Density functional theory study of possible mechanisms of folic acid photodecomposition
Density functional theory study of possible mechanisms of folic acid photodecomposition
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DOI：
10.1016/j.jphotochem.2009.07.025
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发表时间：
2009-11-15
影响因子：
4.3
通讯作者：
Soniat, Michael
中科院分区：
文献类型：
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作者：
Martin, Christopher B.;Walker, David;Soniat, Michael
为了进一步了解叶酸光分解的厌氧机理，在B3 LYP/6-31+G*//B3 LYP/6- 31 G * 水平上对叶酸、蝶呤和对氨基苯甲酸（PABA）进行了理论计算.在350 nm处初始激发蝶呤环后，发生从PABA环到蝶呤的能量有利的分子内电子转移反应（使用水作为介电常数的~ 11.9 kcal/mol：PCM）。所得两性离子物质然后经历放热的异裂键裂解，其导致PABA和蝶呤环之间的键断裂（~ 15.9kcal/mol）。然后假设蝶呤自由基进行氧化以产生报道的6-羧基蝶呤。自然群体分析（NPA）油所有的自由基和自由基离子的结构，以建立合理的共振结构用于拟议的叶酸的光解机制，通过确定最合理的位置的自由基和离子油的芳香环。然后提出了一个建议的机制，在没有氧气的情况下，叶酸的光解提出的DFT计算的基础上，同意与目前现有的数据，这一过程。(C)2009 Elsevier B. V.保留所有权利。
Density functional theory (DFT) Calculations were performed at the B3LYP/6-31+G*//B3LYP/6-31G* level of theory oil a series of folic acid, pterin, and p-aminobenzoic acid (PABA) models to further understand the anaerobic mechanism of folic acid photodecomposition. After initial excitation of the pterin ring at 350 nm, an energetically favored intramolecular electron-transfer reaction occurs from the PABA ring to the pterin (-11.9 kcal/mol: PCM using water as the dielectric constant). The resulting zwitterionic species call then undergo an exothermic heterolytic bond cleavage which results in bond fragmentation between the PABA and pterin rings (-15.9 kcal/mol). The pterin radical is then hypothesized to undergo oxidation to produce the reported 6-carboxypterin. Natural population analyses (NPA) were performed oil all radical and radical ion structures to establish reasonable resonance structures used in the proposed photodecomposition mechanism of folic acid by determining the most reasonable location of the radicals and ions oil the aromatic rings. A proposed mechanism of the photolysis of folic acid in the absence of oxygen is then proposed based upon the DFT calculations which agree well with the currently existing data of this process. (C) 2009 Elsevier B.V. All rights reserved.