Light scattering studies on interaction of Ca2+ with phosphatidylserine liposomes: triggering action of pH.

A novel dependence of interaction of Ca2+ with phosphatidylserine liposomes on pH at different temperatures has been observed. Triggering action of pH, in the range of pH 7 to 9, on Ca2+-induced aggregation/fusion of phosphatidylserine liposomes, with probable involvement of the amino group in the polar headgroup of the lipid, is reported here. Probable role of bound water layer around polar headgroup in the initial stage of Ca2+-induced aggregation/fusion has been suggested. Possible use of triggering action of pH as a mechanism to control fusion processes in biological systems is also suggested.