Formation of Tethered Bilayer Lipid Membranes(TBLM) from Mixed Lipid-Detergent Micelles

Abstract

tBLMs are solid-supported lipid bilayers separated by a ∼ 2 nm thick hydration layer from the substrate. Compared to cell membranes, they are simpler in their chemical composition and can therefore be quantitatively studied with a variety of experimental techniques. Compared to free-standing or vesicle membranes, they are more long-term stable even though their in-plane fluidity equals that of free bilayers.1 tBLMs can be formed by rapid solvent exchange (RSE),2,3 which leads to highly electrically insulating, defect-free bilayers, or by vesicle fusion. Here we develop an alternative way of forming tBLMs by fusing mixed lipid-detergent micelles. Self-assembled monolayers (SAMs) of tether lipid are formed on gold surface and incubated with mixed lipid-detergent micelles. At this point, the mixed micelles are stable and lipid will not interact with the SAM. However, upon dilution with buffer to a detergent concentration smaller than the CMC, micelles disintegrate. Because the CMC of phospholipids is high, they deposit on the SAM while detergent molecules dissolve as monomers in solution. The deposition process is simultaneously monitored by surface plasmon resonance (SPR) and electrochemical impedance spectroscopy (EIS). EIS reveals that the resistances of resulting tBLM are comparable to that of tBLMs formed by RSE or vesicle fusion. To demonstrate the general applicability of this method, we studied the formation of tBLMs from mixed micelles of DPhyPC + CHAPS, DOPC + CHAPS and DPhyPC + decylmaltoside. Formation of tBLM by this method could be used to incorporate integral membranes protein into tBLMs in which the use of detergent is unavoidable.1. Shenoy et al, Soft Matter, 2010, 6, 1263.2. McGillivray DJ et al, Biointerphases, 2007, 2, 21.3. Heinrich F et al, Langmuir, 2009, 25, 4219.