Department of Chemistry and Centre for Research in Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3.
Org Biomol Chem. 2011 Nov 7;9(21):7384-92. doi: 10.1039/c1ob05968h. Epub 2011 Sep 6.
Two different chemical methods have been used to form glutathione radical cations: (1) collision-induced dissociations (CIDs) of the ternary complex [Cu(II)(tpy)(M)]˙(2+) (M = GSH, tpy = 2,2':6',2''-terpyridine) and (2) homolysis of the S-NO bond in protonated S-nitrosoglutathione. The radical cations, M˙(+), were trapped and additional CIDs were performed. They gave virtually identical CID spectra, suggesting a facile interconversion between initial structures prior to fragmentation. DFT calculations at the B3LYP/6-31++G(d,p) level of theory have been used to study interconversion between different isomers of the glutathione radical cation and to examine mechanisms by which these ions fragment. The N-terminal α-carbon-centred radical cation, strongly stabilized by the captodative effect, is at the global minimum, which is 8.5 kcal mol(-1) lower in enthalpy than the lowest energy conformer of the S-centred radical cation. The barrier against interconversion is 18.1 kcal mol(-1) above the S-centred radical.
（1）三元配合物[Cu(II)(tpy)(M)]˙(2+)（M = GSH，tpy = 2,2':6',2''-三联吡啶）的碰撞诱导解离（CID），以及（2）质子化 S-亚硝酰谷胱甘肽中 S-NO 键的均裂。自由基阳离子，M˙(+)，被捕获并进行了额外的 CID。它们给出了几乎相同的 CID 谱，表明在碎片化之前初始结构之间易于相互转换。在 B3LYP/6-31++G(d,p)理论水平上进行的密度泛函理论（DFT）计算用于研究谷胱甘肽自由基阳离子不同异构体之间的转换，并研究这些离子碎片化的机制。N-末端α-碳中心自由基阳离子受到加电子效应的强烈稳定，处于全局最小值，其焓低于 S-中心自由基阳离子的最低能量构象低 8.5 kcal mol(-1)。S-中心自由基阳离子之上的相互转换的能垒为 18.1 kcal mol(-1)。
