Tyrosine side-chain catalyzed proton transfer in the YG a₂ ion revealed by theory and IR spectroscopy in the 鈥榝ingerprint鈥?and XH (X = C, N, O) stretching regions

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• 作者：Benjamin J. Bythell^a ; Oscar Hernandez^b ; Vincent Steinmetz^b ; Bé ; la Paizs^a ; ^{B.Paizs@dkfz-heidelberg.de} ; Philippe Maî ; tre^b ; ^{Philippe.Maitre@u-psud.fr}
• 关键词：Peptide Fragmentation ; CID ; Gas-phase ion structure ; IRMPD spectroscopy ; Tandem mass spectrometry ; Density functional theory
• 刊名：International Journal of Mass Spectrometry
• 出版年：2012
• 期刊代码：43_13873806
• 类别：ch
• 出版时间：15 April, 2012
• 卷：316-318
• 期：Complete
• 页码：227-234
• 文件大小：820 K

摘要

IRMPD spectroscopy in the 鈥榝ingerprint鈥?and XH (X = C, N, O) stretching regions was used to probe the structures of the YG a₂ ions generated from protonated YGGFL and doubly protonated YGGFLR. Our experiments indicate a mixture of cyclic and rearranged 鈥榠mine-amide鈥?structures. The cyclic isomer is generated from the initially formed protonated imine terminated linear structure by head-to-tail cyclization. Proton transfer between the secondary amine of the ring and the amide nitrogen followed by ring opening leads to the rearranged 鈥榠mine-amide鈥?isomer. Quantum chemical calculations demonstrate that this proton transfer is catalyzed by the tyrosine side chain ring for the YG a₂ ion. Isomer specific IRMPD bands observed in the two spectral regions clearly show the presence of the cyclic and rearranged 鈥榠mine-amide鈥?isomers, the latter being characterized by an IR signature at 鈭?545 cm^鈭? associated with the C-terminal amide NH₂ asymmetric stretch.