Nuclear magnetic relaxation spectroscopy in solutions of bovine hemoglobin.

The longitudinal proton relaxation time Tt of aqueous solutions of bovine ferrihemoglobin and carboxilated hemoglobin was measured in the Larmor frequency range 3-103 Hz to 1,2 -108 Hz. The dispersion curves are explained by diamagnetic and electron paramagnetic relaxation mechanisms. An efficient direct dipolar coupling between the paramagnetic heme-groups and the water protons in ferrihemoglobin solutions can be excluded. The flat dispersion behaviour of the diamagnetic contribution suggests a broad distribution of molecular motions i. e. a certain flexibility of the hemoglobin molecule.