MYOGLOBIN AND HEMOGLOBIN ROTATIONAL DIFFUSION IN THE CELL

The detection of the H-1 NMR signal of myoglobin (Mb) in tissue opens an opportunity to examine its cellular diffusion property, which is ce ntral to its purported role in facilitating oxygen transport. In perfu sed myocardium the field-dependent transverse relaxation analysis of t he deoxy Mb proximal histidyl NdeltaH indicates that the Mb rotational correlation time in the cell is only similar to 1.4 times longer than it is in solution. Such a mobility is consistent with the theory that Mb facilitates oxygen diffusion from the sarcoplasm to the mitochondr ia. The microviscosities of the erythrocyte and myocyte environment ar e different. The hemoglobin (Hb) rotational correlation time is 2.2 lo nger in the cell than in solution, Because both the overlapping Hb and Mb signals are visible in vivo, a relaxation-based NMR strategy has b een developed to discriminate between them.