Differentiation of peptide isomers by excited-state photodissociation and ion–molecule interactions
Differentiation of peptide isomers by excited-state photodissociation and ion–molecule interactions
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通过激发态光解和离子-分子相互作用区分肽异构体
DOI：
10.1039/d0cp04111d
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发表时间：
2020
影响因子：
3.3
通讯作者：
Julian, Ryan R.
中科院分区：
文献类型：
--
作者：
Van Orman, Brielle L.;Wu, Hoi-Ting;Julian, Ryan R.
溶蚀效应最常与溶液相现象联系在一起。然而，在气相中，溶剂的缺乏导致分子内溶剂化，这种溶剂化可以由包括氢键和离子偶极子相互作用在内的强作用力驱动。在这里，我们研究是否在一个肽的单一残基异构化导致结构变化足以改变光的吸收附加的发色团。通过在质谱仪内进行实验，我们可以很容易地监测光解离产率，作为发色团激发的读数。在266 nm和213 nm光激发下，检测了一系列不同长度、不同电荷态、不同异构残基位置和特性的多肽。结果表明，分子内溶剂化的差异在许多情况下确实会导致溶剂色偏移。此外，光激发后的主要产物是自由基。离子-分子与这种自由基和不定式氧的反应被监测，也发现作为同分异构体状态的函数而变化。在这种情况下，分子内溶剂化的差异改变了活性自由基的可用性。总的来说，结果表明，单个氨基酸的微小变化可以影响整体结构集合，足以改变多个气相反应的效率。
Solvochromatic effects are most frequently associated with solution-phase phenomena. However, in the gas phase, the absence of solvent leads to intramolecular solvation that can be driven by strong forces including hydrogen bonds and ion–dipole interactions. Here we examine whether isomerization of a single residue in a peptide results in structural changes sufficient to shift the absorption of light by an appended chromophore. By carrying out the experiments inside a mass spectrometer, we can easily monitor photodissociation yield as a readout for chromophore excitation. A series of peptides of different lengths, charge states, and position and identity of the isomerized residue were examined by excitation with both 266 and 213 nm light. The results reveal that differences in intramolecular solvation do lead to solvochromatic shifts in many cases. In addition, the primary product following photoexcitation is a radical. Ion–molecule reactions with this radical and adventitious oxygen were monitored and also found to vary as a function of isomeric state. In this case, differences in intramolecular solvation alter the availability of the reactive radical. Overall, the results reveal that small changes in a single amino acid can influence the overall structural ensemble sufficient to alter the efficiency of multiple gas-phase reactions.