Abstract: The conformation of linear enkephalin pentapeptide, N-Tyr¹-Gly²-Gly³-Phe⁴-Leu⁵, in DMSO-d₆ has been investigated on Bruker AM-400 NMR spectrometer at 300K,318K and 336K. The NH-chemical shift temperature gradients, the constraints for torsion angles φ and χ', and the constraints for ¹H-¹H NOE distance were obtained from 1D and 2D NMR measurements. The calculations of enkephalin conformation at 300K, 318K and 336K were carried out on VAX8700 by means of variable target function method. The insight into the backbone conformation is obtained from variable temperature measurements and the results seem to indicate that the backbone is flexible and the peptide is involved in a conformational equilibrium.

Key words: Chemical shift temperature gradients, NMR conformation, Enkephalin, DADAS program