Theoretical study of the main fragmentation pathways for protonated glycylglycine.
Theoretical study of the main fragmentation pathways for protonated glycylglycine.
复制标题
质子化甘氨酰甘氨酸主要裂解途径的理论研究。
DOI：
--
复制
发表时间：
2001
影响因子：
2
通讯作者：
S. Suhai
中科院分区：
文献类型：
--
作者：
B. Paizs;S. Suhai
对质子化甘氨酰甘氨酸进行了量子化学和 RRKM 计算，以确定导致 a1 和 y1 离子形成的主要断裂途径的原子细节。考虑了两种可能的机制。第一条路径导致消除作为所形成的 y1 离子的中性对应物的氮丙啶酮。我们的计算表明，该途径具有相对较高的阈值能量（48.6 kcal/mol），并且即使在内能较大时，相应的单分子速率常数也相当小。然而，从能量学和动力学的角度来看，本文提出的另一种途径（a1-y1）似乎比上述“氮丙啶酮”途径更受青睐。 “a1-y1”途径导致同时形成 a1 和 y1 离子，其比例取决于特定二肽的碎片物质的能量分布。然而，即使 y1 离子通过“a1-y1”途径形成，消除的相应中性子也不具有应变的环状氮丙啶酮结构。相反，在两步过程中，CO 和 NHCH2 的形成导致中性产物比氮丙啶酮更受青睐。本文重新评估的现有实验数据为“a1-y1”途径提供了支持。
Quantum chemical and RRKM calculations were carried out on protonated glycylglycine in order to determine the atomic details of the main fragmentation pathways leading to formation of a1 and y1 ions. Two possible mechanisms were considered. The first path results in elimination of aziridinone as a neutral counterpart of the y1 ion formed. Our calculations show that this pathway has a relatively high threshold energy (48.6 kcal/mol) and the corresponding unimolecular rate constants are quite small even at large internal energy. An alternative pathway (a1-y1) proposed in the present paper seems, however, to be favored against the above 'aziridinone' one from the points of view of both energetics and kinetics. The 'a1-y1' pathway leads to simultaneous formation of a1 and y1 ions, the ratio of which depends on the energy distribution of the fragmenting species for a particular dipeptide. However, even if y1 ions are formed via the 'a1-y1' pathway, the corresponding neutrals eliminated do not have a strained cyclic aziridinone structure. Instead, in a two-step process, CO and NHCH2 are formed leading to neutral products energetically more favored than aziridinone. The available experimental data reevaluated in the present paper lend support to the 'a1-y1' pathway.
DOI：
10.1002/bms.1200160119
发表时间：
1988-10-01
期刊：
BIOMEDICAL AND ENVIRONMENTAL MASS SPECTROMETRY
影响因子：
--
作者：
BIEMANN, K
通讯作者：
BIEMANN, K