For example, we have a special molecule, a chemical known as Cygn bromide. And what it does is it cleaves our peptide at the carboxyl side of methionine amino acids. For trypsin. This is a biological molecule that is found in our digestive system. And what trypsin basically does is it cleaves our peptide at a specific site. So at the carboxyl side of Lysine and Arginine are two basic amino acids.