Complexes of Cu(II) with Asn-Ser-Phe-Arg-Tyr-NH2; an example of metal ion-promoted conformational organization which results in exceptionally high complex stability.

The pentapeptide fragment of ANF, Asn-Ser-Phe-Arg-Tyr-NH2, coordinates to Cu(II) using the same four nitrogen donor centers as simple pentapeptides such as pentaalanine yet the complexes are of much higher stability as a result of a highly organized side-chain structure which is present in the complex but absent from the free ligand.