Hydroxyproline is a common variation of proline, with diverse biological roles. The hydroxylation of proline gives rise to several (natural and/or synthetic) isomeric forms, including both positional isomers and stereoisomers. While mass spectrometry is widely touted as a very selective analytical technique, the identification of closely related isomers often poses a challenge. In these cases, allied technologies become helpful in providing full characterization. Here, infrared multiple photon dissociation (IRMPD) spectroscopy is used to differentiate between three isomers, namely cis-3-hydroxyproline, cis-4-hydroxyproline, and trans-4-hydroxyproline. In contrast to the protonated species which show only minor variations in their IRMPD spectra, lithiated species were found to display significant spectral differences, making their differentiation more straightforward. The conformational origin of these spectral differences was investigated by complementary quantum-chemical calculations.

中文翻译：

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羟脯氨酸异构体的组合红外光谱和计算化学研究。

羟脯氨酸是脯氨酸的常见变体，具有多种生物学作用。脯氨酸的羟基化产生几种（天然和/或合成）异构体形式，包括位置异构体和立体异构体。尽管质谱被广泛吹捧为一种非常有选择性的分析技术，但鉴定密切相关的异构体通常会带来挑战。在这些情况下，相关技术将有助于提供完整的特性。在这里，红外多光子离解（IRMPD）光谱用于区分三种异构体，即顺式3-羟脯氨酸，顺式4-羟脯氨酸和反式-4-羟脯氨酸。与质子化物种的IRMPD光谱仅显示微小变化相比，锂化物种显示出明显的光谱差异，使他们的区分更加直接。通过互补的量子化学计算研究了这些光谱差异的构象起源。