SMS 201–995, an octapeptide somatostatin analogue.

Abstract

The possible conformations of SMS 201–995, an active analogue of somastostatin, have been studied in dimethylsulfoxide solution by 500 MHz proton n.m.r. spectroscopy. The assignments have been made by use of 2D‐correlated methods to detect long‐range coupling connectivities in aromatic residues and between the α protons of consecutive residues. NOESY experiments enabled us to correlate amide and α protons of neighbouring amino acid residues, which indicate a less flexible situation than in water. Measurements of temperature coefficients of the amide protons, of NH‐C α H coupling constants and NOE effects are in favour of one predominant conformation with a β turn, of type II', involving amino acids Phe 3 to Thr 6 .