th  - 1987 - 51st ENC Conference

WF2
LrIII~ITY OF NUC].FAR OVERHAUSER EXPERIMENTS IN THE S'IXJDY OF
]-IEME PROTEINS
V. Thanabal, W. S. Smith, M. J. Chatfield, S. D. Emerson,
J. L. McGourty, J. Hauksson, D. H. Peyton, J. T. J. Lecomte,
K.-B. Lee, and G. N. La Mar*
Dept. of Chemistry, University of California, Davis, CA 95616
The paramagnetic center of heme proteins also contributes
significantly to relaxation such that it becomes very difficult to
saturate resonances which arise from protons near the iron without
significantly perturbing the rest of the spectrum via off-resonance
effects. In addition, the systems have high molecular weights,
leading to the usual spin-diffusion effects.
We have developed methods of using the nuclear Overhauser
effect in paramagnetic hemoproteins in the light of the problems
mentioned above. Included in this study are numerical solutions of
the Bloch equations evaluating the off-resonance effects expected
when using high saturating power on a system of fast-relaxing
protons. Further, we provide examples of uses we have found for
nuclear Overhauser effect studies in paramagnetic heine proteins
with molecular weights ranging up to greater than 75,000.