title: Conformational analysis of cyclic partially modified retro-inverso enkephalin analogues by proton NMR.
abstract: The conformations of five cyclic retro-inverso enkephalin analogues have been probed by proton NMR. After assignment of peaks, intramolecularly hydrogen-bonded amide protons were detected by temperature perturbation. Carbonyl hydrogen-bond acceptors were surmised from the computer simulations of minimum energy conformations of Hassan and Goodman [Hassan, M., & Goodman, M. (1986) Biochemistry (preceding paper in this issue)]. Hydrogen bonds were identified in dimethyl-d6 sulfoxide solutions and monitored as H2O was added. One hydrogen bond was observed in each of the retro-inverso-modified enkephalin analogues although in the parent analogue H-Tyr-c-(D-A2bu-Gly-Phe-Leu) two were detected. The change in solvent altered the conformations of two of the analogues.
mesh_terms: D000595:Amino Acid Sequence; D004745:Enkephalins; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D010456:Peptides, Cyclic; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D004745:Enkephalins; D010456:Peptides, Cyclic