A LITMUS-TEST FOR MOLECULAR RECOGNITION USING ARTIFICIAL MEMBRANES

Background: Sensitive and selective molecular recognition is important throughout biology. Certain organisms and toxins use specific binding at the cell surface as a first step towards invasion. A new series of biomolecular materials, with novel optical and interfacial properties , have been designed to sense molecular recognition events. These poly mers, the diacetylenic lipids, have previously been shown to undergo c hromatic transitions in response to virus binding to the surface of th e material. Results: Gangliosides that specifically bind cholera toxin , heat-labile Escherichia coli enterotoxin and botulinum neurotoxin we re incorporated into a matrix oi diacetylenic lipids, 5-10% of which w ere derivatized with sialic acid. The lipids were self-assembled into Langmuir-Blodgett layers and polymerized with ultraviolet irradiation, yielding a polydiacetylene membrane with a characteristic blue color into which the ganglioside is non-covalently incorporated. When toxin is added, the polymerized membrane turns red. The response is specific and selective, and can be quantified by visible absorption spectropho tometry. Conclusions: Polydiacetylenic Lipid membranes offer a general 'litmus test' for molecular recognition at the surface of a membrane. A concentration of 20 ppm of protein could be detected using polymeri zed thin films. The speed, sensitivity and simplicity of the design of fers a new and general approach towards the direct colorimetric detect ion of a variety of different molecules.