Conformational states of enkephalins in solution

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Abstract

Two pentapeptides with opiate activity, [Met5] enkephalin and [Leu5] enkephalin, were studied by means of PMR, CMR, UV and CD spectroscopies in different solvents and at different concentrations. The primary result which we report is the demonstration of a concentration dependence. Spectral properties which are characteristically used to evaluate conformation are shown to differ at different concentrations. This provides an explanation for conflicting results of previous studies.

Two conformational states of enkephalins which are consistent with the data are considered: i) A monomeric form, containing a β-turn with Gly3 and Phe4 at the corners, a 7-atom H-bond and the folding of the Tyr1 aromatic side chain over the molecule stabilized by an interaction of its OH proton with the Gly3 CO. ii) An associated form with an antiparallel cross-β-structure stabilized by four intermolecular H-bonds and with a “head to tail” interaction.

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Cited by (106)

  • Conformational features of linear and cyclic enkephalins. A computational study

    2001, Journal of Molecular Structure: THEOCHEM
    Citation Excerpt :

    We have also observed 34 conformations stabilized by the interaction between the Phe4 N–H group and the Gly2 carbonyl group together with the interaction between the Leu5 N–H group and the Gly3 carbonyl group as described in Ref. [9], but the relative energy of these conformations exceeded 8.0 kcal/mol. We have compared the structures found in this study with results obtained by X-ray [38–41] and NMR analyses [27,42]. The coordinates were obtained from literature and from the Cambridge Structural Database [43].

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