Water proton magnetic resonance studies of normal and sickle erythrocytes Temperature and volume dependence

Abstract

The temperature and cell volume dependence of the NMR water proton linewidth, spin-lattice, and spin-spin relaxation times have been studied for normal and sickle erythrocytes as well as hemoglobin A and hemoglobin S solutions. Upon deoxygenation, the spin-spin relaxation time ( T 2) decreases by a factor of 2 for sickle cells and hemoglobin S solutions but remains relatively constant for normal cells and hemoglobin A solutions. The spin-lattice relaxation time ( T 1) shows no significant change upon dexygenation for normal or sickle packed red cells. Studies of the change in the NMR linewidth, T 1 and T 2 as the cell hydration is changed indicate that these parameters only slightly by a 10–20% cell dehydration. This result suggests that the reported 10% cell dehydration observed with sickling is not important in the altered NMR properties. Low temperature studies of the linewidth and T 1 for oxy and deoxy hemoglobin A and hemoglobin S solutions suggest that the “bound” water possesses similar properties for all four species. The low temperature linewidth ranges from about 250 Hz at −15°C to 500 Hz at −36°C and analysis of the NMR curves yield hydration values near 0.4 g water/g hemoglobin for all four species. The low temperature T 1 data go through a minimum at −35°C for measurements at 44.4 MHz and −50°C for measurements at 17.1 MHz and are similar for oxy and deoxy hemoglobin A and hemoglobin S. These similarities in the low temperature NMR data for oxy and deoxy hemoglobin A and hemoglobin S suggest a hydrophobically driven sickling mechanism. The room temperature and low temperature relaxation time data for normal and sickle cells are interpreted in terms of a three-state model for intracellular water. In the context of this model the relaxation time data imply that type III, or irratationally bound water, is altered during the sickling process.