Solubilization of planar bilayers with detergent.

The interaction of the nonionic detergent Triton X-100 with supported phosphatidylcholine planar lipid bilayers has been investigated by optically monitoring changes in the bilayer, using the technique of optical waveguide lightmode spectroscopy (OWLS). This technique has several advantages over the methods applied to the problem hitherto, including: high sensitivity; measurement in situ with good time resolution; the fact that the free detergent concentration is well-defined, and the lipid concentration in solution is zero; ease of studying the reversibility of the interaction; and the readiness with which absolute rather than effective amounts of detergent incorporated into the lipid can be determined. The main finding is that as the free Triton concentration increases, the detergent is first incorporated reversibly into the bilayer, then partly but never completely removes lipid, and finally (at or above the cmc) completely solubilizes the bilayer. The behaviour of the lanar supported lipid bilayers is thus similar to that previously reported for lipid vesicles. Copyright 1998 Elsevier Science B.V.