Heterolytic N-Cα bond cleavage in electron capture and transfer dissociation of peptide cations.

摘要: Mass spectrometry techniques employing electron capture and transfer dissociation represent powerful approaches for the analysis of biological samples. Despite routine employment in analytical fields, underlying physical processes dictating peptide fragmentation remain less understood. Among most accepted mechanisms, Cornell proposal McLafferty postulates that homolytic cleavage N-C-alpha bonds located backbone occurs on right (C-terminal) side a hydrogen acceptor carbonyl group. Here, we illustrate an alternative "enol" mechanism, based hetetolytic bond left (N-terminal) group, not only is thermodynamically viable but also often represents energetically preferred route.