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Buratto, Suelen Cristina - One of the best experts on this subject based on the ideXlab platform.
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Reações de propanólise de triésteres de fosfato catalisadas por MgO e Al2O3
2014Co-Authors: Buratto, Suelen CristinaAbstract:Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2014.Neste trabalho, foram investigadas as propriedades catalíticas de dois óxidos comerciais, Al2O3 e MgO, em reações de propanólise de triésteres de fosfato. Resultados de análises termogravimétricas mostram que materiais residuais são eliminados de ambos os sólidos em temperaturas superiores a 400°C. Após tratamento térmico adequado, avaliou-se a adsorção física de nitrogênio (métodos BET e BJH), e foram obtidas isotermas de adsorção/dessorção características de materiais mesoporosos, sendo o raio médio de poro de MgO sutilmente maior que o de Al2O3 (45,2 e 35,9 Å, respectivamente). Adicionalmente, resultados de dessorção de CO2 à temperatura programada indicam maior basicidade dos sítios de MgO em comparação àqueles de Al2O3. A atividade catalítica dos sólidos foi avaliada na reação de propanólise do triéster dimetil 4-nitrofenil fosfato (DMPNPhP), e foram obtidos incrementos de cerca de 106 e 105 vezes nas constantes de velocidade observadas em presença de MgO e Al2O3, respectivamente, em comparação com a propanólise espontânea do substrato. Considerando a maior atividade catalítica de MgO, consistentes com suas propriedades texturais superiores e a maior básicidade dos sítios, o estudo com este catalisador foi estendido a uma série de triésteres fosfóricos dialquil arílicos e triarílicos, e os incrementos catalíticos chegam a ordem de 106 vezes. Significativamente, com os triésteres triarílicos, observou-se a eliminação de dois ou três equivalentes do grupo de saída através de reações de primeira ordem consecutivas. Resultados de caracterização de produtos por cromatografia líquida acoplada à espectrometria de massas (LC-MS/MS) confirmam a formação de triésteres trialquílicos, estruturalmente análogos a uma classe de compostos retardadores de chamas. Com DMPNPhP, analisou-se o reuso do MgO em três ciclos e não observou-se perda significativa de atividade catalítica.Abstract : In this work, it was investigated the catalytic properties of two commercially available oxides, Al2O3 and MgO, in the propanolysis reactions of Phosphate triesters. Thermogravimetric analyses show that residual materials are eliminated from the solids at temperatures higher than 400°C. The evaluation of physical adsorption of nitrogen (BET and BJH methods) shows that the corresponding adsorption/desorption isotherms are characteristic of mesoporous materials, being the MgO mean pore radius slightly larger than that of Al2O3 (45.2 and 35.0 Å, respectively). Additionally, results of temperature programmed desorption of CO2 indicate that MgO sites are more basic than those of Al2O3. The catalytic activities of the solids were evaluated in the propanolysis reaction of dimethyl 4-nitrophenyl Phosphate (DMPNPhP), and enhancements in the observed rate constants were c.a. 106 and 105-fold in presence of MgO and Al2O3, respectively. Considering the greater activity of MgO, consistent with its higher textural properties and more basic sites, the investigation with this catalyst was extended to a series of dialkyl aryl and triaryl Phosphate triesters, and rate enhancements are up to 106-fold. Significantly, in the case of the triaryl substrates, it was observed the displacement of two or three equivalents of the leaving group through consecutive first order reactions. The characterization of the products by liquid chromatography-mass spectrometry (LC-MS/MS) confirms the formation of Trialkyl Phosphate esters, structurally analogous to a class of flame retardant compounds. The reuse of MgO in the propanolysis of DMPNPhP was evaluated in three cycles and it was not observed signficant loss of catalytic activity
Jaffres Paul-alain - One of the best experts on this subject based on the ideXlab platform.
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Cationic TrialkylPhosphates: Synthesis and Transfection Efficacies Compared to Phosphoramidate Analogues
'Wiley', 2014Co-Authors: Le Corre Stéphanie, Berchel Mathieu, Le Gall Tony, Haelters Pierre, Lehn Pierre, Montier Tristan, Jaffres Paul-alainAbstract:International audienceWe report herein the synthesis of a novel family of cationic lipids, characterized by a trimethylammonium headgroup linked through a Phosphate function to either two identical or two different lipid chains. The novelty of this study arises from the use of a Trialkyl Phosphate group to associate the hydrophobic domain to the cationic polar head. The structure of these new cationic lipids, which differs from that of previously reported lipophosphoramidates, is closer to the phospholipids encountered in the plasma membrane, and possesses a phosphocholine polar head. Evaluation of the transfection activity allowed us to compare the efficacy of cationic lipoPhosphates with that of lipophosphoramidates. These results demonstrate that cationic lipoPhosphates and lipophosphoramidates having otherwise identical chemical structures exhibit similar transfection efficacies. The second conclusion is that the structure of the lipid domain is a much more important parameter in governing transfection efficacy than the composition of the linker moiety. The best results were obtained with cationic lipoPhosphates or lipophosphoramidates possessing two different lipid chains, for example one oleyl chain with one phytanyl chain. These nonsymmetric cationic lipids exhibited transfection efficacies that were 10- to 200-fold better than those obtained with Lipofectamine used as a commercial standard
Peter J Cragg - One of the best experts on this subject based on the ideXlab platform.
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experimental and computational study of the inclusion complexes of β cyclodextrin with the chemical warfare agent soman gd and commonly used simulants
RSC Advances, 2017Co-Authors: Mark R Sambrook, Jack C Vincent, Jayne A Ede, Ian A Gass, Peter J CraggAbstract:The hydrophobically driven inclusion complexation of the Chemical Warfare Agent (CWA) pinacolyl methylphosphonofluoridate (soman, or GD) by β-cyclodextrin (β-CD) is studied both experimentally and computationally. Semiempirical modelling (PM6) adds further insight to the understanding of the CD–GD complex and the preferential binding of P(+) isomers over P(−). Comparison of the CD–GD complex to those formed by β-CD with commonly used Trialkyl Phosphate and dialkyl methylphosphonate simulants furnishes preliminary supramolecular agent–simulant correlation data. Such comparison studies will have utility in the design of new CWA-responsive materials.
Le Corre Stéphanie - One of the best experts on this subject based on the ideXlab platform.
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Cationic TrialkylPhosphates: Synthesis and Transfection Efficacies Compared to Phosphoramidate Analogues
'Wiley', 2014Co-Authors: Le Corre Stéphanie, Berchel Mathieu, Le Gall Tony, Haelters Pierre, Lehn Pierre, Montier Tristan, Jaffres Paul-alainAbstract:International audienceWe report herein the synthesis of a novel family of cationic lipids, characterized by a trimethylammonium headgroup linked through a Phosphate function to either two identical or two different lipid chains. The novelty of this study arises from the use of a Trialkyl Phosphate group to associate the hydrophobic domain to the cationic polar head. The structure of these new cationic lipids, which differs from that of previously reported lipophosphoramidates, is closer to the phospholipids encountered in the plasma membrane, and possesses a phosphocholine polar head. Evaluation of the transfection activity allowed us to compare the efficacy of cationic lipoPhosphates with that of lipophosphoramidates. These results demonstrate that cationic lipoPhosphates and lipophosphoramidates having otherwise identical chemical structures exhibit similar transfection efficacies. The second conclusion is that the structure of the lipid domain is a much more important parameter in governing transfection efficacy than the composition of the linker moiety. The best results were obtained with cationic lipoPhosphates or lipophosphoramidates possessing two different lipid chains, for example one oleyl chain with one phytanyl chain. These nonsymmetric cationic lipids exhibited transfection efficacies that were 10- to 200-fold better than those obtained with Lipofectamine used as a commercial standard
Mark R Sambrook - One of the best experts on this subject based on the ideXlab platform.
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experimental and computational study of the inclusion complexes of β cyclodextrin with the chemical warfare agent soman gd and commonly used simulants
RSC Advances, 2017Co-Authors: Mark R Sambrook, Jack C Vincent, Jayne A Ede, Ian A Gass, Peter J CraggAbstract:The hydrophobically driven inclusion complexation of the Chemical Warfare Agent (CWA) pinacolyl methylphosphonofluoridate (soman, or GD) by β-cyclodextrin (β-CD) is studied both experimentally and computationally. Semiempirical modelling (PM6) adds further insight to the understanding of the CD–GD complex and the preferential binding of P(+) isomers over P(−). Comparison of the CD–GD complex to those formed by β-CD with commonly used Trialkyl Phosphate and dialkyl methylphosphonate simulants furnishes preliminary supramolecular agent–simulant correlation data. Such comparison studies will have utility in the design of new CWA-responsive materials.
