Trypsin specifically hydrolyzes peptide bonds at the carboxylic sides of lysine and arginine residues. Promega Trypsin has been modified by reductive methylation, rendering it extremely resistant to autolytic digestion. The sequencing grade of modified trypsin has been further improved by TPCK treatment followed by affinity purification yielding a highly active and stable molecule. For more details of the product, visit http://www.promega.com/catalog/catalogproducts.aspx?categoryname=productleaf_354