Institute of Molecules and Crystals Physics, Ufa Research Center of Russian Academy of Sciences, Prospekt Oktyabrya 151, 450075, Ufa, Russia.
Rapid Commun Mass Spectrom. 2012 Apr 15;26(7):828-34. doi: 10.1002/rcm.6156.
Dipeptide molecules are good model systems for investigation of resonant reactions of low-energy electrons with proteins. The present work is devoted to the study of the processes of formation and fragmentation of negative ions in aliphatic dipeptides glycyl-glycine and glycyl-alanine. The metastable decays of negative ions were detected in these objects, and have been investigated with the aim of clarification of the mechanisms of fragmentation.
The effective yield curves for negative ions as functions of electron energy were obtained using a magnetic sector mass spectrometer rebuilt for generation and detection of negative ions. For analysis of the observed metastable decays statistical and thermochemical approaches have been used.
The ions structures, the enthalpies of formation of neutral and charged particles, and the rate constants of dissociative reactions have been found.
Comparison of the experimental results with theoretical data leads to the conclusion that metastable ion decay proceeds with minimal structural changes avoiding complicated rearrangements and isomerization processes.
二肽分子是研究低能电子与蛋白质共振反应的良好模型体系。本工作致力于研究脂肪族二肽甘氨酰-甘氨酸和甘氨酰-丙氨酸中负离子形成和碎裂的过程。在这些物体中检测到负离子的亚稳衰变，并进行了研究，目的是澄清碎裂的机制。
使用为生成和检测负离子而重建的磁扇形质谱仪，获得了作为电子能量函数的负离子的有效产率曲线。为了分析观察到的亚稳衰变，使用了统计和热化学方法。
发现了离子结构、中性和带电粒子的生成焓以及离解反应的速率常数。
将实验结果与理论数据进行比较得出结论，亚稳离子衰变以最小的结构变化进行，避免了复杂的重排和异构化过程。
