Ultraviolet photodissociation or UVPD is an increasingly popular option for tandem-mass spectrometry experiments. UVPD can be carried out at many wavelengths, and it is important to understand how the results will be impacted by this choice. Here, we explore the utility of 213 nm photons for initiating bond-selective fragmentation. It is found that bonds previously determined to be labile at 266 nm, including carbon-iodine and sulfur-sulfur bonds, can also be cleaved with high selectivity at 213 nm. In addition, many carbon-sulfur bonds that are not subject to direct dissociation at 266 nm can be selectively fragmented at 213 nm. This capability can be used to site-specifically create alaninyl radicals that direct backbone dissociation at the radical site, creating diagnostic d-ions. Furthermore, the additional carbon-sulfur bond fragmentation capability leads to signature triplets for fragmentation of disulfide bonds. Absorption of amide bonds can enhance dissociation of nearby labile carbon-sulfur bonds and can be used for stochastic backbone fragmentation typical of UVPD experiments at shorter wavelengths. Several potential applications of the bond-selective fragmentation chemistry observed at 213 nm are discussed.

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紫外光解离或UVPD是串联质谱实验中越来越受欢迎的选择。UVPD可以在许多波长下进行，因此了解此选择将如何影响结果非常重要。在这里，我们探索了213 nm光子用于启动键选择性断裂的效用。发现先前确定在266 nm处不稳定的键，包括碳-碘键和硫-硫键，也可​​以在213 nm处高选择性地裂解。此外，许多未在266 nm处直接解离的碳-硫键可以在213 nm处选择性断裂。该功能可用于位点特异性地形成丙氨酸基团，该基团将主链解离引导至自由基位点，从而产生诊断性的d离子。此外，额外的碳硫键断裂能力会导致特征性三联体断裂二硫键。酰胺键的吸收可增强附近不稳定的碳-硫键的离解，可用于较短波长的UVPD实验中典型的随机骨架断裂。讨论了在213 nm观察到的键选择性断裂化学的几种潜在应用。

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