Peptide synthesis

Polypeptides can be chemically synthesized through covalently connecting amino acids to the end of a growing polypeptide chain. In solid step peptide synthesis the growing polypeptide chain is covalently anchored at its C-terminus to an insoluble support like as polystyrene beads.  The forward amino acid in the sequence has to react with the free α-amino group on the tethered peptide, but it has a free α-amino group itself that will also react. To defeat this problem the free amino acid has its α-amino group chemically protected or blocked so that it does not react with other molecules.  Once the latest amino   acid is coupled  it’s now  N-terminal  α-amino group  is  deprotected  or deblocked so  in which  the  next peptide  bond  can  be  formed.  Each cycle of amino acid addition thus needs a coupling step and a deblocking step. Additionally, reactive side-chain groups must also be blocked to prevent unwanted reactions occurring.