Optical amplification of ligand-receptor binding using liquid crystals.

Liquid crystals (LCs) were used to amplify and transduce receptor-mediated binding of proteins at surfaces into optical outputs. Spontaneously organized surfaces were designed so that protein molecules, upon binding to ligands hosted on these surfaces, triggered changes in the orientations of 1- to 20-micrometer-thick films of supported LCs, thus corresponding to a reorientation of approximately 10(5) to 10(6) mesogens per protein. Binding-induced changes in the intensity of light transmitted through the LC were easily seen with the naked eye and could be further amplified by using surfaces designed so that protein-ligand recognition causes twisted nematic LCs to untwist. This approach to the detection of ligand-receptor binding does not require labeling of the analyte, does not require the use of electroanalytical apparatus, provides a spatial resolution of micrometers, and is sufficiently simple that it may find use in biochemical assays and imaging of spatially resolved chemical libraries.

Langmuir-Blodgett films of cytochrome P450scc and its complex with adrenodoxin.

Langmuir-Blodgett films prepared from cytochrome P450scc and its complex with adrenodoxin have been prepared and studied. Adrenodoxin was preliminarily selectively modified with fluorescein isothiocyanate and the effect of this modification on the interaction with cytochrome P450scc was studied. Using selectively modified adrenodoxin the ratio of the proteins in the film was found to be 1 mole of adrenodoxin per 2 moles of cytochrome P450scc. Langmuir-Blodgett films were also prepared from adrenodoxin-reductase and it was shown that this flavoprotein is transferred to the substrate as an apo-protein. It is also shown that the adrenodoxin-binding region of cytochrome P450scc is exposed to the subphase under all pressures in the interval studied. The relationship between the orientation of cytochrome P450scc-adrenodoxin complex in monolayers on the water-air interface and the pressure produced at the interface at the moment of monolayer formation was found. Our data are in excellent accordance with ideas on the molecular organization of cytochrome P450scc in the inner adrenocortical membrane and allows the use of this approach to model membrane structures containing cytochrome P450.