Homayoon Zahra, Macaluso Veronica, Martin-Somer Ana, Muniz Maria Carolina Nicola Barbosa, Borges Itamar, Hase William L, Spezia Riccardo
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061 USA.
Phys Chem Chem Phys. 2018 Jan 31;20(5):3614-3629. doi: 10.1039/c7cp06818b.
Gas phase unimolecular fragmentation of the two model doubly protonated tripeptides threonine-isoleucine-lysine (TIK) and threonine-leucine-lysine (TLK) is studied using chemical dynamics simulations. Attention is focused on different aspects of collision induced dissociation (CID): fragmentation pathways, energy transfer, theoretical mass spectra, fragmentation mechanisms, and the possibility of distinguishing isoleucine (I) and leucine (L). Furthermore, discussion is given regarding the differences between single collision CID activation, which results from a localized impact between the ions and a colliding molecule N, and previous thermal activation simulation results; Z. Homayoon, S. Pratihar, E. Dratz, R. Snider, R. Spezia, G. L. Barnes, V. Macaluso, A. Martin-Somer and W. L. Hase, J. Phys. Chem. A, 2016, 120, 8211-8227. Upon thermal activation unimolecular fragmentation is statistical and in accord with RRKM unimolecular rate theory. Simulations show that in collisional activation some non-statistical fragmentation occurs, including shattering, which is not present when the ions dissociate statistically. Products formed by non-statistical shattering mechanisms may be related to characteristic mass spectrometry peaks which distinguish the two isomers I and L.
利用化学动力学模拟研究了两种模型双质子化三肽苏氨酸 - 异亮氨酸 - 赖氨酸（TIK）和苏氨酸 - 亮氨酸 - 赖氨酸（TLK）的气相单分子裂解。注意力集中在碰撞诱导解离（CID）的不同方面：裂解途径、能量转移、理论质谱、裂解机制以及区分异亮氨酸（I）和亮氨酸（L）的可能性。此外，还讨论了离子与碰撞分子N之间局部碰撞导致的单次碰撞CID活化与先前热活化模拟结果之间的差异；Z. 霍马永、S. 普拉蒂哈尔、E. 德拉茨、R. 斯奈德、R. 斯佩齐亚、G. L. 巴恩斯、V. 马卡卢索、A. 马丁 - 索默和W. L. 哈斯，《物理化学杂志A》，2016年，120卷，8211 - 8227页。在热活化时，单分子裂解是统计性的，符合RRKM单分子速率理论。模拟表明，在碰撞活化中会发生一些非统计性裂解，包括破碎，而当离子进行统计性解离时不存在这种情况。由非统计性破碎机制形成 的产物可能与区分两种异构体I和L的特征质谱峰有关。
