Macdonald Brandon I, Thachuk Mark
Chemistry Department, University of British Columbia, Vancouver, BC, Canada.
Rapid Commun Mass Spectrom. 2008 Sep;22(18):2946-54. doi: 10.1002/rcm.3697.
Pathways for proton transfer in the histidylglycine cation are examined in the gas-phase environment with the goal of understanding the mechanism by which protons may become mobile in proteins with basic amino acid residues. An extensive search of the potential energy surface is performed using density functional theory (DFT) methods. After corrections for zero-point energy are included, it is found that all the lowest energy barriers for proton transfer between the N-terminus and the imidazole ring have heights of only a few kcal/mol, while those between the imidazole ring and the backbone amide oxygen have heights of approximately 15 kcal/mol when the proton is moving from the ring to the backbone and only a few kcal/mol when moving from the backbone to the imidazole ring. In mass spectrometric techniques employing collision-induced dissociation to dissociate protein complex ions or to fragment peptides, these barriers can be overcome, and the protons mobilized.
在气相环境中研究了组氨酰甘氨酸阳离子中质子转移的途径，目的是了解质子在含有碱性氨基酸残基的蛋白质中可能变得可移动的机制。使用密度泛函理论（DFT）方法对势能面进行了广泛搜索。在考虑零点能校正后，发现N端和咪唑环之间质子转移的所有最低能量势垒高度仅为几千卡/摩尔，而当质子从环向主链移动时，咪唑环和主链酰胺氧之间的能量势垒高度约为15千卡/摩尔，而从主链向咪唑环移动时仅为几千卡/摩尔。在采用碰撞诱导解离来解离蛋白质复合离子或使肽片段化的质谱技术中，这些势垒可以被克服，质子也能被移动。
