Conformational Space and Stability of ETD Charge Reduction Products of Ubiquitin

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• 作者：Frederik Lermyte ; Mateusz Krzysztof Łącki&#8230
• 关键词：ETD ; PTR ; Charge reduction ; Ion mobility ; Protein conformation ; Ubiquitin
• 刊名：Journal of The American Society for Mass Spectrometry
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：28
• 期：1
• 页码：69-76
• 全文大小：
• 刊物主题：Analytical Chemistry; Biotechnology; Organic Chemistry; Proteomics; Bioinformatics;
• 出版者：Springer US
• ISSN：1879-1123
• 卷排序：28

文摘

Owing to its versatility, electron transfer dissociation (ETD) has become one of the most commonly utilized fragmentation techniques in both native and non-native top-down mass spectrometry. However, several competing reactions—primarily different forms of charge reduction—occur under ETD conditions, as evidenced by the distorted isotope patterns usually observed. In this work, we analyze these isotope patterns to compare the stability of nondissociative electron transfer (ETnoD) products, specifically noncovalent c/z fragment complexes, across a range of ubiquitin conformational states. Using ion mobility, we find that more extended states are more prone to fragment release. We obtain evidence that for a given charge state, populations of ubiquitin ions formed either directly by electrospray ionization or through collapse of more extended states upon charge reduction, span a similar range of collision cross-sections. Products of gas-phase collapse are, however, less stabilized towards unfolding than the native conformation, indicating that the ions retain a memory of previous conformational states. Furthermore, this collapse of charge-reduced ions is promoted if the ions are ‘preheated’ using collisional activation, with possible implications for the kinetics of gas-phase compaction.