Melting and interdigitation of microstructured solid supported membranes quantified by imaging ellipsometry

Abstract

The phase transition of individually addressable microstructured lipid bilayers was investigated by means of noncontact imaging ellipsometry. Two-dimensional membrane compartments were created on silicon substrates by micromolding in capillaries and the phase transition of supported dimyristoylphosphadiylcholine ͑DMPC͒ and dipentadecoylphosphatidylcholine ͑DiC 15 PC͒ membranes was determined measuring area expansion and thickness of the bilayer as a function of temperature, ethanol concentration, and cholesterol content. Apart from measuring the thermotropic behavior of DMPC on glass slides and silicon wafers, the authors were able to visualize the reversible induction of an interdigitated phase by partitioning of ethanol into the microstructured lipid bilayers. Interdigitation induced by addition of ethanol was measured as a function of cholesterol content and shifts of the main phase transition temperature T M of microstructured DiC 15 PC were quantified as a function of ethanol concentration. They observed that cholesterol abolishes interdigitation at higher concentrations and found a biphasic behavior of T M as a function of ethanol concentration in good accordance to what is known from vesicles in solution.

Interdigitation in spin-coated lipid layers in air

“…Zscale DPPC images = 25nm, z-scale DSPC images = 50 nm.Lower regions or thinning were not observed in DLPC and DMPC samples independently of the solvent used (data not shown). These results are in contrast with what observed on hydrated samples, where for instance alcohols produced the thinning of DMPC[53].…”

Effect of tetracaine on DMPC and DMPC+cholesterol biomembrane models: Liposomes and monolayers

“…The results presented in the literature relatively to the effect of CHOL in these processes are contradictory. Mostly CHOL, at a high concentration, seems to inhibit the interdigitation process [44], Error! Bookmark not defined.…”

Biomimetic approaches for studying membrane processes

“…79 Membrane properties were studied by imaging ellipsometry, an imaging technique based upon solid-supported monolayer thickness measurement. 81 The researchers analyzed interdigitation of lipid molecules composing a lipid film and the effect of lipid mixing upon the monolayer phase transitions. The technique was further employed to determine the effect of cholesterol, a prominent modulator of membrane organization and fluidity, on the extent of acyl-chain mixing.…”