LINE TENSION BETWEEN LIQUID DOMAINS IN LIPID MONOLAYERS

Hydrodynamic shear distorts the shapes of lipid domains at the air-water interface. When the shear stress is removed, the domains relax to their original shapes. The relaxation rate of bolas-shaped domains provides a novel means of measuring the line tension between coexisting immiscible liquid phases. This line tension was measured in a binary mixture of average critical composition 30 mol % cholesterol, 70 mol % dimyristoylphosphatidylcholine (DMPC), as a function of monolayer pressure. The line tension is approximately a linear function of the difference between the applied pressure and the critical pressure. The line tension varied from (1.6 +/- 0.4) X 10(-7) dyn, at 1 dyn/cm pressure, to zero at the critical pressure.