Frison Gilles, van der Rest Guillaume, Turecek Frantisek, Besson Thierry, Lemaire Joël, Maître Philippe, Chamot-Rooke Julia
Laboratoire des Mécanismes Réactionnels, Department of Chemistry, Ecole Polytechnique and CNRS, 91128 Palaiseau, France.
J Am Chem Soc. 2008 Nov 12;130(45):14916-7. doi: 10.1021/ja805257v. Epub 2008 Oct 21.
In this study, we propose the first spectroscopic structural characterization of c-type ions produced by ECD of a peptide. The structure of c-type ions formed by electron capture dissociation and the overall mechanism leading to their formation are still a question of debate. Depending on the mechanism, c-type ions have been proposed to have either an enol-imine structure (-C(OH)NH) or an amide one (-C(O)-NH2). Since these ions are isomeric, mass spectrometry only cannot discriminate between them, but infrared spectroscopy can bring experimental evidence and help determine which scheme is operative. Using the coupling between a tunable free electron laser and a FT-ICR mass spectrometer, we show that c-type ions have an amide structure, characterized by an IR signature of the C=O stretch at 1731 cm(-1). This result is particularly interesting from the perspective of the elucidation of the ECD mechanism.
在本研究中，我们提出了对肽段电子捕获解离（ECD）产生的c型离子的首次光谱结构表征。由电子捕获解离形成的c型离子的结构以及导致其形成的整体机制仍是一个有争议的问题。根据不同的机制，有人提出c型离子具有烯醇亚胺结构（-C(OH)NH）或酰胺结构（-C(O)-NH2）。由于这些离子是同分异构体，仅靠质谱无法区分它们，但红外光谱可以提供实验证据并有助于确定哪种结构起作用。通过将可调谐自由电子激光与傅里叶变换离子回旋共振（FT-ICR）质谱仪联用，我们表明c型离子具有酰胺结构，其特征在于C=O伸缩振动的红外特征峰位于1731 cm(-1)。从阐明ECD机制的角度来看，这一结果特别有趣。
