There are six major objectives in our proposed research: (1) to understand the molecular mechanism for the cooperative oxygenation of human adult hemoglobin (Hb A); (2) to correlate the structure-function relationships in human abnormal hemoglobins (found in hemoglobinopathies); (3) to investigate the structure-function relationship in sickle cell hemoglobin (Hb S), with special emphasis on (a) elucidating the conformational differences between Hb A and Hb S, (b) elucidating the intermolecular contacts in the Hb S fiber, (c) monitoring the polymerization of Hb S molecules, (d) developing magnetic resonance techniques using nitroxide and nuclear spin labels to investigate the dynamics and the roles of erythrocyte membrane in the sickling process, and (e) providing a rational basis for the design of a safe and effective antisickling drug; (4) to monitor intracellular environment of normal and abnormal blood samples by 1H and 31P nuclear magnetic resonance (NMR) spectroscopy; (5) to monitor the oxygenation of Hb inside intact erythrocytes by 1H NMR spectroscopy; and (6) to make a critical comparison of the Hb structure in solution and crystalline states by high-reoslution and modern solid-state NMR techniques. We have shown that proton NMR spectroscopy can povide detailed and in some cases unique information about the tertiary structure around the heme groups, functional properties of individual alpha and beta chains within an intact tetrameric Hb molecule, the nature of the tertiary and quaternary structures, structural changes, and roles of the intermediate structures during the oxygenation process. We believe that the best way to correlate the structure-function relationships in proteins in solution is to combine the information obtained from X-ray crystallography, proton NMR spectroscopy, and genetics. Our HB research is an excellent demonstration of the power of this approach. Our research also provides a unique opportunity to correlate the properties of hemoglobin obtained in solution with those obtained inside intact erythrocytes by the same technique and under essentially identical experimental conditions.