Analysis of non-covalent protein complexes up to 290 kDa using electrospray ionization and ion trap mass spectrometry

Non-covalently-bound subunit complexes of proteins have been measured by an ion trap mass spectrometer equipped with an orthogonal electrospray ioniza tion source. For the analysis of the generated molecular ions with high mas s/charge ratios, the mass/charge range of the ion trap was extended by incr easing its radio frequency (rf) voltage to 15 kV (V0-p) and by resonant ion ejection. Ions of the non-covalent dimer of bovine serum albumin (BSA), as well as of subunit complexes of alcohol dehydrogenase (ADH) from bakers' y east and from horse liver, have been detected at mass/charge values between 3000-9000 Th, The maximum observed molecular weight was that of a non-cova lently-bound subunit-octamer of bakers' yeast ADH (two non-covalently-bound subunit-tetramers) at ca, 290 kDa, Copyright (C) 2000 John Wiley & Sons, L td.