805-1813, 2013, ISSN: 0717-9707. @article{RN172, title = {Modeling the Relationships between Molecular Structure and Inhibition of Virus-Induced Cytophatic Effects: Anti-Hiv-1 and Anti-H1n1 (Influenza a) Activities as Examples}, author = { D.A. Alarcon and F. Gatica-D\'{i}az and J.S. G\'{o}mez-Jeria}, url = {https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0717-97072013000300002&nrm=iso}, issn = {0717-9707}, year = {2013}, date = {2013-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {58}, pages = {1805-1813}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2012 |
Carcamo, J J; Aliaga, A E; Clavijo, E; Branes, M; Campos-Vallette, M Raman Study of the Shockwave Effect on Collagens Artículo de revista Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy, 86 , pp. 360-365, 2012, ISSN: 1386-1425. Resumen | Enlaces | BibTeX | Etiquetas: amino-acids, collagens, conformation, dependence, infrared-spectra, raman, scattering, shockwaves, spectroscopy, time tissues @article{carcamo2012raman, title = {Raman Study of the Shockwave Effect on Collagens}, author = { J.J. Carcamo and A.E. Aliaga and E. Clavijo and M. Branes and M. Campos-Vallette}, url = {/brokenurl#<Go to ISI>://WOS:000300515500052}, doi = {10.1016/j.saa.2011.10.049}, issn = {1386-1425}, year = {2012}, date = {2012-01-01}, journal = {Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy}, volume = {86}, pages = {360-365}, publisher = {2011 Elsevier B.V.}, abstract = {The Raman spectra (1800-200 cm(-1)) of isolated dried collagen types land ill were recorded at different times after shockwave (SW) application in aqueous media. SWs were applied in a single session. One week after the SW application the vibrational data analysis indicates changes in the conformation of the collagens; orientational changes are also inferred. During the next three weeks collagens tended to recover the conformation and orientation existing before SW application.}, keywords = {amino-acids, collagens, conformation, dependence, infrared-spectra, raman, scattering, shockwaves, spectroscopy, time tissues}, pubstate = {published}, tppubtype = {article} } The Raman spectra (1800-200 cm(-1)) of isolated dried collagen types land ill were recorded at different times after shockwave (SW) application in aqueous media. SWs were applied in a single session. One week after the SW application the vibrational data analysis indicates changes in the conformation of the collagens; orientational changes are also inferred. During the next three weeks collagens tended to recover the conformation and orientation existing before SW application. |
Soto-Delgado, J; Aizman, A; Contreras, R; Domingo, L R On the Catalytic Effect of Water in the Intramolecular Diels-Alder Reaction of Quinone Systems: A Theoretical Study Artículo de revista Molecules, 17 (11), pp. 13687-13703, 2012, ISSN: 1420-3049. Resumen | Enlaces | BibTeX | Etiquetas: catalysis, characterization, chemistry density dft dft, diels-alder difference electrophilicity, functionals, index, indices, intramolecular local molecules, polar quantitative reactions, reactivity regioselectivity, solvent, thermochemistry, water @article{sotodelgado2012catalytic, title = {On the Catalytic Effect of Water in the Intramolecular Diels-Alder Reaction of Quinone Systems: A Theoretical Study}, author = { J. Soto-Delgado and A. Aizman and R. Contreras and L.R. Domingo}, url = {/brokenurl#<Go to ISI>://WOS:000311428400087}, doi = {10.3390/molecules171113687}, issn = {1420-3049}, year = {2012}, date = {2012-01-01}, journal = {Molecules}, volume = {17}, number = {11}, pages = {13687-13703}, abstract = {The mechanism of the intramolecular Diels-Alder (IMDA) reaction of benzoquinone 1, in the absence and in the presence of three water molecules, 1w, has been studied by means of density functional theory (DFT) methods, using the M05-2X and B3LYP functionals for exploration of the potential energy surface (PES). The energy and geometrical results obtained are complemented with a population analysis using the NBO method, and an analysis based on the global, local and group electrophilicity and nucleophilicity indices. Both implicit and explicit solvation emphasize the increase of the polarity of the reaction and the reduction of activation free energies associated with the transition states (TSs) of this IMDA process. These results are reinforced by the analysis of the reactivity indices derived from the conceptual DFT, which show that the increase of the electrophilicity of the quinone framework by the hydrogen-bond formation correctly explains the high polar character of this intramolecular process. Large polarization at the TSs promoted by hydrogen-bonds and implicit solvation by water together with a high electrophilicity-nucleophilicity difference consistently explains the catalytic effects of water molecules.}, keywords = {catalysis, characterization, chemistry density dft dft, diels-alder difference electrophilicity, functionals, index, indices, intramolecular local molecules, polar quantitative reactions, reactivity regioselectivity, solvent, thermochemistry, water}, pubstate = {published}, tppubtype = {article} } The mechanism of the intramolecular Diels-Alder (IMDA) reaction of benzoquinone 1, in the absence and in the presence of three water molecules, 1w, has been studied by means of density functional theory (DFT) methods, using the M05-2X and B3LYP functionals for exploration of the potential energy surface (PES). The energy and geometrical results obtained are complemented with a population analysis using the NBO method, and an analysis based on the global, local and group electrophilicity and nucleophilicity indices. Both implicit and explicit solvation emphasize the increase of the polarity of the reaction and the reduction of activation free energies associated with the transition states (TSs) of this IMDA process. These results are reinforced by the analysis of the reactivity indices derived from the conceptual DFT, which show that the increase of the electrophilicity of the quinone framework by the hydrogen-bond formation correctly explains the high polar character of this intramolecular process. Large polarization at the TSs promoted by hydrogen-bonds and implicit solvation by water together with a high electrophilicity-nucleophilicity difference consistently explains the catalytic effects of water molecules. |
Garrido, C; Aliaga, A E; Gomez-Jeria, J S; Carcamo, J J; Clavijo, E; Campos-Vallette, M Interaction of the C-Terminal Peptide from Pigeon Cytochrome C with Silver Nanoparticles. A Raman, Sers and Theoretical Study Artículo de revista Vibrational Spectroscopy, 61 , pp. 94-98, 2012, ISSN: 0924-2031. Resumen | Enlaces | BibTeX | Etiquetas: amino-acids, approximations aromatic-hydrocarbons, charge, enhanced extended hartree-fock huckel hydrophobicity, molecular-orbital net pcc87-104 peptide, polycyclic proteins, raman raman, scattering, spectroscopy, surface, surface-enhanced theories, theory, type @article{garrido2012interaction, title = {Interaction of the C-Terminal Peptide from Pigeon Cytochrome C with Silver Nanoparticles. A Raman, Sers and Theoretical Study}, author = { C. Garrido and A.E. Aliaga and J.S. Gomez-Jeria and J.J. Carcamo and E. Clavijo and M. Campos-Vallette}, url = {/brokenurl#<Go to ISI>://WOS:000304686400014}, doi = {10.1016/j.vibspec.2012.01.011}, issn = {0924-2031}, year = {2012}, date = {2012-01-01}, journal = {Vibrational Spectroscopy}, volume = {61}, pages = {94-98}, publisher = {2012 Elsevier B.V.}, abstract = {The Raman and surface-enhanced Raman scattering (SERS) spectra of the C-terminal peptide of pigeon cytochrome C (PCC87-104). were recorded. This peptide is widely used to study the immune response in vivo. Hydrophobicity and net charge parameters of PCC87-104, allowed prediction of the nature of its interaction with colloidal nanostructured silver surfaces. The SERS spectrum provided information about the organization and orientation of PCC87-104 on the surface of silver nanoparticles (AgNPs). The batch to batch reproducible SERS spectra were obtained by adding the colloidal AgNPs solution onto the dried analyte sample. On the basis of the SERS information and the analysis of the net charge of each amino acid residue in the peptide sequence, it is concluded that the interaction of the peptide and the AgNPs is mainly induced and oriented by the lysine residues. The spectroscopic results are supported by quantum chemical calculations, performed by using Extended Huckel theory for a model of PCC87-104 interacting with a silver surface.}, keywords = {amino-acids, approximations aromatic-hydrocarbons, charge, enhanced extended hartree-fock huckel hydrophobicity, molecular-orbital net pcc87-104 peptide, polycyclic proteins, raman raman, scattering, spectroscopy, surface, surface-enhanced theories, theory, type}, pubstate = {published}, tppubtype = {article} } The Raman and surface-enhanced Raman scattering (SERS) spectra of the C-terminal peptide of pigeon cytochrome C (PCC87-104). were recorded. This peptide is widely used to study the immune response in vivo. Hydrophobicity and net charge parameters of PCC87-104, allowed prediction of the nature of its interaction with colloidal nanostructured silver surfaces. The SERS spectrum provided information about the organization and orientation of PCC87-104 on the surface of silver nanoparticles (AgNPs). The batch to batch reproducible SERS spectra were obtained by adding the colloidal AgNPs solution onto the dried analyte sample. On the basis of the SERS information and the analysis of the net charge of each amino acid residue in the peptide sequence, it is concluded that the interaction of the peptide and the AgNPs is mainly induced and oriented by the lysine residues. The spectroscopic results are supported by quantum chemical calculations, performed by using Extended Huckel theory for a model of PCC87-104 interacting with a silver surface. |
Carcamo, J J; Aliaga, A E; Clavijo, E; Garrido, C; Gomez-Jeria, J S; Campos-Vallette, M Proline and Hydroxyproline Deposited on Silver Nanoparticles. A Raman, Sers and Theoretical Study Artículo de revista Journal of Raman Spectroscopy, 43 (6), pp. 750-755, 2012, ISSN: 0377-0486. Resumen | Enlaces | BibTeX | Etiquetas: amino-acids, approximations, calculations, l-proline, molecular-orbital raman raman, scattering, spectra spectroscopy, surface-enhanced theoretical theories, trans-4-hydroxy- @article{carcamo2012proline, title = {Proline and Hydroxyproline Deposited on Silver Nanoparticles. A Raman, Sers and Theoretical Study}, author = { J.J. Carcamo and A.E. Aliaga and E. Clavijo and C. Garrido and J.S. Gomez-Jeria and M. Campos-Vallette}, url = {/brokenurl#<Go to ISI>://WOS:000305391800012}, doi = {10.1002/jrs.3092}, issn = {0377-0486}, year = {2012}, date = {2012-01-01}, journal = {Journal of Raman Spectroscopy}, volume = {43}, number = {6}, pages = {750-755}, publisher = {2011 John Wiley & Sons, Ltd.}, abstract = {The Raman and surface-enhanced Raman scattering (SERS) spectra of l-proline (Pro) and trans-4-hydroxy- l-proline (Hyp) were recorded. SERS spectra were obtained on colloidal Ag prepared by reduction with hydroxylamine. Allowing sufficient time for Pro and Hyp to adjust in the colloidal solution resulted fundamentally in obtaining unique and reproducible SERS spectra. Hyp stabilizes on the surface more rapidly than Pro. The spectral analysis indicates that Pro interacts with the Ag surface through the carboxylate group. The interaction of Hyp with the metal surface occurs through the amino, methylene and carboxylate moieties of the molecule. The spectroscopic results are supported by quantum chemical calculations, performed using extended Huckel theory (EHT) of the title compounds interacting with an Ag cluster model. The assignment of the Raman bands was supported by a normal coordinate analysis performed through Becke, three-parameter, LeeYangParr/6-311?G*?+?calculations.}, keywords = {amino-acids, approximations, calculations, l-proline, molecular-orbital raman raman, scattering, spectra spectroscopy, surface-enhanced theoretical theories, trans-4-hydroxy-}, pubstate = {published}, tppubtype = {article} } The Raman and surface-enhanced Raman scattering (SERS) spectra of l-proline (Pro) and trans-4-hydroxy- l-proline (Hyp) were recorded. SERS spectra were obtained on colloidal Ag prepared by reduction with hydroxylamine. Allowing sufficient time for Pro and Hyp to adjust in the colloidal solution resulted fundamentally in obtaining unique and reproducible SERS spectra. Hyp stabilizes on the surface more rapidly than Pro. The spectral analysis indicates that Pro interacts with the Ag surface through the carboxylate group. The interaction of Hyp with the metal surface occurs through the amino, methylene and carboxylate moieties of the molecule. The spectroscopic results are supported by quantum chemical calculations, performed using extended Huckel theory (EHT) of the title compounds interacting with an Ag cluster model. The assignment of the Raman bands was supported by a normal coordinate analysis performed through Becke, three-parameter, LeeYangParr/6-311?G*?+?calculations. |
Aguilera-Venegas, B; Olea-Azar, C; Aran, V J; Maya, J D; Kemmerling, U; Speisky, H; Mendizabal, F Electrochemical, Esr and Theoretical Insights into the Free Radical Generation by 1,1 '-Hydrocarbylenebisindazoles and Its Evaluation as Potential Bio-Active Compounds Artículo de revista International Journal of Electrochemical Science, 7 (7), pp. 5837-5863, 2012, ISSN: 1452-3981. Resumen | Enlaces | BibTeX | Etiquetas: antiprotozoal biological bisnitroindazoles, carbonyl chagas-disease control, density-functional derivatives, electron-spin-resonance, evaluation, free metabolism microsomal oxidative production, radical, reductase, reduction, ros spin stress, theory, thiol trapping, trypanosoma-cruzi, trypanothione @article{RN425, title = {Electrochemical, Esr and Theoretical Insights into the Free Radical Generation by 1,1 '-Hydrocarbylenebisindazoles and Its Evaluation as Potential Bio-Active Compounds}, author = { B. Aguilera-Venegas and C. Olea-Azar and V.J. Aran and J.D. Maya and U. Kemmerling and H. Speisky and F. Mendizabal}, url = {/brokenurl#<Go to ISI>://WOS:000306399700009}, issn = {1452-3981}, year = {2012}, date = {2012-01-01}, journal = {International Journal of Electrochemical Science}, volume = {7}, number = {7}, pages = {5837-5863}, abstract = {A comprehensive multidisciplinary study is conducted here in order to assess the electrochemical behavior of a series of 1,1'-hydrocarbylenebisindazoles derivatives and its potential use as anti-T.cruzi drugs. At first, we have determined the electrochemical reduction mechanisms of this family by cyclic voltammetry (CV) studies, from which three kind of reduction mechanisms -depending on the substituent at positions 3 and 3'-were established, but sharing a first common step corresponding to the generation of a nitro anion radical, which was corroborated by ESR spectroscopy, showing a comparable hyperfine splitting pattern and a strong influence on the ESR spectral linewidths due to the radical-solvent interactions. Furthermore, in order to give a rational description about the electrochemical and ESR results, open- and closed-shell structures of bisindasoles were subjected to theoretical estimations at different levels of theory. For open-shell structures, the hyperfine splitting patterns were confirmed while for the closed-shell systems case, clear evidence about the electrochemical reactivity -in terms of their frontiers orbitals-were obtained. To conclude, all these compounds were assayed as growth inhibitors against T. cruzi, from which some degree of activity was observed for this family, highlighting a compound almost as active as the reference drug. Finally, in order to get some information about the potential action mechanisms involved in the trypanocidal activity, molecular modeling and spin trapping studies were also done.}, keywords = {antiprotozoal biological bisnitroindazoles, carbonyl chagas-disease control, density-functional derivatives, electron-spin-resonance, evaluation, free metabolism microsomal oxidative production, radical, reductase, reduction, ros spin stress, theory, thiol trapping, trypanosoma-cruzi, trypanothione}, pubstate = {published}, tppubtype = {article} } A comprehensive multidisciplinary study is conducted here in order to assess the electrochemical behavior of a series of 1,1'-hydrocarbylenebisindazoles derivatives and its potential use as anti-T.cruzi drugs. At first, we have determined the electrochemical reduction mechanisms of this family by cyclic voltammetry (CV) studies, from which three kind of reduction mechanisms -depending on the substituent at positions 3 and 3'-were established, but sharing a first common step corresponding to the generation of a nitro anion radical, which was corroborated by ESR spectroscopy, showing a comparable hyperfine splitting pattern and a strong influence on the ESR spectral linewidths due to the radical-solvent interactions. Furthermore, in order to give a rational description about the electrochemical and ESR results, open- and closed-shell structures of bisindasoles were subjected to theoretical estimations at different levels of theory. For open-shell structures, the hyperfine splitting patterns were confirmed while for the closed-shell systems case, clear evidence about the electrochemical reactivity -in terms of their frontiers orbitals-were obtained. To conclude, all these compounds were assayed as growth inhibitors against T. cruzi, from which some degree of activity was observed for this family, highlighting a compound almost as active as the reference drug. Finally, in order to get some information about the potential action mechanisms involved in the trypanocidal activity, molecular modeling and spin trapping studies were also done. |
Bernales, V S; Marenich, A V; Contreras, R; Cramer, C J; Truhlar, D G Quantum Mechanical Continuum Solvation Models for Ionic Liquids Artículo de revista Journal of Physical Chemistry B, 116 (30), pp. 9122-9129, 2012, ISSN: 1520-6106. Resumen | Enlaces | BibTeX | Etiquetas: ab-initio, approach, carbon-dioxide, density dielectric-constant, free-energies, functionals, gas-phase green kinetics, molecular-dynamics simulations, solvents, static thermochemical universal @article{RN105, title = {Quantum Mechanical Continuum Solvation Models for Ionic Liquids}, author = { V.S. Bernales and A.V. Marenich and R. Contreras and C.J. Cramer and D.G. Truhlar}, url = {/brokenurl#<Go to ISI>://WOS:000306989800043}, doi = {10.1021/jp304365v}, issn = {1520-6106}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Chemistry B}, volume = {116}, number = {30}, pages = {9122-9129}, abstract = {The quantum mechanical SMD continuum universal solvation model can be applied to predict the free energy of solvation of any solute in any solvent following specification of various macroscopic solvent parameters. For three ionic liquids where these descriptors are readily available, the SMD solvation model exhibits a mean unsigned error of 0.48 kcal/mol for 93 solvation free energies of neutral solutes and a mean unsigned error of 1.10 kcal/mol for 148 water-to-IL transfer free energies. Because the necessary solvent parameters are not always available for a given ionic liquid, we determine average values for a set of ionic liquids over which measurements have been made in order to define a generic ionic liquid solvation model, SMD-GIL. Considering 11 different ionic liquids, the SMD-GIL solvation model exhibits a mean unsigned error of 0.43 kcal/mol for 344 solvation free energies of neutral solutes and a mean unsigned error of 0.61 kcal/mol for 431 water-to-IL transfer free energies. As these errors are similar in magnitude to those typically observed when applying continuum solvation models to ordinary liquids, we conclude that the SMD universal solvation model may be applied to ionic liquids as well as ordinary liquids.}, keywords = {ab-initio, approach, carbon-dioxide, density dielectric-constant, free-energies, functionals, gas-phase green kinetics, molecular-dynamics simulations, solvents, static thermochemical universal}, pubstate = {published}, tppubtype = {article} } The quantum mechanical SMD continuum universal solvation model can be applied to predict the free energy of solvation of any solute in any solvent following specification of various macroscopic solvent parameters. For three ionic liquids where these descriptors are readily available, the SMD solvation model exhibits a mean unsigned error of 0.48 kcal/mol for 93 solvation free energies of neutral solutes and a mean unsigned error of 1.10 kcal/mol for 148 water-to-IL transfer free energies. Because the necessary solvent parameters are not always available for a given ionic liquid, we determine average values for a set of ionic liquids over which measurements have been made in order to define a generic ionic liquid solvation model, SMD-GIL. Considering 11 different ionic liquids, the SMD-GIL solvation model exhibits a mean unsigned error of 0.43 kcal/mol for 344 solvation free energies of neutral solutes and a mean unsigned error of 0.61 kcal/mol for 431 water-to-IL transfer free energies. As these errors are similar in magnitude to those typically observed when applying continuum solvation models to ordinary liquids, we conclude that the SMD universal solvation model may be applied to ionic liquids as well as ordinary liquids. |
Copaja, S; Bravo, H; Munoz, P Adsorption of Fungicides in Chilean Soils Incubated with Biosolids Artículo de revista Journal of the Chilean Chemical Society, 57 (2), pp. 1091-1094, 2012, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: biosolids, captan, degradation, desorption, dissolved fungicide, hplc, mobility, organic-matter, pesticides, sludge, soil, sorption, thiram thiram @article{RN55, title = {Adsorption of Fungicides in Chilean Soils Incubated with Biosolids}, author = { S. Copaja and H. Bravo and P. Munoz}, url = {/brokenurl#<Go to ISI>://WOS:000305169800006}, doi = {0.4067/S0717-97072012000200006}, issn = {0717-9707}, year = {2012}, date = {2012-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {57}, number = {2}, pages = {1091-1094}, abstract = {The efficiency of the adsorption process of the fungicides Captan and Thiram was studied in four Chilean soils from the VI [O'Higgins, (HGS)], VII [Talearehue, (THL)] VIII [Diguillin, (DIG)] and Metropolitan [Maipo, (MAO)] regions of Chile. Changes in the efficiency of adsorption when the natural soils were incubated with biosolids were analyzed., The values of parameters Kf and n from the Freundlich equation indicated an increase in the adsorption of fungicides incubated with biosolids (1% and 10%) with respect to natural soil. A high Kf value (12.1) for DIG-Thiram and a lower Kf value (4.3) for MAO-Captan interaction were observed for natural soils, while in soils incubated with biosolids (10%) the greatest value was (20.3) for DIG-Thiram and the lowest Kf value (10.2) for MAO-Captan. In general the high la values for Caplan and Thiram were correlated with organic carbon content in the natural and incubated soils, except for the interaction THL-Thiram, in which inorganic compounds of soils (clay) were dominant., The distribution constant between solid-liquid phases (Kd) increased in soils incubated with biosolids; the magnitude of this constant was more significant with Thiram. The same behavior was observed for the constant related to organic carbon constants (Koc)., The results of this work confirm that amending soils with biosolids is beneficial for immobilizing fungicides and helps prevent the percolation of Caplan and Thiram through the soil profile and into groundwater}, keywords = {biosolids, captan, degradation, desorption, dissolved fungicide, hplc, mobility, organic-matter, pesticides, sludge, soil, sorption, thiram thiram}, pubstate = {published}, tppubtype = {article} } The efficiency of the adsorption process of the fungicides Captan and Thiram was studied in four Chilean soils from the VI [O'Higgins, (HGS)], VII [Talearehue, (THL)] VIII [Diguillin, (DIG)] and Metropolitan [Maipo, (MAO)] regions of Chile. Changes in the efficiency of adsorption when the natural soils were incubated with biosolids were analyzed., The values of parameters Kf and n from the Freundlich equation indicated an increase in the adsorption of fungicides incubated with biosolids (1% and 10%) with respect to natural soil. A high Kf value (12.1) for DIG-Thiram and a lower Kf value (4.3) for MAO-Captan interaction were observed for natural soils, while in soils incubated with biosolids (10%) the greatest value was (20.3) for DIG-Thiram and the lowest Kf value (10.2) for MAO-Captan. In general the high la values for Caplan and Thiram were correlated with organic carbon content in the natural and incubated soils, except for the interaction THL-Thiram, in which inorganic compounds of soils (clay) were dominant., The distribution constant between solid-liquid phases (Kd) increased in soils incubated with biosolids; the magnitude of this constant was more significant with Thiram. The same behavior was observed for the constant related to organic carbon constants (Koc)., The results of this work confirm that amending soils with biosolids is beneficial for immobilizing fungicides and helps prevent the percolation of Caplan and Thiram through the soil profile and into groundwater |
Wu, X B; Garcia-Estrada, C; Vaca, I; Martin, J F Motifs in the C-Terminal Region of the Penicillium Chrysogenum Acv Synthetase Are Essential for Valine Epimerization and Processivity of Tripeptide Formation Artículo de revista Biochimie, 94 (2), pp. 354-364, 2012, ISSN: 0300-9084. Resumen | Enlaces | BibTeX | Etiquetas: biosynthesis, biosynthetic cephalosporin cluster, enzyme, epimerase, functional genes, isopenicillin-n, l-valine non-ribosomal nonribosomal penicillin penicillin, peptide peptide-synthesis, repeats, syntethase, synthetase, synthetases, tandem @article{RN30d, title = {Motifs in the C-Terminal Region of the Penicillium Chrysogenum Acv Synthetase Are Essential for Valine Epimerization and Processivity of Tripeptide Formation}, author = { X.B. Wu and C. Garcia-Estrada and I. Vaca and J.F. Martin}, url = {/brokenurl#<Go to ISI>://WOS:000300270900010}, doi = {10.1016/j.biochi.2011.08.002}, issn = {0300-9084}, year = {2012}, date = {2012-01-01}, journal = {Biochimie}, volume = {94}, number = {2}, pages = {354-364}, publisher = {2011 Elsevier Masson SAS.}, abstract = {The first step in the penicillin biosynthetic pathway is the non-ribosomal condensation of L-alpha-aminoadipic acid, L-cysteine and L-valine into the tripeptide delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV). This reaction is catalysed by the multienzyme ACV synthetase (ACVS), which is encoded in the filamentous fungus Penicillium chrysogenum by the pcbAB gene. This enzyme contains at least ten catalytic domains. The precise role of the C-terminal domain of this multidomain NRPS still remains obscure. The C-terminal region of ACVS bears the epimerase and the thioesterase domains and may be involved in the epimerization of LLL-ACV to LLD-ACV and in the hydrolysis of the thioester bond. In this work, the conserved motifs (3371)EGHGRE(3376) (located in the putative epimerase domain) and (3629)GWSFG(3633) (located in the thioesterase domain) were changed by site-directed-mutagenesis to LGFGLL and GWAFG, respectively. In addition, the whole thioesterase domain (230 amino acids) and the different parts of this domain were deleted. The activity of these mutant enzymes was assessed in vivo by two different procedures: i) through the quantification of bisACV produced by the fungus and ii) by quantifying the benzylpenicillin production using tailored strains of P. chrysogenum, which lack the pcbAB gene, as host strains. All indicated mutant enzymes showed lower or null activity than the control strain confirming that E3371, H3373, R3375 and E3376 belong to the epimerase active centre. Different fragments included in the C-terminal region of ACVS control thioester hydrolysis. Overexpression of the sequence encoding the ACVS integrated thioesterase domain as a separate (stand-alone) transcriptional unit complemented mutants lacking the integrated thioesterase domain, although with low ACV releasing activity, suggesting that the stand-alone thio-esterease interacts with the other ACVS domains.}, keywords = {biosynthesis, biosynthetic cephalosporin cluster, enzyme, epimerase, functional genes, isopenicillin-n, l-valine non-ribosomal nonribosomal penicillin penicillin, peptide peptide-synthesis, repeats, syntethase, synthetase, synthetases, tandem}, pubstate = {published}, tppubtype = {article} } The first step in the penicillin biosynthetic pathway is the non-ribosomal condensation of L-alpha-aminoadipic acid, L-cysteine and L-valine into the tripeptide delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV). This reaction is catalysed by the multienzyme ACV synthetase (ACVS), which is encoded in the filamentous fungus Penicillium chrysogenum by the pcbAB gene. This enzyme contains at least ten catalytic domains. The precise role of the C-terminal domain of this multidomain NRPS still remains obscure. The C-terminal region of ACVS bears the epimerase and the thioesterase domains and may be involved in the epimerization of LLL-ACV to LLD-ACV and in the hydrolysis of the thioester bond. In this work, the conserved motifs (3371)EGHGRE(3376) (located in the putative epimerase domain) and (3629)GWSFG(3633) (located in the thioesterase domain) were changed by site-directed-mutagenesis to LGFGLL and GWAFG, respectively. In addition, the whole thioesterase domain (230 amino acids) and the different parts of this domain were deleted. The activity of these mutant enzymes was assessed in vivo by two different procedures: i) through the quantification of bisACV produced by the fungus and ii) by quantifying the benzylpenicillin production using tailored strains of P. chrysogenum, which lack the pcbAB gene, as host strains. All indicated mutant enzymes showed lower or null activity than the control strain confirming that E3371, H3373, R3375 and E3376 belong to the epimerase active centre. Different fragments included in the C-terminal region of ACVS control thioester hydrolysis. Overexpression of the sequence encoding the ACVS integrated thioesterase domain as a separate (stand-alone) transcriptional unit complemented mutants lacking the integrated thioesterase domain, although with low ACV releasing activity, suggesting that the stand-alone thio-esterease interacts with the other ACVS domains. |
Rivas, J; Toral, M I; Richter, P Sorption of Polybrominated Diphenyl Ethers in Biosolid Model Samples Artículo de revista Journal of the Chilean Chemical Society, 57 (2), pp. 1087-1090, 2012, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: biosolid brominated developmental exposure, extraction feed, fish flame low-dose matter, microextraction, model organic organic-matter, partition-coefficients, pbde-99, pbdes, phase polychlorinated-biphenyls, retardants, sample, sorption, thyroid-hormone @article{RN57, title = {Sorption of Polybrominated Diphenyl Ethers in Biosolid Model Samples}, author = { J. Rivas and M.I. Toral and P. Richter}, url = {/brokenurl#<Go to ISI>://WOS:000305169800005}, doi = {10.4067/S0717-97072012000200005}, issn = {0717-9707}, year = {2012}, date = {2012-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {57}, number = {2}, pages = {1087-1090}, abstract = {Biosolid model samples (BMSs) were developed to study the capacity of various matrixes to adsorb polybrominated diphenyl ethers (PBDEs) as a function of their composition. A commercial standard reference samples for biosolids containing a certified amount of PBDEs is currently not available for extraction evaluation. Therefore, this study will allow for the selection of an appropriate concentration of PBDEs to produce a reference material for analytes associated with the matrix., The sorption of PBDEs increased clearly concomitantly with the amount of organic matter present in the model, revealing that organic matter rather than the inorganic fraction is mainly responsible for the analyte-matrix interaction. Hydrophobic interactions are predominant in the retention of PBDEs in the biosolid matrix because more hydrophobic congeners are generally sorbed to a higher extent than those that are less hydrophobic., In order to know the probable PBDE sorption mechanism on the model sample of biosolid, the Gibbs free energies were calculated using the Freundlich model, giving values between -8 and -10 kJ/mol. These results suggest that the sorption mechanism of the PBDEs is through physiosorption. Therefore, the Freundlich model should be satisfactory for describing the analyte behavior.}, keywords = {biosolid brominated developmental exposure, extraction feed, fish flame low-dose matter, microextraction, model organic organic-matter, partition-coefficients, pbde-99, pbdes, phase polychlorinated-biphenyls, retardants, sample, sorption, thyroid-hormone}, pubstate = {published}, tppubtype = {article} } Biosolid model samples (BMSs) were developed to study the capacity of various matrixes to adsorb polybrominated diphenyl ethers (PBDEs) as a function of their composition. A commercial standard reference samples for biosolids containing a certified amount of PBDEs is currently not available for extraction evaluation. Therefore, this study will allow for the selection of an appropriate concentration of PBDEs to produce a reference material for analytes associated with the matrix., The sorption of PBDEs increased clearly concomitantly with the amount of organic matter present in the model, revealing that organic matter rather than the inorganic fraction is mainly responsible for the analyte-matrix interaction. Hydrophobic interactions are predominant in the retention of PBDEs in the biosolid matrix because more hydrophobic congeners are generally sorbed to a higher extent than those that are less hydrophobic., In order to know the probable PBDE sorption mechanism on the model sample of biosolid, the Gibbs free energies were calculated using the Freundlich model, giving values between -8 and -10 kJ/mol. These results suggest that the sorption mechanism of the PBDEs is through physiosorption. Therefore, the Freundlich model should be satisfactory for describing the analyte behavior. |
Lopez-Cabana, Z; Navas, D; Benavente, E; Santa-Ana, M A; Lavayen, V; González, G Hybrid Laminar Organic-Inorganic Semiconducting Nanocomposites Artículo de revista Molecular Crystals and Liquid Crystals, 554 , pp. 119-134, 2012, ISSN: 1542-1406. Resumen | Enlaces | BibTeX | Etiquetas: nanocomposites, semiconductors, v2o5, zno @article{RN79, title = {Hybrid Laminar Organic-Inorganic Semiconducting Nanocomposites}, author = { Z. Lopez-Cabana and D. Navas and E. Benavente and M.A. Santa-Ana and V. Lavayen and G. Gonz\'{a}lez}, url = {/brokenurl#<Go to ISI>://WOS:000302299300014}, doi = {10.1080/15421406.2011.633852}, issn = {1542-1406}, year = {2012}, date = {2012-01-01}, journal = {Molecular Crystals and Liquid Crystals}, volume = {554}, pages = {119-134}, abstract = {Hybrid two-dimensional nanocomposites of transition metal semiconductors based on molybdenum disulfide, zinc oxide, and vanadium pentoxide, in which ultra-thin sheets of the inorganic component are stabilized by insertion into a bilayer of organic amphiphiles, are described. The resulting solids are commensurate species with characteristic stoichiometries, extremely high aspect ratio, and large organic-inorganic interfaces. Synthesis procedures and changes in the properties of the nanocomposites with respect to those of their components, depend on the structural nature of the pristine semiconductor. Derivatives of the laminar semiconductor MoS2 are obtained by quasi-topotactic intercalation of amphiphiles into the layered inorganic matrix, being changes in the properties mainly associated to guest-host charge transfer without altering significantly the electronic structure of the sulfide. In the case of the structurally isotropic ZnO bottom-up sol-gel synthesis procedures, it is necessary to use amphiphiles as templates, producing the two dimensional confinement with significant changes in the band gap of the semiconductor. Vanadium oxide, because of bonding asymmetry, may be easily intercalated. However due to its low laying conduction band, this leads to mixed valence species. Beyond size and dimension induced bang-gap changes, the optical properties of the products, as appreciated in their absorption and emission spectra, are in general qualitatively similar to those of pristine semiconductors.}, keywords = {nanocomposites, semiconductors, v2o5, zno}, pubstate = {published}, tppubtype = {article} } Hybrid two-dimensional nanocomposites of transition metal semiconductors based on molybdenum disulfide, zinc oxide, and vanadium pentoxide, in which ultra-thin sheets of the inorganic component are stabilized by insertion into a bilayer of organic amphiphiles, are described. The resulting solids are commensurate species with characteristic stoichiometries, extremely high aspect ratio, and large organic-inorganic interfaces. Synthesis procedures and changes in the properties of the nanocomposites with respect to those of their components, depend on the structural nature of the pristine semiconductor. Derivatives of the laminar semiconductor MoS2 are obtained by quasi-topotactic intercalation of amphiphiles into the layered inorganic matrix, being changes in the properties mainly associated to guest-host charge transfer without altering significantly the electronic structure of the sulfide. In the case of the structurally isotropic ZnO bottom-up sol-gel synthesis procedures, it is necessary to use amphiphiles as templates, producing the two dimensional confinement with significant changes in the band gap of the semiconductor. Vanadium oxide, because of bonding asymmetry, may be easily intercalated. However due to its low laying conduction band, this leads to mixed valence species. Beyond size and dimension induced bang-gap changes, the optical properties of the products, as appreciated in their absorption and emission spectra, are in general qualitatively similar to those of pristine semiconductors. |
Seguel, R J; Morales, R G E; Leiva, M A Ozone Weekend Effect in Santiago, Chile Artículo de revista Environmental Pollution, 162 , pp. 72-79, 2012, ISSN: 0269-7491. Resumen | Enlaces | BibTeX | Etiquetas: effect, environmental chemistry, focus, nox ozone, phoenix, photochemistry, ratio, surface voc/nox weekday, weekend @article{RN35d, title = {Ozone Weekend Effect in Santiago, Chile}, author = { R.J. Seguel and R.G.E. Morales and M.A. Leiva}, url = {/brokenurl#<Go to ISI>://WOS:000301087800009}, doi = {10.1016/j.envpol.2011.10.019}, issn = {0269-7491}, year = {2012}, date = {2012-01-01}, journal = {Environmental Pollution}, volume = {162}, pages = {72-79}, publisher = {2011 Elsevier Ltd.}, abstract = {The study examined weekday-weekend differences in ozone, NOx (NO and NO2) and VOC concentrations in Santiago, Chile, from 1999 to 2007. The results provide evidence for the occurrence of an atmospheric phenomenon that produces higher ozone concentrations during weekends despite lower concentrations of ozone precursors. This phenomenon is known as the weekend effect (WE)., The overall ozone decrease since the spring of 2004 was a consequence of the implementation of several urban pollution control measures. Although these measures caused a decline in the number of days that exceed the national standard from two-thirds to one-third of summer days, the WE, which became statistically significant beginning in September 2004, could not be eliminated. Furthermore. VOC/NOx ratios decreased during the same period (2004), especially in the most industrialized area of Santiago. Similarly, under these regimes, the VOC/NOx ratios were higher on Sundays than on weekdays and caused higher ozone concentrations on Sundays.}, keywords = {effect, environmental chemistry, focus, nox ozone, phoenix, photochemistry, ratio, surface voc/nox weekday, weekend}, pubstate = {published}, tppubtype = {article} } The study examined weekday-weekend differences in ozone, NOx (NO and NO2) and VOC concentrations in Santiago, Chile, from 1999 to 2007. The results provide evidence for the occurrence of an atmospheric phenomenon that produces higher ozone concentrations during weekends despite lower concentrations of ozone precursors. This phenomenon is known as the weekend effect (WE)., The overall ozone decrease since the spring of 2004 was a consequence of the implementation of several urban pollution control measures. Although these measures caused a decline in the number of days that exceed the national standard from two-thirds to one-third of summer days, the WE, which became statistically significant beginning in September 2004, could not be eliminated. Furthermore. VOC/NOx ratios decreased during the same period (2004), especially in the most industrialized area of Santiago. Similarly, under these regimes, the VOC/NOx ratios were higher on Sundays than on weekdays and caused higher ozone concentrations on Sundays. |
Barrientos-Poblete, L; Allende-González, P; Orellana, C; Jara, P Ordered Arrangements of Metal Nanoparticles on Alpha-Cyclodextrin Inclusion Complexes by Magnetron Sputtering Artículo de revista Inorganica Chimica Acta, 380 , pp. 372-377, 2012, ISSN: 0020-1693. Resumen | Enlaces | BibTeX | Etiquetas: catalysis, colloids, gold guest host interaction, magnetron metal metal-guest molecules, monolayer, nanoparticles, nanostructures, particles, size, sputtering, stabilization, supramolecular surface @article{RN81, title = {Ordered Arrangements of Metal Nanoparticles on Alpha-Cyclodextrin Inclusion Complexes by Magnetron Sputtering}, author = { L. Barrientos-Poblete and P. Allende-Gonz\'{a}lez and C. Orellana and P. Jara}, url = {/brokenurl#<Go to ISI>://WOS:000300180100050}, doi = {10.1016/j.ica.2011.10.032}, issn = {0020-1693}, year = {2012}, date = {2012-01-01}, journal = {Inorganica Chimica Acta}, volume = {380}, pages = {372-377}, publisher = {2011 Elsevier B.V.}, abstract = {An ordered self-assembly of copper, silver and gold nanoparticles onto crystal faces of alpha-cyclodextrin/1-octanethiol and 2 alpha-cyclodextrin/1-octylamine inclusion complexes by means of physical vapor deposition (magnetron sputtering) has been achieved. The preferential deposition on the (001) plane of the supramolecular crystal occurs because the -SH and -NH2 groups from the guest molecules found within the alpha-cyclodextrin protrude into that plane. These functional groups form a two-dimensional hexagonal lattice that interacts with the metal nanoparticles, arranging them in an ordered way.}, keywords = {catalysis, colloids, gold guest host interaction, magnetron metal metal-guest molecules, monolayer, nanoparticles, nanostructures, particles, size, sputtering, stabilization, supramolecular surface}, pubstate = {published}, tppubtype = {article} } An ordered self-assembly of copper, silver and gold nanoparticles onto crystal faces of alpha-cyclodextrin/1-octanethiol and 2 alpha-cyclodextrin/1-octylamine inclusion complexes by means of physical vapor deposition (magnetron sputtering) has been achieved. The preferential deposition on the (001) plane of the supramolecular crystal occurs because the -SH and -NH2 groups from the guest molecules found within the alpha-cyclodextrin protrude into that plane. These functional groups form a two-dimensional hexagonal lattice that interacts with the metal nanoparticles, arranging them in an ordered way. |
Diaz-Fleming, G; Celis, F; Aracena, A; Campos-Vallette, M; Aliaga, A E; Koch, R Vibrational and Scaled Quantum Chemical Study of O,O-Dimethyl S-Methylcarbamoylmethyl Phosphorodithioate, Dimethoate Artículo de revista Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy, 89 , pp. 222-230, 2012, ISSN: 1386-1425. Resumen | Enlaces | BibTeX | Etiquetas: analysis, assignment basis, calculations, compounds, coordinate dft dimethoate, field, force force-constants, gaussian-type infrared, infrared-spectra, methods, molecular-orbital monosubstituted normal organic-molecules, phosphorus raman, sqm @article{RN97, title = {Vibrational and Scaled Quantum Chemical Study of O,O-Dimethyl S-Methylcarbamoylmethyl Phosphorodithioate, Dimethoate}, author = { G. Diaz-Fleming and F. Celis and A. Aracena and M. Campos-Vallette and A.E. Aliaga and R. Koch}, url = {/brokenurl#<Go to ISI>://WOS:000301471600032}, doi = {10.1016/j.saa.2011.12.032}, issn = {1386-1425}, year = {2012}, date = {2012-01-01}, journal = {Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy}, volume = {89}, pages = {222-230}, publisher = {2011 Elsevier B.V.}, abstract = {Infrared and Raman spectra of O,O-dimethyl S-methylcarbamoylmethylphosphorodithioate, dimethoate, have been recorded. Density functional theory, DFT, with the B3LYP functional was used for the optimization of the ground state geometry and simulation of the infrared and Raman spectra of this molecule. Calculated geometrical parameters fit very well with the experimental ones. Based on the recorded data, the DFT results and a normal coordinate analysis based on a scaled quantum mechanical (SQM) force field approach, a complete vibrational assignment was made for the first time.}, keywords = {analysis, assignment basis, calculations, compounds, coordinate dft dimethoate, field, force force-constants, gaussian-type infrared, infrared-spectra, methods, molecular-orbital monosubstituted normal organic-molecules, phosphorus raman, sqm}, pubstate = {published}, tppubtype = {article} } Infrared and Raman spectra of O,O-dimethyl S-methylcarbamoylmethylphosphorodithioate, dimethoate, have been recorded. Density functional theory, DFT, with the B3LYP functional was used for the optimization of the ground state geometry and simulation of the infrared and Raman spectra of this molecule. Calculated geometrical parameters fit very well with the experimental ones. Based on the recorded data, the DFT results and a normal coordinate analysis based on a scaled quantum mechanical (SQM) force field approach, a complete vibrational assignment was made for the first time. |
Castro-Castillo, V; Galdámez, A; Rebolledo-Fuentes, M; Cassels, B K H-1 and C-13 Nmr Spectral Assignments and X-Ray Crystallography of 4,5,8,12b-Tetrahydro-Isoindolo[1,2-a]Isoquinoline and Derivatives Artículo de revista Journal of the Chilean Chemical Society, 57 (1), pp. 972-976, 2012, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: crystal-structure dqcauchile @article{RN25d, title = {H-1 and C-13 Nmr Spectral Assignments and X-Ray Crystallography of 4,5,8,12b-Tetrahydro-Isoindolo[1,2-a]Isoquinoline and Derivatives}, author = { V. Castro-Castillo and A. Gald\'{a}mez and M. Rebolledo-Fuentes and B.K. Cassels}, url = {/brokenurl#<Go to ISI>://WOS:000302755900004}, doi = {10.4067/S0717-97072012000100004}, issn = {0717-9707}, year = {2012}, date = {2012-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {57}, number = {1}, pages = {972-976}, abstract = {12b-Hydroxy-5,6,8,12b-tetrahydroisoindolo[1,2-a]isoquinolin-8-one (4), 5,6,8,12b-tetrahydroisoindolo[1,2-a]isoquinoline (5) and 12b-hydroxy-5,6,8,12b-tetrahydroisoindolo[1,2-a]isoquinoline (6) were obtained by reduction of 4,5,8,12b-tetrahydroisoindolo[1,2-a]isoquinolin-8-one (3) with LiAlH4/THF/N-2. The precursor and products were characterized by NMR spectroscopy and the X-ray crystal structure of 5 hydrochloride monohydrate (5a) was determined. H-1 and C-13 NMR spectra were completely assigned for compounds 3, 4, and 5a, using two-dimensional experiments (H-H COSY, HMQC, HMBC and H-H NOESY).}, keywords = {crystal-structure dqcauchile}, pubstate = {published}, tppubtype = {article} } 12b-Hydroxy-5,6,8,12b-tetrahydroisoindolo[1,2-a]isoquinolin-8-one (4), 5,6,8,12b-tetrahydroisoindolo[1,2-a]isoquinoline (5) and 12b-hydroxy-5,6,8,12b-tetrahydroisoindolo[1,2-a]isoquinoline (6) were obtained by reduction of 4,5,8,12b-tetrahydroisoindolo[1,2-a]isoquinolin-8-one (3) with LiAlH4/THF/N-2. The precursor and products were characterized by NMR spectroscopy and the X-ray crystal structure of 5 hydrochloride monohydrate (5a) was determined. H-1 and C-13 NMR spectra were completely assigned for compounds 3, 4, and 5a, using two-dimensional experiments (H-H COSY, HMQC, HMBC and H-H NOESY). |
Leyton, P; Saladino, R; Crestini, C; Campos-Vallette, M; Paipa, C; Berrios, A; Fuentes, S; Zarate, R A Influence of Tio2 on Prebiotic Thermal Synthesis of the Gly-Gln Polymer Artículo de revista Amino Acids, 42 (6), pp. 2079-2088, 2012, ISSN: 0939-4451. Resumen | Enlaces | BibTeX | Etiquetas: amino-acids, chemistry, condensation conditions, crystalline diketopiperazine, dioxide, dynamics, earth formation ft-ir glutamic glycine, peptide prebiotic primitive reaction, self-disproportionation, spectra, spectroscopy, synthesis, thermal titanium vibrational @article{RN29d, title = {Influence of Tio2 on Prebiotic Thermal Synthesis of the Gly-Gln Polymer}, author = { P. Leyton and R. Saladino and C. Crestini and M. Campos-Vallette and C. Paipa and A. Berrios and S. Fuentes and R.A. Zarate}, url = {/brokenurl#<Go to ISI>://WOS:000304150300004}, doi = {10.1007/s00726-011-0939-6}, issn = {0939-4451}, year = {2012}, date = {2012-01-01}, journal = {Amino Acids}, volume = {42}, number = {6}, pages = {2079-2088}, abstract = {The role of the titanium dioxide (rutile and anatase) with and without room light on the thermal synthesis of the glycine--glutamine (Gly-Gln) polymer is described. The efficiency in percentage of polymerization with room light was increased in 6% in the presence of rutile and in 23% in the presence of anatase. The thermal synthesis in the molten state was carried out in the absence and presence of both oxides. In all cases, the vibrational spectra showed characteristic group frequencies corresponding to a polypeptide structure. No spectral differences were observed by room light effect on the polymer on rutile. However, the polymer obtained in the presence of anatase and room light shows spectral changes associated with the formation of shorter new abundant and conformationally different species compared with the original polymer. The SEM-EDX characterization of the solid phase involved in the thermal synthesis showed that the morphology of the polypeptide is different in the presence of rutile compared to anatase. The SDS-PAGE and GPC results suggest that smaller chains are formed in the presence of both oxides and the distribution of the size and weight of each polymer molecule is completely different when the condensation is performed in the presence of anatase or rutile. Nuclear magnetic resonance analyses confirmed the incorporation of both Gly and Gln residues in the polymers, with a prevalence of Gly. Both possible sequences -GlyGln- and -GlnGly- were also detected.}, keywords = {amino-acids, chemistry, condensation conditions, crystalline diketopiperazine, dioxide, dynamics, earth formation ft-ir glutamic glycine, peptide prebiotic primitive reaction, self-disproportionation, spectra, spectroscopy, synthesis, thermal titanium vibrational}, pubstate = {published}, tppubtype = {article} } The role of the titanium dioxide (rutile and anatase) with and without room light on the thermal synthesis of the glycine--glutamine (Gly-Gln) polymer is described. The efficiency in percentage of polymerization with room light was increased in 6% in the presence of rutile and in 23% in the presence of anatase. The thermal synthesis in the molten state was carried out in the absence and presence of both oxides. In all cases, the vibrational spectra showed characteristic group frequencies corresponding to a polypeptide structure. No spectral differences were observed by room light effect on the polymer on rutile. However, the polymer obtained in the presence of anatase and room light shows spectral changes associated with the formation of shorter new abundant and conformationally different species compared with the original polymer. The SEM-EDX characterization of the solid phase involved in the thermal synthesis showed that the morphology of the polypeptide is different in the presence of rutile compared to anatase. The SDS-PAGE and GPC results suggest that smaller chains are formed in the presence of both oxides and the distribution of the size and weight of each polymer molecule is completely different when the condensation is performed in the presence of anatase or rutile. Nuclear magnetic resonance analyses confirmed the incorporation of both Gly and Gln residues in the polymers, with a prevalence of Gly. Both possible sequences -GlyGln- and -GlnGly- were also detected. |
Pérez, E G; Cassels, B K; Eibl, C; Gündisch, D Synthesis and Evaluation of N1-Alkylindole-3-Ylalkylammonium Compounds as Nicotinic Acetylcholine Receptor Ligands Artículo de revista Bioorganic & Medicinal Chemistry, 20 (12), pp. 3719-3727, 2012, ISSN: 0968-0896. Resumen | Enlaces | BibTeX | Etiquetas: @article{RN67, title = {Synthesis and Evaluation of N1-Alkylindole-3-Ylalkylammonium Compounds as Nicotinic Acetylcholine Receptor Ligands}, author = { E.G. P\'{e}rez and B.K. Cassels and C. Eibl and D. G\"{u}ndisch}, url = {http://www.sciencedirect.com/science/article/pii/S0968089612003471}, doi = {10.1016/j.bmc.2012.04.050}, issn = {0968-0896}, year = {2012}, date = {2012-01-01}, journal = {Bioorganic & Medicinal Chemistry}, volume = {20}, number = {12}, pages = {3719-3727}, abstract = {In this study thirty-three novel indole derivatives were designed and synthesized based on the structure of deformylflustrabromine B (1), a metabolite isolated from the marine bryozoan Flustra foliacea L. The syntheses were carried out using standard methodologies and in good yields. The molecules were tested for their affinities for the α4β2∗, α3β4∗, α7∗ and (α1)2β1γδ nicotinic acetylcholine receptor (nAChR) subtypes. Binding assays showed that, among these ligands, compound 7c exhibited the highest affinity with Ki=136.1, 93.9 and 862.4nM for the α4β2∗, α3β4∗, and α7∗ nAChRs subtypes, respectively. These results indicated that the indole core might be a useful scaffold for the development of new potent and selective nAChR ligands.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study thirty-three novel indole derivatives were designed and synthesized based on the structure of deformylflustrabromine B (1), a metabolite isolated from the marine bryozoan Flustra foliacea L. The syntheses were carried out using standard methodologies and in good yields. The molecules were tested for their affinities for the α4β2∗, α3β4∗, α7∗ and (α1)2β1γδ nicotinic acetylcholine receptor (nAChR) subtypes. Binding assays showed that, among these ligands, compound 7c exhibited the highest affinity with Ki=136.1, 93.9 and 862.4nM for the α4β2∗, α3β4∗, and α7∗ nAChRs subtypes, respectively. These results indicated that the indole core might be a useful scaffold for the development of new potent and selective nAChR ligands. |
Carcamo, J J; Aliaga, A E; Clavijo, E; Branes, M; Campos-Vallette, M Raman and Surface-Enhanced Raman Scattering in the Study of Human Rotator Cuff Tissues after Shock Wave Treatment Artículo de revista Journal of Raman Spectroscopy, 43 (2), pp. 248-254, 2012, ISSN: 0377-0486. Resumen | Enlaces | BibTeX | Etiquetas: amino-acids, collagen, collagens, cuff, gold infrared-spectra, nanoparticles, raman, rotator sers, shockwaves, silver, single-molecule, spectroscopy @article{RN39i, title = {Raman and Surface-Enhanced Raman Scattering in the Study of Human Rotator Cuff Tissues after Shock Wave Treatment}, author = { J.J. Carcamo and A.E. Aliaga and E. Clavijo and M. Branes and M. Campos-Vallette}, url = {/brokenurl#<Go to ISI>://WOS:000300836900011}, doi = {10.1002/jrs.3019}, issn = {0377-0486}, year = {2012}, date = {2012-01-01}, journal = {Journal of Raman Spectroscopy}, volume = {43}, number = {2}, pages = {248-254}, publisher = {2011 John Wiley & Sons, Ltd.}, abstract = {Important improvements of diseases of the rotator cuff supraspinatus tendons are seen after shock wave (SW) treatment. Neo-angiogenesis stimulation and hypercellularization result from short periods of treatment. The present work is an attempt to provide a first approach to these bioprocesses, most likely associated with structural aspects resulting from biochemical changes brought about by the SW. Immunohistochemical data indicate that collagen areas in the tissues are influenced the most by the SW. Presence of additional collagens I and III by the SW treatment is inferred from an observed increase of the tissue's tinctorial properties. The tools selected for our studies are Raman spectroscopy and the ultrasensitive surface-enhanced Raman scattering (SERS). Here we extract information from 1016 SERS spectra of 52 biopsies of human tendon tissues on Ag nanoparticles before and after the SW treatment. The spectral information is analyzed on the basis of Raman and SERS data of collagen types I and III and their most abundant amino acid components. SERS spectra of tissues reveal the presence of characteristic modes related mainly to amino acids. It has been found that the main differences between both tissue samples could be correlated with the structural conformational aspects of collagen.}, keywords = {amino-acids, collagen, collagens, cuff, gold infrared-spectra, nanoparticles, raman, rotator sers, shockwaves, silver, single-molecule, spectroscopy}, pubstate = {published}, tppubtype = {article} } Important improvements of diseases of the rotator cuff supraspinatus tendons are seen after shock wave (SW) treatment. Neo-angiogenesis stimulation and hypercellularization result from short periods of treatment. The present work is an attempt to provide a first approach to these bioprocesses, most likely associated with structural aspects resulting from biochemical changes brought about by the SW. Immunohistochemical data indicate that collagen areas in the tissues are influenced the most by the SW. Presence of additional collagens I and III by the SW treatment is inferred from an observed increase of the tissue's tinctorial properties. The tools selected for our studies are Raman spectroscopy and the ultrasensitive surface-enhanced Raman scattering (SERS). Here we extract information from 1016 SERS spectra of 52 biopsies of human tendon tissues on Ag nanoparticles before and after the SW treatment. The spectral information is analyzed on the basis of Raman and SERS data of collagen types I and III and their most abundant amino acid components. SERS spectra of tissues reveal the presence of characteristic modes related mainly to amino acids. It has been found that the main differences between both tissue samples could be correlated with the structural conformational aspects of collagen. |
Bahamonde-Padilla, V E; Martinez-Cifuentes, M; Munoz-Masson, D; Ruiz, A I; Ahumada, H; Araya-Maturana, R; Soto-Delgado, J; Weiss-Lopez, B Location, Orientation and Dynamics of Two Molecules with Mitochondrial Activity Dissolved in Anionic Lyomesophase. A H-2-Nmr and Md Study Artículo de revista Journal of the Chilean Chemical Society, 57 (3), pp. 1295-1300, 2012, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: antioxidant, derivatives, deuterium dipalmitoylphosphatidylcholine, hydration, hydroquinones, longitudinal lyomesophase, parathion, peptides, proteins quadrupole quinones, relaxation respiration, simulations, splitting, time, tumor-cell @article{RN100, title = {Location, Orientation and Dynamics of Two Molecules with Mitochondrial Activity Dissolved in Anionic Lyomesophase. A H-2-Nmr and Md Study}, author = { V.E. Bahamonde-Padilla and M. Martinez-Cifuentes and D. Munoz-Masson and A.I. Ruiz and H. Ahumada and R. Araya-Maturana and J. Soto-Delgado and B. Weiss-Lopez}, url = {/brokenurl#<Go to ISI>://WOS:000309315300021}, doi = {10.4067/S0717-97072012000300021}, issn = {0717-9707}, year = {2012}, date = {2012-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {57}, number = {3}, pages = {1295-1300}, abstract = {4,4-Dimethyl-5,8-dihydroanthracene-1,9,10(4H)-trione (Q1) and 9,10-Dihydroxy-4,4-dimethyl-5,8-dihydro-1 (4H)-anthracenone (Q2), two molecules that inhibit cancer cell respiration, were selectively deuterated and dissolved in an anionic discotic nematic lyotropic liquid crystal (dnllc) solution. The solution provides a magnetic field oriented anisotropic medium, where the location, average orientation and dynamics of Q(1) and Q(2) were examined by measuring H-2-NMR quadrupole splittings (Delta v(Q)) and H-2 longitudinal relaxation times (T-1). The NMR data shows that both molecules are strongly attached to the aggregate and, when dissolved, increase the alignment of the interface components with the magnetic field. However they present different average orientations. To assist with the interpretation of the experimental results, 300ns Molecular Dynamics (MD) trajectories of a bilayer model of the aggregate were calculated. The results show that both molecules spontaneously diffuse inside the bilayer, to locate in the limit between the hydrophobic core and the interface. The orientations of both molecules in the aggregate are determined by the formation of H-bonds with water.}, keywords = {antioxidant, derivatives, deuterium dipalmitoylphosphatidylcholine, hydration, hydroquinones, longitudinal lyomesophase, parathion, peptides, proteins quadrupole quinones, relaxation respiration, simulations, splitting, time, tumor-cell}, pubstate = {published}, tppubtype = {article} } 4,4-Dimethyl-5,8-dihydroanthracene-1,9,10(4H)-trione (Q1) and 9,10-Dihydroxy-4,4-dimethyl-5,8-dihydro-1 (4H)-anthracenone (Q2), two molecules that inhibit cancer cell respiration, were selectively deuterated and dissolved in an anionic discotic nematic lyotropic liquid crystal (dnllc) solution. The solution provides a magnetic field oriented anisotropic medium, where the location, average orientation and dynamics of Q(1) and Q(2) were examined by measuring H-2-NMR quadrupole splittings (Delta v(Q)) and H-2 longitudinal relaxation times (T-1). The NMR data shows that both molecules are strongly attached to the aggregate and, when dissolved, increase the alignment of the interface components with the magnetic field. However they present different average orientations. To assist with the interpretation of the experimental results, 300ns Molecular Dynamics (MD) trajectories of a bilayer model of the aggregate were calculated. The results show that both molecules spontaneously diffuse inside the bilayer, to locate in the limit between the hydrophobic core and the interface. The orientations of both molecules in the aggregate are determined by the formation of H-bonds with water. |
Diaz, C; Valenzuela, M L; Garrido, D; Aguirre, P Sol-Gel Incorporation of Organometallic Compounds into Silica: Useful Precursors to Metallic Nanostructured Materials Artículo de revista Journal of the Chilean Chemical Society, 57 (2), pp. 1155-1162, 2012, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: bridged magnetic-properties, materials, matrix, mesoporous molecular nanoclusters nanocomposites, nanoparticles, nanostructured, nanowires, organic-inorganic polysilsesquioxanes, precursors, pyrophosphates, silica, sol-gel, source thermolytic transformation @article{RN87, title = {Sol-Gel Incorporation of Organometallic Compounds into Silica: Useful Precursors to Metallic Nanostructured Materials}, author = { C. Diaz and M.L. Valenzuela and D. Garrido and P. Aguirre}, url = {/brokenurl#<Go to ISI>://WOS:000305169800021}, issn = {0717-9707}, year = {2012}, date = {2012-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {57}, number = {2}, pages = {1155-1162}, abstract = {Inclusion of the organometallic MLn = [HOC5H4N center dot Cp2TiCl][PF6] (I), HOC5H4N center dot W(CO)(5) (2), HOC5H4N center dot Mo(CO)(5) (3), [HOC6H4CH2CN center dot Cp2TiCl][PF6] (4), HOC6H4CH2CN center dot W(CO)(5) (5) and HOC6H4CH2CN center dot Mo(CO)(5) (6) into amorphous silica using the gelator precursor TEOS and N3P3N-H[CH2](3)Si[OEt](3)(6) afford the gels (MLn)(SiO2)(n). The inorganic-organic hybrid nanocomposites were pyrolyzed under air at 800 degrees C to give nanostructured metal oxides and/or metal pyrophosphates (phosphates) included in the silica matrices. The morphology of the monolithic nanocomposites exhibited a strong dependence on the gel precursor used being mainly laminar for those prepared using N2P3NH[CH2](3)Si[OEt](3) as gelator. TEm images show different shape and size such as circular nanoparticles, nanocables and agglomerates in some cases with sizes of 20 nm for the circular nanostructures, and diameter about 25 nm for the nanocables.}, keywords = {bridged magnetic-properties, materials, matrix, mesoporous molecular nanoclusters nanocomposites, nanoparticles, nanostructured, nanowires, organic-inorganic polysilsesquioxanes, precursors, pyrophosphates, silica, sol-gel, source thermolytic transformation}, pubstate = {published}, tppubtype = {article} } Inclusion of the organometallic MLn = [HOC5H4N center dot Cp2TiCl][PF6] (I), HOC5H4N center dot W(CO)(5) (2), HOC5H4N center dot Mo(CO)(5) (3), [HOC6H4CH2CN center dot Cp2TiCl][PF6] (4), HOC6H4CH2CN center dot W(CO)(5) (5) and HOC6H4CH2CN center dot Mo(CO)(5) (6) into amorphous silica using the gelator precursor TEOS and N3P3N-H[CH2](3)Si[OEt](3)(6) afford the gels (MLn)(SiO2)(n). The inorganic-organic hybrid nanocomposites were pyrolyzed under air at 800 degrees C to give nanostructured metal oxides and/or metal pyrophosphates (phosphates) included in the silica matrices. The morphology of the monolithic nanocomposites exhibited a strong dependence on the gel precursor used being mainly laminar for those prepared using N2P3NH[CH2](3)Si[OEt](3) as gelator. TEm images show different shape and size such as circular nanoparticles, nanocables and agglomerates in some cases with sizes of 20 nm for the circular nanostructures, and diameter about 25 nm for the nanocables. |
Cedillo, A; Contreras, R A Local Extension of the Electrophilicity Index Concept Artículo de revista Journal of the Mexican Chemical Society, 56 (3), pp. 257-260, 2012, ISSN: 1870-249x. Resumen | Enlaces | BibTeX | Etiquetas: chemical chemical-reactivity, concept, density density-functional descriptors, electrophilicity, fukui function, functional hardness, intermolecular local parameter philicity reactivity, selectivity, softness, theory @article{RN107, title = {A Local Extension of the Electrophilicity Index Concept}, author = { A. Cedillo and R. Contreras}, url = {/brokenurl#<Go to ISI>://WOS:000311506100005}, issn = {1870-249x}, year = {2012}, date = {2012-01-01}, journal = {Journal of the Mexican Chemical Society}, volume = {56}, number = {3}, pages = {257-260}, abstract = {A local measure of the electrophilicity has been recently proposed to analyze the chemical reactivity of several kinds of molecules. In this work a theoretical rationalization of the local extension is proposed following the quantitative definition of the molecular electrophilic power and a variational method for the distribution of the transferred charge. A condensation scheme to atoms or fragments follows from its relation to the Fukui function and the local softness. Differences between these quantities are discussed and they are tested in a model system. The analysis shows that the local electrophilicity is more appropriate to describe differences among a set of substituted molecules.}, keywords = {chemical chemical-reactivity, concept, density density-functional descriptors, electrophilicity, fukui function, functional hardness, intermolecular local parameter philicity reactivity, selectivity, softness, theory}, pubstate = {published}, tppubtype = {article} } A local measure of the electrophilicity has been recently proposed to analyze the chemical reactivity of several kinds of molecules. In this work a theoretical rationalization of the local extension is proposed following the quantitative definition of the molecular electrophilic power and a variational method for the distribution of the transferred charge. A condensation scheme to atoms or fragments follows from its relation to the Fukui function and the local softness. Differences between these quantities are discussed and they are tested in a model system. The analysis shows that the local electrophilicity is more appropriate to describe differences among a set of substituted molecules. |
Ormazabal-Toledo, R; Castro, E A; Santos, J G; Millan, D; Canete, A; Contreras, R; Campodonico, P R Predicting the Reaction Mechanism of Nucleophilic Substitutions at Carbonyl and Thiocarbonyl Centres of Esters and Thioesters Artículo de revista Journal of Physical Organic Chemistry, 25 (12), pp. 1359-1364, 2012, ISSN: 0894-3230. Resumen | Enlaces | BibTeX | Etiquetas: aminolysis, carbonyl carboxylic center, contrasting density derivatives, dithiocarbonates, electron electrophilic esters, fukui function, group group, kinetic kinetics, leaving measurements, mechanisms, o-ethyl phenyl, reaction reactivity, reorganization, secondary @article{RN103, title = {Predicting the Reaction Mechanism of Nucleophilic Substitutions at Carbonyl and Thiocarbonyl Centres of Esters and Thioesters}, author = { R. Ormazabal-Toledo and E.A. Castro and J.G. Santos and D. Millan and A. Canete and R. Contreras and P.R. Campodonico}, url = {/brokenurl#<Go to ISI>://WOS:000313125800038}, doi = {10.1002/poc.3048}, issn = {0894-3230}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Organic Chemistry}, volume = {25}, number = {12}, pages = {1359-1364}, publisher = {2012 John Wiley & Sons, Ltd.}, abstract = {In nucleophilic substitution reactions at carbonyl centres, there are two possible channels. The first one occurs when the attack of nucleophilic agents takes place simultaneously with the departure of the nucleofuge. This process is named as concerted. The second possibility is the formation of a reaction intermediate, typically a tetrahedral intermediate from which the nucleofuge departs after passing through a second transition state. This second mechanism is defined as stepwise. Whether a concerted or stepwise mechanism is to be expected for a given reaction depends on several factors. Among these determinants are the nucleophilicity of the attacking group, the leaving group ability of the nucleofuge, and the solvent, which affects both the stability of the intermediate or the transition states involved. The role of the electrophilic centre can however become an important factor that can determine the reaction mechanism. In this work we show that the group nucleophilic Fukui function model may be used to rationalize and to predict the reaction mechanism of the title compounds towards alicyclic amines. In general, when the electrophilic carbon centre is attached to the soft sulfur atom, the reaction mechanism is predicted to follow a stepwise route. When the electrophilic carbon atom is attached to a harder oxygen centre, the reaction mechanism is determined by chemical substitution at the nucleofuge moiety. Experimental verification for a set of four substrates is presented.}, keywords = {aminolysis, carbonyl carboxylic center, contrasting density derivatives, dithiocarbonates, electron electrophilic esters, fukui function, group group, kinetic kinetics, leaving measurements, mechanisms, o-ethyl phenyl, reaction reactivity, reorganization, secondary}, pubstate = {published}, tppubtype = {article} } In nucleophilic substitution reactions at carbonyl centres, there are two possible channels. The first one occurs when the attack of nucleophilic agents takes place simultaneously with the departure of the nucleofuge. This process is named as concerted. The second possibility is the formation of a reaction intermediate, typically a tetrahedral intermediate from which the nucleofuge departs after passing through a second transition state. This second mechanism is defined as stepwise. Whether a concerted or stepwise mechanism is to be expected for a given reaction depends on several factors. Among these determinants are the nucleophilicity of the attacking group, the leaving group ability of the nucleofuge, and the solvent, which affects both the stability of the intermediate or the transition states involved. The role of the electrophilic centre can however become an important factor that can determine the reaction mechanism. In this work we show that the group nucleophilic Fukui function model may be used to rationalize and to predict the reaction mechanism of the title compounds towards alicyclic amines. In general, when the electrophilic carbon centre is attached to the soft sulfur atom, the reaction mechanism is predicted to follow a stepwise route. When the electrophilic carbon atom is attached to a harder oxygen centre, the reaction mechanism is determined by chemical substitution at the nucleofuge moiety. Experimental verification for a set of four substrates is presented. |
Rojas-Blanco, L; Urzúa, M; Ramirez-Bon, R; Beltran, F J E Photocatalytic Thin Films Containing Tio2:N Nanopowders Obtained by the Layer-by-Layer Self-Assembling Method Artículo de revista Applied Surface Science, 258 (6), pp. 2103-2106, 2012, ISSN: 0169-4332. Resumen | Enlaces | BibTeX | Etiquetas: by degradation, doping, layer layer, nitrogen nitrogen-doped oxide, photocatalysis, photoelectrochemical properties, srilankite, tio2, titanium urea @article{RN93, title = {Photocatalytic Thin Films Containing Tio2:N Nanopowders Obtained by the Layer-by-Layer Self-Assembling Method}, author = { L. Rojas-Blanco and M. Urz\'{u}a and R. Ramirez-Bon and F.J.E. Beltran}, url = {/brokenurl#<Go to ISI>://WOS:000298670300042}, doi = {10.1016/j.apsusc.2011.03.150}, issn = {0169-4332}, year = {2012}, date = {2012-01-01}, journal = {Applied Surface Science}, volume = {258}, number = {6}, pages = {2103-2106}, publisher = {2011 Elsevier B. V.}, abstract = {In this work, TiO2-N powders were synthesized by high-energy ball milling, using commercial titanium dioxide (TiO2) in the anatase phase and urea to introduce nitrogen into TiO2 in order to enhance their photocatalytic properties in the visible spectral region. Several samples were prepared by milling a mixture of TiO2-urea during 2, 4, 8, 12 and 24 h and characterized by spectroscopic and analytical techniques. X-ray diffraction (XRD) results showed the coexistence of anatase and high-pressure srilankite TiO2 crystalline phases in the samples. Scanning electron microscopy (SEM) revealed that the grain size of the powder samples decreases to 200 nm at 24 h milling time. UV-Vis diffuse reflectance spectroscopic data showed a clear red-shift in the onset of light absorption from 387 to 469 nm as consequence of nitrogen doping in the samples. The photocatalytic activity of the TiO2-N samples was evaluated by methylene blue degradation under visible light irradiation. It was found that TiO2-N samples had higher photocatalytic activity than undoped TiO2 samples, which could be assigned to the effect of introducing N atoms and XPS results confirm it. Using polyethylenimine (PEI), transparent thin films of TiO2-N nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 15 min.}, keywords = {by degradation, doping, layer layer, nitrogen nitrogen-doped oxide, photocatalysis, photoelectrochemical properties, srilankite, tio2, titanium urea}, pubstate = {published}, tppubtype = {article} } In this work, TiO2-N powders were synthesized by high-energy ball milling, using commercial titanium dioxide (TiO2) in the anatase phase and urea to introduce nitrogen into TiO2 in order to enhance their photocatalytic properties in the visible spectral region. Several samples were prepared by milling a mixture of TiO2-urea during 2, 4, 8, 12 and 24 h and characterized by spectroscopic and analytical techniques. X-ray diffraction (XRD) results showed the coexistence of anatase and high-pressure srilankite TiO2 crystalline phases in the samples. Scanning electron microscopy (SEM) revealed that the grain size of the powder samples decreases to 200 nm at 24 h milling time. UV-Vis diffuse reflectance spectroscopic data showed a clear red-shift in the onset of light absorption from 387 to 469 nm as consequence of nitrogen doping in the samples. The photocatalytic activity of the TiO2-N samples was evaluated by methylene blue degradation under visible light irradiation. It was found that TiO2-N samples had higher photocatalytic activity than undoped TiO2 samples, which could be assigned to the effect of introducing N atoms and XPS results confirm it. Using polyethylenimine (PEI), transparent thin films of TiO2-N nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 15 min. |
Amim, J; Maia, F C B; Miranda, P B; Urzúa, M; Petri, D F S Structural Aspects of Polyanion and Hydrophobically Modified Polycation Multilayers on Hydrophilic or Hydrophobic Surfaces Artículo de revista Soft Matter, 8 (24), pp. 6462-6470, 2012, ISSN: 1744-683x. Resumen | Enlaces | BibTeX | Etiquetas: behavior, buildup, by-layer deposition, films, multilayers, polyelectrolyte surfaces, terminated virus @article{RN92, title = {Structural Aspects of Polyanion and Hydrophobically Modified Polycation Multilayers on Hydrophilic or Hydrophobic Surfaces}, author = { J. Amim and F.C.B. Maia and P.B. Miranda and M. Urz\'{u}a and D.F.S. Petri}, url = {/brokenurl#<Go to ISI>://WOS:000304665400008}, doi = {10.1039/c2sm25658d}, issn = {1744-683x}, year = {2012}, date = {2012-01-01}, journal = {Soft Matter}, volume = {8}, number = {24}, pages = {6462-6470}, abstract = {Multilayer films of carboxymethylcellulose (CMC), a polyanion, and bromide salts of poly(4-vinylpyridine) quaternized with linear aliphatic chains of 2 (ethyl) and 5 (pentyl) carbon atoms, coded as QPVP-C2 and QPVP-C5, respectively, were fabricated by layer-by-layer (LbL) self-assembly onto Si/SiO2 wafers (hydrophilic substrate) or polystyrene, PS, films (hydrophobic substrate). The films were characterized by means of ex situ and in situ ellipsometry, atomic force microscopy (AFM), contact angle measurements and sum frequency generation vibrational spectroscopy (SFG). Antimicrobial tests were used to assess the exposure of pyridinium moieties to the aqueous medium. In situ ellipsometry indicated that for Si/SiO2 the chains were more expanded than the PS films and both substrates systems composed of QPVP-C5 were thicker than those with QPVP-C2. For dried layers, the alkyl side group size had a small effect on the thickness evolution, regardless of the substrate. At pH 2 the multilayers showed high resistance, evidencing that the build-up is driven not only by cooperative polymer-polymer ion pairing, but also by hydrophobic interactions between the alkyl side chains. The LbL films became irregular as the number of depositions increased. After the last deposition, the wettability of QPVP-C2 or QPVP-C5 terminated systems on the Si/SiO2 wafers and PS films were similar, except for QPVP-C2 on Si/SiO2 wafers. Unlike the morphology observed for LbL films on Si/SiO2 wafers, PS induced the formation of porous structures. SFG showed that in air the molecular orientation of pyridinium groups in multilayers with QPVP-C5 was stronger than in those containing QPVP-C2. The exposure of pyridinium moieties to the aqueous medium was more pronounced when the LbL were assembled on Si/SiO2 wafers.}, keywords = {behavior, buildup, by-layer deposition, films, multilayers, polyelectrolyte surfaces, terminated virus}, pubstate = {published}, tppubtype = {article} } Multilayer films of carboxymethylcellulose (CMC), a polyanion, and bromide salts of poly(4-vinylpyridine) quaternized with linear aliphatic chains of 2 (ethyl) and 5 (pentyl) carbon atoms, coded as QPVP-C2 and QPVP-C5, respectively, were fabricated by layer-by-layer (LbL) self-assembly onto Si/SiO2 wafers (hydrophilic substrate) or polystyrene, PS, films (hydrophobic substrate). The films were characterized by means of ex situ and in situ ellipsometry, atomic force microscopy (AFM), contact angle measurements and sum frequency generation vibrational spectroscopy (SFG). Antimicrobial tests were used to assess the exposure of pyridinium moieties to the aqueous medium. In situ ellipsometry indicated that for Si/SiO2 the chains were more expanded than the PS films and both substrates systems composed of QPVP-C5 were thicker than those with QPVP-C2. For dried layers, the alkyl side group size had a small effect on the thickness evolution, regardless of the substrate. At pH 2 the multilayers showed high resistance, evidencing that the build-up is driven not only by cooperative polymer-polymer ion pairing, but also by hydrophobic interactions between the alkyl side chains. The LbL films became irregular as the number of depositions increased. After the last deposition, the wettability of QPVP-C2 or QPVP-C5 terminated systems on the Si/SiO2 wafers and PS films were similar, except for QPVP-C2 on Si/SiO2 wafers. Unlike the morphology observed for LbL films on Si/SiO2 wafers, PS induced the formation of porous structures. SFG showed that in air the molecular orientation of pyridinium groups in multilayers with QPVP-C5 was stronger than in those containing QPVP-C2. The exposure of pyridinium moieties to the aqueous medium was more pronounced when the LbL were assembled on Si/SiO2 wafers. |
Cerda-Monje, A; Aizman, A; Tapia, R A; Chiappe, C; Contreras, R Solvent Effects in Ionic Liquids: Empirical Linear Energy-Density Relationships Artículo de revista Physical Chemistry Chemical Physics, 14 (28), pp. 10041-10049, 2012, ISSN: 1463-9076. Resumen | Enlaces | BibTeX | Etiquetas: ab-initio, catalysis, dielectric-constant, diels-alder electrophilicity field-theory, functional index, models molecular-dynamics, reaction, solvation, static theory @article{RN106, title = {Solvent Effects in Ionic Liquids: Empirical Linear Energy-Density Relationships}, author = { A. Cerda-Monje and A. Aizman and R.A. Tapia and C. Chiappe and R. Contreras}, url = {/brokenurl#<Go to ISI>://WOS:000305890300028}, doi = {10.1039/c2cp40619e}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {28}, pages = {10041-10049}, abstract = {Multiparameter linear energy-density relationships to model solvent effects in room temperature ionic liquids (RTILs) are introduced and tested. The model incorporates two solvent dependent and two specific solute-solvent parameters represented by a set of electronic indexes derived from the conceptual density functional theory. The specific solute-solvent interactions are described in terms of the electronic chemical potential for proton migration between the anion or cation and the transition state structure of a specific reaction. These indexes provide a quantitative estimation of the hydrogen bond (HB) acceptor basicity and the hydrogen bond donor acidity of the ionic solvent, respectively. A sound quantitative scale of HB strength is thereby obtained. The solvent dependent contributions are described by the global electrophilicity of the cation and nucleophilicity of the anion forming the ionic liquid. The model is illustrated for the kinetics of cycloaddition of cyclopentadiene towards acrolein. In general, cation HB acidity outweighs the remaining parameters for this reaction.}, keywords = {ab-initio, catalysis, dielectric-constant, diels-alder electrophilicity field-theory, functional index, models molecular-dynamics, reaction, solvation, static theory}, pubstate = {published}, tppubtype = {article} } Multiparameter linear energy-density relationships to model solvent effects in room temperature ionic liquids (RTILs) are introduced and tested. The model incorporates two solvent dependent and two specific solute-solvent parameters represented by a set of electronic indexes derived from the conceptual density functional theory. The specific solute-solvent interactions are described in terms of the electronic chemical potential for proton migration between the anion or cation and the transition state structure of a specific reaction. These indexes provide a quantitative estimation of the hydrogen bond (HB) acceptor basicity and the hydrogen bond donor acidity of the ionic solvent, respectively. A sound quantitative scale of HB strength is thereby obtained. The solvent dependent contributions are described by the global electrophilicity of the cation and nucleophilicity of the anion forming the ionic liquid. The model is illustrated for the kinetics of cycloaddition of cyclopentadiene towards acrolein. In general, cation HB acidity outweighs the remaining parameters for this reaction. |
Ponce, I; Silva, J F; Onate, R; Rezende, M C; Paez, M; Zagal, J H; Pavez, J; Mendizabal, F; Miranda-Rojas, S; Munoz-Castro, A; Arratia-Perez, R Journal of Physical Chemistry C, 116 (29), pp. 15329-15341, 2012, ISSN: 1932-7447. Resumen | Enlaces | BibTeX | Etiquetas: activity, alkylation, density-functional electrocatalytic electronic-structure, electroreductive hydrogen-peroxide, iron materials, metal-complexes molecular oxygen phthalocyanine, reduction, scanning-tunneling-microscopy, theory @article{RN83, title = {Enhancement of the Catalytic Activity of Fe Phthalocyanine for the Reduction of O-2 Anchored to Au(111) Via Conjugated Self-Assembled Mono Layers of Aromatic Thiols as Compared to Cu Phthalocyanine}, author = { I. Ponce and J.F. Silva and R. Onate and M.C. Rezende and M. Paez and J.H. Zagal and J. Pavez and F. Mendizabal and S. Miranda-Rojas and A. Munoz-Castro and R. Arratia-Perez}, url = {/brokenurl#<Go to ISI>://WOS:000306725200017}, doi = {10.1021/jp301093q}, issn = {1932-7447}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {29}, pages = {15329-15341}, abstract = {We have prepared self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (Fe Pc) and copper phthalocyanine (Cu Pc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/MPc was examined for the reduction of O-2 in aqueous solutions and compared to that of bare gold and with gold coated directly with preadsorbed MPc molecules. Scanning tunneling microscopy (STM) studies confirm the functionalization of the 4-ATP by MPc. STM images reveal that iron phthalocyanine molecules are chemically anchored to 4-aminothiophenol organic monolayers, probably having an "umbrella" type orientation with regards to the surface. The electrocatalytic studies carried out with Au/4-ATP/FePc and Au/MDPP/FePc electrodes show that the O-2 reduction takes place by the transfer of 4-electron to give water in contrast to a 2-electron transfer process observed for the bare gold. The modified electrode obtained by simple adsorption of FePc directly to the Au(111) surface still promotes the 4-electron reduction process, but it shows a lower activity than the electrodes involving SAMs with FePc molecules positioned at the outmost portion of the self-assembled monolayers. The activity of the electrodes increases as follow: Au < Au/FePc < Au/4-ATP/FePc < Au/MDPP/FePc with the highest activity when FePc molecules are more separated from the Au surface. In contrast, the less active CuPc shows almost the same activity in all three configurations. Theoretical calculations suggest the importance of the back-bonding into the adduct formation, showing the relevance of the supporting gold surface on the electron-transfer process mediated by anchoring ligands.}, keywords = {activity, alkylation, density-functional electrocatalytic electronic-structure, electroreductive hydrogen-peroxide, iron materials, metal-complexes molecular oxygen phthalocyanine, reduction, scanning-tunneling-microscopy, theory}, pubstate = {published}, tppubtype = {article} } We have prepared self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (Fe Pc) and copper phthalocyanine (Cu Pc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/MPc was examined for the reduction of O-2 in aqueous solutions and compared to that of bare gold and with gold coated directly with preadsorbed MPc molecules. Scanning tunneling microscopy (STM) studies confirm the functionalization of the 4-ATP by MPc. STM images reveal that iron phthalocyanine molecules are chemically anchored to 4-aminothiophenol organic monolayers, probably having an "umbrella" type orientation with regards to the surface. The electrocatalytic studies carried out with Au/4-ATP/FePc and Au/MDPP/FePc electrodes show that the O-2 reduction takes place by the transfer of 4-electron to give water in contrast to a 2-electron transfer process observed for the bare gold. The modified electrode obtained by simple adsorption of FePc directly to the Au(111) surface still promotes the 4-electron reduction process, but it shows a lower activity than the electrodes involving SAMs with FePc molecules positioned at the outmost portion of the self-assembled monolayers. The activity of the electrodes increases as follow: Au < Au/FePc < Au/4-ATP/FePc < Au/MDPP/FePc with the highest activity when FePc molecules are more separated from the Au surface. In contrast, the less active CuPc shows almost the same activity in all three configurations. Theoretical calculations suggest the importance of the back-bonding into the adduct formation, showing the relevance of the supporting gold surface on the electron-transfer process mediated by anchoring ligands. |
Diaz, C; Valenzuela, M L; Lavayen, V; O'dwyer, C Layered Graphitic Carbon Host Formation During Liquid-Free Solid State Growth of Metal Pyrophosphates Artículo de revista Inorganic Chemistry, 51 (11), pp. 6228-6236, 2012, ISSN: 0020-1669. Resumen | Enlaces | BibTeX | Etiquetas: characterization, nanocomposites, nanoparticles, nanotubes, nanowires precursor, pyrolysis, spectroscopic @article{RN89, title = {Layered Graphitic Carbon Host Formation During Liquid-Free Solid State Growth of Metal Pyrophosphates}, author = { C. Diaz and M.L. Valenzuela and V. Lavayen and C. O'dwyer}, url = {/brokenurl#<Go to ISI>://WOS:000304728500029}, doi = {10.1021/ic300767h}, issn = {0020-1669}, year = {2012}, date = {2012-01-01}, journal = {Inorganic Chemistry}, volume = {51}, number = {11}, pages = {6228-6236}, abstract = {We report a successful ligand- and liquid-free solid state route to form metal pyrophosphates within a layered graphitic carbon matrix through a single step approach involving pyrolysis of previously synthesized organometallic derivatives of a cyclotriphosphazene. In this case, we show how single crystal Mn2P2O7 can be formed on either the micro- or the nanoscale in the complete absence of solvents or solutions by an efficient combustion process using rationally designed macromolecular trimer precursors, and present evidence and a mechanism for layered graphite host formation. Using in situ Raman spectroscopy, infrared spectroscopy, X-ray diffraction, high resolution electron microscopy, thermogravimetric and differential scanning calorimetric analysis, and near-edge X-ray absorption fine structure examination, we monitor the formation process of a layered, graphitic carbon in the matrix. The identification of thermally and electrically conductive graphitic carbon host formation is important for the further development of this general ligand-free synthetic approach for inorganic nanocrystal growth in the solid state, and can be extended to form a range of transition metals pyrophosphates. For important energy storage applications, the method gives the ability to form oxide and (pyro)phosphates within a conductive, intercalation possible, graphitic carbon as host-guest composites directly on substrates for high rate Li-ion battery and emerging alternative positive electrode materials.}, keywords = {characterization, nanocomposites, nanoparticles, nanotubes, nanowires precursor, pyrolysis, spectroscopic}, pubstate = {published}, tppubtype = {article} } We report a successful ligand- and liquid-free solid state route to form metal pyrophosphates within a layered graphitic carbon matrix through a single step approach involving pyrolysis of previously synthesized organometallic derivatives of a cyclotriphosphazene. In this case, we show how single crystal Mn2P2O7 can be formed on either the micro- or the nanoscale in the complete absence of solvents or solutions by an efficient combustion process using rationally designed macromolecular trimer precursors, and present evidence and a mechanism for layered graphite host formation. Using in situ Raman spectroscopy, infrared spectroscopy, X-ray diffraction, high resolution electron microscopy, thermogravimetric and differential scanning calorimetric analysis, and near-edge X-ray absorption fine structure examination, we monitor the formation process of a layered, graphitic carbon in the matrix. The identification of thermally and electrically conductive graphitic carbon host formation is important for the further development of this general ligand-free synthetic approach for inorganic nanocrystal growth in the solid state, and can be extended to form a range of transition metals pyrophosphates. For important energy storage applications, the method gives the ability to form oxide and (pyro)phosphates within a conductive, intercalation possible, graphitic carbon as host-guest composites directly on substrates for high rate Li-ion battery and emerging alternative positive electrode materials. |
Burgos, D; Olea-Azar, C; Mendizabal, F Theoretical Study of the Local Reactivity of Electrophiles of the Type Mpr (3) (+) (M = Cu, Ag, Au ;R = -H, -Me, -Ph) Artículo de revista Journal of Molecular Modeling, 18 (5), pp. 2021-2029, 2012, ISSN: 1610-2940. Resumen | Enlaces | BibTeX | Etiquetas: approximation, chemistry complexes, effects, electrophile fragments, gold, hardness, quasi-relativistic reactivity, stability @article{RN86, title = {Theoretical Study of the Local Reactivity of Electrophiles of the Type Mpr (3) (+) (M = Cu, Ag, Au ;R = -H, -Me, -Ph)}, author = { D. Burgos and C. Olea-Azar and F. Mendizabal}, url = {/brokenurl#<Go to ISI>://WOS:000303541900031}, doi = {10.1007/s00894-011-1213-2}, issn = {1610-2940}, year = {2012}, date = {2012-01-01}, journal = {Journal of Molecular Modeling}, volume = {18}, number = {5}, pages = {2021-2029}, abstract = {Reactivity prediction in the series of MPR (3) (+) fragments ( M = Au, Ag, Cu; R = -H, -Me, -Ph) has been achieved at the ab initio (HF and MP2) and density functional theory (B3LYP and PBE) levels. We have used global and local descriptors based on conceptual DFT such as hardness, Fukui function and electrophilicity index. For all methods and fragments, we have found an equal trend in reactivity using both the global and local electrophilicity index: QR-AuPR (3) (+) > CuPR (3) (+) a parts per thousand aEuro parts per thousand AgPR (3) (+) > NR-AuPR (3) (+) . It is also found that the electrophilicity power decreases as the volume of R increases.}, keywords = {approximation, chemistry complexes, effects, electrophile fragments, gold, hardness, quasi-relativistic reactivity, stability}, pubstate = {published}, tppubtype = {article} } Reactivity prediction in the series of MPR (3) (+) fragments ( M = Au, Ag, Cu; R = -H, -Me, -Ph) has been achieved at the ab initio (HF and MP2) and density functional theory (B3LYP and PBE) levels. We have used global and local descriptors based on conceptual DFT such as hardness, Fukui function and electrophilicity index. For all methods and fragments, we have found an equal trend in reactivity using both the global and local electrophilicity index: QR-AuPR (3) (+) > CuPR (3) (+) a parts per thousand aEuro parts per thousand AgPR (3) (+) > NR-AuPR (3) (+) . It is also found that the electrophilicity power decreases as the volume of R increases. |
Diaz, C; Valenzuela, M L; Carrillo, D; Riquelme, J; Diaz, R The Inclusion of Organometallic Derivatives of Cyclotriphosphazenes inside Sio2 Matrix and Their Conversion to Nanostructured Metal-Oxides and Phosphates Artículo de revista Journal of Inorganic and Organometallic Polymers and Materials, 22 (5), pp. 1101-1112, 2012, ISSN: 1574-1443. Resumen | Enlaces | BibTeX | Etiquetas: bridged catalyst, copper cyclotriphospahzenes, mesoporous metallic nanoparticles, nanostructures, phosphoric-acid polysilsesquioxanes, precursors, silica, sol-gel sol-gel, synthesis, thermolytic thin-films, transformation, xerogel @article{RN88, title = {The Inclusion of Organometallic Derivatives of Cyclotriphosphazenes inside Sio2 Matrix and Their Conversion to Nanostructured Metal-Oxides and Phosphates}, author = { C. Diaz and M.L. Valenzuela and D. Carrillo and J. Riquelme and R. Diaz}, url = {/brokenurl#<Go to ISI>://WOS:000307754600022}, doi = {10.1007/s10904-012-9692-x}, issn = {1574-1443}, year = {2012}, date = {2012-01-01}, journal = {Journal of Inorganic and Organometallic Polymers and Materials}, volume = {22}, number = {5}, pages = {1101-1112}, abstract = {Organometallic derivatives of the cyclotriphosphazene N3P3[OC6H4CH2CN center dot TiClCp2](6) (1), N3P3(O6H5)(5)[OC6H4N center dot W(CO)(5)] (2), N3P3[OC6H4CH2CN center dot Mo(CO)(5)](6) (3), [N3P3(O6H5)(5)(OC5H4N center dot CpRu(PPh3)(2))][PF6] (4), [N3P3(O2C12H8)(2)OC5H4N center dot Ag(PPh3)][OSO2CF3] (5), N3P3[OC6H5](5) [OC5H4N center dot Cu][PF6] (6) and N3P3[OC6H4CH2CN center dot CuCl](6)[PF6](6) (7),were incorporated inside SiO2 through the sol-gel method. The metal-organic nanocomposites of the general formula N3P3[OC6H4CH2CN center dot TiClCp2](6)center dot nSiO(2) (G (1) ), N3P3[OC6H4N center dot W(CO)(5)]center dot nSiO(2) (G (2) ), N3P3[OC6H4CH2CN center dot Mo(CO)(5)](6)center dot nSiO(2) (G (3) ), N3P3(O6H5)(5)OC5H4N center dot CpRu(PPh3)(2)][PF6]center dot nSiO(2) (G (4) ), [N3P3(O2C12H8)(2)OC5H4N center dot Ag(PPh3)][OSO2CF3]center dot nSiO(2) (G (5) ), N3P3[OC6H5](5)[OC5H4N center dot Cu][PF6]center dot(SiO2) (n) (G (6) ), and N3P3[OC6H4CH2CN center dot CuCl](6)[PF6](6)center dot(SiO2) (n) (G (7) ), were characterized by IR spectroscopy; C-12, (31) P and Si-29 MAS NMR measurements as well as UV-Visible diffuse reflectance spectra, indicating the presence of the respective organometallic derivatives of the cyclotriphosphazene incorporated into SiO2. Pyrolysis of these nanocomposites under air at 800 A degrees C gives rise to nanostructured metal-oxides and metal phosphates incorporated into amorphous SiO2, with the presence in some cases of complexes phase mixtures. From some precursors, we obtained metal-oxides/phosphates nanoparticles separated from the SiO2 nanoparticles instead the oxides/phosphates nanoparticles inside the SiO2 matrix. Additionally and for comparison purposes, we used the compound N3P3[NH(CH2)(3)Si(OEt)(3)](6) as gelator. Nanocomposites (G' (1) ), (G' (2) ) and (G' (3) ) exhibited mainly morphological differences while in some cases composition differences when using TEOS as gelator., Some simple metal-containing compounds as (O3SCF3)Ag(PPh3)(HOC5H4N), [CuCl2 center dot NC5H4OH] and [CuCl2 center dot NCCH2C6H4OH]-which are useful models of the most complexes (G (5) ), (G (6) ) and (G (7) ) were also prepared and incorporated in amorphous silica. Their pyrolytic products were compared with those of more complex cyclotriphosphazene analogous. Interestingly, the pyrolysis of the nanocomposite [(O3SCF3)Ag(PPh3)(HOC5H4N)][SiO2] (n) affords the firstly-reported materials containing Ag2O along with SiO2 nanoparticles.}, keywords = {bridged catalyst, copper cyclotriphospahzenes, mesoporous metallic nanoparticles, nanostructures, phosphoric-acid polysilsesquioxanes, precursors, silica, sol-gel sol-gel, synthesis, thermolytic thin-films, transformation, xerogel}, pubstate = {published}, tppubtype = {article} } Organometallic derivatives of the cyclotriphosphazene N3P3[OC6H4CH2CN center dot TiClCp2](6) (1), N3P3(O6H5)(5)[OC6H4N center dot W(CO)(5)] (2), N3P3[OC6H4CH2CN center dot Mo(CO)(5)](6) (3), [N3P3(O6H5)(5)(OC5H4N center dot CpRu(PPh3)(2))][PF6] (4), [N3P3(O2C12H8)(2)OC5H4N center dot Ag(PPh3)][OSO2CF3] (5), N3P3[OC6H5](5) [OC5H4N center dot Cu][PF6] (6) and N3P3[OC6H4CH2CN center dot CuCl](6)[PF6](6) (7),were incorporated inside SiO2 through the sol-gel method. The metal-organic nanocomposites of the general formula N3P3[OC6H4CH2CN center dot TiClCp2](6)center dot nSiO(2) (G (1) ), N3P3[OC6H4N center dot W(CO)(5)]center dot nSiO(2) (G (2) ), N3P3[OC6H4CH2CN center dot Mo(CO)(5)](6)center dot nSiO(2) (G (3) ), N3P3(O6H5)(5)OC5H4N center dot CpRu(PPh3)(2)][PF6]center dot nSiO(2) (G (4) ), [N3P3(O2C12H8)(2)OC5H4N center dot Ag(PPh3)][OSO2CF3]center dot nSiO(2) (G (5) ), N3P3[OC6H5](5)[OC5H4N center dot Cu][PF6]center dot(SiO2) (n) (G (6) ), and N3P3[OC6H4CH2CN center dot CuCl](6)[PF6](6)center dot(SiO2) (n) (G (7) ), were characterized by IR spectroscopy; C-12, (31) P and Si-29 MAS NMR measurements as well as UV-Visible diffuse reflectance spectra, indicating the presence of the respective organometallic derivatives of the cyclotriphosphazene incorporated into SiO2. Pyrolysis of these nanocomposites under air at 800 A degrees C gives rise to nanostructured metal-oxides and metal phosphates incorporated into amorphous SiO2, with the presence in some cases of complexes phase mixtures. From some precursors, we obtained metal-oxides/phosphates nanoparticles separated from the SiO2 nanoparticles instead the oxides/phosphates nanoparticles inside the SiO2 matrix. Additionally and for comparison purposes, we used the compound N3P3[NH(CH2)(3)Si(OEt)(3)](6) as gelator. Nanocomposites (G' (1) ), (G' (2) ) and (G' (3) ) exhibited mainly morphological differences while in some cases composition differences when using TEOS as gelator., Some simple metal-containing compounds as (O3SCF3)Ag(PPh3)(HOC5H4N), [CuCl2 center dot NC5H4OH] and [CuCl2 center dot NCCH2C6H4OH]-which are useful models of the most complexes (G (5) ), (G (6) ) and (G (7) ) were also prepared and incorporated in amorphous silica. Their pyrolytic products were compared with those of more complex cyclotriphosphazene analogous. Interestingly, the pyrolysis of the nanocomposite [(O3SCF3)Ag(PPh3)(HOC5H4N)][SiO2] (n) affords the firstly-reported materials containing Ag2O along with SiO2 nanoparticles. |
González-Suarez, M; Aizman, A; Soto-Delgado, J; Contreras, R Bond Fukui Functions as Descriptor of the Electron Density Reorganization in Pi Conjugated Systems Artículo de revista Journal of Organic Chemistry, 77 (1), pp. 90-95, 2012, ISSN: 0022-3263. Resumen | Enlaces | BibTeX | Etiquetas: characterization, cycloaddition diels-alder electrophilicity, hardness molecules, quantitative reactions, reactivity, regioselectivity @article{RN108, title = {Bond Fukui Functions as Descriptor of the Electron Density Reorganization in Pi Conjugated Systems}, author = { M. Gonz\'{a}lez-Suarez and A. Aizman and J. Soto-Delgado and R. Contreras}, url = {/brokenurl#<Go to ISI>://WOS:000298827600008}, doi = {10.1021/jo201465g}, issn = {0022-3263}, year = {2012}, date = {2012-01-01}, journal = {Journal of Organic Chemistry}, volume = {77}, number = {1}, pages = {90-95}, abstract = {The bond Fukui function is introduced and tested as a new reactivity index capable of predicting the evolution of bond breaking and formation processes during an organic reaction involving pi conjugated systems. As an illustration, we examine many cases where substituted ethylenes and dienes may respond to different reagents to yield cycloaddition, Michael addition, and other reactions at double bonds.}, keywords = {characterization, cycloaddition diels-alder electrophilicity, hardness molecules, quantitative reactions, reactivity, regioselectivity}, pubstate = {published}, tppubtype = {article} } The bond Fukui function is introduced and tested as a new reactivity index capable of predicting the evolution of bond breaking and formation processes during an organic reaction involving pi conjugated systems. As an illustration, we examine many cases where substituted ethylenes and dienes may respond to different reagents to yield cycloaddition, Michael addition, and other reactions at double bonds. |
Lara, N; Aranda, P; Ruiz, A I; Manriquez, V; Ruiz-Hitzky, E Intercalation and Electrical Behavior of Taxmo1-Xs2 (X > 0.5) Layered Mixed Disulfides Artículo de revista Journal of the Brazilian Chemical Society, 23 (3), pp. 415-+, 2012, ISSN: 0103-5053. Resumen | Enlaces | BibTeX | Etiquetas: chalcogenides, complexes, conducting conductivity, dichalcogenides, encapsulation, intercalation, lithium molybdenum-disulfide, mos2, nanocomposites, peo, polymers, pyridine, solids sulfides, transition-metal @article{RN90, title = {Intercalation and Electrical Behavior of Taxmo1-Xs2 (X > 0.5) Layered Mixed Disulfides}, author = { N. Lara and P. Aranda and A.I. Ruiz and V. Manriquez and E. Ruiz-Hitzky}, url = {/brokenurl#<Go to ISI>://WOS:000302461200007}, doi = {10.1590/S0103-50532012000300007}, issn = {0103-5053}, year = {2012}, date = {2012-01-01}, journal = {Journal of the Brazilian Chemical Society}, volume = {23}, number = {3}, pages = {415-+}, abstract = {This work reports a systematic study of the structural and electrical behavior of three ternary phases of the TaxMo1-xS2 system (x = 0.55, 0.75 and 0.90) and their intercalation compounds resulting from both chemical and electrochemical lithium insertions, as well as from pyridine and poly(ethylene oxide) intercalations. The three ternary phases were prepared by direct reaction of their constituting elements, without any other additive, at 900 degrees C in inert atmosphere. The resulting compounds were characterized by means of X-ray powder diffractometry (XRD), thermogravimetric and differential thermal (TGA/DTA) analyses, energy dispersive X-ray fluorescence (EDX) and field emission-scanning electron microscopy (FE-SEM). The electrical conductivity of the different products was measured in the 1.5-300 K temperature range using the conventional four probe van der Pauw method in the presence of a 9 T magnetic field in order to verify the occurrence of magnetoresistivity phenomena.}, keywords = {chalcogenides, complexes, conducting conductivity, dichalcogenides, encapsulation, intercalation, lithium molybdenum-disulfide, mos2, nanocomposites, peo, polymers, pyridine, solids sulfides, transition-metal}, pubstate = {published}, tppubtype = {article} } This work reports a systematic study of the structural and electrical behavior of three ternary phases of the TaxMo1-xS2 system (x = 0.55, 0.75 and 0.90) and their intercalation compounds resulting from both chemical and electrochemical lithium insertions, as well as from pyridine and poly(ethylene oxide) intercalations. The three ternary phases were prepared by direct reaction of their constituting elements, without any other additive, at 900 degrees C in inert atmosphere. The resulting compounds were characterized by means of X-ray powder diffractometry (XRD), thermogravimetric and differential thermal (TGA/DTA) analyses, energy dispersive X-ray fluorescence (EDX) and field emission-scanning electron microscopy (FE-SEM). The electrical conductivity of the different products was measured in the 1.5-300 K temperature range using the conventional four probe van der Pauw method in the presence of a 9 T magnetic field in order to verify the occurrence of magnetoresistivity phenomena. |
Sotomayor-Zarate, R; Quirozi, G; Araya, K A; Abarea, J; Ibanez, M R; Montecinos, A; Guajardo, C; Nunez, G; Fierro, A; Moya, P R; Iturriaga-Vasquez, P; Gomez-Molina, C; Gysling, K; Reyes-Parada, M 4-Methylthioamphetamine Increases Dopamine in the Rat Striatum and Has Rewarding Effects in Vivo Artículo de revista Basic & Clinical Pharmacology & Toxicology, 111 (6), pp. 371-379, 2012, ISSN: 1742-7835. Resumen | Enlaces | BibTeX | Etiquetas: @article{RN72, title = {4-Methylthioamphetamine Increases Dopamine in the Rat Striatum and Has Rewarding Effects in Vivo}, author = { R. Sotomayor-Zarate and G. Quirozi and K.A. Araya and J. Abarea and M.R. Ibanez and A. Montecinos and C. Guajardo and G. Nunez and A. Fierro and P.R. Moya and P. Iturriaga-Vasquez and C. Gomez-Molina and K. Gysling and M. Reyes-Parada}, url = {/brokenurl#<Go to ISI>://WOS:000311055700004}, doi = {10.1111/j.1742-7843.2012.00926.x}, issn = {1742-7835}, year = {2012}, date = {2012-01-01}, journal = {Basic & Clinical Pharmacology & Toxicology}, volume = {111}, number = {6}, pages = {371-379}, abstract = {4-Methylthioamphetamine (MTA) is a phenylisopropylamine derivative whose use has been associated with severe intoxications. MTA is usually regarded as a selective serotonin-releasing agent. Nevertheless, previous data have suggested that its mechanism of action probably involves a catecholaminergic component. As little is known about dopaminergic effects of this drug, in this work the actions of MTA upon the dopamine (DA) transporter (DAT) were studied in vitro, in vivo and in silico. Also, the possible abuse liability of MTA was behaviourally assessed. MTA exhibited an in vitro affinity for the rat DAT in the low micromolar range (6.01 mu M) and induced a significant, dose-dependent increase in striatal DA. MTA significantly increased c-Fos-positive cells in striatum and nucleus accumbens, induced conditioned place preference and increased locomotor activity. Docking experiments were performed in a homology model of the DAT. In conclusion, our results show that MTA is able to increase extracellular striatal DA levels and that its administration has rewarding properties. These effects were observed at concentrations or doses that can be relevant to its use in human beings.}, keywords = {}, pubstate = {published}, tppubtype = {article} } 4-Methylthioamphetamine (MTA) is a phenylisopropylamine derivative whose use has been associated with severe intoxications. MTA is usually regarded as a selective serotonin-releasing agent. Nevertheless, previous data have suggested that its mechanism of action probably involves a catecholaminergic component. As little is known about dopaminergic effects of this drug, in this work the actions of MTA upon the dopamine (DA) transporter (DAT) were studied in vitro, in vivo and in silico. Also, the possible abuse liability of MTA was behaviourally assessed. MTA exhibited an in vitro affinity for the rat DAT in the low micromolar range (6.01 mu M) and induced a significant, dose-dependent increase in striatal DA. MTA significantly increased c-Fos-positive cells in striatum and nucleus accumbens, induced conditioned place preference and increased locomotor activity. Docking experiments were performed in a homology model of the DAT. In conclusion, our results show that MTA is able to increase extracellular striatal DA levels and that its administration has rewarding properties. These effects were observed at concentrations or doses that can be relevant to its use in human beings. |
Mera-Adasme, R; Mendizabal, F; González, M; Miranda-Rojas, S; Olea-Azar, C; Sundholm, D Computational Studies of the Metal-Binding Site of the Wild-Type and the H46r Mutant of the Copper, Zinc Superoxide Dismutase Artículo de revista Inorganic Chemistry, 51 (10), pp. 5561-5568, 2012, ISSN: 0020-1669. Resumen | Enlaces | BibTeX | Etiquetas: amyotrophic-lateral-sclerosis, approximation, correlation-energy, crystal-structures, cu, density efficient, functionals, sod1, solvents zn @article{RN85, title = {Computational Studies of the Metal-Binding Site of the Wild-Type and the H46r Mutant of the Copper, Zinc Superoxide Dismutase}, author = { R. Mera-Adasme and F. Mendizabal and M. Gonz\'{a}lez and S. Miranda-Rojas and C. Olea-Azar and D. Sundholm}, url = {/brokenurl#<Go to ISI>://WOS:000304215200011}, doi = {10.1021/ic202416d}, issn = {0020-1669}, year = {2012}, date = {2012-01-01}, journal = {Inorganic Chemistry}, volume = {51}, number = {10}, pages = {5561-5568}, abstract = {Impairment of the Zn(II)-binding site of the copper, zinc superoxide dismutase (CuZnSOD) protein is involved in a number of hypotheses and explanations for the still unknown toxic gain of function mutant varieties of CuZnSOD that are associated with familial forms of amyotrophic lateral sclerosis (ALS). In this work, computational chemistry methods have been used for studying models of the metal-binding site of the ALS-linked H46R mutant of CuZnSOD and of the wild-type variety of the enzyme. By comparing the energy and electronic structure of these models, a plausible explanation for the effect of the H46R mutation on the zinc site is obtained. The computational study clarifies the role of the D124 and D125 residues for keeping the structural integrity of the Zn(II)-binding site, which was known to exist but its mechanism has not been explained. Earlier results suggest that the explanation for the impairment of the Zn(II)-site proposed in this work may be useful for understanding the mechanism of action of the ALS-linked mutations in CuZnSOD in general.}, keywords = {amyotrophic-lateral-sclerosis, approximation, correlation-energy, crystal-structures, cu, density efficient, functionals, sod1, solvents zn}, pubstate = {published}, tppubtype = {article} } Impairment of the Zn(II)-binding site of the copper, zinc superoxide dismutase (CuZnSOD) protein is involved in a number of hypotheses and explanations for the still unknown toxic gain of function mutant varieties of CuZnSOD that are associated with familial forms of amyotrophic lateral sclerosis (ALS). In this work, computational chemistry methods have been used for studying models of the metal-binding site of the ALS-linked H46R mutant of CuZnSOD and of the wild-type variety of the enzyme. By comparing the energy and electronic structure of these models, a plausible explanation for the effect of the H46R mutation on the zinc site is obtained. The computational study clarifies the role of the D124 and D125 residues for keeping the structural integrity of the Zn(II)-binding site, which was known to exist but its mechanism has not been explained. Earlier results suggest that the explanation for the impairment of the Zn(II)-site proposed in this work may be useful for understanding the mechanism of action of the ALS-linked mutations in CuZnSOD in general. |
Morales, R G E; Llanos, A; Merino, M; González-Rojas, C A Semi-Empirical Method of Pm-10 Atmospheric Pollution Forecast at Santiago De Chile City Artículo de revista Nature Environment and Pollution Technology, 11 , pp. 5, 2012. Resumen | Enlaces | BibTeX | Etiquetas: @article{RN101, title = {A Semi-Empirical Method of Pm-10 Atmospheric Pollution Forecast at Santiago De Chile City}, author = { R.G.E. Morales and A. Llanos and M. Merino and C. Gonz\'{a}lez-Rojas}, url = {http://www.neptjournal.com/upload-images/NL-38-1-(1)B-1855.pdf}, year = {2012}, date = {2012-01-01}, journal = {Nature Environment and Pollution Technology}, volume = {11}, pages = {5}, abstract = {Santiago de Chile city, localized in the west side of the Andes Mountain (550 m.s.l.), South America, every year presents high levels of atmospheric pollution by PM-10 in autumn-winter periods. Therefore, forecast model research is a subject of high public interest in order to develop useful and appropriate tools for health impacts prevention on the population. In this work, we present a PM-10 atmospheric pollution semi-empirical forecast method developed from a singular behaviour observed on the relative humidity trends detected in Lo Prado Hill meteorological station previous to critical episodes of urban atmospheric pollution by PM-10. This meteorological station is localized at the top of the coastal mountains (1035 m.s.l.), in the west side of the city. From systematic observations between 1998 and 2006 in this particular meteorological station, we have detected how the relative humidity follows a typical descendent behaviour when a type A synoptic weather condition arrives to central Chile and induces a PM-10 pre-emergency episode of urban atmospheric pollution. Our semi-empirical method is based on a sigmoidal behaviour of the relative humidity as a time function, observed in this meteorological station under a type A synoptic weather condition. We have confronted the present forecast method to different pre-emergency critical episodes occurred in the city between 1999 and 2006. Our results are amazing due to these pre-emergency episodes can be predicted at least by 34 hours before to the PM-10 pollution concentration reaches the maximum peak at the city. Contrarily to this specific station, the remainder eight stations localized in the surface of the city are not able to describe this particular phenomenon.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Santiago de Chile city, localized in the west side of the Andes Mountain (550 m.s.l.), South America, every year presents high levels of atmospheric pollution by PM-10 in autumn-winter periods. Therefore, forecast model research is a subject of high public interest in order to develop useful and appropriate tools for health impacts prevention on the population. In this work, we present a PM-10 atmospheric pollution semi-empirical forecast method developed from a singular behaviour observed on the relative humidity trends detected in Lo Prado Hill meteorological station previous to critical episodes of urban atmospheric pollution by PM-10. This meteorological station is localized at the top of the coastal mountains (1035 m.s.l.), in the west side of the city. From systematic observations between 1998 and 2006 in this particular meteorological station, we have detected how the relative humidity follows a typical descendent behaviour when a type A synoptic weather condition arrives to central Chile and induces a PM-10 pre-emergency episode of urban atmospheric pollution. Our semi-empirical method is based on a sigmoidal behaviour of the relative humidity as a time function, observed in this meteorological station under a type A synoptic weather condition. We have confronted the present forecast method to different pre-emergency critical episodes occurred in the city between 1999 and 2006. Our results are amazing due to these pre-emergency episodes can be predicted at least by 34 hours before to the PM-10 pollution concentration reaches the maximum peak at the city. Contrarily to this specific station, the remainder eight stations localized in the surface of the city are not able to describe this particular phenomenon. |
2011 |
x y hhhh, sssss Artículo de revista 2011. BibTeX | Etiquetas: @article{xxx, title = {sssss}, author = {x y hhhh}, year = {2011}, date = {2011-12-31}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Mendizabal, F; Donoso, D; Burgos, D Theoretical Study of the Protonation of [Pt-3(Mu-L)(3)(L ')(3)] (L = Co, So2, Cnh; L ' = Ph3, Cnh) Artículo de revista Chemical Physics Letters, 514 (4-6), pp. 374-378, 2011, ISSN: 0009-2614. Resumen | Enlaces | BibTeX | Etiquetas: approximation, chemistry, cluster complexes, electrophilicity hydride, index, molecules, systems, units @article{mendizabal2011theoretical, title = {Theoretical Study of the Protonation of [Pt-3(Mu-L)(3)(L ')(3)] (L = Co, So2, Cnh; L ' = Ph3, Cnh)}, author = { F. Mendizabal and D. Donoso and D. Burgos}, url = {/brokenurl#<Go to ISI>://WOS:000295831700035}, doi = {10.1016/j.cplett.2011.08.068}, issn = {0009-2614}, year = {2011}, date = {2011-01-01}, journal = {Chemical Physics Letters}, volume = {514}, number = {4-6}, pages = {374-378}, publisher = {2011 Elsevier B. V.}, abstract = {Ab initio calculations suggest that a series of clusters of the [Pt-3(mu-L)(3)(L')(3)(mu(3)-H](+) type (L = CO, SO2, CNH; L' = PH3, CNH) are stable. We have studied these clusters at the HF, MP2, B3LYP, PBE and TPSS theory levels. The magnitude of the interaction energies and distances indicates a substantial covalent character of the Pt-3-H bond, confirmed by orbital diagrams. In addition, the Fukui index of electrophilic attack and electrophilicity index on the unprotonated clusters were used to explore possible sites where chemical reactivity may play a role.}, keywords = {approximation, chemistry, cluster complexes, electrophilicity hydride, index, molecules, systems, units}, pubstate = {published}, tppubtype = {article} } Ab initio calculations suggest that a series of clusters of the [Pt-3(mu-L)(3)(L')(3)(mu(3)-H](+) type (L = CO, SO2, CNH; L' = PH3, CNH) are stable. We have studied these clusters at the HF, MP2, B3LYP, PBE and TPSS theory levels. The magnitude of the interaction energies and distances indicates a substantial covalent character of the Pt-3-H bond, confirmed by orbital diagrams. In addition, the Fukui index of electrophilic attack and electrophilicity index on the unprotonated clusters were used to explore possible sites where chemical reactivity may play a role. |
Toral, M I; Sanchez, G; Fernandez, P; Pizarro, P; Moncada, V; Rivas, J; Richter, P Ferrospectral Sorbed on Deae Sephadex a-25 for the Solid Phase Spectrophotometric Determination of Iron and Cobalt by Batch and Continuous Flow Modes Artículo de revista Journal of the Chilean Chemical Society, 56 (2), pp. 682-687, 2011, ISSN: 0717-9324. Resumen | Enlaces | BibTeX | Etiquetas: continuous determination, determinations, electrode, elements extraction, fe food heavy-metal ions, mixtures, phase samples, sephadex solid spectrometric spectrometry, stripping voltammetry, water @article{RN21, title = {Ferrospectral Sorbed on Deae Sephadex a-25 for the Solid Phase Spectrophotometric Determination of Iron and Cobalt by Batch and Continuous Flow Modes}, author = { M.I. Toral and G. Sanchez and P. Fernandez and P. Pizarro and V. Moncada and J. Rivas and P. Richter}, url = {/brokenurl#<Go to ISI>://WOS:000293676300013}, doi = {10.4067/S0717-97072011000200013}, issn = {0717-9324}, year = {2011}, date = {2011-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {56}, number = {2}, pages = {682-687}, abstract = {In this work, Ferrospectral;3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine (FST) sorbed on DEAE Sephadex A-25 is used as solid phase for spectrophotometric determination of iron and cobalt by batch and continuos flow modes. In batch simultaneous determination, the second derivative at 536.0 and 601.4 nm were used for iron and cobalt determination, respectively. In this modality, the detection limits (3 sigma criterion), for iron and cobalt were 1.3, 9.1, mu g L(-1) and the determination ranges were: 4.3 to 220 and 30.3 to 800 mu g L(-1). The method by FIA mode was carried out by stopped flow and then the analytical signal was evaluated by second derivative at 560.9 and 482.3 nm for iron and cobalt determination; respectively. In FIA modality, the detection limits for iron and cobalt were 6.4, 31 mu g L(-1), and the determination ranges 21 to 200 and 106 to 1000 mu g L(-1) iron and cobalt, respectively. In both modalities the repeatability for iron and cobalt were <4% and the recovery was near to 100%. These methods were applied successfully in drinking water and soil samples.}, keywords = {continuous determination, determinations, electrode, elements extraction, fe food heavy-metal ions, mixtures, phase samples, sephadex solid spectrometric spectrometry, stripping voltammetry, water}, pubstate = {published}, tppubtype = {article} } In this work, Ferrospectral;3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine (FST) sorbed on DEAE Sephadex A-25 is used as solid phase for spectrophotometric determination of iron and cobalt by batch and continuos flow modes. In batch simultaneous determination, the second derivative at 536.0 and 601.4 nm were used for iron and cobalt determination, respectively. In this modality, the detection limits (3 sigma criterion), for iron and cobalt were 1.3, 9.1, mu g L(-1) and the determination ranges were: 4.3 to 220 and 30.3 to 800 mu g L(-1). The method by FIA mode was carried out by stopped flow and then the analytical signal was evaluated by second derivative at 560.9 and 482.3 nm for iron and cobalt determination; respectively. In FIA modality, the detection limits for iron and cobalt were 6.4, 31 mu g L(-1), and the determination ranges 21 to 200 and 106 to 1000 mu g L(-1) iron and cobalt, respectively. In both modalities the repeatability for iron and cobalt were <4% and the recovery was near to 100%. These methods were applied successfully in drinking water and soil samples. |
Publicaciones 2011-2020
