title: Spin-label detection of hemoglobin-membrane interaction at physiological pH.
abstract: The interaction between hemoglobin and the cytoplasmic surface of human erythrocyte membranes at physiological pH was studied by monitoring the electron paramagnetic resonance (EPR) signal of spin-labeled membrane ghosts in hemoglobin solutions of various concentrations. The EPR spectra indicate the existence of a significant hemoglobin-membrane interaction which exhibits a substantial hemoglobin concentration dependence over the concentration range 0-12 mg/mL. An equilibrium binding model yields a hemoglobin-membrane dissociation constant, Kd, on the order of 10(-4) M, at and above physiological pH; the interaction is classified as very low-affinity binding. The interaction increases significantly when the pH is decreased. Half-saturation of the binding sites occurs at a ratio of about 10(8) hemoglobins per cell.
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008433:Mathematics; D011485:Protein Binding; D012710:Serum Albumin, Bovine
chemical_list: D006454:Hemoglobins; D012710:Serum Albumin, Bovine