Sensitive Criteria for the Critical Size for Helix Formation in Oligopeptides

Author(s): Murray Goodman, Antonio S. Verdini, Claudio Toniolo, William D. Phillips and Frank A. Bovey

Pp: 133-139 (7)

* (Excluding Mailing and Handling)

Abstract

We studied the conformation of a series of γ-ethyl-L-glutamate oligopeptides by circular dichroism and 220 MHz nuclear magnetic resonance spectroscopy. By use of the first technique we noted enhancement of the n→0 π*and splitting of the ir π→πr* transitions commencing with the heptamer in trimethylphosphate and trifluoroethanol. With the second method we found changes in chemical shifts for the amide protons consistent with the onset of helicity at the heptamer in the solvents noted above. When DMSO-d6 is used as a solvent, no such chemical shift changes occur because the oligopeptides do not assume helical conformations.

Keywords: opioid receptors, non-peptide agonists, binding domain, pharmacophore models, morphine-like agonists, non-morphine-like agonists

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