So let's suppose this is the protein and in the protein we have these two polypeptides and they are connected to one another at two locations by disulfide bond. So this is disulfide bond number one and disulfide bond number two. Now what we want to do initially is we want to take this protein and expose it to some type of proteolytic enzyme. And we want to make sure that that proteolytic enzyme does not break these disulfide bonds. So we take our protein, we expose it to our proteolytic chemical. And what that proteoly chemical does is it cleaves at different sections on these two polypeptides.