OBSERVATION OF LARGE SUBUNIT PROTEIN COMPLEXES BY ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

Mass spectrometry with electrospray ionization and a magnetic sector i nstrument was used to detect multiply charged molecules for the non-co valently bound dimeric subunit protein complexes of horse liver alcoho l dehydrogenase (M(r) similar to 80 000) and the tetrameric complexes of yeast alcohol dehydrogenase (M(r) similar to 147 000) and rabbit mu scle pyruvate kinase (M(r) similar to 232 000). Ions for the pyruvate kinase complex represent one of the largest intact protein complexes r esolved by mass spectrometry. Solvation of the large gas phase complex es is indicated by the mass spectrometric results.