th  - 1987 - 51st ENC Conference

MK5
Abstract: 28th ENC, Asilomar, CA. April 5- 9, 1987
INTERNUCLEAR DISTANCES AND CORRELATION TIMES FROM TRANSVERSE AND
LONGITUDINAL CROSS-RELAXATION RATES
Donald G. Davis, NIEHS, PO Box 12233, Research Triangle Park, NC 27709
A novel method for determining correlation times and proton-
proton distances for molecules in solution is demonstrated. These
experiments may be done at a single field strength and require no
priori assumptions about fixed internuclear distances or the cor-
relation functions for different pairs of spins in the molecule.
The success of the method is based on the fact that the longitudinal
(~111) and transverse ((~'~) cross-relaxation rates have different
dependencies on ~c such that in the range Ilog~dR~l, the ratio of
(~lltO ~goes from 1.0 to -0.5. Accurate measurements of ~require
that careful attention be given to offset corrections and to mini-
mizing Hartmann- Hahn cross-polarization(I). Experimental details and
data analysis for the determination of internuclear distances and
correlation times of the cyclic peptide Gramicidin-S in DHSO-d 6 will
be shown.
References: A. Bax and D. G. Davis, J. Hagn. Reson. 6~, 207-213,(1985).