Anusiewicz Iwona, Berdys-Kochanska Joanna, Skurski Piotr, Simons Jack
Department of Chemistry and Henry Eyring Center for Theoretical Chemistry, University of Utah, Salt Lake City, Utah 84112, USA.
J Phys Chem A. 2006 Feb 2;110(4):1261-6. doi: 10.1021/jp052914j.
Ab initio electronic structure methods, including stabilization method tools for handling electronically metastable states, are used to treat a model system designed to probe the electron-transfer event characterizing electron-transfer dissociation (ETD) mass spectroscopic studies of peptides. The model system consists of a cation H(3)C-(C=O)NH-CH(2)-CH(2)-NH(3)(+), containing a protonated amine site and an amide site, that undergoes collisions with a CH(3)(-) anion. Cross-sections for electron transfer from CH(3)(-) to the protonated amine site are shown to exceed those for transfer to the Coulomb-stabilized amide site by 2 orders of magnitude. Moreover, it is shown that the fates of the amine-attached and amide-attached species are similar in that both eventually lead to the same carbon-centered radical species H(3)C-((*)C-OH)NH-CH(2)-CH(2)-NH(2), although the reaction pathways by which the two species produce this radical are somewhat different. The implications for understanding peptide fragmentation patterns under ETD conditions are also discussed in light of this work's findings.
从头算电子结构方法，包括用于处理电子亚稳态的稳定化方法工具，被用于处理一个模型系统，该系统旨在探究表征肽的电子转移解离（ETD）质谱研究的电子转移事件。该模型系统由一个阳离子H(3)C-(C=O)NH-CH(2)-CH(2)-NH(3)(+)组成，它含有一个质子化胺位点和一个酰胺位点，与一个CH(3)(-)阴离子发生碰撞。从CH(3)(-)到质子化胺位点的电子转移截面显示比转移到库仑稳定的酰胺位点的截面大2个数量级。此外，研究表明，与胺相连和与酰胺相连的物种的命运相似，尽管这两种物种产生该自由基的反应途径略有不同，但最终都会导致形成相同的以碳为中心的自由基物种H(3)C-((*)C-OH)NH-CH(2)-CH(2)-NH(2)。鉴于这项工作的发现，还讨论了对理解ETD条件下肽片段化模式的影响。
