Desorption/ionization on silicon (DIOS): A diverse mass spectrometry platform for protein characterization

Since the advent of matrix-assisted laser desorption/ionization and electro spray ionization, mass spectrometry has played an increasingly important ro le in protein functional characterization, increasingly important role in p rotein functional characterization. identification, and structural analysis . Expanding this role, desorption/ionization on silicon (DIOS) is a new app roach that allows for the analysis of proteins and related small molecules, Despite the absence of matrix, DIGS-MS yields little or no fragmentation a nd is relatively tolerant of moderate amounts of contaminants commonly foun d in biological samples. Here, functional assays were performed on an ester ase, a glycosidase, a lipase, as well as exo- and endoproteases by using en zyme-specific substrates. Enzyme activity also was monitored in the presenc e of inhibitors, successfully demonstrating the ability of DIGS to be used as an inhibitor screen, Because DIGS is a matrix-free desorption technique, it also can be used as a platform for multiple analyses to be performed on the same protein. This unique advantage was demonstrated with acetylcholin e esterase for qualitative and quantitative characterization and also by it s subsequent identification directly from the DIGS platform.