Surface plasmon resonance (SPR) spectroscopy has been used to follow incorporation and light-induced conformational changes in bovine rhodopsin reconstituted into an egg phosphatidylcholine bilayer deposited on a thin silver film. The magnitude of the SPR spectral changes caused by light varies with pH in a manner paralleling that in flash photolysis experiments, which monitor formation of metarhodopsin II. Irradiation produces an increase of approximately 4 Å in the average thickness of the proteolipid layer, consistent with exposure of recognition sites for the G protein. The results demonstrate that the SPR technology described herein may be used to monitor conformational events in membraneassociated receptors such as rhodopsin.
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