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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Gas Phase Photochemistry Can Distinguish Different Conformations of Unhydrated Photoaffinity-Labeled Peptide Ions
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Gas Phase Photochemistry Can Distinguish Different Conformations of Unhydrated Photoaffinity-Labeled Peptide Ions

机译：气相光化学可以区分未水合的光亲和标记肽离子的不同构象

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摘要

Peptide containing the chromophore, benzophenone (as the amino acid, 4-benzoyl-phenylalanine (Bpa)), have been synthesized to explore the feasibility of gas-phase photochemical cross-linking to investigate the conformations of unsolvated peptides. The main product of UV irradiation of a BP-containing peptide is CO_2 loss from the peptide C terminus. To test whether decarboxylation results from hydrogen abstraction from acidic residues, we synthesized peptides designed to limit the contact between the Bpa and the peptide C terminus. Such contact is necessary for hydrogen abstraction. The peptide, Ac-Bpa-Ala_(10)-Lys, forms an extended α-helix in the gas phase, thus preventing the N-terminal Bpa from approaching the C terminus. In contrast, Ac-Bpa-Gly_(10)-Lys is a flexible peptide that can adopt multiple "random globule" conformations in the gas phase, some of which could allow contact between the termini and thus photoinduced reaction. On simultaneous UV irradiation of a mixture of both electrosprayed gas-phase peptides in a Fourier transform ion cyclotron resonance ion trap, the degree of decarboxylation is 50-fold less for the α-helical alanine-based peptide than for the flexible glycine-based peptide. The results suggest that intimate contact between the photoexcited Bpa and the C terminus is necessary for decarboxylation, implicating hydrogen atom abstraction as the photochemical mechanism. These results establish the feasibility of probing gas-phase peptide/protein ion conformations by photochemistry of photoaffinity-labeled ions.
机译：已经合成了含有发色团二苯甲酮（作为氨基酸的4-苯甲酰基-苯丙氨酸（Bpa））的肽，以探索气相光化学交联的可行性，以研究未溶剂化的肽的构象。紫外线照射含BP肽的主要产物是肽C末端的CO_2损失。为了测试脱羧是否是由于酸性残基的夺氢而导致的，我们合成了旨在限制Bpa和C肽末端接触的肽。这种接触对于夺氢是必需的。肽Ac-Bpa-Ala_（10）-Lys在气相中形成一个延伸的α-螺旋，从而防止N末端Bpa接近C末端。相反，Ac-Bpa-Gly_（10）-Lys是一种柔性肽，可以在气相中采用多个“随机小球”构象，其中某些构象可能使末端之间发生接触，从而引起光诱导的反应。在傅立叶变换离子回旋共振离子阱中同时对两种电喷雾气相肽的混合物进行紫外线照射时，基于α-螺旋丙氨酸的肽的脱羧度比基于柔性甘氨酸的肽的脱羧度低50倍。结果表明，光激发的Bpa和C末端之间的紧密接触对于脱羧是必要的，这暗示着氢原子的提取是光化学机理。这些结果建立了通过光亲和标记的离子的光化学探测气相肽/蛋白质离子构象的可行性。

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