Hydrophobic affinity partition in aqueous two-phase systems of erythrocytes from different species: Systems containing polyethylene glycol-palmitate

We have examined the partition of erythrocytes from different species in dextran-polyethylene glycol aqueous two-phase systems containing sodium chloride and small quantities of polyethylene glycol-palmitate. The partition of erythrocytes in these phases depends on the hydrophobic affinity of the membrane surface to the palmitoyl residue. It was shown that: 1. 1. The partition coefficient of human erythrocytes is not decreased by neuraminidase treatment indicating that membrane charge of cells is not a determinant of their partition. 2. 2. The partition of erythrocytes is species-specific and appears to depend, to a great extent, on the ratio of poly/mono-unsaturated fatty acids in their membranes. 3. 3. By combining isotopic labeling techniques with countercurrent distribution of rat red cells age-dependent alterations in the partition coefficient of erythrocytes were found which ( a) reflect changes in the membrane lipid composition of red cells during maturation and aging; and ( b) are different from the changes observed in a dextran-polyethylene glycol two-phase system with phosphate but no polyethylene glycol-palmitate (a system which reflects membrane charge [3]). 4. 4. Changes in partition coefficient of human erythrocytes as a function of storage occur.