H-1-NMR AND C-13-NMR INVESTIGATION OF COMPLEXES OF MN2-2(6))DIMETHYLSULFOXIDE( WITH OCYTOCIN ANALOGS IN (H)

Several ocytocin analogues were synthesised by substitution of the Pro residue with sarcosine or N-methylalanine, the glutamine residue with threonine and one of tile cysteines with 2-mercaptopropionic acid. Al l the derivatives were investigated by NMR in dimethylsulfoxide soluti ons and evidence was obtained for similar preferred conformations in t he solution free state. All peptides were shown to form complexes with Mn2+ in solution by the strong paramagnetic effects experienced by se veral proton resonances. Two structures could be determined; one forme d by peptides containing threonine and tile other by the remaining pep tides. The two structures were delineated by molecular modelling using the Mn2+-proton distances obtained by NMR as restraints.