Conformation of a cyclic opioid peptide analog by NMR and molecular dynamics simulation.

The conformation of a new Ty-c[Lys-Phe-Asp]-NH2 cyclic opioid peptide synthesized by solid phase method, has been determined from two-dimensional NMR and distance geometry followed by restrained molecular dynamics simulation. The conformation of the ring is well-defined, but the exocylic Tyr-1 and Phe-3 side-chain moiety possesses significant orientational freedom.