The peptides XxxProGlyGly (Xxx = His, Lys, Arg) were incubated in ethanol at various temperatures. Solution-phase fragmentation of the parent peptide to yield XxxPro was monitored by electrospray ionization-ion mobility spectrometry-mass spectrometry. The presence of an induction period indicates that some sequence of parent conformations must be involved, but they are invisible in this experiment: electrosprayed XxxProGlyGly all yield the same conformation of [XxxProGlyGly+H]+ in the gas phase. The data were fit by assuming a series of intermediates separated by activation barriers of equal height; the number of intermediates is optimized to give the best fitting statistics over the full set of data. Arrhenius analysis of the determined rate constants yields ΔH‡, ΔS‡, and ΔG‡ for each peptide.

Measurement of the activation parameters for fragmentation at penultimate proline in three tetrapeptides

255th National Meeting (2018)

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