NMR studies of new arginine vasopressin analogs modified with α-2-indanylglycine enantiomers at position 2 bound to sodium dodecyl sulfate micelles

In this paper, we use NMR spectroscopy and molecular modeling to examine four new vasopressin analogs modified with α-2-indanylglycine (Igl) at position 2, [L-Igl2]AVP (I), [D-Igl2]AVP (II), [Mpa1,L-Igl2]AVP (III) and [Mpa1,D-Igl2]AVP (IV), embedded in a sodium dodecyl sulfate (SDS) micelle. All the analogs display antiuterotonic activity. In addition, the analogs with D-Igl reveal antipressor properties.Each analog exhibits the tendency to adopt β-turns at positions 2, 3 and/or 3, 4, which is characteristic of oxytocin-like peptides. Mutual arrangement of aromatic residues at positions 2 and 3 has been found to be crucial for binding antagonists with the OT and V1a receptors. The orientation of the Gln4 side chain seems to be important for the V1a receptor affinity. In each of the peptides studied, the Gln4 side chain is folded back over the ring moiety. However, it lies on the opposite face of the tocin moiety in analogs with L and D enantiomers of Igl.