Electrostatic interactions at charged lipid membranes. Kinetics of the electrostatically triggered phase transition

Charged lipid membranes of dimyristoylmethylphosphatidic acid were mixed rapidly in a stopped-flow cell with protons or Ca2+ to compensate the charges and thereby trigger the ordered-fluid phase transition. The kinetics of the transition was studied by following the time development of the fluorescence anisotropy of diphenylhexatriene. A relaxation process was observed with a characteristic time in the range 10-200 ms. By comparison with existing theories of non-equilibrium relaxation it was concluded that the relaxation process is governed by a nucleation step.