PMSF solution is widely used as a serine protease inhibitor in biochemical and molecular biology applications. It prevents protein degradation by inhibiting enzymes such as trypsin, chymotrypsin, and thrombin during cell lysis and protein extraction. Commonly added to lysis buffers, it helps maintain protein integrity for assays like Western blotting, immunoprecipitation, and enzyme activity studies. Due to its instability in aqueous solutions, it is typically prepared fresh or stored at low temperatures and used at low concentrations. PMSF is also used in purification protocols where active proteases could interfere with results. Caution is required during handling as it is toxic and can inhibit other serine hydrolases, including acetylcholinesterase.