Interaction between Ca2+ and dipalmitoylphosphatidylcholine membranes. I. Transition anomalies of ultrasonic properties.
The effect of Ca2+ on a gel-to-liquid crystal transition as well as the mechanical properties of dipalmitoylphosphatidylcholine bilayers was studied by an ultrasonic technique. Transition temperature increased with increase in Ca2+ concentration, whereas the variation of ultrasonic anomalies indicated that dipalmitoylphosphatidylcholine bilayers exhibited maximum pseudocritical fluctuation at a Ca2+ concentration of about 10 mM. Hardening of dipalmitoylphosphatidylcholine membranes due to the Ca2+ binding was observed above 10 mM CaCl2, suggesting the lateral compression of the lipid bilayer by bound Ca2+. Long-range attraction between bound Ca2+ and the head groups of surrounding lipid molecules was proposed from these calcium effects.
D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism*; D008560:Membrane Fluidity / Q000187:drug effects; D011663:Pulmonary Surfactants / Q000378:metabolism*; D013696:Temperature; D014465:Ultrasonics
D008051:Lipid Bilayers; D008081:Liposomes; D011663:Pulmonary Surfactants; D002118:Calcium