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.
The molecular order and lateral diffusion in fluid cationic bilayers of chain perdeuterated DPTAP (1,2dipalmitoyl-d62-trimethylammonium-propane) on a spherical solid support were studied by deuterium NMR and microcalorimetry. In comparison to the zwitterionic perdeuterated DPPC (1,2-dipalmitoyl-d62sn-glycero-3-phosphocholine), the molecular order parameter profile of the palmitoyl chains of DPTAP shows significantly higher molecular order toward the interface while similar values were obtained in the vicinity of the bilayer center. The lateral diffusion coefficient D of DPTAP is D ) (13.2 ( 1.5) × 10 -12 m 2 /s at 60 °C, slightly below that of DPPC at this temperature. Increasing the ionic strength caused the value of D to decrease further. The results suggest that despite the cationic charge the supported DPTAP bilayer features tighter molecular packing and a reduced lateral diffusivity of its constituents than for the zwitterionic DPPC on a solid support.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.