排序方式: 共有73条查询结果,搜索用时 46 毫秒
21.
Manuel E. Medina Annia Galano Ángel Trigos 《Journal of Physical Organic Chemistry》2015,28(7):504-508
The density functional and the transition state theories were used to estimate detailed thermochemical and kinetic data for the oxidative damage to cholesterol induced by peroxyl radicals (ROO?) in lipid media. Two mechanisms of reactions were considered, the hydrogen transfer and the radical adduct formation, and it was found that hydrogen transfer is the only important route in this case, particularly at allylic sites. 7α products are predicted to represent more than 90% of the total initial damage, albeit 7β products are expected to be found in small but not negligible proportion. The chlorination degree was found to play an important role in the extent of the oxidative damage to cholesterol inflicted by the ROO? family. The estimated rate constants are 2.74 × 105, 1.32 × 105, 3.09 × 102, 6.07 × 101, and 8.75 × 10?1 M?1 s?1 for the reactions with ?OOCHCl2, ?OOCCl3, ?OOCH2Cl, ?OOH, and ?OOCH3, respectively. These values indicate that only chlorinated peroxyl radicals represent a significant hazard to the chemical integrity of cholesterol. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
22.
23.
Galano A 《The journal of physical chemistry. A》2006,110(29):9153-9160
A theoretical study of the mechanism and kinetics of the OH hydrogen abstraction from hydroxyacetone is presented. Optimum geometries and frequencies have been computed at the BH and HLYP/6-311++G(d,p) level of theory for all stationary points. Energy values have been improved by single-point calculations at the above geometries using CCSD(T)/ 6-311++G(d,p). The rate coefficients are calculated for the temperature range 280-500 K by using conventional transition state theory (TST), including tunneling corrections. Our analysis supports a stepwise mechanism involving the formation of a reactant complex in the entrance channel and a product complex in the exit channel, for all the modeled paths. Four experimental values of the rate constant at 298 K have been previously reported: three of them in great agreement (approximately 3 x 10(-12) cm(3) molecule(-1) s(-1)), and one of them twice larger. The calculations in the present work support the smaller value. A curved Arrhenius plot was found in the studied temperature range; thus the expression that best describes the obtained data is k(280-500)(overall) = 5.29 x 10(-23)T(3.4)e(1623/T) cm(3) molecule(-1) s(-1). The activation energy was found to vary with temperature from -1.33 to +0.15 kcal/mol. 相似文献
24.
Adsorption processes of thiophene and benzothiophene on pristine carbon nanotubes (CNTs), and on CNTs doped with Si or Ge, have been modeled with Density Functional. This is the first study on the chemical reactivity of such doped tubes. The calculated data suggest that the presence of silicon or germanium atoms in CNTs increases their reactivity toward thiophene, and benzothiophene. The adsorption of these species on pristine CNTs seems very unlikely to occur, while the addition products involving doped CNTs were found to be very stable, with respect to the isolated reactants, in terms of Gibbs free energy. Several of these adsorption processes were found to be significantly exergonic (ΔG < 0) in non-polar liquid phase. The results reported in this work suggest that Si and Ge defects on CNTs increase their reactivity toward unsaturated species, and could make them useful in the removal processes of aromatic sulfur compounds from oil-hydrocarbons. However, according to our results, CNTs doped with Si atoms are expected to be more efficient as aromatic sulfur compounds scavengers than those doped with Ge. These results also suggest that the presence of silicon and germanium atoms in the CNTs structures enhances their reactivity toward nucleophilic molecules, compared to pristine carbon nanotubes. 相似文献
25.
26.
Total Syntheses and In Vivo Quantitation of Novel Neurofuran and Dihomo‐isofuran Derived from Docosahexaenoic Acid and Adrenic Acid 下载免费PDF全文
Aurélien de la Torre Yiu Yiu Lee Attilio Mazzoni Dr. Alexandre Guy Dr. Valérie Bultel‐Poncé Dr. Thierry Durand Dr. Camille Oger Dr. Jetty Chung‐Yung Lee Dr. Jean‐Marie Galano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2442-2446
Neurofurans (NeuroFs) and dihomo‐isofurans (dihomo‐IsoFs) are produced in vivo by non‐enzymatic free‐radical pathways from docosahexaenoic and adrenic acids, respectively. As these metabolites are produced in minute amounts, their analyses in biological samples remain challenging. Syntheses of neurofuran and dihomo‐isofurans described are based on a pivotal strategy, thanks to an enantiomerically enriched intermediate, which allowed, for the first time, access to both families: the alkenyl and enediol. Owing to this formation, quantitation of specific NeuroF and dihomo‐IsoFs in biological samples was attainable. 相似文献
27.
The accurate prediction of rate constants for chemical reactions in solution, using computational methods, is a challenging task. In this work, a computational protocol designed to be a reliable tool in the study of radical‐molecule reactions in solution is presented. It is referred to as quantum mechanics‐based test for overall free radical scavenging activity (QM‐ORSA) because it is mainly intended to provide a universal and quantitative way of evaluating the free radical scavenging activity of chemical compounds. That is, its primary antioxidant activity. However, it can also be successfully applied to obtain accurate kinetic data for other chemical reactions in solution. The QM‐ORSA protocol has been validated by comparison with experimental results, and its uncertainties have been proven to be no larger than those arising from experiments. Further applications of QM‐ORSA are expected to contribute increasing the kinetic data for free radical‐molecule reactions relevant to oxidative stress, which is currently rather scarce. © 2013 Wiley Periodicals, Inc. 相似文献
28.
Aurlien deLaTorre Yiu Yiu Lee Camille Oger Per Torp Sangild Thierry Durand Jetty Chung‐Yung Lee Jean‐Marie Galano 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(24):6363-6366
The growing importance of lipidomics, and the interest of non‐enzymatic metabolites of polyunsaturated fatty acids (PUFAs) prompted us to initiate the synthesis of novel dihomo‐IsoF compounds. Such metabolites of adrenic acid, the main PUFA in white matter, were synthesized using a divergent approach based on an orthoester cyclization. LC‐MS/MS investigation on pig brains showed the potential of this novel biomarker for the first time, as a powerful new tool for brain lipid peroxidation assessment. 相似文献
29.
Oxygenated Metabolites of n‐3 Polyunsaturated Fatty Acids as Potential Oxidative Stress Biomarkers: Total Synthesis of 8‐F3t‐IsoP, 10‐F4t‐NeuroP and [D4]‐10‐F4t‐NeuroP 下载免费PDF全文
Dr. Alexandre Guy Dr. Camille Oger Dr. Johannes Heppekausen Dr. Cinzia Signorini Claudio De Felice Prof. Alois Fürstner Dr. Thierry Durand Dr. Jean‐Marie Galano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6374-6380
A wide variety of metabolic products of polyunsaturated fatty acids is of paramount importance for improving our medical knowledge in the field of oxidized lipids. Two novel metabolites of n‐3 polyunsaturated fatty acids, 8‐F3t‐IsoP and 10‐F4t‐NeuroP as well as a deuterated derivative thereof were synthesized based on an acetylenic intermediate. An original approach achieved lateral chain insertion of 8‐F3t‐IsoP by a ring‐closing alkyne metathesis/semi‐reduction strategy together with a temporary tether. 相似文献
30.