Disulfide vs. Backbone Bond Cleavage in Electron Capture Dissociation of Proteins

摘要

The competition between disulfide and backbone cleavage in ECD is puzzling. Our data shows no evidence for disulfide bond cleavage by ECD alone. However, with vibrational excitation, fragment ions from backbone cleavage in regions of the protein that are bridged by disulfide bonds are observed. For all proteins studied, these fragment ions increased in abundance with increasing vibrational excitation. Moreover, because it is unlikely that a single electron can simultaneously cleave a total of three distant bonds in aprotinin (two disulfides and one backbone), we propose that vibrational excitation is largely responsible for disulfide bond cleavage in multiply protonated proteins.