Gas-phase conformation-specific photofragmentation of proline-containing peptide ions
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- Kim, T., Valentine, S.J., Clemmer, D.E. et al. J Am Soc Mass Spectrom (2010) 21: 1455. doi:10.1016/j.jasms.2010.04.007
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Singly-protonated proline-containing peptides with N-terminal arginine are photodissociated with vacuum ultraviolet (VUV) light in an ESI linear ion trap/orthogonal-TOF (LIT/o-TOF). When proline is the nth residue from the N-terminus, unusual bn + 2 and an + 2 ions are observed. Their formation is explained by homolytic cleavage of the Cα− C bond in conjunction with a rearrangement of electrons and an amide hydrogen. The latter is facilitated by a proline-stabilized gas-phase peptide conformation.