Halil Bayraktar, Alexander P. Fields, Joel M. Kralj, John L. Spudich, Kenneth J. Rothschild and Adam E. Cohen Ultrasensitive Measurements of Microbial Rhodopsin Photocycles Using Photochromic FRET Photochemistry and Photobiology 88
Article first published online: 17 NOV 2011 | DOI: 10.1111/j.1751-1097.2011.01011.x
Blue proteorhodopsin and Sensory Rhodopsin II are transmembrane proteins with a light-induced photocycle. The retinal chromophore undergoes dramatic shifts in absorption spectrum during the photocycle, but absorption measurements lack sensitivity to detect these shifts in microscopic samples. We generated a fluorescence-based readout of the photocycle by appending a small organic fluorophore to the protein. The fluorescence was quenched during phases of the photocycle in which the absorption spectrum of the retinal overlapped with the emission spectrum of the dye, an effect called photochromic fluorescence resonance energy transfer. We observed the photocycle in samples as small three molecules.
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