Photoelectron Transfer Dissociation Reveals Surprising Favorability of Zwitterionic States in Large Gaseous Peptides and Proteins.
Photoelectron Transfer Dissociation Reveals Surprising Favorability of Zwitterionic States in Large Gaseous Peptides and Proteins.
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DOI：
10.1021/jacs.7b02428
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发表时间：
2017-08-02
影响因子：
15
通讯作者：
Julian RR
中科院分区：
文献类型：
--
作者：
Bonner J;Lyon YA;Nellessen C;Julian RR
蛋白质在气相中的结构表征正变得越来越受欢迎，突出了需要更好地了解蛋白质在没有溶剂的情况下的行为。很明显，由于强的库仑和氢键相互作用，带电残基对气相中的结构产生重大影响。气体离子的净电荷很容易通过质谱法识别，但两性离子对或盐桥的存在以前更难检测。我们表明，这些网站可以揭示光诱导电子转移解离，产生特征的c和z离子，只有当两性离子物种存在。虽然以前对小分子的研究表明，两性离子对很少在气相中稳定，但我们现在证明电荷分离态在较大分子中更受欢迎。事实上，我们已经在肽和蛋白质中检测到两性离子对，其中净电荷等于碱性位点的数量，需要在非碱性残基处进行额外的质子化。例如，小蛋白泛素可以维持两性离子构象的所有电荷状态高达14+，尽管只有13个碱性位点。如果酸性和碱性残基都存在并且总电荷密度低，则本文检查的几乎所有肽/蛋白质都含有两性离子位点。这种偏向有利于电荷分离状态的努力，通过计算分析，不仅应考虑电荷状态的异构体，包括盐桥，但也质子化在非碱性残基模拟气态蛋白质具有重要的后果。
Structural characterization of proteins in the gas phase is becoming increasingly popular, highlighting the need for a greater understanding of how proteins behave in the absence of solvent. It is clear that charged residues exert significant influence over structures in the gas phase due to strong Coulombic and hydrogen-bonding interactions. The net charge for a gaseous ion is easily identified by mass spectrometry, but the presence of zwitterionic pairs or salt bridges has previously been more difficult to detect. We show that these sites can be revealed by photoinduced electron transfer dissociation, which produces characteristic c and z ions only if zwitterionic species are present. Although previous work on small molecules has shown that zwitterionic pairs are rarely stable in the gas phase, we now demonstrate that charge-separated states are favored in larger molecules. Indeed, we have detected zwitterionic pairs in peptides and proteins where the net charge equals the number of basic sites, requiring additional protonation at nonbasic residues. For example, the small protein ubiquitin can sustain a zwitterionic conformer for all charge states up to 14+, despite having only 13 basic sites. Virtually all of the peptides/proteins examined herein contain zwitterionic sites if both acidic and basic residues are present and the overall charge density is low. This bias in favor of charge-separated states has important consequences for efforts to model gaseous proteins via computational analysis, which should consider not only charge state isomers that include salt bridges but also protonation at nonbasic residues.
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影响因子：
4.9
作者：
Ly, Tony;Zhang, Xing;Julian, Ryan R.
通讯作者：
Julian, Ryan R.
影响因子：
4.2
作者：
Goeth, Melanie;Lermyte, Frederik;Pagel, Kevin
通讯作者：
Pagel, Kevin
影响因子：
15
作者：
Burke, Nicole L.;DeBlase, Andrew F.;Zwier, Timothy S.
通讯作者：
Zwier, Timothy S.
影响因子：
6.8
作者：
Benesch JL;Ruotolo BT
通讯作者：
Ruotolo BT
DOI：
10.1007/s13361-017-1594-2
发表时间：
2017-04
影响因子：
3.2
作者：
Ewing SA;Donor MT;Wilson JW;Prell JS
通讯作者：
Prell JS