Dissociation Chemistry of Hydrogen-Deficient Radical Peptide Anions
Dissociation Chemistry of Hydrogen-Deficient Radical Peptide Anions
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DOI：
10.1007/s13361-011-0318-2
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发表时间：
2012-03-01
影响因子：
3.2
通讯作者：
Julian, Ryan R.
中科院分区：
文献类型：
--
作者：
Moore, Benjamin;Sun, Qingyu;Julian, Ryan R.
研究了阴离子去质子化缺氢自由基多肽的断裂化学。碳碘键与266 nm光的均裂光解离用于产生自由基物质，其随后经受碰撞活化以诱导进一步解离。电荷在片段化化学中不起核心作用;因此，通过自由基定向解离片段化的去质子化肽通过先前已报道的质子化肽的机制来进行。然而，电荷极性确实影响肽的整体片段化。例如，不存在移动的质子有利于单去质子化肽的自由基定向解离。类似地，在N-末端起始的有利解离机制对于其中N-末端未质子化（其抑制该机制）的阴离子肽更显著。此外，含有碳-碘键的阴离子肽的碰撞活化导致均裂裂解和自由基物质的产生，这对于质子化肽没有观察到，推测是由于来自较低能量解离通道的竞争。最后，对于多重去质子化的自由基肽，电子脱离成为一个竞争性的通道，在初始的光活化和随后的碰撞激活的自由基。可能的机制，可能占这种新的碰撞诱导电子脱离进行了讨论。
The fragmentation chemistry of anionic deprotonated hydrogen-deficient radical peptides is investigated. Homolytic photodissociation of carbon-iodine bonds with 266 nm light is used to generate the radical species, which are subsequently subjected to collisional activation to induce further dissociation. The charges do not play a central role in the fragmentation chemistry; hence deprotonated peptides that fragment via radical directed dissociation do so via mechanisms which have been reported previously for protonated peptides. However, charge polarity does influence the overall fragmentation of the peptide. For example, the absence of mobile protons favors radical directed dissociation for singly deprotonated peptides. Similarly, a favorable dissociation mechanism initiated at the N-terminus is more notable for anionic peptides where the N-terminus is not protonated (which inhibits the mechanism). In addition, collisional activation of the anionic peptides containing carbon-iodine bonds leads to homolytic cleavage and generation of the radical species, which is not observed for protonated peptides presumably due to competition from lower energy dissociation channels. Finally, for multiply deprotonated radical peptides, electron detachment becomes a competitive channel both during the initial photoactivation and following subsequent collisional activation of the radical. Possible mechanisms that might account for this novel collision-induced electron detachment are discussed.