And this is the last amino acid that contains the r group RN. And so this is the amino acid that we began with. And this is the final amino acid that is found on the alpha amino terminal N, while this is the one that is found on the alpha carboxyl terminal end of that polypeptide chain. Now, in the final step, once we actually form this polypeptide chain, what we have to do is a, we have to break this bond here and detach our polypeptide from this solid surface and b, we also want to remove this T bog group. Now, the tea bog group can be simply removed by mixing it with this molecule here. But how do we break this bond here?