Abstract
A replacement of both Cys residues byHis in oxytocin (OXT) sequence allows for the formation of the stable complex with the {NH2, N-Im, N-Im(macrochelate)} binding mode at the physiological pH. The detailed potentiometric and spectroscopic studies on the Cu(II) complexes of [His(1,6)] OXT, together with high resolution NMR investigations on 3D structures of Cu(II) complexes with [His(1,6)] OXT and [His(1,6)] AVP analogues are presented and discussed. Exchange of the Cys-S-S-Cys bridge by the His-Cu(II)-His motif is very promising, because the resulting complexes retain topological similarity to the native S-S bridged AVP and OXT at pH values corresponding to the physiological pH.