th  - 1987 - 51st ENC Conference

Tuesday - PM
WKI2- POSTERS
QUANTITATIVE INTERPRETATION OF A SINGLE 2D NOE SPECTRUM
Peter A. Mirau
AT&T Bell Laboratories
Murray Hill, NJ 07974
A new method is suggested for the quantitative in-
terpretation of 2D NOE data using selective relaxation rates
and matrix techniques. This approach reduces the experimen-
tal time from one week to one day, gives proton-proton dis-
tances with a precision of 10.1 A, and can be used to
characterize the internal dynamics. With this approach the
structural and dynamic properties of Gramicidin S were
determined from a single 2D NOE spectrum with a mixing time
of 0.2 s. The peak volumes in the 2D experiment were scaled
via the measured selective relaxation of Phe NH and Orn
protons and the matrix of scaled peak volumes was solved to
yield the relaxation rate matrix. The distances measured by
this approach were indistinguishable (~0.1 A ) from those
measured from 1D NOE experiments, the buildup of cross peaks
in the 2D NOE experiments, and the distances expected from
the crystal structure. The dynamics were determined from
the ratio of the sum of all the cross relaxation rates to
the rate of decay of the diagonal peak which, for isotropic
motion, depends only the the correlation time. This
analysis showed a correlation time for the NH and H ~ protons
of 0.9~0.1 nsec; the close correspondence between the ob-
served and expected values show that the peptide backbone is
rigid in solution over the time scale of molecular tumbling.
Internal motions of make a significant contribution to the
relaxation of some side chain groups. The implications and
limitations of this approach and the applications to DNA
structure determination will be discussed.