Charge state dependent fragmentation of gaseous protein ions in a quadrupole ion trap: bovine ferri-, ferro-, and apo-cytochrome c

Abstract

The dissociation behavior of bovine ferri-, ferro-, and apo-cytochrome c ions formed by electrospray ionization has been studied as a function of precursor ion charge state under quadrupole ion trap collisional activation conditions. Tandem mass spectrometry data collected under solution conditions in which the oxidation state of the heme-iron is known show that cytochrome c ions dissociate by oxidation state dependent channels. Dissociation of precursor ions in the oxidized form [Fe(III)heme] yields predominantly b- and y-type ion backbone cleavages with preferential cleavages observed C-terminal to basic residues including lysine, arginine and histidine, C-terminal to aspartic and glutamic..