is a serine protease inhibitor commonly used in the preparation of cell lysates. PMSF does not inhibit all serine proteases[citation needed]. It is rapidly degraded in water and stock solutions are usually made up in anhydrous ethanol, isopropanol, corn oil, or DMSO. Proteolytic inhibition occurs when a concentration between 0.1 - 1 mM PMSF is used. The half-life is short in aqueous solutions