Effect of cationic lipids in the formation of asymmetries in supported bilayers.
We have studied the formation of a supported bilayer containing both cationic and zwitterionic lipids by fusion of small unilamellar vesicles (SUV) onto the solid surface at low salt conditions using a combination of attenuated total reflection infrared (ATR-IR) and deuterium NMR spectroscopy with microcalorimetry. The data suggest that a significant cationic lipid asymmetry between the outer (distal) and the inner (proximal) monolayer of a supported bilayer results under conditions of prolonged incubation times of the solid support with the SUV coating solution. For a SUV composition of DPPC/DHDAB (4:1) we observed an enrichment of the cationic component in the proximal monolayer of up to 200% compared to the distal monolayer after 12 h incubation. It is suggested that the electrostatic potential arising from the solid surface is the driving force for the creation of this asymmetry by means of directed flip-flop between the monolayers and/or by temporary fusion between SUV from the bulk with the supported bilayer.
Käsbauer
M
M
Universität Würzburg, Physikalisches Institut EP-5, D-97074 Würzburg, Germany.
Junglas
M
M
Bayerl
T M
TM
D055592:Biophysical Phenomena; D001703:Biophysics; D002152:Calorimetry, Differential Scanning; D002412:Cations; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008561:Membrane Fusion; D013055:Spectrophotometry, Infrared; D055672:Static Electricity
D002412:Cations; D008051:Lipid Bilayers; D008081:Liposomes