Interactions of haemoglobin with erythrocyte membrane phospholipids in monomolecular lipid layers

The role of red cell membrane lipids in the membrane-haemoglobin interaction was studied by measuring the surface potential and surface pressure of monomolecular lipid layers interacting with haemoglobin. Lipids of the outer and inner half of the red cell membrane were compared in respect to their haemoglobin-binding capacity. It was shown, that haemoglobin molecules interacted readily with the inner layer lipid film in acidic pH regions. This interaction is reduced as pH is increasing but still exists in the physiological pH range. It is in contrast with the increasing but still exists in the physiological pH range. It is in contrast with the findings for the outer layer lipid film, where only a partial interaction could be shown at pH 4, which was reduced to zero reaching the physiological pH range. It can be concluded from titration experiments that the process of haemoglobin binding as reflected in the measured parameters is irreversible. The result of this model experiments support the hypothesis on phosphatidylserine binding sites for haemoglobin in the inner side of red cell membrane.