Issue 3, 2009

Changes in molecular composition and packing during lipidmembrane reconstitution from phospholipid–surfactant micelles

Abstract

Total internal reflection (TIR) Raman spectroscopy was used to investigate changes in the properties of phospholipid bilayers at the quartzwater interface during the process of membrane reconstitution from lipiddetergent micelles. The non-ionic detergent β-D-dodecyl maltoside (β-DDM) was used in 9 : 1 ratio to deuterated and non-deuterated dipalmitoylphosphatidyl choline (DPPC and d75-DPPC) to form detergentlipid micelles. Exposure of the quartz surface to decreasing concentrations of such detergentlipid solutions resulted in the formation of a d75-DPPC bilayer indistinguishable from that of a bilayer formed by fusion of small unilamellar vesicles of the pure lipid, indicating that the use of detergent micelles does not alter the packing or conformation of lipids, or leave a residue of surfactant in the bilayer. Polarised measurements of d75DPPC spectra in the C–H and C–D regions at each step of the process showed that the lipid surface density increases as the detergent is removed by rinsing and replaced by more lipid. The absence of shifts in the frequencies demonstrates that DPPC is in a gel-like conformation even at high relative surfactant fractions. The TIR geometry also allowed us to record high resolution spectra in the low frequency C–D bending region of d75-DPPC, which showed that the lipid molecules have an upright orientation with respect to the support surface.

Graphical abstract: Changes in molecular composition and packing during lipid membrane reconstitution from phospholipid–surfactant micelles

Article information

Article type
Paper
Submitted
24 Jul 2008
Accepted
09 Oct 2008
First published
18 Nov 2008

Soft Matter, 2009,5, 568-575

Changes in molecular composition and packing during lipid membrane reconstitution from phospholipidsurfactant micelles

C. Lee, H. Wacklin and C. D. Bain, Soft Matter, 2009, 5, 568 DOI: 10.1039/B812768A

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