Conformation of somatostatin using scalar coupling constants from 270 and 600 MHz simulated proton magnetic resonance spectra.

The conformation of the 14 amino acid peptide hormone somatostatin in aqueous solution was investigated through a proton magnetic resonance (PMR) scalar coupling analysis. Experiments were performed at two fields, 270 and 600 MHz, and included double and triple resonance difference scalar decoupling, resolution enhancement and computer simulation. The agreement between simulated and observed spectra at both fields provided support for the correctness of the analysis. The resultant scalar coupling constants, 3J alpha H-NH and 3J alpha B, gave information on the backbone (phi) and side chain (chi 1) torsional angles, respectively, which eliminated either of the proposed conformations of somatostatin as describing a predominant conformer of the molecule in solution under our conditions.