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- Day 2, May 16（Wed.） Poster
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2P-45（2B-O3-M-1835） PDF
Spontaneous Isomerization of Peptide Cation Radical [DAAR + H]+ Following ETD Revealed by UV-Vis Photodissociation Action Spectroscopy
Electron transfer dissociation of multiply charged peptide ions produces radical [z + H]+ ions by N-Cα bond cleavage. The [z + H]+ ions are usually presented as N-terminally deaminated radicals with the charge being carried by a protonated basic residue. However, recent studies of UV-Vis photodissociation action spectroscopy suggested that [z + H]+ ions spontaneously isomerize depending on constituent amino acid residues. In this study we focused on the peptide that contains Asp residue and investigated its isomerization. The [DAAR + H]+ ions was generated by ETD in the ion trap, selected by mass and exposed to laser pulses generated by an Nd:YAG laser source equipped with an optical parametric oscillator. The intensities of the resulting fragment ions were monitored as a function of wavelength, normalized to the laser output power at each wavelength, and plotted to provide action spectra. A comparison of the action spectrum with the calculated absorption spectra indicates that the [DAAR + H]+ ions produced by ETD did not consist of a single species but comprised a mixture of radical isomers. It was concluded that Asp residue facilitates hydrogen atom migrations in [z + H]+ cation-radicals occurring spontaneously upon electron transfer dissociation of peptide dications.