# BAPNA --- **BAPNA**, which stands for **Nα-benzoyl-l-arginine-p-nitroanilide** is a "synthetic peptide" that we can use to in the [[labs]] to detect the activity of a [[protease]] like trypsin or pepsin. - It's colorless when the [[pigment]], **nitroanilide**, is bound to the [[amino acids|arginine]]. - when we add trypsin to it, it breaks the bond between arginine + nitroaniline (a pigment) - turns yellow The assay - you start with a buffer and some salt - Add BAPNA and trypsin - see how yellow it turns ___