PROTON NUCLEAR MAGNETIC RESONANCE STUDIES OF SICKLE CELL HEMOGLOBIN

Abstract

Both high-resolution proton nuclear magnetic resonance and nuclear relaxation techniques have been used to investigate normal and sickle cell hemoglobins in solution at neutral pH. By choosing appropriate mutant and chemically modified hemoglobins, high-resolution proton nuclear magnetic resonance spectroscopy allows us to assign several proton resonances to C2 and C4 protons of specific histidyl residues in the hemoglobin molecule. By monitoring these proton resonances as a function of pH, we have determined the pK values of these residues. We have found that there are differences in the chemical shifts and pK values of certain histidyl residues between normal and sickle cell hemoglobins in both deoxy and carbonmonoxy forms. By means of pulse proton nuclear magnetic resonance techniques, we have determined both spin-lattice and spin-spin relaxation times of the histidyl residues of normal and sickle deoxyhemoglobins. Our high-resolution proton nuclear magnetic resonance results suggest that there are specific surface conformational differences between normal and sickle cell hemoglobins, and preliminary analysis of our proton relaxation results indicate that both spin-lattice and spin-spin relaxation times of the histidyl residues are valuable dynamic probes to investigate these differences.