Conformations of Boc-pentapeptide (Boc-b-Ala-Trp-Met-Asp-PheNH2) and Boc-tetrapeptide (Boc-Trp-Met-Asp-PheNH2) of gastrin in DMSO solns. were investigated by 2-dimensional (2D) NMR spectrometry. 2D COSY, Relayed-COSY, DQF-J Resolved Spectroscopy and NOESY were applied to assign all resonance lines completely, F dihedral angles, rotamer populations, and their energy differences were calculated According to NOE, conditions of distance constraints were obtained. Taken together with F and rotamer populations, the model of conformation for Boc-pentapeptide was obtained. Conformations of Boc-pentapeptide and Boc-tetrapeptide are characterized by half turn in DMSO solution In their main rotamers, indole of Trp and S atom of Met form a 3-dimensional structure similar to 5,1-benzothiazocine, and this structure may be the cause of biol. potency.

Key words: OLIGOPEPTIDE, CONFORMATION, TROPICAL FOREST, 2D NMR SPECTROMETRY, GASTRIN, PENTAPEPTIDE