2011 |
Cretton, S; Bartholomeusz, T A; Humam, M; Marcourt, L; Allenbach, Y; Jeannerat, D; Munoz, O; Christen, P Grahamines a-E, Cyclobutane-Centered Tropane Alkaloids from the Aerial Parts of Schizanthus Grahamii Artículo de revista Journal of Natural Products, 74 (11), pp. 2388-2394, 2011, ISSN: 0163-3864. Resumen | Enlaces | BibTeX | Etiquetas: @article{RN24b, title = {Grahamines a-E, Cyclobutane-Centered Tropane Alkaloids from the Aerial Parts of Schizanthus Grahamii}, author = { S. Cretton and T.A. Bartholomeusz and M. Humam and L. Marcourt and Y. Allenbach and D. Jeannerat and O. Munoz and P. Christen}, url = {/brokenurl#<Go to ISI>://WOS:000297274900010}, doi = {10.1021/np200450y}, issn = {0163-3864}, year = {2011}, date = {2011-01-01}, journal = {Journal of Natural Products}, volume = {74}, number = {11}, pages = {2388-2394}, abstract = {Schizanthus grahamii is an endemic Chilean plant that is known to contain tropane alkaloids. Five new alkaloids, grahamines A-E (1-5), were isolated and characterized by extensive spectroscopic analysis. Their structures were determined to be 2-[(3 alpha-hydroxytropo-6 beta-yl)oxy]carbonyl-2-methyl-3-[((6 beta-angeloyloxy)-3 alpha-yl)oxy]carbonyl-4- phenylcyclobutanecarboxylic acid (1), 2-[(3 alpha-hydroxytropo-6 beta-yl)oxy]-carbonyl-2-methy1-3-[((6 beta-tigloyloxy)-3 alpha-yl)oxy]carbonyl-4-phenylcyclobutanecarboxylic acid (2), 1-methyl-2-[(3 alpha-hydroxytropo-6 beta-yl)-oxy]carbonyl-4-[((6-angeloyloxy)-3 alpha-yl)oxy]carbonyl-3-phenylcy- clobutanecarboxylic acid (3), 1,2-bis[(3 alpha-hydroxytropo-6 beta-yl)oxy]-carbonyl)-2-methyl-3-[((6 beta-angeloyloxy)-3 alpha-yl)oxy]carbonyl-4-phenylcyclobutanecarboxylate (4), and 1-[(3 alpha-mesaconyloxytropo-6 beta-yl)-oxy]carbonyl-2-[(3 alpha-hydroxytropo-6 beta-yl)oxy]carbonyl-2-methyl-3-[((6 beta-angeloyloxy)-3 alpha-yl)oxy]carbonyl-4-phenylcyclobutanecarboxylate (5).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Schizanthus grahamii is an endemic Chilean plant that is known to contain tropane alkaloids. Five new alkaloids, grahamines A-E (1-5), were isolated and characterized by extensive spectroscopic analysis. Their structures were determined to be 2-[(3 alpha-hydroxytropo-6 beta-yl)oxy]carbonyl-2-methyl-3-[((6 beta-angeloyloxy)-3 alpha-yl)oxy]carbonyl-4- phenylcyclobutanecarboxylic acid (1), 2-[(3 alpha-hydroxytropo-6 beta-yl)oxy]-carbonyl-2-methy1-3-[((6 beta-tigloyloxy)-3 alpha-yl)oxy]carbonyl-4-phenylcyclobutanecarboxylic acid (2), 1-methyl-2-[(3 alpha-hydroxytropo-6 beta-yl)-oxy]carbonyl-4-[((6-angeloyloxy)-3 alpha-yl)oxy]carbonyl-3-phenylcy- clobutanecarboxylic acid (3), 1,2-bis[(3 alpha-hydroxytropo-6 beta-yl)oxy]-carbonyl)-2-methyl-3-[((6 beta-angeloyloxy)-3 alpha-yl)oxy]carbonyl-4-phenylcyclobutanecarboxylate (4), and 1-[(3 alpha-mesaconyloxytropo-6 beta-yl)-oxy]carbonyl-2-[(3 alpha-hydroxytropo-6 beta-yl)oxy]carbonyl-2-methyl-3-[((6 beta-angeloyloxy)-3 alpha-yl)oxy]carbonyl-4-phenylcyclobutanecarboxylate (5). |
Lopez-De-Luzuriaga, J M; Monge, M; Olmos, M E; Rodriguez-Castillo, M; Laguna, A; Mendizabal, F Basicity of Bisperhalophenyl Aurates toward Closed-Shell Metal Ions: Metallophilicity and Additional Interactions Artículo de revista Theoretical Chemistry Accounts, 129 (3-5), pp. 593-602, 2011, ISSN: 1432-881x. Resumen | Enlaces | BibTeX | Etiquetas: au, chemistry, complexes copper, gold, interactions, metal-metal silver, thallium, theoretical @article{RN6c, title = {Basicity of Bisperhalophenyl Aurates toward Closed-Shell Metal Ions: Metallophilicity and Additional Interactions}, author = { J.M. Lopez-De-Luzuriaga and M. Monge and M.E. Olmos and M. Rodriguez-Castillo and A. Laguna and F. Mendizabal}, url = {/brokenurl#<Go to ISI>://WOS:000290572300031}, doi = {10.1007/s00214-011-0902-3}, issn = {1432-881x}, year = {2011}, date = {2011-01-01}, journal = {Theoretical Chemistry Accounts}, volume = {129}, number = {3-5}, pages = {593-602}, abstract = {The interaction of bisperhalophenyl aurates [AuR2](-) (R = C6F5, C6F3Cl2, and C6Cl5) with the closed-shell Ag+, Cu+, and Tl+ ions has been studied theoretically and compared with the experimentally known X-ray diffraction crystal structures. Initially, the aurates have been fully optimized at MP2 level of theory in a D (2h) symmetry. The analysis of the basicity of the three aurates [AuR2](-) (R = C6F5, C6F3Cl2 and C6Cl5) against Ag+ ions in a C (2v) symmetry has been calculated in point-by-point bsse-corrected interaction energy analysis at HF and MP2 levels of theory. Taking into account the experimental observation of additional interactions between the heterometals and C (ipso) atoms at the perhalophenyl rings or halogen atoms at the ortho position of the perhalophenyl rings, dinuclear models of the type [AuR2](-)center dot center dot center dot Ag+ (R = C6Cl5, and C6F5); [AuR2](-)center dot center dot center dot Cu+ (R = C6F5, and C6Cl5) and [AuR2](-)center dot center dot center dot Tl+ (R = C6F5, and C6Cl5) with a C (2v) , C (2) , and C (s) symmetries have been optimized at DFT-B3LYP level. The interaction energies have been computed through bsse-corrected single point HF and MP2 calculations. The energy stabilization provided and the heterometal preference have been analyzed and compared with the experimental results.}, keywords = {au, chemistry, complexes copper, gold, interactions, metal-metal silver, thallium, theoretical}, pubstate = {published}, tppubtype = {article} } The interaction of bisperhalophenyl aurates [AuR2](-) (R = C6F5, C6F3Cl2, and C6Cl5) with the closed-shell Ag+, Cu+, and Tl+ ions has been studied theoretically and compared with the experimentally known X-ray diffraction crystal structures. Initially, the aurates have been fully optimized at MP2 level of theory in a D (2h) symmetry. The analysis of the basicity of the three aurates [AuR2](-) (R = C6F5, C6F3Cl2 and C6Cl5) against Ag+ ions in a C (2v) symmetry has been calculated in point-by-point bsse-corrected interaction energy analysis at HF and MP2 levels of theory. Taking into account the experimental observation of additional interactions between the heterometals and C (ipso) atoms at the perhalophenyl rings or halogen atoms at the ortho position of the perhalophenyl rings, dinuclear models of the type [AuR2](-)center dot center dot center dot Ag+ (R = C6Cl5, and C6F5); [AuR2](-)center dot center dot center dot Cu+ (R = C6F5, and C6Cl5) and [AuR2](-)center dot center dot center dot Tl+ (R = C6F5, and C6Cl5) with a C (2v) , C (2) , and C (s) symmetries have been optimized at DFT-B3LYP level. The interaction energies have been computed through bsse-corrected single point HF and MP2 calculations. The energy stabilization provided and the heterometal preference have been analyzed and compared with the experimental results. |
Rodriguez-Castillo, M; Monge, M; Lopez-De-Luzuriaga, J M; Olmos, M E; Laguna, A; Mendizabal, F Theoretical Study of the Closed-Shell D(10)-D(10) Au(I)-Cu(I) Attraction in Complexes in Extended Unsupported Chains Artículo de revista Computational and Theoretical Chemistry, 965 (1), pp. 163-167, 2011, ISSN: 2210-271x. Resumen | Enlaces | BibTeX | Etiquetas: @article{RN50, title = {Theoretical Study of the Closed-Shell D(10)-D(10) Au(I)-Cu(I) Attraction in Complexes in Extended Unsupported Chains}, author = { M. Rodriguez-Castillo and M. Monge and J.M. Lopez-De-Luzuriaga and M.E. Olmos and A. Laguna and F. Mendizabal}, url = {/brokenurl#<Go to ISI>://WOS:000289496300021}, doi = {10.1016/j.comptc.2011.01.040}, issn = {2210-271x}, year = {2011}, date = {2011-01-01}, journal = {Computational and Theoretical Chemistry}, volume = {965}, number = {1}, pages = {163-167}, publisher = {2011 Elsevier B.V.}, abstract = {Model compounds are used to study the metallophilic attraction between gold and copper atoms. Ab initio calculations on dimers and tetramers in different distributions of the simplified units are analyzed. An attraction is found for all models and there is a reasonable agreement between the experimental and theoretical geometries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Model compounds are used to study the metallophilic attraction between gold and copper atoms. Ab initio calculations on dimers and tetramers in different distributions of the simplified units are analyzed. An attraction is found for all models and there is a reasonable agreement between the experimental and theoretical geometries. |
Mera-Adasme, R; Mendizabal, F; Olea-Azar, C; Miranda-Rojas, S; Fuentealba, P A Computationally Efficient and Reliable Bond Order Measure Artículo de revista Journal of Physical Chemistry A, 115 (17), pp. 4397-4405, 2011, ISSN: 1089-5639. Resumen | Enlaces | BibTeX | Etiquetas: auxiliary basis-sets, density, electron elements, exchange, localization, natural program resonance split-valence, superoxide-dismutase, theory, zinc @article{RN13, title = {A Computationally Efficient and Reliable Bond Order Measure}, author = { R. Mera-Adasme and F. Mendizabal and C. Olea-Azar and S. Miranda-Rojas and P. Fuentealba}, url = {/brokenurl#<Go to ISI>://WOS:000289824500031}, doi = {10.1021/jp107498h}, issn = {1089-5639}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry A}, volume = {115}, number = {17}, pages = {4397-4405}, abstract = {Bond order indexes are useful measures that connect quantum mechanical results with chemical understanding. One of these measures, the natural bond order index, based on the natural resonance theory procedure and part of the natural bond orbital analysis tools, has been proved to yield reliable results for many systems. The procedure's computational requirements, nevertheless, scales so highly with the number of functions in the basis set and the delocalization of the system, that the calculation of this bond order is limited to small or medium size molecules. We present in this work a bond order index, the first order perturbation theory bond order (fopBO), which is based on and strongly connected to the natural bond orbital analysis tools. We present the methodology for the calculation of the fopBO index and a number of test calculations that shows that it is as reliable as the natural bond orbital index, with the same weak sensitivity to variations among commonly used basis sets and, as opposed to the natural bond order index, suitable for the study of large systems, such as most of those of biological interest.}, keywords = {auxiliary basis-sets, density, electron elements, exchange, localization, natural program resonance split-valence, superoxide-dismutase, theory, zinc}, pubstate = {published}, tppubtype = {article} } Bond order indexes are useful measures that connect quantum mechanical results with chemical understanding. One of these measures, the natural bond order index, based on the natural resonance theory procedure and part of the natural bond orbital analysis tools, has been proved to yield reliable results for many systems. The procedure's computational requirements, nevertheless, scales so highly with the number of functions in the basis set and the delocalization of the system, that the calculation of this bond order is limited to small or medium size molecules. We present in this work a bond order index, the first order perturbation theory bond order (fopBO), which is based on and strongly connected to the natural bond orbital analysis tools. We present the methodology for the calculation of the fopBO index and a number of test calculations that shows that it is as reliable as the natural bond orbital index, with the same weak sensitivity to variations among commonly used basis sets and, as opposed to the natural bond order index, suitable for the study of large systems, such as most of those of biological interest. |
Saavedra, R; Soto, C; Yanez, J; Toral, M I Determination of Cobalt in Water Samples by Photoacoustic Spectroscopy with a Solid-Phase Spectrophotometry Approach Using 3-(2-Pyridyl)-5,6-Bis (4-Sulfophenyl)-1,2,4-Triazine Artículo de revista Microchemical Journal, 98 (2), pp. 220-224, 2011, ISSN: 0026-265x. Resumen | Enlaces | BibTeX | Etiquetas: atomic-absorption-spectrometry, chelating cobalt, emission-spectrometry, extraction, ferrozine ferrozine, icp-ms, nickel, online optothermal phase photoacoustic preconcentration, resin, solid spectroscopy, trace-metals, window @article{RN16, title = {Determination of Cobalt in Water Samples by Photoacoustic Spectroscopy with a Solid-Phase Spectrophotometry Approach Using 3-(2-Pyridyl)-5,6-Bis (4-Sulfophenyl)-1,2,4-Triazine}, author = { R. Saavedra and C. Soto and J. Yanez and M.I. Toral}, url = {/brokenurl#<Go to ISI>://WOS:000290749600008}, doi = {10.1016/j.microc.2011.02.003}, issn = {0026-265x}, year = {2011}, date = {2011-01-01}, journal = {Microchemical Journal}, volume = {98}, number = {2}, pages = {220-224}, publisher = {2011 Elsevier B.V.}, abstract = {This work forms part of an investigation which seeks to determine metal complexes in a solid phase by photoacoustic spectrometry (PAS). Results of spectral determination of Co(II) complexes are introduced. The method is based on Co(II) calorimetric reaction with 3-(2-pyridyl)-5,6-bis(4-sulfophenyl)-1,2,4-triazine (FST, ferrozine) retained on an anion-exchange resin, DEAE Sephadex A-25. The immobilization of Co(II) on the solid phase is combined with PAS measurement. A numerical approach is applied to reduce noise in the spectral data. At lambda = 477 nm, the calibration for Co(II) is linear over the range 14-300 mu gL(-1). The Co(II) concentration in water samples was determined by conventional photoacoustic measurement. The relative standard deviation (R.S.D.) of the method for the calibration is <5%. Under optimized conditions, the obtained analytical features were LOD 14 mu gL(-1) and LOQ 45 mu gL(-1).}, keywords = {atomic-absorption-spectrometry, chelating cobalt, emission-spectrometry, extraction, ferrozine ferrozine, icp-ms, nickel, online optothermal phase photoacoustic preconcentration, resin, solid spectroscopy, trace-metals, window}, pubstate = {published}, tppubtype = {article} } This work forms part of an investigation which seeks to determine metal complexes in a solid phase by photoacoustic spectrometry (PAS). Results of spectral determination of Co(II) complexes are introduced. The method is based on Co(II) calorimetric reaction with 3-(2-pyridyl)-5,6-bis(4-sulfophenyl)-1,2,4-triazine (FST, ferrozine) retained on an anion-exchange resin, DEAE Sephadex A-25. The immobilization of Co(II) on the solid phase is combined with PAS measurement. A numerical approach is applied to reduce noise in the spectral data. At lambda = 477 nm, the calibration for Co(II) is linear over the range 14-300 mu gL(-1). The Co(II) concentration in water samples was determined by conventional photoacoustic measurement. The relative standard deviation (R.S.D.) of the method for the calibration is <5%. Under optimized conditions, the obtained analytical features were LOD 14 mu gL(-1) and LOQ 45 mu gL(-1). |
Ponce, I; Silva, J F; Onate, R; Miranda-Rojas, S; Munoz-Castro, A; Arratia-Perez, R; Mendizabal, F; Zagal, J H Journal of Physical Chemistry C, 115 (47), pp. 23512-23518, 2011, ISSN: 1932-7447. Resumen | Enlaces | BibTeX | Etiquetas: @article{RN49, title = {Theoretical and Experimental Study of Bonding and Optical Properties of Self-Assembly Metallophthalocyanines Complexes on a Gold Surface. A Survey of the Substrate-Surface Interaction}, author = { I. Ponce and J.F. Silva and R. Onate and S. Miranda-Rojas and A. Munoz-Castro and R. Arratia-Perez and F. Mendizabal and J.H. Zagal}, url = {/brokenurl#<Go to ISI>://WOS:000297195200031}, doi = {10.1021/jp208734f}, issn = {1932-7447}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry C}, volume = {115}, number = {47}, pages = {23512-23518}, abstract = {The formation of self-assembly monolayers (SAMs) based on a gold substrate and a thiolate ligand as "anchor" fragment of metallophtalocyanine has been employed as strategy toward the obtention of modified electrodes. In this Article, the formation of SAM's involving iron and cobalt phtalocyanines anchored by 4-aminothiophenol (4-ATP) and 4-mercatopyridine (4-MP) to the Au(111) surface is explored by both experimental and theoretical studies for a better understanding of their bonding pattern and optical properties. The self-assembly metallophthalocyanines complexes on gold electrode exhibits an interesting charge donation from the 4-ATP or 4-MP toward both gold substrate and phtalocyanine, denoting an effective gold-MPc interaction mediated by the titled anchor ligands. In addition, the optical properties of the self-assembled complexes supported on the gold electrode exhibit in conjuction with the well-described Q-band an interesting charge transfer from the Pc (pi) toward the gold surface, as could be observed in the FePc-4MP-Au-26 assembly.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The formation of self-assembly monolayers (SAMs) based on a gold substrate and a thiolate ligand as "anchor" fragment of metallophtalocyanine has been employed as strategy toward the obtention of modified electrodes. In this Article, the formation of SAM's involving iron and cobalt phtalocyanines anchored by 4-aminothiophenol (4-ATP) and 4-mercatopyridine (4-MP) to the Au(111) surface is explored by both experimental and theoretical studies for a better understanding of their bonding pattern and optical properties. The self-assembly metallophthalocyanines complexes on gold electrode exhibits an interesting charge donation from the 4-ATP or 4-MP toward both gold substrate and phtalocyanine, denoting an effective gold-MPc interaction mediated by the titled anchor ligands. In addition, the optical properties of the self-assembled complexes supported on the gold electrode exhibit in conjuction with the well-described Q-band an interesting charge transfer from the Pc (pi) toward the gold surface, as could be observed in the FePc-4MP-Au-26 assembly. |
Espinosa, Y; Trebotich, J; Sepulveda, F; Cadena, J; Vargas-Straube, M J; Vaca, I; Bull, P; Levican, G; Chavez, R Production of a Heterologous Recombinant Protein Using Fragments of the Glyceraldehyde-3-Phosphate Dehydrogenase Promoter from Penicillium Camemberti Artículo de revista World Journal of Microbiology & Biotechnology, 27 (12), pp. 3019-3023, 2011, ISSN: 0959-3993. Resumen | Enlaces | BibTeX | Etiquetas: aspergillus-nidulans, beta-galactosidase, camemberti, cloning, dehydrogenase elements, expression, functional gene, glyceraldehyde-3-phosphate gpda heterologous nidulans penicillium promoter, protein region sequence-analysis, transformation, yeast @article{RN37c, title = {Production of a Heterologous Recombinant Protein Using Fragments of the Glyceraldehyde-3-Phosphate Dehydrogenase Promoter from Penicillium Camemberti}, author = { Y. Espinosa and J. Trebotich and F. Sepulveda and J. Cadena and M.J. Vargas-Straube and I. Vaca and P. Bull and G. Levican and R. Chavez}, url = {/brokenurl#<Go to ISI>://WOS:000297594400033}, doi = {10.1007/s11274-011-0782-7}, issn = {0959-3993}, year = {2011}, date = {2011-01-01}, journal = {World Journal of Microbiology & Biotechnology}, volume = {27}, number = {12}, pages = {3019-3023}, abstract = {The biotechnological applications of cheese-ripening fungi have been limited by a lack of genetics tools, in particular the identification and characterization of suitable promoters for protein expression. In this study, the suitability of the glyceraldehyde-3-phosphate dehydrogenase (gpdP) promoter from Penicillium camemberti to drive the production of a recombinant protein was evaluated. The gpdP gene and its promoter were isolated using PCR and Genome Walker. The promoter of gpdP has two regions with high identity to the regulatory elements gpd-box and ct-box previously described in Aspergillus nidulans. Two fragments of the promoter containing the gpd- and ct-box or the ct-box alone were used to drive the in vivo production of recombinant beta-galactosidase using A. nidulans as host. Our results indicate that larger fragment containing gpd-box enhances the production of beta-galactosidase activity levels respect to ct-box alone, and that both boxes are necessary to obtain maximal enzymatic activity production. The smaller fragment (187 nt) containing the ct-box alone was able to trigger up to 27% of beta-galactosidase activity, and to our knowledge this is the smallest fragment from a gpd gene used to produce a recombinant protein. Differences were not observed when glycerol, galactose or glucose were used as carbon sources, suggesting that the promoter activity is carbohydrate-independent. This is the first report in which a Penicillium gpd promoter is used for recombinant protein production. Our results open the way for the future development of a system for recombinant proteins expression in the biotechnologically important cheese-ripening fungus P. camemberti.}, keywords = {aspergillus-nidulans, beta-galactosidase, camemberti, cloning, dehydrogenase elements, expression, functional gene, glyceraldehyde-3-phosphate gpda heterologous nidulans penicillium promoter, protein region sequence-analysis, transformation, yeast}, pubstate = {published}, tppubtype = {article} } The biotechnological applications of cheese-ripening fungi have been limited by a lack of genetics tools, in particular the identification and characterization of suitable promoters for protein expression. In this study, the suitability of the glyceraldehyde-3-phosphate dehydrogenase (gpdP) promoter from Penicillium camemberti to drive the production of a recombinant protein was evaluated. The gpdP gene and its promoter were isolated using PCR and Genome Walker. The promoter of gpdP has two regions with high identity to the regulatory elements gpd-box and ct-box previously described in Aspergillus nidulans. Two fragments of the promoter containing the gpd- and ct-box or the ct-box alone were used to drive the in vivo production of recombinant beta-galactosidase using A. nidulans as host. Our results indicate that larger fragment containing gpd-box enhances the production of beta-galactosidase activity levels respect to ct-box alone, and that both boxes are necessary to obtain maximal enzymatic activity production. The smaller fragment (187 nt) containing the ct-box alone was able to trigger up to 27% of beta-galactosidase activity, and to our knowledge this is the smallest fragment from a gpd gene used to produce a recombinant protein. Differences were not observed when glycerol, galactose or glucose were used as carbon sources, suggesting that the promoter activity is carbohydrate-independent. This is the first report in which a Penicillium gpd promoter is used for recombinant protein production. Our results open the way for the future development of a system for recombinant proteins expression in the biotechnologically important cheese-ripening fungus P. camemberti. |
Galdámez, A; Garcia-Beltran, O; Cassels, B K Hydrogen-Bonded Supramolecular Array in the Crystal Structure of Ethyl 7-Hydroxy-2-Oxo-2h-Chromene-3-Carboxylate Monohydrate Artículo de revista Journal of the Chilean Chemical Society, 56 (1), pp. 546-548, 2011, ISSN: 0717-9324. Resumen | Enlaces | BibTeX | Etiquetas: coumarins, crystal design diffraction, patterns, structure, x-ray @article{RN26b, title = {Hydrogen-Bonded Supramolecular Array in the Crystal Structure of Ethyl 7-Hydroxy-2-Oxo-2h-Chromene-3-Carboxylate Monohydrate}, author = {A. Gald\'{a}mez and O. Garcia-Beltran and B.K. Cassels}, url = {/brokenurl#<Go to ISI>://WOS:000290700500005}, doi = {10.4067/S0717-97072011000100005}, issn = {0717-9324}, year = {2011}, date = {2011-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {56}, number = {1}, pages = {546-548}, abstract = {The crystal structure of ethyl 7-hydroxy-2-oxo-2H-chromene-3-carboxylate monohydrate (1), C(12)H(10)O(5).H(2)O, was established by X-ray crystallographic analysis. The molecule of the title compound is essentially planar except for the carboxylate substituent group. The crystal packing supramolecular array arises from hydrogen bonds and intermolecular C-H center dot center dot center dot O=C contacts of the organic molecules and solvent water molecules, with graph-Set descriptor R(4)(2)(8), R(1)(2) (6), R(4)(4)(20) and C(5) motifs. The water molecules are involved as donors and acceptors. The hydrogen bond and intermolecular interaction network is reinforced by stacking of the sheet through pi-pi interactions.}, keywords = {coumarins, crystal design diffraction, patterns, structure, x-ray}, pubstate = {published}, tppubtype = {article} } The crystal structure of ethyl 7-hydroxy-2-oxo-2H-chromene-3-carboxylate monohydrate (1), C(12)H(10)O(5).H(2)O, was established by X-ray crystallographic analysis. The molecule of the title compound is essentially planar except for the carboxylate substituent group. The crystal packing supramolecular array arises from hydrogen bonds and intermolecular C-H center dot center dot center dot O=C contacts of the organic molecules and solvent water molecules, with graph-Set descriptor R(4)(2)(8), R(1)(2) (6), R(4)(4)(20) and C(5) motifs. The water molecules are involved as donors and acceptors. The hydrogen bond and intermolecular interaction network is reinforced by stacking of the sheet through pi-pi interactions. |
Humam, M; Kehrli, T; Jeannerat, D; Munoz, O; Hostettmann, K; Christen, P Schizanthines N, O, and P, Tropane Alkaloids from the Aerial Parts of Schizanthus Tricolor Artículo de revista Journal of Natural Products, 74 (1), pp. 50-53, 2011, ISSN: 0163-3864. Resumen | Enlaces | BibTeX | Etiquetas: bark erythroxylum, genus @article{RN42c, title = {Schizanthines N, O, and P, Tropane Alkaloids from the Aerial Parts of Schizanthus Tricolor}, author = { M. Humam and T. Kehrli and D. Jeannerat and O. Munoz and K. Hostettmann and P. Christen}, url = {/brokenurl#<Go to ISI>://WOS:000286577800010}, doi = {10.1021/np1005423}, issn = {0163-3864}, year = {2011}, date = {2011-01-01}, journal = {Journal of Natural Products}, volume = {74}, number = {1}, pages = {50-53}, abstract = {Three tropane alkaloids, named schizanthines N, O, and P (1-3), have been isolated from the crude alkaloid extract of the endemic Chilean plant Schizanthus tricolor. On the basis of extensive NMR studies and MS fragmentation analysis, their structures were determined to be 3 alpha-(E)-4-hydroxysenecioyloxy-6 beta-angeloyloxytropane (1), 3 alpha-(E)-4-hydroxysenecioyloxy-6 beta-senecioyloxytropane (2), and 3 alpha-mesaconyloxy-6 beta-senecioyloxytropane (3). Compounds 1 and 2 are the first isomeric alkaloids in the tropane series possessing a hydroxysenecioyl substituent as an esterifying moiety.}, keywords = {bark erythroxylum, genus}, pubstate = {published}, tppubtype = {article} } Three tropane alkaloids, named schizanthines N, O, and P (1-3), have been isolated from the crude alkaloid extract of the endemic Chilean plant Schizanthus tricolor. On the basis of extensive NMR studies and MS fragmentation analysis, their structures were determined to be 3 alpha-(E)-4-hydroxysenecioyloxy-6 beta-angeloyloxytropane (1), 3 alpha-(E)-4-hydroxysenecioyloxy-6 beta-senecioyloxytropane (2), and 3 alpha-mesaconyloxy-6 beta-senecioyloxytropane (3). Compounds 1 and 2 are the first isomeric alkaloids in the tropane series possessing a hydroxysenecioyl substituent as an esterifying moiety. |
Faini, F; Torres, R; Rodilla, J M; Labbe, C; Delporte, C; Jana, F Chemistry and Bioactivity of Haplopappus Remyanus ("Bailahuen"), a Chilean Medicinal Plant Artículo de revista Journal of the Brazilian Chemical Society, 22 (12), pp. 2344-U2134, 2011, ISSN: 0103-5053. Resumen | Enlaces | BibTeX | Etiquetas: anti-inflammatory antioxidant, arachidonic-acid, constituents, cytotoxic esters, exudate, flavonoids, haplopappus inflammation remyanus, resinous @article{RN10b, title = {Chemistry and Bioactivity of Haplopappus Remyanus ("Bailahuen"), a Chilean Medicinal Plant}, author = { F. Faini and R. Torres and J.M. Rodilla and C. Labbe and C. Delporte and F. Jana}, url = {/brokenurl#<Go to ISI>://WOS:000299000600014}, doi = {10.1590/S0103-50532011001200015}, issn = {0103-5053}, year = {2011}, date = {2011-01-01}, journal = {Journal of the Brazilian Chemical Society}, volume = {22}, number = {12}, pages = {2344-U2134}, abstract = {Chromatography on the resinous extract of aerial parts of Haplopappus remyanus led to the isolation of 18-acetoxy-labda-7,13E-dien-15-oic acid along with the monoterpene derivatives 9-hydroxy-alpha-terpineol, 9-benzoyloxy-alpha-terpineol, 7-hydroxy-9-benzoyloxy-alpha-terpineol and 9-benzoyloxy-(1-formyl)-alpha-terpineol. Structures for the new compounds are proposed on spectroscopic evidence. The presence of quercetin and five other known flavonoids identified in this study could account for the reported high antioxidant activity and the moderate topic anti-inflammatory effect on induced ear oedema. MTT assay with CCRF-CEM tumor cells showed 50% of the cytotoxic activity displayed by doxorubicin under the same conditions. Quantitative differences in chemical composition were detected in comparison with previous studies of the species that could be attributed to environmental factors.}, keywords = {anti-inflammatory antioxidant, arachidonic-acid, constituents, cytotoxic esters, exudate, flavonoids, haplopappus inflammation remyanus, resinous}, pubstate = {published}, tppubtype = {article} } Chromatography on the resinous extract of aerial parts of Haplopappus remyanus led to the isolation of 18-acetoxy-labda-7,13E-dien-15-oic acid along with the monoterpene derivatives 9-hydroxy-alpha-terpineol, 9-benzoyloxy-alpha-terpineol, 7-hydroxy-9-benzoyloxy-alpha-terpineol and 9-benzoyloxy-(1-formyl)-alpha-terpineol. Structures for the new compounds are proposed on spectroscopic evidence. The presence of quercetin and five other known flavonoids identified in this study could account for the reported high antioxidant activity and the moderate topic anti-inflammatory effect on induced ear oedema. MTT assay with CCRF-CEM tumor cells showed 50% of the cytotoxic activity displayed by doxorubicin under the same conditions. Quantitative differences in chemical composition were detected in comparison with previous studies of the species that could be attributed to environmental factors. |
Garcia-Beltran, O; Mena, N; Perez, E G; Cassels, B K; Nunez, M; Werlinger, F; Zavala, D; Aliaga, M E; Pavez, P The Development of a Fluorescence Turn-on Sensor for Cysteine, Glutathione and Other Biothiols. A Kinetic Study Artículo de revista Tetrahedron Letters, 52 (49), pp. 6606-6609, 2011, ISSN: 0040-4039. Resumen | Enlaces | BibTeX | Etiquetas: addition, biothiols, coumarin-based derivatives, disease, fluorescence homocysteine, michael probe, probes, thiols, water @article{RN17e, title = {The Development of a Fluorescence Turn-on Sensor for Cysteine, Glutathione and Other Biothiols. A Kinetic Study}, author = { O. Garcia-Beltran and N. Mena and E.G. Perez and B.K. Cassels and M. Nunez and F. Werlinger and D. Zavala and M.E. Aliaga and P. Pavez}, url = {/brokenurl#<Go to ISI>://WOS:000297442400022}, doi = {10.1016/j.tetlet.2011.09.137}, issn = {0040-4039}, year = {2011}, date = {2011-01-01}, journal = {Tetrahedron Letters}, volume = {52}, number = {49}, pages = {6606-6609}, publisher = {2011 Elsevier Ltd.}, abstract = {Two fluorescence probes for the detection of cysteine (Cys), glutathione (GSH) and other biothiols, such as homocysteine (Hcy) and cysteinyl-glycine (Cys-Gly), were developed. These molecular probes are coumarin-based derivatives containing a chalcone-like moiety that reacts with biothiols through a Michael addition reaction, leading to strong fluorescence enhancements. The reactivity of the tested biothiols toward both probes (ChC1 and ChC2) follows the order Cys > GSH > Hcy > Cys-Gly, ChC1 being less reactive than ChC2. Possible interference with other amino acids was assessed. ChC1 and ChC2 display a highly selective fluorescence enhancement with thiols, allowing these probes to be used for fluorimetric thiol determination in SH-SY5Y cells.}, keywords = {addition, biothiols, coumarin-based derivatives, disease, fluorescence homocysteine, michael probe, probes, thiols, water}, pubstate = {published}, tppubtype = {article} } Two fluorescence probes for the detection of cysteine (Cys), glutathione (GSH) and other biothiols, such as homocysteine (Hcy) and cysteinyl-glycine (Cys-Gly), were developed. These molecular probes are coumarin-based derivatives containing a chalcone-like moiety that reacts with biothiols through a Michael addition reaction, leading to strong fluorescence enhancements. The reactivity of the tested biothiols toward both probes (ChC1 and ChC2) follows the order Cys > GSH > Hcy > Cys-Gly, ChC1 being less reactive than ChC2. Possible interference with other amino acids was assessed. ChC1 and ChC2 display a highly selective fluorescence enhancement with thiols, allowing these probes to be used for fluorimetric thiol determination in SH-SY5Y cells. |
Arrau, S; Delporte, C; Cartagena, C; Rodriguez-Diaz, M; González, P; Silva, X; Cassels, B K; Miranda, H F Antinociceptive Activity of Quillaja Saponaria Mol. Saponin Extract, Quillaic Acid and Derivatives in Mice Artículo de revista Journal of Ethnopharmacology, 133 (1), pp. 164-167, 2011, ISSN: 0378-8741. Resumen | Enlaces | BibTeX | Etiquetas: activity, analgesic assay, derivatives, drugs hot-plate models, pain, quillaic quillaja saponaria, tail-flick @article{RN4m, title = {Antinociceptive Activity of Quillaja Saponaria Mol. Saponin Extract, Quillaic Acid and Derivatives in Mice}, author = { S. Arrau and C. Delporte and C. Cartagena and M. Rodriguez-Diaz and P. Gonz\'{a}lez and X. Silva and B.K. Cassels and H.F. Miranda}, url = {/brokenurl#<Go to ISI>://WOS:000286854100023}, doi = {10.1016/j.jep.2010.09.016}, issn = {0378-8741}, year = {2011}, date = {2011-01-01}, journal = {Journal of Ethnopharmacology}, volume = {133}, number = {1}, pages = {164-167}, publisher = {2010 Elsevier Ireland Ltd.}, abstract = {Ethnopharmacological relevance: Quillaja saponaria bark contains a high percentage of triterpene saponins and has been used for centuries as a cleansing and analgesic agent in Chilean folk medicine., Aim of the study: The topical and systemic analgesic effects of a commercial partially purified saponin extract, 3 beta,16 alpha-dihydroxy-23-oxoolean-12-en-28-oic acid (quillaic acid), methyl 3 beta,16 alpha-dihydroxy-23-oxoolean-12-en-28-oate and methyl 4-nor-3,16-dioxoolean-12-en-28-oate., Materials and methods: The samples were assessed in mice using the topical tail-flick and i.p. hot-plate tests, respectively., Results: All the samples showed activity in both analgesic tests in a dose-dependent manner. The most active against tail flick test was commercial partially purified saponin extract (EC50 27.9 mg%, w/v) and more than the ibuprofen sodium. On hot-plate test, methyl 4-nor-3, 16-dioxoolean-12-en-28-oate was the most active (ED50 12.2 mg/kg) and more than the ibuprofen sodium., Conclusions: The results of the present study demonstrated that Quillaja saponaria saponins, quillaic acid, its methyl ester, and one of the oxidized derivatives of the latter, elicit dose-dependent antinociceptive effects in two murine thermal models.}, keywords = {activity, analgesic assay, derivatives, drugs hot-plate models, pain, quillaic quillaja saponaria, tail-flick}, pubstate = {published}, tppubtype = {article} } Ethnopharmacological relevance: Quillaja saponaria bark contains a high percentage of triterpene saponins and has been used for centuries as a cleansing and analgesic agent in Chilean folk medicine., Aim of the study: The topical and systemic analgesic effects of a commercial partially purified saponin extract, 3 beta,16 alpha-dihydroxy-23-oxoolean-12-en-28-oic acid (quillaic acid), methyl 3 beta,16 alpha-dihydroxy-23-oxoolean-12-en-28-oate and methyl 4-nor-3,16-dioxoolean-12-en-28-oate., Materials and methods: The samples were assessed in mice using the topical tail-flick and i.p. hot-plate tests, respectively., Results: All the samples showed activity in both analgesic tests in a dose-dependent manner. The most active against tail flick test was commercial partially purified saponin extract (EC50 27.9 mg%, w/v) and more than the ibuprofen sodium. On hot-plate test, methyl 4-nor-3, 16-dioxoolean-12-en-28-oate was the most active (ED50 12.2 mg/kg) and more than the ibuprofen sodium., Conclusions: The results of the present study demonstrated that Quillaja saponaria saponins, quillaic acid, its methyl ester, and one of the oxidized derivatives of the latter, elicit dose-dependent antinociceptive effects in two murine thermal models. |
Munoz, O; Decap, S; Ruiz, F; Arbildua, J; Monasterio, O Determination of 10-Hydroxy-2-Decenoic Acid in Royal Jelly by Capillary Electrophoresis Artículo de revista Journal of the Chilean Chemical Society, 56 (3), pp. 738-740, 2011, ISSN: 0717-9324. Resumen | Enlaces | BibTeX | Etiquetas: capillary electrophoresis, fatty-acids, in-vitro jelly, royal @article{RN15d, title = {Determination of 10-Hydroxy-2-Decenoic Acid in Royal Jelly by Capillary Electrophoresis}, author = { O. Munoz and S. Decap and F. Ruiz and J. Arbildua and O. Monasterio}, url = {/brokenurl#<Go to ISI>://WOS:000296753600004}, doi = {10.4067/S0717-97072011000300004}, issn = {0717-9324}, year = {2011}, date = {2011-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {56}, number = {3}, pages = {738-740}, abstract = {Two commercial samples of Royal Jelly sold in Chile, consisting of two imported sample and another sample of known origin obtained freshly harvested from beekeepers were analyzed. The application of capillary electrophoresis (CE) for the separation and determination of the active compound, 10 hydroxy 2 decenoic acid, in Royal Jelly (RJ) in a capillary column with UV detection at 214 nm is described. In addition, the physicochemical composition of commercial samples was analyzed by determining moisture, ash, lipid and other properties., The importance of determining the 10-HDA acid lies in the fact that it is the main difference between Royal Jelly and the other bee products, i.e., it is what confers this product its unique characteristics, generating a marked difference. Therefore, a low 10-HDA content implies a low Royal Jelly activity, ascribed to decomposition, poor quality, or something else to the commercialization of a product other than Royal Jelly. This determination was conducted by comparison with a pure 10-HDA standard.}, keywords = {capillary electrophoresis, fatty-acids, in-vitro jelly, royal}, pubstate = {published}, tppubtype = {article} } Two commercial samples of Royal Jelly sold in Chile, consisting of two imported sample and another sample of known origin obtained freshly harvested from beekeepers were analyzed. The application of capillary electrophoresis (CE) for the separation and determination of the active compound, 10 hydroxy 2 decenoic acid, in Royal Jelly (RJ) in a capillary column with UV detection at 214 nm is described. In addition, the physicochemical composition of commercial samples was analyzed by determining moisture, ash, lipid and other properties., The importance of determining the 10-HDA acid lies in the fact that it is the main difference between Royal Jelly and the other bee products, i.e., it is what confers this product its unique characteristics, generating a marked difference. Therefore, a low 10-HDA content implies a low Royal Jelly activity, ascribed to decomposition, poor quality, or something else to the commercialization of a product other than Royal Jelly. This determination was conducted by comparison with a pure 10-HDA standard. |
San-Martin, A; Rovirosa, J; Vaca, I; Vergara, K; Acevedo, L; Vina, D; Orallo, F; Chamy, M C New Butyrolactone from a Marine-Derived Fungus Aspergillus Sp Artículo de revista Journal of the Chilean Chemical Society, 56 (1), pp. 625-627, 2011, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: aspergillus dibenzylbutyrolactone, fungus, marine-derived sesterterpenoids, sp strain @article{RN33e, title = {New Butyrolactone from a Marine-Derived Fungus Aspergillus Sp}, author = { A. San-Martin and J. Rovirosa and I. Vaca and K. Vergara and L. Acevedo and D. Vina and F. Orallo and M.C. Chamy}, url = {/brokenurl#<Go to ISI>://WOS:000290700500023}, doi = {10.4067/S0717-97072011000100023}, issn = {0717-9707}, year = {2011}, date = {2011-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {56}, number = {1}, pages = {625-627}, abstract = {Four compounds that belong to two structure types, namely dibenzylbutyrolactone and sesterterpenoids, were obtained from the extract of the strain Aspergillus sp. (2P-22), isolated from a marine sponge, Cliona chilensis. Among them, compound I was identified as new, namely butylrolactone-VI. The structures of these compounds were characterized on the basis of spectroscopic data. Biological activities of these fungal metabolites, are described.}, keywords = {aspergillus dibenzylbutyrolactone, fungus, marine-derived sesterterpenoids, sp strain}, pubstate = {published}, tppubtype = {article} } Four compounds that belong to two structure types, namely dibenzylbutyrolactone and sesterterpenoids, were obtained from the extract of the strain Aspergillus sp. (2P-22), isolated from a marine sponge, Cliona chilensis. Among them, compound I was identified as new, namely butylrolactone-VI. The structures of these compounds were characterized on the basis of spectroscopic data. Biological activities of these fungal metabolites, are described. |
Pereira, D M; Cheel, J; Areche, C; San-Martin, A; Rovirosa, J; Silva, L R; Valentao, P; Andrade, P B Anti-Proliferative Activity of Meroditerpenoids Isolated from the Brown Alga Stypopodium Flabelliforme against Several Cancer Cell Lines Artículo de revista Marine Drugs, 9 (5), pp. 852-862, 2011, ISSN: 1660-3397. Resumen | Enlaces | BibTeX | Etiquetas: activity, anti-proliferative, antimicrobial antimicrobial, assay epitaondiol, extracts, flabelliforme, marine-algae, meroditerpenoids, natural-products, stypopodium @article{RN3_28, title = {Anti-Proliferative Activity of Meroditerpenoids Isolated from the Brown Alga Stypopodium Flabelliforme against Several Cancer Cell Lines}, author = { D.M. Pereira and J. Cheel and C. Areche and A. San-Martin and J. Rovirosa and L.R. Silva and P. Valentao and P.B. Andrade}, url = {/brokenurl#<Go to ISI>://WOS:000292632500013}, doi = {10.3390/md9050852}, issn = {1660-3397}, year = {2011}, date = {2011-01-01}, journal = {Marine Drugs}, volume = {9}, number = {5}, pages = {852-862}, abstract = {The sea constitutes one of the most promising sources of novel compounds with potential application in human therapeutics. In particular, algae have proved to be an interesting source of new bioactive compounds. In this work, six meroditerpenoids (epitaondiol, epitaondiol diacetate, epitaondiol monoacetate, stypotriol triacetate, 14-ketostypodiol diacetate and stypodiol) isolated from the brown alga Stypopodium flabelliforme were tested for their cell proliferation inhibitory activity in five cell lines. Cell lines tested included human colon adenocarcinoma (Caco-2), human neuroblastoma (SH-SY5Y), rat basophilic leukemia (RBL-2H3), murine macrophages (RAW. 267) and Chinese hamster fibroblasts (V79). Antimicrobial activity of the compounds was also evaluated against Staphylococcus aureus, Salmonella typhimurium, Proteus mirabilis, Bacillus cereus, Enterococcus faecalis and Micrococcus luteus. Overall, the compounds showed good activity against all cell lines, with SH-SY5Y and RAW. 267 being the most susceptible. Antimicrobial capacity was observed for epitaondiol monoacetate, stypotriol triacetate and stypodiol, with the first being the most active. The results suggest that these molecules deserve further studies in order to evaluate their potential as therapeutic agents.}, keywords = {activity, anti-proliferative, antimicrobial antimicrobial, assay epitaondiol, extracts, flabelliforme, marine-algae, meroditerpenoids, natural-products, stypopodium}, pubstate = {published}, tppubtype = {article} } The sea constitutes one of the most promising sources of novel compounds with potential application in human therapeutics. In particular, algae have proved to be an interesting source of new bioactive compounds. In this work, six meroditerpenoids (epitaondiol, epitaondiol diacetate, epitaondiol monoacetate, stypotriol triacetate, 14-ketostypodiol diacetate and stypodiol) isolated from the brown alga Stypopodium flabelliforme were tested for their cell proliferation inhibitory activity in five cell lines. Cell lines tested included human colon adenocarcinoma (Caco-2), human neuroblastoma (SH-SY5Y), rat basophilic leukemia (RBL-2H3), murine macrophages (RAW. 267) and Chinese hamster fibroblasts (V79). Antimicrobial activity of the compounds was also evaluated against Staphylococcus aureus, Salmonella typhimurium, Proteus mirabilis, Bacillus cereus, Enterococcus faecalis and Micrococcus luteus. Overall, the compounds showed good activity against all cell lines, with SH-SY5Y and RAW. 267 being the most susceptible. Antimicrobial capacity was observed for epitaondiol monoacetate, stypotriol triacetate and stypodiol, with the first being the most active. The results suggest that these molecules deserve further studies in order to evaluate their potential as therapeutic agents. |
Aguayo, T; Clavijo, E; Eisner, F; Ossa-Izquierdo, C; Campos-Vallette, M Raman Spectroscopy in the Diagnosis of the Wall Painting History of Concepcion, Chile Artículo de revista Journal of Raman Spectroscopy, 42 (12), pp. 2143-2148, 2011, ISSN: 0377-0486. Resumen | Enlaces | BibTeX | Etiquetas: analysis, art, calcium, conservation, cultural-heritage, fluorescence ft-raman, identification, nondestructive of painting, pigment pigments, raman spectra, spectroscopy, wall work @article{RN40b, title = {Raman Spectroscopy in the Diagnosis of the Wall Painting History of Concepcion, Chile}, author = { T. Aguayo and E. Clavijo and F. Eisner and C. Ossa-Izquierdo and M. Campos-Vallette}, url = {/brokenurl#<Go to ISI>://WOS:000298581500013}, doi = {10.1002/jrs.2978}, issn = {0377-0486}, year = {2011}, date = {2011-01-01}, journal = {Journal of Raman Spectroscopy}, volume = {42}, number = {12}, pages = {2143-2148}, publisher = {2011 John Wiley & Sons, Ltd.}, abstract = {Pigments and fresco-related materials from the wall painting Historia de Concepcion by Gregorio De La Fuente in Concepcion, Chile were identified by Raman microscopy. The pigments were compared with those obtained from the artist's studio, and results allowed inference about subsequent interventions. Materials coming from processes such as salt efflorescence were also studied. The results contribute to the diagnosis of the current conservation state of the wall painting for its future restoration.}, keywords = {analysis, art, calcium, conservation, cultural-heritage, fluorescence ft-raman, identification, nondestructive of painting, pigment pigments, raman spectra, spectroscopy, wall work}, pubstate = {published}, tppubtype = {article} } Pigments and fresco-related materials from the wall painting Historia de Concepcion by Gregorio De La Fuente in Concepcion, Chile were identified by Raman microscopy. The pigments were compared with those obtained from the artist's studio, and results allowed inference about subsequent interventions. Materials coming from processes such as salt efflorescence were also studied. The results contribute to the diagnosis of the current conservation state of the wall painting for its future restoration. |
Cassels, B K; Asencio, M Anti-Hiv Activity of Natural Triterpenoids and Hemisynthetic Derivatives 2004-2009 Artículo de revista Phytochemistry Reviews, 10 (4), pp. 545-564, 2011, ISSN: 1568-7767. Resumen | Enlaces | BibTeX | Etiquetas: activity, kadsura-longipedunculata, modification, momordica-charantia, mushroom natural oleanane-type products, protease schisandra-lancifolia, skeleton, structural triterpenes, triterpenoids, unique @article{RN2_40, title = {Anti-Hiv Activity of Natural Triterpenoids and Hemisynthetic Derivatives 2004-2009}, author = { B.K. Cassels and M. Asencio}, url = {/brokenurl#<Go to ISI>://WOS:000297151800007}, doi = {10.1007/s11101-010-9172-2}, issn = {1568-7767}, year = {2011}, date = {2011-01-01}, journal = {Phytochemistry Reviews}, volume = {10}, number = {4}, pages = {545-564}, abstract = {The continued advance of HIV-AIDS makes the development of relatively inexpensive, freely accessible, and mechanistically more diverse antiviral therapies an urgent need. Natural products are, directly or indirectly, an important potential source of compounds meeting these conditions. A review of the recent literature indicates that some hemisynthetic triterpenoid derivatives, particularly belonging to the lupane, oleanane and ursane series, may be nearing a stage where they can be used to complement existing therapeutic approaches. On the other hand, although some natural derivatives of tetracyclic terpenoid families have revealed many novel structures and some promise as anti-HIV substances, their chemical modification to improve their potency and selectivity remains practically untouched. While ongoing work with the more 'classical' pentacyclic triterpenoids will continue to be a fertile field for HIV-AIDS drug discovery, the other structural groups offer unprecedented opportunities for the development of additional substances with useful properties and for the discovery of novel targets for antiviral therapy.}, keywords = {activity, kadsura-longipedunculata, modification, momordica-charantia, mushroom natural oleanane-type products, protease schisandra-lancifolia, skeleton, structural triterpenes, triterpenoids, unique}, pubstate = {published}, tppubtype = {article} } The continued advance of HIV-AIDS makes the development of relatively inexpensive, freely accessible, and mechanistically more diverse antiviral therapies an urgent need. Natural products are, directly or indirectly, an important potential source of compounds meeting these conditions. A review of the recent literature indicates that some hemisynthetic triterpenoid derivatives, particularly belonging to the lupane, oleanane and ursane series, may be nearing a stage where they can be used to complement existing therapeutic approaches. On the other hand, although some natural derivatives of tetracyclic terpenoid families have revealed many novel structures and some promise as anti-HIV substances, their chemical modification to improve their potency and selectivity remains practically untouched. While ongoing work with the more 'classical' pentacyclic triterpenoids will continue to be a fertile field for HIV-AIDS drug discovery, the other structural groups offer unprecedented opportunities for the development of additional substances with useful properties and for the discovery of novel targets for antiviral therapy. |
Leyton, P; Zarate, R A; Fuentes, S; Paipa, C; Gomez-Jeria, J S; Leyton, Y Influence of Aluminum Oxide on the Prebiotic Thermal Synthesis of Gly-Glu-(Gly-Glu)(N) Polymer Artículo de revista Biosystems, 104 (2-3), pp. 118-126, 2011, ISSN: 0303-2647. Resumen | Enlaces | BibTeX | Etiquetas: amino-acid-sequences, analysis, bond chemistry, conditions, crystalline diketopiperazine, earth formation formation, glutamic glycine ir-spectra, peptide prebiotic primitive pyroglutamic reaction, spectroscopy, synthesis, thermal vibrational @article{RN27d, title = {Influence of Aluminum Oxide on the Prebiotic Thermal Synthesis of Gly-Glu-(Gly-Glu)(N) Polymer}, author = { P. Leyton and R.A. Zarate and S. Fuentes and C. Paipa and J.S. Gomez-Jeria and Y. Leyton}, url = {/brokenurl#<Go to ISI>://WOS:000290194500006}, doi = {10.1016/j.biosystems.2011.01.008}, issn = {0303-2647}, year = {2011}, date = {2011-01-01}, journal = {Biosystems}, volume = {104}, number = {2-3}, pages = {118-126}, publisher = {2011 Elsevier Ireland Ltd.}, abstract = {The effect of the aluminum oxide on the thermal synthesis of the glycine-glutamic acid (Gly-Glu-(Gly-Glu)(n) polymer is described. The thermal synthesis in the molten state was carried out in the absence and presence of the oxide. In both cases, the vibrational spectra showed characteristic group frequencies corresponding predominantly to a Gly-Glu-(Gly-Glu)(n) sequence in the polymeric structure. The theoretical spectral data support the experimental proposed Gly-Glu-(Gly-Glu)(n) sequence for the polymer. The SEM-EDX characterization of the solid phase involved in the thermal synthesis showed that the aluminum oxide participates as a site for nucleation and growth of the polymer, explaining the increase of 25% efficiency in the presence of aluminum oxide. Electrophoresis data show shorter polypeptide chains in the presence of aluminum oxide.}, keywords = {amino-acid-sequences, analysis, bond chemistry, conditions, crystalline diketopiperazine, earth formation formation, glutamic glycine ir-spectra, peptide prebiotic primitive pyroglutamic reaction, spectroscopy, synthesis, thermal vibrational}, pubstate = {published}, tppubtype = {article} } The effect of the aluminum oxide on the thermal synthesis of the glycine-glutamic acid (Gly-Glu-(Gly-Glu)(n) polymer is described. The thermal synthesis in the molten state was carried out in the absence and presence of the oxide. In both cases, the vibrational spectra showed characteristic group frequencies corresponding predominantly to a Gly-Glu-(Gly-Glu)(n) sequence in the polymeric structure. The theoretical spectral data support the experimental proposed Gly-Glu-(Gly-Glu)(n) sequence for the polymer. The SEM-EDX characterization of the solid phase involved in the thermal synthesis showed that the aluminum oxide participates as a site for nucleation and growth of the polymer, explaining the increase of 25% efficiency in the presence of aluminum oxide. Electrophoresis data show shorter polypeptide chains in the presence of aluminum oxide. |
Aliaga, A E; Ahumada, H; Sepulveda, K; Gomez-Jeria, J S; Garrido, C; Weiss-Lopez, B; Campos-Vallette, M Sers, Molecular Dynamics and Molecular Orbital Studies of the Mrkdv Peptide on Silver and Membrane Surfaces Artículo de revista Journal of Physical Chemistry C, 115 (10), pp. 3982-3989, 2011, ISSN: 1932-7447. Resumen | Enlaces | BibTeX | Etiquetas: @article{RN43, title = {Sers, Molecular Dynamics and Molecular Orbital Studies of the Mrkdv Peptide on Silver and Membrane Surfaces}, author = { A.E. Aliaga and H. Ahumada and K. Sepulveda and J.S. Gomez-Jeria and C. Garrido and B. Weiss-Lopez and M. Campos-Vallette}, url = {/brokenurl#<Go to ISI>://WOS:000288113400022}, doi = {10.1021/jp1107153}, issn = {1932-7447}, year = {2011}, date = {2011-01-01}, journal = {Journal of Physical Chemistry C}, volume = {115}, number = {10}, pages = {3982-3989}, abstract = {The MRKDV peptide, structurally associated with an immunomodulatory protein, was studied using surface enhanced Raman scattering (SERS), molecular dynamics (MD) simulations, and quantum chemical calculations. The SEAS spectrum of the MRKDV peptide adsorbed on the silver surface is dominated by signals coming from the guanidinium moiety of the arginine amino acid (R). Guanidinium is the intrinsic probe that drives the orientation of the peptide onto the silver surface. Molecular mechanics and extended Huckel calculations of a model of MRKDV interacting with a silver surface support the experimental results. MD calculations representing the evolution of the peptide toward a model membrane were also performed. The guanidinium moiety interacts with the phospholipidic membrane surface. A hydrophobic C-terminal modification favors the peptide membrane affinity.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The MRKDV peptide, structurally associated with an immunomodulatory protein, was studied using surface enhanced Raman scattering (SERS), molecular dynamics (MD) simulations, and quantum chemical calculations. The SEAS spectrum of the MRKDV peptide adsorbed on the silver surface is dominated by signals coming from the guanidinium moiety of the arginine amino acid (R). Guanidinium is the intrinsic probe that drives the orientation of the peptide onto the silver surface. Molecular mechanics and extended Huckel calculations of a model of MRKDV interacting with a silver surface support the experimental results. MD calculations representing the evolution of the peptide toward a model membrane were also performed. The guanidinium moiety interacts with the phospholipidic membrane surface. A hydrophobic C-terminal modification favors the peptide membrane affinity. |
Munoz, O; Christen, P; Cretton, S; Barrero, A F; Lara, A; Herrador, M M Comparison of the Essential Oils of Leaves and Stem Bark from Two Different Populations of Drimys Winteri a Chilean Herbal Medicine Artículo de revista Natural Product Communications, 6 (6), pp. 879-882, 2011, ISSN: 1934-578x. Resumen | Enlaces | BibTeX | Etiquetas: antiinflammatory composition, drimys essential monoterpenes, oil sesquiterpenes, winteraceae, winteri @article{RN12f, title = {Comparison of the Essential Oils of Leaves and Stem Bark from Two Different Populations of Drimys Winteri a Chilean Herbal Medicine}, author = { O. Munoz and P. Christen and S. Cretton and A.F. Barrero and A. Lara and M.M. Herrador}, url = {/brokenurl#<Go to ISI>://WOS:000291838300030}, doi = {10.1177/1934578X1100600630}, issn = {1934-578x}, year = {2011}, date = {2011-01-01}, journal = {Natural Product Communications}, volume = {6}, number = {6}, pages = {879-882}, abstract = {The chemical composition of the essential oils obtained by hydrodistillation of stem bark and leaves of Drimys winteri J.R. et G. Foster var. chilensis /DC A. Gray (Winteraceae) from Chiloe Island (ID) and Continental Chile (Santiago) (CD) were studied by GC and GC/MS. Sesquiterpene hydrocarbons constituted the main chemical groups in the stem bark oils, with alpha-santalene, trans-beta-bergamotene and curcumenes as the major components. Monoterpenes constituted the main chemical groups in the leaves of Island plants with alpha-pinene (23.1%) beta-pinene (43.6%) and linalool (10.5%) as the main components whereas sesquiterpenes (germacrene D 17.6%) and phenylpropanoids (safrole 20.8%) are the most abundant in the leaves of Continental plants.}, keywords = {antiinflammatory composition, drimys essential monoterpenes, oil sesquiterpenes, winteraceae, winteri}, pubstate = {published}, tppubtype = {article} } The chemical composition of the essential oils obtained by hydrodistillation of stem bark and leaves of Drimys winteri J.R. et G. Foster var. chilensis /DC A. Gray (Winteraceae) from Chiloe Island (ID) and Continental Chile (Santiago) (CD) were studied by GC and GC/MS. Sesquiterpene hydrocarbons constituted the main chemical groups in the stem bark oils, with alpha-santalene, trans-beta-bergamotene and curcumenes as the major components. Monoterpenes constituted the main chemical groups in the leaves of Island plants with alpha-pinene (23.1%) beta-pinene (43.6%) and linalool (10.5%) as the main components whereas sesquiterpenes (germacrene D 17.6%) and phenylpropanoids (safrole 20.8%) are the most abundant in the leaves of Continental plants. |
Dobado, J A; Gomez-Tamayo, J C; Calvo-Flores, F G; Martinez-Garcia, H; Cardona, W; Weiss-Lopez, B; Ramirez-Rodriguez, O; Pessoa-Mahana, H; Araya-Maturana, R Nmr Assignment in Regioisomeric Hydroquinones Artículo de revista Magnetic Resonance in Chemistry, 49 (6), pp. 358-365, 2011, ISSN: 0749-1581. Resumen | Enlaces | BibTeX | Etiquetas: basis-sets, c-13 calculations, chemical-shifts, coupling-constants, derivatives, dft, diels-alder giao, h, h-1 hmbc, hmqc, hydroquinone, nmr, o3lyp, organic-molecules, reaction, respiration, sensitivity, spin theoretical tumor-cell @article{RN34e, title = {Nmr Assignment in Regioisomeric Hydroquinones}, author = { J.A. Dobado and J.C. Gomez-Tamayo and F.G. Calvo-Flores and H. Martinez-Garcia and W. Cardona and B. Weiss-Lopez and O. Ramirez-Rodriguez and H. Pessoa-Mahana and R. Araya-Maturana}, url = {/brokenurl#<Go to ISI>://WOS:000291114500009}, doi = {10.1002/mrc.2745}, issn = {0749-1581}, year = {2011}, date = {2011-01-01}, journal = {Magnetic Resonance in Chemistry}, volume = {49}, number = {6}, pages = {358-365}, publisher = {2011 John Wiley & Sons, Ltd.}, abstract = {A set of regioisomeric pairs of tricyclic hydroquinones, analogues of antitumor 9,10-dihydroxy-4,4-dimethyl-5,8dihydroanthracen- 1(4H)-one (1) and other derivatives, were synthesized and their regiochemistry and NMR spectra assigned by using 1H-detected one-bond(C-H) HMQC and long-range C-HHMBC, in good agreement with theoretical O3LYP/Alhrichs-pVTZ calculations. The 5-hydroxymethyl derivatives (11, 15, 19) showed a 3 integral H,H coupling constant of methylene protons evidencing the presence of a seven-membered intramolecular hydrogen bonded ring, not observed for the 8-hydroxymethyl isomers.}, keywords = {basis-sets, c-13 calculations, chemical-shifts, coupling-constants, derivatives, dft, diels-alder giao, h, h-1 hmbc, hmqc, hydroquinone, nmr, o3lyp, organic-molecules, reaction, respiration, sensitivity, spin theoretical tumor-cell}, pubstate = {published}, tppubtype = {article} } A set of regioisomeric pairs of tricyclic hydroquinones, analogues of antitumor 9,10-dihydroxy-4,4-dimethyl-5,8dihydroanthracen- 1(4H)-one (1) and other derivatives, were synthesized and their regiochemistry and NMR spectra assigned by using 1H-detected one-bond(C-H) HMQC and long-range C-HHMBC, in good agreement with theoretical O3LYP/Alhrichs-pVTZ calculations. The 5-hydroxymethyl derivatives (11, 15, 19) showed a 3 integral H,H coupling constant of methylene protons evidencing the presence of a seven-membered intramolecular hydrogen bonded ring, not observed for the 8-hydroxymethyl isomers. |
Galdámez, A; Gutierrez-Hernandez, M; Cassels, B K; Saez-Briones, P Crystal Structure of (1r,5s)-9-Nitro-1,2,3,4,5,6-Hexahydro-1,5-Methanopyrido[1,2-a][1,5] Diazocin-8-One (9-Nitrocytisine), C11h13o3n3 Artículo de revista Journal of the Chilean Chemical Society, 56 (1), pp. 595-597, 2011, ISSN: 0717-9324. Resumen | Enlaces | BibTeX | Etiquetas: agonists, alpha-4-beta-2, crystal cytisine cytisinoid, derivatives, design diffraction, halogenated hydrogen-bond, in-vivo, nicotinic patterns, smoking-cessation, structure, therapeutic-efficacy, x-ray @article{RN14g, title = {Crystal Structure of (1r,5s)-9-Nitro-1,2,3,4,5,6-Hexahydro-1,5-Methanopyrido[1,2-a][1,5] Diazocin-8-One (9-Nitrocytisine), C11h13o3n3}, author = {A. Gald\'{a}mez and M. Gutierrez-Hernandez and B.K. Cassels and P. Saez-Briones}, url = {/brokenurl#<Go to ISI>://WOS:000290700500016}, doi = {10.4067/S0717-97072011000100016}, issn = {0717-9324}, year = {2011}, date = {2011-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {56}, number = {1}, pages = {595-597}, abstract = {The title compound (1, trivial name: 9 (or 3)-nitrocytisine) crystallizes with two independent molecules in the asymmetric unit. In its structure two rings form a bispidine framework that is fused to a 3-nitro-2-pyridone group. The half-normal probability plot reveals that the two molecules do not show any significant geometrical differences, except in conformations of the nitro-group, which is involved in intermolecular interactions. The crystal packing structure of the title compound is described in terms of three-dimensional supramolecular arrays built up from chains of N-H center dot center dot center dot O (nitro-group), hydrogen bonds and weak intermolecular C-H center dot center dot center dot O=C interactions, with graph-set descriptors C-2(2)(6) and C-2(2)(10) motifs, which together result in R-4(4)(26) rings motifs. These chains are additionally stabilized by intermolecular NO2.pi interactions.}, keywords = {agonists, alpha-4-beta-2, crystal cytisine cytisinoid, derivatives, design diffraction, halogenated hydrogen-bond, in-vivo, nicotinic patterns, smoking-cessation, structure, therapeutic-efficacy, x-ray}, pubstate = {published}, tppubtype = {article} } The title compound (1, trivial name: 9 (or 3)-nitrocytisine) crystallizes with two independent molecules in the asymmetric unit. In its structure two rings form a bispidine framework that is fused to a 3-nitro-2-pyridone group. The half-normal probability plot reveals that the two molecules do not show any significant geometrical differences, except in conformations of the nitro-group, which is involved in intermolecular interactions. The crystal packing structure of the title compound is described in terms of three-dimensional supramolecular arrays built up from chains of N-H center dot center dot center dot O (nitro-group), hydrogen bonds and weak intermolecular C-H center dot center dot center dot O=C interactions, with graph-set descriptors C-2(2)(6) and C-2(2)(10) motifs, which together result in R-4(4)(26) rings motifs. These chains are additionally stabilized by intermolecular NO2.pi interactions. |
Areche, C; San-Martin, A; Rovirosa, J; Sepulveda, B Gastroprotective Activity of Epitaondiol and Sargaol Artículo de revista Natural Product Communications, 6 (8), pp. 1073-1074, 2011, ISSN: 1934-578x. Resumen | Enlaces | BibTeX | Etiquetas: activity, epitaondiol, flabelliforme gastroprotective sargaol, stypopodium @article{RN22f, title = {Gastroprotective Activity of Epitaondiol and Sargaol}, author = { C. Areche and A. San-Martin and J. Rovirosa and B. Sepulveda}, url = {/brokenurl#<Go to ISI>://WOS:000294035300005}, doi = {10.1177/1934578X1100600805}, issn = {1934-578x}, year = {2011}, date = {2011-01-01}, journal = {Natural Product Communications}, volume = {6}, number = {8}, pages = {1073-1074}, abstract = {The effects of epitaondiol (1) and sargaol (2), isolated from the brown alga Stypopodium flabelliforme on HCl/ethanol-induced gastric lesions in mice were evaluated and compared with that of lansoprazole. Epitaondiol and sargaol (6.25- 50 mg/kg) dose-dependently inhibited the appearance of gastric lesions in mice, displaying similar values to lansoprazole at 20 mg/kg. Both epitaondiol and sargaol showed gastroprotective activity with ED50 values of 40 mg/kg and 35 mg/kg, respectively. The results suggest that epitaondiol and sargaol protect the gastric mucosa in the HCl/EtOH model in mice.}, keywords = {activity, epitaondiol, flabelliforme gastroprotective sargaol, stypopodium}, pubstate = {published}, tppubtype = {article} } The effects of epitaondiol (1) and sargaol (2), isolated from the brown alga Stypopodium flabelliforme on HCl/ethanol-induced gastric lesions in mice were evaluated and compared with that of lansoprazole. Epitaondiol and sargaol (6.25- 50 mg/kg) dose-dependently inhibited the appearance of gastric lesions in mice, displaying similar values to lansoprazole at 20 mg/kg. Both epitaondiol and sargaol showed gastroprotective activity with ED50 values of 40 mg/kg and 35 mg/kg, respectively. The results suggest that epitaondiol and sargaol protect the gastric mucosa in the HCl/EtOH model in mice. |
Ormazabal-Toledo, R; Campodonico, P R; Contreras, R Are Electrophilicity and Electrofugality Related Concepts? A Density Functional Theory Study Artículo de revista Organic Letters, 13 (4), pp. 822-824, 2011, ISSN: 1523-7060. Resumen | Enlaces | BibTeX | Etiquetas: combinations, indexes, nucleofugality, nucleophilicity, parameter, scales @article{RN5h, title = {Are Electrophilicity and Electrofugality Related Concepts? A Density Functional Theory Study}, author = { R. Ormazabal-Toledo and P.R. Campodonico and R. Contreras}, url = {/brokenurl#<Go to ISI>://WOS:000287122800072}, doi = {10.1021/ol103033j}, issn = {1523-7060}, year = {2011}, date = {2011-01-01}, journal = {Organic Letters}, volume = {13}, number = {4}, pages = {822-824}, abstract = {It is proposed that the electrofugality of a fragment within a molecule is determined by its group nucleophilicity. The variation of electrofugality should be tightly related to the electron releasing ability of the substituent attached to the electrofuge moiety. This contribution closes the set of relationships between philicity and fugality quantities: while nucleofugality appears related to the group electrophilicity of the leaving group, electrofugality is related to the group nucleophilicity of the permanent group.}, keywords = {combinations, indexes, nucleofugality, nucleophilicity, parameter, scales}, pubstate = {published}, tppubtype = {article} } It is proposed that the electrofugality of a fragment within a molecule is determined by its group nucleophilicity. The variation of electrofugality should be tightly related to the electron releasing ability of the substituent attached to the electrofuge moiety. This contribution closes the set of relationships between philicity and fugality quantities: while nucleofugality appears related to the group electrophilicity of the leaving group, electrofugality is related to the group nucleophilicity of the permanent group. |
Diaz-Fleming, G; Celis, F; Campos-Vallette, M; Aliaga, A E; Escobar, M; Koch, R Raman, Infrared, Sers and Theoretical Study of 3-(1-Phenylpropan-2-Ylamino) Propanenitrile, Fenproporex Artículo de revista Journal of Raman Spectroscopy, 42 (7), pp. 1497-1504, 2011, ISSN: 0377-0486. Resumen | Enlaces | BibTeX | Etiquetas: calculations, density-functional dft elements, fenproporex, gold, infrared, raman, scattering, sers, silver, spectroscopy, surface-enhanced temperature theory @article{RN41f, title = {Raman, Infrared, Sers and Theoretical Study of 3-(1-Phenylpropan-2-Ylamino) Propanenitrile, Fenproporex}, author = { G. Diaz-Fleming and F. Celis and M. Campos-Vallette and A.E. Aliaga and M. Escobar and R. Koch}, url = {/brokenurl#<Go to ISI>://WOS:000293001000003}, doi = {10.1002/jrs.2882}, issn = {0377-0486}, year = {2011}, date = {2011-01-01}, journal = {Journal of Raman Spectroscopy}, volume = {42}, number = {7}, pages = {1497-1504}, publisher = {2011 John Wiley & Sons, Ltd.}, abstract = {Infrared, Raman and surface-enhanced Raman scattering (SERS) spectra of 3-(1-phenylpropan-2-ylamino) propanenitrile (fenproporex) have been recorded. Density functional theory (DFT) with the B3LYP functional was used for optimizations of ground state geometries and simulation of Raman and SERS vibrational spectra of this molecule. Bands of the vibrational spectra were assigned in detail. The comparison of SERS spectra obtained by using colloidal silver and gold nanoparticles with the corresponding Raman spectrum reveals enhancement and shifts in bands, suggesting a possible partial charge-transfer mechanism in the SERS effect. Information about the orientation of fenproporex on the nanometer-sized metal structures is also obtained.}, keywords = {calculations, density-functional dft elements, fenproporex, gold, infrared, raman, scattering, sers, silver, spectroscopy, surface-enhanced temperature theory}, pubstate = {published}, tppubtype = {article} } Infrared, Raman and surface-enhanced Raman scattering (SERS) spectra of 3-(1-phenylpropan-2-ylamino) propanenitrile (fenproporex) have been recorded. Density functional theory (DFT) with the B3LYP functional was used for optimizations of ground state geometries and simulation of Raman and SERS vibrational spectra of this molecule. Bands of the vibrational spectra were assigned in detail. The comparison of SERS spectra obtained by using colloidal silver and gold nanoparticles with the corresponding Raman spectrum reveals enhancement and shifts in bands, suggesting a possible partial charge-transfer mechanism in the SERS effect. Information about the orientation of fenproporex on the nanometer-sized metal structures is also obtained. |
Gajardo, F; Barrera, M; Vargas, R; Crivelli, I; Loeb, B Inorganic Chemistry, 50 (13), pp. 5910-5924, 2011, ISSN: 0020-1669. Resumen | Enlaces | BibTeX | Etiquetas: charge-transfer conversion, correlation-energy, density, excited-states, films, light, nanocrystalline optical-properties, sensitizers, tio2 @article{RN28i, title = {Influence of the Nature of the Absorption Band on the Potential Performance of High Molar Extinction Coefficient Ruthenium(Ii) Polypyridinic Complexes as Dyes for Sensitized Solar Cells}, author = { F. Gajardo and M. Barrera and R. Vargas and I. Crivelli and B. Loeb}, url = {/brokenurl#<Go to ISI>://WOS:000292010000012}, doi = {10.1021/ic1020862}, issn = {0020-1669}, year = {2011}, date = {2011-01-01}, journal = {Inorganic Chemistry}, volume = {50}, number = {13}, pages = {5910-5924}, abstract = {When tested in solar cells, ruthenium polypyridinic dyes with extended pi systems show an enhanced light-harvesting capacity that is not necessarily reflected by a high (collected electrons)/(absorbed photons) ratio. Provided that metal-to-ligand charge transfer bands, MLCT, are more effective, due to their directionality, than intraligand (IL) pi-pi* bands for the electron injection process in the solar cell, it seems important to explore and clarify the nature of the absorption bands present in these types of dyes. This article aims to elucidate if all the absorbed photons of these dyes are potentially useful in the generation of electric current. In other words, their potentiality as dyes must also be analyzed from the point of view of their contribution to the generation of excited states potentially useful for direct injection. Focusing on the assignment of the absorption bands and the nature of the emitting state, a systematic study for a series of ruthenium complexes with 4,4'-distyryl-2,2'-dipyridine (LH) and 4,4'-bis[p-(dimethylamino)-alpha-styryl]-2,2'-bipyridine (LNMe2) "chromophoric" ligands was undertaken. The observed experimental results were complemented with TDDFT calculations to elucidate the nature of the absorption bands, and a theoretical model was proposed to predict the available energy that could be injected from a singlet or a triplet excited state. For the series studied, the results indicate that the percentage of MLCT character to the anchored ligand for the lower energy absorption band follows the order [Ru(deebpy)(2)(LNMe2)](PF6)(2) > [Ru(deebpy)(2)(LH)] (PF6)(2) > [Ru(deebpy)(LH)(2)](PF6)(2), where deebpy is 4,4'-bis(ethoxycarbonyl)-2,2'-bipyridine, predicting that, at least from this point of view, their efficiency as dyes should follow the same trend.}, keywords = {charge-transfer conversion, correlation-energy, density, excited-states, films, light, nanocrystalline optical-properties, sensitizers, tio2}, pubstate = {published}, tppubtype = {article} } When tested in solar cells, ruthenium polypyridinic dyes with extended pi systems show an enhanced light-harvesting capacity that is not necessarily reflected by a high (collected electrons)/(absorbed photons) ratio. Provided that metal-to-ligand charge transfer bands, MLCT, are more effective, due to their directionality, than intraligand (IL) pi-pi* bands for the electron injection process in the solar cell, it seems important to explore and clarify the nature of the absorption bands present in these types of dyes. This article aims to elucidate if all the absorbed photons of these dyes are potentially useful in the generation of electric current. In other words, their potentiality as dyes must also be analyzed from the point of view of their contribution to the generation of excited states potentially useful for direct injection. Focusing on the assignment of the absorption bands and the nature of the emitting state, a systematic study for a series of ruthenium complexes with 4,4'-distyryl-2,2'-dipyridine (LH) and 4,4'-bis[p-(dimethylamino)-alpha-styryl]-2,2'-bipyridine (LNMe2) "chromophoric" ligands was undertaken. The observed experimental results were complemented with TDDFT calculations to elucidate the nature of the absorption bands, and a theoretical model was proposed to predict the available energy that could be injected from a singlet or a triplet excited state. For the series studied, the results indicate that the percentage of MLCT character to the anchored ligand for the lower energy absorption band follows the order [Ru(deebpy)(2)(LNMe2)](PF6)(2) > [Ru(deebpy)(2)(LH)] (PF6)(2) > [Ru(deebpy)(LH)(2)](PF6)(2), where deebpy is 4,4'-bis(ethoxycarbonyl)-2,2'-bipyridine, predicting that, at least from this point of view, their efficiency as dyes should follow the same trend. |
Vaca, I; Casqueiro, J; Ullan, R V; Rumbero, A; Chavez, R; Martin, J F Journal of Antibiotics, 64 (6), pp. 447-451, 2011, ISSN: 0021-8820. Resumen | Enlaces | BibTeX | Etiquetas: biosynthesis, cephalosporin-c, chrysogenum, conversion, hplc, isopenicillin liquid-chromatography n, natural-products, penicillium-chrysogenum, purification, stability, storage, system temperature @article{RN36h, title = {A Preparative Method for the Purification of Isopenicillin N from Genetically Blocked Acremonium Chrysogenum Strain Td189: Studies on the Degradation Kinetics and Storage Conditions}, author = { I. Vaca and J. Casqueiro and R.V. Ullan and A. Rumbero and R. Chavez and J.F. Martin}, url = {/brokenurl#<Go to ISI>://WOS:000292090800006}, doi = {10.1038/ja.2011.30}, issn = {0021-8820}, year = {2011}, date = {2011-01-01}, journal = {Journal of Antibiotics}, volume = {64}, number = {6}, pages = {447-451}, abstract = {A protocol for preparative isopenicillin N (IPN) purification, a highly interesting and hitherto unavailable intermediate of the penicillin and cephalosporin biosynthetic pathway due to its high unstability, is described. Culture broths of Acremonium chrysogenum TD189, a strain blocked in cephalosporin biosynthesis that accumulates this metabolite, were treated with acetone and filtered though charcoal and a hydrophobic resin in a single step as tandem columns. The cleared broth was then lyophilized and passed though a Sephadex G-25 column. The last step was the purification to homogeneity of IPN in a semipreparative HPLC equipment and, optionally, a desalting step by Sephadex G-10 column. Once purified, a complete analysis of the stability of the compound and the conditions for its long-term storage was carried out. Our results suggest a first-order model for IPN decomposition for all the pH and temperature analyzed. IPN is more stable at neutral pH, and once lyophilized, can be stored under vacuum and -75 degrees C with a half-life of 770 days. The Journal of Antibiotics (2011); published online 27 April 2011}, keywords = {biosynthesis, cephalosporin-c, chrysogenum, conversion, hplc, isopenicillin liquid-chromatography n, natural-products, penicillium-chrysogenum, purification, stability, storage, system temperature}, pubstate = {published}, tppubtype = {article} } A protocol for preparative isopenicillin N (IPN) purification, a highly interesting and hitherto unavailable intermediate of the penicillin and cephalosporin biosynthetic pathway due to its high unstability, is described. Culture broths of Acremonium chrysogenum TD189, a strain blocked in cephalosporin biosynthesis that accumulates this metabolite, were treated with acetone and filtered though charcoal and a hydrophobic resin in a single step as tandem columns. The cleared broth was then lyophilized and passed though a Sephadex G-25 column. The last step was the purification to homogeneity of IPN in a semipreparative HPLC equipment and, optionally, a desalting step by Sephadex G-10 column. Once purified, a complete analysis of the stability of the compound and the conditions for its long-term storage was carried out. Our results suggest a first-order model for IPN decomposition for all the pH and temperature analyzed. IPN is more stable at neutral pH, and once lyophilized, can be stored under vacuum and -75 degrees C with a half-life of 770 days. The Journal of Antibiotics (2011); published online 27 April 2011 |
Toral, M I; Orellana, S L; Soto, C A; Richter, P Extraction and Determination of Oxytetracycline Hydrochloride and Oxolinic Acid in Fish Feed by Derivative Spectrophotometry of First Order Artículo de revista Food Analytical Methods, 4 (4), pp. 497-504, 2011, ISSN: 1936-9751. Resumen | Enlaces | BibTeX | Etiquetas: animal antibiotics, chlortetracycline, derivative detection, extractions, feed, feeds, flumequine, fluorescence liquid-chromatography, oxolinic oxytetracycline, performance premixes, products, seawater spectrophotometry, tetracycline water @article{RN20j, title = {Extraction and Determination of Oxytetracycline Hydrochloride and Oxolinic Acid in Fish Feed by Derivative Spectrophotometry of First Order}, author = { M.I. Toral and S.L. Orellana and C.A. Soto and P. Richter}, url = {/brokenurl#<Go to ISI>://WOS:000296883500006}, doi = {10.1007/s12161-011-9195-3}, issn = {1936-9751}, year = {2011}, date = {2011-01-01}, journal = {Food Analytical Methods}, volume = {4}, number = {4}, pages = {497-504}, abstract = {In this work is proposed the extraction and determination of oxytetracycline (OTC) and oxolinic acid (OA) in fish feed by first-derivative spectrophotometry. The extractions are carried out by parallel modality, where OTC is extracted in the presence of OA in a sample, and in another is extracted OA in the presence of OTC, and the sequential modality, where OTC is extracted first and then followed by OA in a single feed sample. A phosphate buffer, pH 7.0, was selected for OTC extraction and acetonitrile for OA extraction. These solvents were used in both extraction modalities. The extraction percentages obtained by parallel mode are better than those obtained by sequential extraction. In both cases, the limits of extraction were 25 mg kg(-1) for OTC and 10 mg kg(-1) for OA. However, it is proposed to work with the parallel extraction for its efficiency, accuracy, precision, and less time requirement.}, keywords = {animal antibiotics, chlortetracycline, derivative detection, extractions, feed, feeds, flumequine, fluorescence liquid-chromatography, oxolinic oxytetracycline, performance premixes, products, seawater spectrophotometry, tetracycline water}, pubstate = {published}, tppubtype = {article} } In this work is proposed the extraction and determination of oxytetracycline (OTC) and oxolinic acid (OA) in fish feed by first-derivative spectrophotometry. The extractions are carried out by parallel modality, where OTC is extracted in the presence of OA in a sample, and in another is extracted OA in the presence of OTC, and the sequential modality, where OTC is extracted first and then followed by OA in a single feed sample. A phosphate buffer, pH 7.0, was selected for OTC extraction and acetonitrile for OA extraction. These solvents were used in both extraction modalities. The extraction percentages obtained by parallel mode are better than those obtained by sequential extraction. In both cases, the limits of extraction were 25 mg kg(-1) for OTC and 10 mg kg(-1) for OA. However, it is proposed to work with the parallel extraction for its efficiency, accuracy, precision, and less time requirement. |
Aguilera-Venegas, B; Olea-Azar, C; Norambuena, E; Aran, V J; Mendizabal, F; Lapier, M; Maya, J D; Kemmerling, U; Lopez-Munoz, R Esr, Electrochemical, Molecular Modeling and Biological Evaluation of 4-Substituted and 1,4-Disubstituted 7-Nitroquinoxalin-2-Ones as Potential Anti-Trypanosoma Cruzi Agents Artículo de revista Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy, 78 (3), pp. 1004-1012, 2011, ISSN: 1386-1425. Resumen | Enlaces | BibTeX | Etiquetas: anion, behavior binding-site, chagas chagas-disease, complexes, crystal-structure, disease, epimastigote, esr, glutathione-reductase, modeling, molecular nifurtimox, nitro nitroquinoxaline, radical-anion, reductase, superoxide trypanothione trypomastigote @article{RN19h, title = {Esr, Electrochemical, Molecular Modeling and Biological Evaluation of 4-Substituted and 1,4-Disubstituted 7-Nitroquinoxalin-2-Ones as Potential Anti-Trypanosoma Cruzi Agents}, author = { B. Aguilera-Venegas and C. Olea-Azar and E. Norambuena and V.J. Aran and F. Mendizabal and M. Lapier and J.D. Maya and U. Kemmerling and R. Lopez-Munoz}, url = {/brokenurl#<Go to ISI>://WOS:000288046600012}, doi = {10.1016/j.saa.2010.12.017}, issn = {1386-1425}, year = {2011}, date = {2011-01-01}, journal = {Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy}, volume = {78}, number = {3}, pages = {1004-1012}, publisher = {2010 Elsevier B.V.}, abstract = {Electrochemical and ESR studies were carried out in this work with the aim of characterizing the reduction mechanisms of 4-substituted and 1,4-disubstituted 7-nitroquinoxalin-2-ones by means of cyclic voltammetry in DMSO as aprotic solvent. Two reduction mechanisms were found for these compounds: the first, for compounds bearing a labile hydrogen by following a self-protonation mechanism (ECE steps), and the second, for compounds without labile hydrogen, based on a purely electrochemical reduction mechanism (typical of nitroheterocycles). The electrochemical results were corroborated using ESR spectroscopy allowing us to propose the hyperfine splitting pattern of the nitro-radical, which was later corroborated by the ESR simulation spectra. All these compounds were assayed as growth inhibitors against Trypanosoma cruzi: first, on the non-proliferative (and infective) form of the parasite (trypomastigote stage), and then, the ones that displayed activity, were assayed on the non-infective form (epimastigote stage). Thus, we found four new compounds highly active against T. cruzi. Finally, molecular modeling studies suggest the inhibition of the trypanothione reductase like one of the possible mechanisms involved in the trypanocidal action.}, keywords = {anion, behavior binding-site, chagas chagas-disease, complexes, crystal-structure, disease, epimastigote, esr, glutathione-reductase, modeling, molecular nifurtimox, nitro nitroquinoxaline, radical-anion, reductase, superoxide trypanothione trypomastigote}, pubstate = {published}, tppubtype = {article} } Electrochemical and ESR studies were carried out in this work with the aim of characterizing the reduction mechanisms of 4-substituted and 1,4-disubstituted 7-nitroquinoxalin-2-ones by means of cyclic voltammetry in DMSO as aprotic solvent. Two reduction mechanisms were found for these compounds: the first, for compounds bearing a labile hydrogen by following a self-protonation mechanism (ECE steps), and the second, for compounds without labile hydrogen, based on a purely electrochemical reduction mechanism (typical of nitroheterocycles). The electrochemical results were corroborated using ESR spectroscopy allowing us to propose the hyperfine splitting pattern of the nitro-radical, which was later corroborated by the ESR simulation spectra. All these compounds were assayed as growth inhibitors against Trypanosoma cruzi: first, on the non-proliferative (and infective) form of the parasite (trypomastigote stage), and then, the ones that displayed activity, were assayed on the non-infective form (epimastigote stage). Thus, we found four new compounds highly active against T. cruzi. Finally, molecular modeling studies suggest the inhibition of the trypanothione reductase like one of the possible mechanisms involved in the trypanocidal action. |
Soto-Delgado, J; Aizman, A; Contreras, R; Domingo, L R A Dft Study of the Regioselectivity in Intramolecular Diels-Alder Reactions with Formation of a Tricyclodecane Skeleton Artículo de revista Letters in Organic Chemistry, 8 (2), pp. 125-131, 2011, ISSN: 1570-1786. Resumen | Enlaces | BibTeX | Etiquetas: charge cycloadditions, electrophilicity electrophilicity, group intramolecular transfer @article{RN18g, title = {A Dft Study of the Regioselectivity in Intramolecular Diels-Alder Reactions with Formation of a Tricyclodecane Skeleton}, author = { J. Soto-Delgado and A. Aizman and R. Contreras and L.R. Domingo}, url = {/brokenurl#<Go to ISI>://WOS:000289085200008}, doi = {10.2174/157017811794697494}, issn = {1570-1786}, year = {2011}, date = {2011-01-01}, journal = {Letters in Organic Chemistry}, volume = {8}, number = {2}, pages = {125-131}, abstract = {Three different intramolecular Diels-Alder (IMDA) reactions associated with the formation of fused and bridged tricyclodecane skeletons have been studied at the B3LYP/6-31G(d) computational level. While substitution on the diene and dienophile fragments modulates the polar character of the reaction, the strain effect produced by the methylene tether affects the activation energy, and its torsion controls the different regioisomeric channels of the IMDA process. Analysis of the reactivity indices recently proposed within the conceptual density functional theory allows for the characterization of the mechanism including the charge transfer within the reagents involved in these IMDA reactions as well as for the direction of the electronic flux in the intramolecular processes.}, keywords = {charge cycloadditions, electrophilicity electrophilicity, group intramolecular transfer}, pubstate = {published}, tppubtype = {article} } Three different intramolecular Diels-Alder (IMDA) reactions associated with the formation of fused and bridged tricyclodecane skeletons have been studied at the B3LYP/6-31G(d) computational level. While substitution on the diene and dienophile fragments modulates the polar character of the reaction, the strain effect produced by the methylene tether affects the activation energy, and its torsion controls the different regioisomeric channels of the IMDA process. Analysis of the reactivity indices recently proposed within the conceptual density functional theory allows for the characterization of the mechanism including the charge transfer within the reagents involved in these IMDA reactions as well as for the direction of the electronic flux in the intramolecular processes. |
Osorio-Roman, I O; Ortega-Vasquez, V; Vargas, V; Aroca, R F Surface-Enhanced Spectra on D-Gluconic Acid Coated Silver Nanoparticles Artículo de revista Applied Spectroscopy, 65 (8), pp. 838-843, 2011, ISSN: 0003-7028. Resumen | Enlaces | BibTeX | Etiquetas: coated d-gluconic emission, enhanced film fluorescence, luminescence, nanoparticles, nanopartides, plasmon raman resonance scattering, see, serrs, silver surface-enhanced @article{RN48, title = {Surface-Enhanced Spectra on D-Gluconic Acid Coated Silver Nanoparticles}, author = { I.O. Osorio-Roman and V. Ortega-Vasquez and V. Vargas and R.F. Aroca}, url = {/brokenurl#<Go to ISI>://WOS:000293206800002}, doi = {10.1366/11-06279}, issn = {0003-7028}, year = {2011}, date = {2011-01-01}, journal = {Applied Spectroscopy}, volume = {65}, number = {8}, pages = {838-843}, abstract = {Coated silver (Ag) colloids synthesized with D-glucose permit the observation of surface-enhanced fluorescence (SEF) and surface-enhanced resonance Raman scattering (SERRS) of the rhodamine B (RhB) molecule. The organic coating formed during the synthesis of the Ag nanostructures was identified by its surface-enhanced Raman scattering (SERS) spectrum as D-gluconic acid. The RhB molecule is used to exemplify the distance dependence of SEF and SERRS on the coated Ag nanostructures. The fluorescence enhancement factor for RhB on D-gluconic acid coated silver nanoparticles was determined experimentally and estimated using a simple model. Further support for the plasmon enhancement is obtained from the fact that the measured fluorescence lifetime of RhB on the silver coated with D-gluconic acid is shorter than that found on a glass surface. A very modest enhancement factor is obtained, as expected for very short distance between RhB and the metal surface. Given the very thin metal fluorophore separation, estimated from the size of the D-gluconic acid, the energy transfer or fluorescence quenching is still efficient and the SEF enhancement is just overcoming the energy transfer. Therefore, both SEF and SERRS are observed. Notably, the aggregation of coated nanoparticles also increases the enhancement factor for SEF.}, keywords = {coated d-gluconic emission, enhanced film fluorescence, luminescence, nanoparticles, nanopartides, plasmon raman resonance scattering, see, serrs, silver surface-enhanced}, pubstate = {published}, tppubtype = {article} } Coated silver (Ag) colloids synthesized with D-glucose permit the observation of surface-enhanced fluorescence (SEF) and surface-enhanced resonance Raman scattering (SERRS) of the rhodamine B (RhB) molecule. The organic coating formed during the synthesis of the Ag nanostructures was identified by its surface-enhanced Raman scattering (SERS) spectrum as D-gluconic acid. The RhB molecule is used to exemplify the distance dependence of SEF and SERRS on the coated Ag nanostructures. The fluorescence enhancement factor for RhB on D-gluconic acid coated silver nanoparticles was determined experimentally and estimated using a simple model. Further support for the plasmon enhancement is obtained from the fact that the measured fluorescence lifetime of RhB on the silver coated with D-gluconic acid is shorter than that found on a glass surface. A very modest enhancement factor is obtained, as expected for very short distance between RhB and the metal surface. Given the very thin metal fluorophore separation, estimated from the size of the D-gluconic acid, the energy transfer or fluorescence quenching is still efficient and the SEF enhancement is just overcoming the energy transfer. Therefore, both SEF and SERRS are observed. Notably, the aggregation of coated nanoparticles also increases the enhancement factor for SEF. |
Diaz, C; Valenzuela, M L; Yutronic, N; Villalobos, V; Barrera, G Nanostructured Vox/Vo(Po4)(N) Using Solid-State Vanadium Containing Phosphazene Precursors: A Useful Potential Bi-Catalyst System Artículo de revista Journal of Cluster Science, 22 (4), pp. 693-704, 2011, ISSN: 1040-7278. Resumen | Enlaces | BibTeX | Etiquetas: autogenic cyclophosphazenes, derivatives, electrochemical elevated-temperature, gold, morphology, nanofibres nanoparticles, organometallic polyphosphazenes, pressure, properties, pyrolysis, template, vanadium @article{RN32i, title = {Nanostructured Vox/Vo(Po4)(N) Using Solid-State Vanadium Containing Phosphazene Precursors: A Useful Potential Bi-Catalyst System}, author = { C. Diaz and M.L. Valenzuela and N. Yutronic and V. Villalobos and G. Barrera}, url = {/brokenurl#<Go to ISI>://WOS:000297250000012}, doi = {10.1007/s10876-011-0415-1}, issn = {1040-7278}, year = {2011}, date = {2011-01-01}, journal = {Journal of Cluster Science}, volume = {22}, number = {4}, pages = {693-704}, abstract = {Pyrolysis of molecular precursors containing vanadium organometallic and cyclic phosphazene affords mixtures of nanostructured vanadium oxides and pyrophosphates. The products from the molecular precursor [N3P3(OC6H5)(5)OC5H4N center dot Cp2VCl][PF6], and of the mixtures Cp2VCl2/N3P3(OC6H4CHO)(6) and Cp2VCl2/[NP(O2C12H8)](3) in several relationships 1:1, 1:3, 1:5 and 1:10, pyrolyzed under air and at 400 A degrees C and 600 A degrees C, give mixtures mainly V2O5 and VO(PO3)(2). Varied morphologies depending on the molecular or mixture precursors and of the temperature used were observed. Nanowires with diameters of approximate 40 nm were observed for the 1:5 Cp2VCl2/[NP(O2C12H8)](3) mixture pyrolyzed at 400 A degrees C, while the same mixture pyrolyzed at 600 A degrees C, affords xerogels of V2O5. The products were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), infra-red (IR) spectroscopy and X-ray diffraction (XRD). The preparation method constitutes a novel one-pot solid-state way to nanostructured materials with potential applications both in oxidative dehydrogenation of light hydrocarbons with V2O5, as well as alkenes oxidations with VO(PO3)(2).}, keywords = {autogenic cyclophosphazenes, derivatives, electrochemical elevated-temperature, gold, morphology, nanofibres nanoparticles, organometallic polyphosphazenes, pressure, properties, pyrolysis, template, vanadium}, pubstate = {published}, tppubtype = {article} } Pyrolysis of molecular precursors containing vanadium organometallic and cyclic phosphazene affords mixtures of nanostructured vanadium oxides and pyrophosphates. The products from the molecular precursor [N3P3(OC6H5)(5)OC5H4N center dot Cp2VCl][PF6], and of the mixtures Cp2VCl2/N3P3(OC6H4CHO)(6) and Cp2VCl2/[NP(O2C12H8)](3) in several relationships 1:1, 1:3, 1:5 and 1:10, pyrolyzed under air and at 400 A degrees C and 600 A degrees C, give mixtures mainly V2O5 and VO(PO3)(2). Varied morphologies depending on the molecular or mixture precursors and of the temperature used were observed. Nanowires with diameters of approximate 40 nm were observed for the 1:5 Cp2VCl2/[NP(O2C12H8)](3) mixture pyrolyzed at 400 A degrees C, while the same mixture pyrolyzed at 600 A degrees C, affords xerogels of V2O5. The products were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), infra-red (IR) spectroscopy and X-ray diffraction (XRD). The preparation method constitutes a novel one-pot solid-state way to nanostructured materials with potential applications both in oxidative dehydrogenation of light hydrocarbons with V2O5, as well as alkenes oxidations with VO(PO3)(2). |
Briones, X; Encinas, M V; Petri, D F S; Pavez, J; Tapia, R A; Yazdani-Pedram, M; Urzúa, M Adsorption Behavior of Hydrophobically Modified Polyelectrolytes onto Amino- or Methyl-Terminated Surfaces Artículo de revista Langmuir, 27 (22), pp. 13524-13532, 2011, ISSN: 0743-7463. Resumen | Enlaces | BibTeX | Etiquetas: anhydride), carboxymethyl cellulose, charge complexes, layers, silica, solid-surfaces, solvent, sulfate @article{RN1_98, title = {Adsorption Behavior of Hydrophobically Modified Polyelectrolytes onto Amino- or Methyl-Terminated Surfaces}, author = { X. Briones and M.V. Encinas and D.F.S. Petri and J. Pavez and R.A. Tapia and M. Yazdani-Pedram and M. Urz\'{u}a}, url = {/brokenurl#<Go to ISI>://WOS:000296598300017}, doi = {10.1021/la2025632}, issn = {0743-7463}, year = {2011}, date = {2011-01-01}, journal = {Langmuir}, volume = {27}, number = {22}, pages = {13524-13532}, abstract = {The adsorption of hydrophobically modified polyelectrolytes derived from poly(maleic anhydride-alt-styrene) (P(MA-alt-St)) containing in their side chain aryl-alkyl groups onto amino- or methyl-terminated silicon wafers was investigated. The effect of the spacer group, the chemical nature of the side chain, molecular weight of polyelectrolyte, and ionic strength of solution on the polyelectrolyte adsorbed amount was studied by null ellipsometry. The adsorbed amount of polyelectrolyte increased with increasing ionic strength, in agreement with the screening-enhanced adsorption regime, indicating that hydrophobic interactions with the surface play an important role in the adsorption process. At constant ionic strength, the adsorbed amount was slightly higher for polyelectrolytes with larger alkyl side chain and decreased with the hydrophobicity of aryl group. The adsorption behavior is discussed in terms of the side chain flexibility of the polymer. Characteristics of the adsorbed layer were studied by atomic force microscopy (AFM) and contact angle measurements. AFM images show the presence of aggregates and closed globular structure of polyelectrolyte onto the amino- or methyl-terminated surface, which agrees with a 3D and 2D growth mechanism, respectively. Fluorescence measurements showed that the aggregation of polyelectrolyte containing the hydrophobic naphthyl group occurs already in the solution. However, the aggregation of polyelectrolytes containing the phenyl group in its side chain is not observed in solution but is induced by the amino-terminated surface. This difference can be explained in terms of the higher flexibility of side chain bearing the phenyl group. The polyelectrolyte films showed a high chemical heterogeneity and moderate hydrophobicity.}, keywords = {anhydride), carboxymethyl cellulose, charge complexes, layers, silica, solid-surfaces, solvent, sulfate}, pubstate = {published}, tppubtype = {article} } The adsorption of hydrophobically modified polyelectrolytes derived from poly(maleic anhydride-alt-styrene) (P(MA-alt-St)) containing in their side chain aryl-alkyl groups onto amino- or methyl-terminated silicon wafers was investigated. The effect of the spacer group, the chemical nature of the side chain, molecular weight of polyelectrolyte, and ionic strength of solution on the polyelectrolyte adsorbed amount was studied by null ellipsometry. The adsorbed amount of polyelectrolyte increased with increasing ionic strength, in agreement with the screening-enhanced adsorption regime, indicating that hydrophobic interactions with the surface play an important role in the adsorption process. At constant ionic strength, the adsorbed amount was slightly higher for polyelectrolytes with larger alkyl side chain and decreased with the hydrophobicity of aryl group. The adsorption behavior is discussed in terms of the side chain flexibility of the polymer. Characteristics of the adsorbed layer were studied by atomic force microscopy (AFM) and contact angle measurements. AFM images show the presence of aggregates and closed globular structure of polyelectrolyte onto the amino- or methyl-terminated surface, which agrees with a 3D and 2D growth mechanism, respectively. Fluorescence measurements showed that the aggregation of polyelectrolyte containing the hydrophobic naphthyl group occurs already in the solution. However, the aggregation of polyelectrolytes containing the phenyl group in its side chain is not observed in solution but is induced by the amino-terminated surface. This difference can be explained in terms of the higher flexibility of side chain bearing the phenyl group. The polyelectrolyte films showed a high chemical heterogeneity and moderate hydrophobicity. |
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