Theoretical conformational analysis of enkephalin analogues related to fluorescence and n.m.r. measurements in aqueous solution

The properties related to non‐radiative energy transfer of a number of enkephalin analogues with tryptophan substituted for phenylalanine in position 4 and n.m.r. 3JNH‐CαH coupling constants of corresponding [Phe4]‐enkephalin analogues are being derived from semi‐empirical conformational energy. The molecules considered contain a glycyl, a D‐alanyl or an L‐alanyl as second residue; two of the compounds are N‐methylated at position 4 or 5. The [Trp4]‐ enkephalin analogues and the corresponding [Phe4]‐enkephalin analogues display nearly parallel affinities in the opiate receptor binding assay (Schiller et al.(1)). The comparison of computed and experimental properties shows that an ensemble of conformers is a satisfactory representation of the state of these molecules in water. © 1981 Munksgaard International Publishers Ltd.SCOPUS: ar.j