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A conformational comparision of two stereoisomeric cyclic dermorphin analogues employing nmr and computer simulations
Author(s) -
Mierke Dale F.,
Schiller Peter W.,
Goodman Murray
Publication year - 1990
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360290607
Subject(s) - chemistry , dermorphin , hydrogen bond , intramolecular force , stereochemistry , ring (chemistry) , proton nmr , molecular dynamics , receptor , molecule , computational chemistry , opioid peptide , opioid , organic chemistry , biochemistry
In a continuation of our program to study the structure–activity relationship of peptide opiates, we report the conformational analysis of two cyclic tetrapeptides related to dermorphin—Tyr‐c[ D ‐Orn‐Phe‐Asp]‐NH 2 and Tyr‐c[ D ‐Asp‐Phe‐Orn]‐NH 2 . These analogues have similar binding properties marked by a high selectivity for the μ‐opioid receptors because of a drastic decrease in the affinity for the δ‐opioid receptor. The conformational preferences of these analogues of dermorphin determined from proton nmr, molecular dynamics, and energy minimizations are quite similar. The constraint of the 13‐membered ring formed from cyclization is quite evident from the conformational analysis. The constrained ring system acts as a template maintaining the relative orientation of the exocyclic tyrosine and side chain of phenylalanine. Two intramolecular hydrogen bonds measured for the D ‐Orn analogue in DMSO were disrupted upon the addition of water. For the D ‐Asp analogue, two intramolecular hydrogen bonds were found stable in DMSO and water. The global conformations of the two peptides determined from nuclear Overhauser effects did not change with the solvent titration. The difference in the hydrogen bonding within the 13‐membered ring may account for the slight differences observed in the efficacy of the analogues at the μ‐opioid receptors.