Diketopiperazine and oxazolone structures: an investigation of the influence of the third residue on b2 structure in QAXIG and NAXIG analogues
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Series/Report no.:2012 Edward F. Hayes Graduate Research Forum. 27th
Variables impacting the formation of b2 ions along the "diketopiperazine" pathway are explored using IRMPD action spectroscopy and gas-phase hydrogen-deuterium exchange for a series of QAXIG and NAXIG pentapeptide analogues. The b2 ion is a unique fragment in peptide fragmentation because it can be one of two main isobaric structures, the diketopiperazine or the oxazolone. The formation of these has been thought to be largely governed by the identity of the first two residues at the N-terminus of the peptide. We show here that a basic residue is not required for the formation of the diketopiperazine structure, as the amide side chain of a glutamine or asparagine residue is implicated in the formation of this structure. Furthermore, the length of the peptide and identity of the third residue of the peptide is shown for the first time to influence the diketopiperazine:oxazolone ratio.
Mathematical and Physical Sciences: 1st Place (The Ohio State University Edward F. Hayes Graduate Research Forum)
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