The conformations of the cyclic peptides 1-desamino-8-D-arginine-vasop
ressin (DDAVP) and its hydrolyzation product (DDAVP-OH) are investigat
ed using C-13 and H-1 NMR spectroscopy in one and two dimensions. In m
ethanolic solution both cyclic disulfides take on conformations of at
least partially restricted mobility fixed by an inverse gamma-turn, wh
ich is formed by a hydrogen bond between the NH proton of N5 and the C
O oxygen of the F3 residue.