Measurement of potential jumps on adsorption of phloretin and phlorezin on the surface of lipid membranes by the intramembrane field compensation method

The intramembrane field compensation method has been used to measure change in the dipole potential on bilayer lipid membranes (b.l.m.) on adsorption of phloretin and phlorezin on one side of the b.l.m. as a function of their concentrations in solution and the ionic strength and pH of the solution. The potentials measured by this method are compared with those determined from change in b.l.m. conductivity induced by nonactin on adsorption of phloretin and phlorezin on both sides of the b.l.m. In the case of phlorezin the results given by the two methods match while for pholretin the steady values of the potentials measured by the first method were lower. The results are explained by the fact that when introduced into the solution on one side of the membrane phlorezin is concentrated on one boundary and phloretin because of passage across the membrane is distributed on both boundaries.