Hydrogen atom attachment to histidine and tryptophan containing peptides in the gas phase

• Published in: Physical chemistry chemical physics : PCCP 2019, Vol.21 (22), p.11633-11641
• Main Authors: Asakawa, Daiki, Takahashi, Hidenori, Iwamoto, Shinichi, Tanaka, Koichi
• Format: Article
• Language: English
• Subjects: Attachment; Cleavage; Density functional theory; Fragmentation; Histidine; Hydrogen; Hydrogen atoms; Imidazole; Mass spectrometry; Peptides; Residues; Tryptophan; Vapor phases
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp00083f

In this study, we use a combination of tandem mass spectrometry and hydrogen radical-mediated fragmentation techniques to analyze the sequence of peptides. We focus on fragmentation induced by the attachment of hydrogen atoms to the histidine and tryptophan residue side-chains in the peptide that occurs in the gas-phase. The hydrogen atom attached to the imidazole and indole rings in the histidine and tryptophan residues, respectively, and the resulting intermediate experienced C α -C β bond cleavage. The detailed fragmentation mechanism is investigated by computational analysis using density functional theory. According to the results, hydrogen attachment occurs at the C-5 position in histidine and at the C-2 position in the tryptophan, which has a lower activation energy compared with the other positions and the resulting intermediate radicals yielded fragments due to C α -C β bond cleavage. For the peptides that contain the histidine and tryptophan residues, cleavages in the C α -C β and N-C α bonds occurred independently. Therefore, the method presented in this study is applicable when analyzing peptides that contain histidine and tryptophan residues. In this study, we focus on the gas-phase fragmentation induced by the attachment of hydrogen atoms to the histidine and tryptophan residue side-chains in the peptide that provides the fragment ions due to C α -C β bond cleavage.