CHARACTERIZATION OF SDS-PAGE-SEPARATED PROTEINS BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY

A new strategy to characterize SDS-PAGE-separated proteins with MALDI MS is described. The proteins, electroblotted onto nitrocellulose afte r SDS-PAGE separation and stained with reversible Ponceau S dye, are r eadily recovered by dissolving the membrane in matrix solutions prepar ed with acetone. The resulting mixtures are amenable to direct MALDI M S analysis, which provides a rapid and accurate means of measuring the molecular weights of SDS-PAGE-separated proteins and of peptides that result from CNBr digestion of proteins on the nitrocellulose membrane . Compared with the traditional elution method, this procedure provide s more efficient detection of proteins and peptides, especially the hi gher molecular weight proteins from the membrane. As little as 3.5 pmo l of lysozyme and 15 pmol of bovine albumin loaded onto a gel can be d etected using this method. The detection sensitivity is higher than or comparable to that of the traditional Coomassie Brilliant Blue staini ng procedure.