Binding of haemoglobin to the red-cell membrane in the presence of copper chloride.

Methaemoglobin may be an important factor for initiation and development of lipid peroxidation in Cu(II)-treated red blood cells. It seems likely that the initiation of peroxidation by methaemoglobin is only possible if direct contact between haemoglobin molecule and the cell membrane is realized. In view of this, the binding of haemoglobin to the red-blood-cell membrane in the presence of CuCl2 was studied. It was found that the haemoglobin quenching of the fluorescence of 12-(9-anthroyl)stearic acid-labelled red-blood-cell membranes greatly increases in the presence of CuCl2. This effect is relatively independent of pH and the ionic strength of the medium, indicating that in this case the binding of haemoglobin is not electrostatic in nature. The haemoglobin quenching of the fluorescence of the inside-out and the right-side-out resealed ghosts were almost the same in the presence of CuCl2. This result suggests that, in the presence of ionic copper, both surfaces of the membrane possess approximately equal amounts of sites for the binding of haemoglobin.