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. And so it leaves those peptide bonds intact. And then we remove our protective groups by using these types of molecules. So for example trifloroacetic acid and at the end we form our polypeptide that we wanted to form.