Benzamidine

Benzamidine is a reversible competitive inhibitor of trypsin, trypsin-like enzymes and serine proteases. As a general inhibitor it can be used at 1 mM. For the most part it is interchangeable with pepstatin A (eg Benzamidine Hydrochloride Hydrate). It is sensitive to oxidation and should be prepared fresh in deionized water up to 50mg/ml (heating may be necessary for solubilization).

It is often used as a ligand in protein crystallography to prevent proteases from degrading a protein of interest; the triangular diamine group at the bottom gives it a very obvious 'stick-man' shape which shows up in difference density maps.