Approaches for peptide and protein cyclisation.

The cyclisation of polypeptides can play a crucial role in exerting biological functions, maintaining stability under harsh conditions and conferring proteolytic resistance, as demonstrated both in nature and in the laboratory. To date, various approaches have been reported for polypeptide cyclisation. These approaches range from the direct linkage of N- and C- termini to the connection of amino acid side chains, which can be applied both in reaction vessels and in living systems.