Electron transfer dissociation of multiply protonated and fixed charge disulfide linked polypeptides
Electron transfer dissociation of multiply protonated and fixed charge disulfide linked polypeptides
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DOI：
10.1016/j.ijms.2007.01.017
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发表时间：
2007-09-01
影响因子：
1.8
通讯作者：
McLuckey, Scott A.
中科院分区：
文献类型：
--
作者：
Gunawardena, Harsha P.;Gorenstein, Lev;McLuckey, Scott A.
多重质子化的二硫键连接的肽和固定电荷的类似物已进行电子转移离子/离子反应，以检查过量质子在诱导电子转移解离中二硫键裂解中的作用。其中所有过量电荷都是由于固定电荷位点（即，季铵基团）比完全质子化的物质显示出稍微更多的二硫键断裂。这一观察结果反对一种机制的主要作用，该机制需要氢转移到二硫键作为其裂解的先决条件。有趣的是，具有混合阳离子位点（一个或多个过量质子和一个或多个固定电荷侧链）的物种显示出比相应的完全质子化或完全衍生化物种更低的二硫键裂解倾向。这种观察结果不太可能通过直接电子转移到库仑稳定的二硫键来解释，因为预计带电位点的身份不会在稳定程度中发挥重要作用。结果似乎是最合理的基础上的“通过键电子转移”机制的西蒙斯等人，结合电荷承载位点之间的速率限制分子内电子转移。电荷位点之间的分子内电子转移可以在介导电子从初始电子捕获位点移动到电子从其转移到二硫化物反键轨道的位点中起作用。(C)2007 Elsevier B. V.保留所有权利。
Multiply protonated disulfide linked peptides and fixed charged analogs have been subjected to electron transfer ion/ion reactions to examine the role of excess protons in inducing cleavage of the disulfide bond in electron transfer dissociation. Systems in which all of the excess charge was due to fixed charge sites (i.e., quaternary ammonium groups) showed somewhat more disulfide bond cleavage than the fully protonated species. This observation argues against a major role for a mechanism that requires hydrogen transfer to the disulfide bond as a prerequisite for its cleavage. Interestingly, species with mixed cation sites (one or more excess protons and one or more fixed charge side chains) showed lower propensities for disulfide bond cleavage than either the corresponding fully protonated or fully derivatized species. This observation is not likely to be accounted for by direct electron transfer to a Coulomb stabilized disulfide bond because the identities of the charge bearing sites are not expected to play a significant role in the degree of stabilization. The results appear to be best rationalized on the basis of the 'through bond electron transfer' mechanism of Simons et al., in conjunction with rate limiting intramolecular electron transfer(s) between charge bearing sites. Intramolecular electron transfer between charge sites can play a role in mediating electron movement from the site of initial electron capture to the site from which an electron is transferred to the disulfide anti-bonding orbital. (C) 2007 Elsevier B.V. All rights reserved.