Journal of the American Society for Mass Spectrometry

, Volume 21, Issue 8, pp 1455-1465

First online:

Gas-phase conformation-specific photofragmentation of proline-containing peptide ions

  • Tae-Young KimAffiliated withDepartment of Chemistry, Indiana University
  • , Stephen J. ValentineAffiliated withDepartment of Chemistry, Indiana University
  • , David E. ClemmerAffiliated withDepartment of Chemistry, Indiana University
  • , James P. ReillyAffiliated withDepartment of Chemistry, Indiana University Email author 


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 b n + 2 and a n + 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.