Some determinants of partitioning behavior of lymphoblasts in aqueous biphasic systems

Partitioning behavior of murine lymphoblasts was examined in biphasic aqueous systems containing dextran and poly(ethylene glycol) with no potential difference across the interface. Persistence of cells in the upper phase of the system could be promoted by addition of the palmitate ester of poly(ethylene glycol). Partitioning effects seen here may derive from affinity of membrane sialic acid residues for dextran-rich lower-phase droplets, and antagonism of these interactions by poly(ethylene glycol) palmitate. Several determinants of partitioning behavior were examined: 1. Membrane glycosylation. Partitioning behavior of P388 and P388/ADR lymphoblasts were compared. The latter has an inherently higher degree of membrane glycosylation, resulting in a lower partition coefficient in poly(ethylene glycol) palmitate-supplemented systems. 2. Degree of esterification. Singly-esterified poly(ethylene glycol) was substantially more effective at promoting cell partition into the upper phase than was doubly-esterified glycol. Use of the latter was associated with cell-cell aggregation. 3. Relative numbers of lower-phase droplets present. Decreasing the numbers of such droplets initially present markedly increased the partition coefficient. 4. Time-dependence. Even in the presence of poly(ethylene glycol) palmitate, the partition coefficient fell with time, indicating an interaction between cells and lower-phase droplets not antagonized by the ester.