羟基自由基诱导脂质过氧化反应的理论模型

Theoretical modeling of hydroxyl-radical-induced lipid peroxidation reactions.

作者信息

Tejero Ismael, Gonzalez-Lafont Angels, Lluch José M, Eriksson Leif A

机构信息

Departament de Química, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.

出版信息

J Phys Chem B. 2007 May 24;111(20):5684-93. doi: 10.1021/jp0650782. Epub 2007 May 2.

Abstract

The OH-radical-induced mechanism of lipid peroxidation, involving hydrogen abstraction followed by O2 addition, is explored using the kinetically corrected hybrid density functional MPWB1K in conjunction with the MG3S basis set and a polarized continuum model to mimic the membrane interior. Using a small nonadiene model of linoleic acid, it is found that hydrogen abstraction preferentially occurs at the mono-allylic methylene groups at the ends of the conjugated segment rather than at the central bis-allylic carbon, in disagreement with experimental data. Using a full linoleic acid, however, abstraction is correctly predicted to occur at the central carbon, giving a pentadienyl radical. The Gibbs free energy for abstraction at the central C11 is approximately 8 kcal/mol, compared to 9 kcal/mol at the end points (giving an allyl radical). Subsequent oxygen addition will occur at one of the terminal atoms of the pentadienyl radical fragment, giving a localized peroxy radical and a conjugated butadiene fragment, but is associated with rather high free energy barriers and low exergonicity at the CPCM-MPWB1K/MG3S level. The ZPE-corrected potential energy surfaces obtained without solvent effects, on the other hand, display considerably lower barriers and more exergonic reactions.

摘要

利用动力学校正的杂化密度泛函MPWB1K结合MG3S基组和极化连续介质模型来模拟膜内部,探索了羟基自由基引发的脂质过氧化机制,该机制涉及氢原子的夺取,随后是氧气的加成。使用亚油酸的一个小的壬二烯模型,发现氢原子夺取优先发生在共轭链段末端的单烯丙基亚甲基上,而不是在中心的双烯丙基碳上,这与实验数据不一致。然而,使用完整的亚油酸时,预测氢原子夺取会正确地发生在中心碳上,生成一个戊二烯基自由基。在中心C11处夺取氢原子的吉布斯自由能约为8千卡/摩尔,而在端点处为9千卡/摩尔(生成一个烯丙基自由基)。随后氧气加成将发生在戊二烯基自由基片段的一个末端原子上,生成一个局部化的过氧自由基和一个共轭丁二烯片段,但在CPCM - MPWB1K/MG3S水平上具有相当高的自由能垒和较低的放能性。另一方面,在没有溶剂效应的情况下获得的零点能校正势能面显示出明显更低的势垒和更多的放能反应。

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