So the question is, how do we break this bond without breaking any of the peptide bonds in that polypeptide chain? Well, we have to mix it with hydrofluoric acid. If we mix it with HF in the presence of this molecule here, that essentially removes this teapot group and any other blocking group found on any of the side chains. And we also basically break this bond here without actually breaking any of those peptide bonds. So at the end of the synthesis the protein is released from the solid surface by adding hydrofluoric acid into our mixture. And this breaks the carboxyl acid bonds to this bond without breaking any of the peptide bonds.