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Abstract

The loosely bound proteins from human erythrocyte membranes, after having been removed from the membrane by 10% acetic acid, freeze-dried and transferred back to aqueous buffers, retain their capacity to associate with lipids. Protein-lipid association between the proteins and liposome bilayers made from total lipids from human erythrocyte membranes was studied. Lipoprotein formation was analyzed by isopycnic sucrose gradient centrifugation and was observed over the full range of conditions investigated: at pH values between 4.5 and 8.5, at ionic strengths be-tween 7mM and 1M, and for protein and lipid concentrations between 0.15 and 1.5 mg/ml. The yield of the association process reached up to more than90 % of both components. It was practically inde-pendent of the protein/lipid ratio in the recombination mixture. The highest yields were observed in the lower part of the pH range studied and, at higher pH values, around physiological values of ionic strength. For pH > 6.5, at both the highest and lowest part of the ionic strength range testet, part of the protein did not associate with lipid. The effect of low ionic strength was, however, neutralized by the presence of divalent cations.