Rotational Jumps of the Tyrosine Side Chain in Crystalline Enkephalin. 2H NMR Line Shapes for Aromatic Ring Motion in Solids

David M. Rice, Richard J. Wittebort, Robert G. Griffin, Eva Meirovitch, Evelyn R. Stimson, Yvonne C. Meinwaid, Jack H. Freed, Harold A. Scheraga

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151 Scopus citations

Abstract

Deuterium NMR spectra of polycrystalline [iyms>ie-3,5-2H2] [Leu5] enkephalin show that the aromatic tyrosyl ring of this pentapeptide is executing 180° flips about the Cβ-Cγ axis in the solid state. Specifically, the axially symmetric powder pattern observed at low temperature collapses to an axially asymmetric pattern with =* 0.6 at high temperature. Computer simulations of the NMR line shapes, which account for spectral distortions induced by the quadrupole echo technique, indicate that at room temperature the flipping rate is approximately 5 X 104 s1 and that it increases to about 106 s1 at 101 °C.

Original languageEnglish
Pages (from-to)7707-7710
Number of pages4
JournalJournal of the American Chemical Society
Volume103
Issue number26
DOIs
StatePublished - Dec 1981
Externally publishedYes

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