GAS-PHASE SEPARATIONS OF PROTEASE DIGESTS

A mixture of peptides from a complete tryptic digest of ubiquitin has been analyzed by ion mobility/time-of-flight mass spectrometry techniq ues. All components of the mixture were electrosprayed and ions were s eparated in the gas phase based on differences in their mobilities thr ough helium before being dispersed into a time-of-flight mass spectrom eter for mass-to-charge analysis. The data show that ions separate int o families primarily according to differences in their charge states a nd, to a lesser extent, differences in conformation. This approach red uces spectral congestion typically associated with electrosprayed mixt ures and provides charge assignments for mass-to-charge ratio data. Ga s-phase separations of ions appear to provide a new physical basis for characterizing components of biological mixtures. (J Am Soc Mass Spec trom 1998, 9, 1213-1216) (C) 1998 American Society for Mass Spectromet ry.