Ultrasensitive measurements of microbial rhodopsin photocycles using photochromic FRET

Halil Bayraktar, Alexander P. Fields, Joel M. Kralj, John L. Spudich, Kenneth J. Rothschild, Adam E. Cohen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


Microbial rhodopsins are an important class of light-activated transmembrane proteins whose function is typically studied on bulk samples. Herein, we apply photochromic fluorescence resonance energy transfer to investigate the dynamics of these proteins with sensitivity approaching the single-molecule limit. The brightness of a covalently linked organic fluorophore is modulated by changes in the absorption spectrum of the endogenous retinal chromophore that occur as the molecule undergoes a light-activated photocycle. We studied the photocycles of blue-absorbing proteorhodopsin and sensory rhodopsin II (SRII). Clusters of 2-3 molecules of SRII clearly showed a light-induced photocycle. Single molecules of SRII showed a photocycle upon signal averaging over several illumination cycles.

Original languageEnglish
Pages (from-to)90-97
Number of pages8
JournalPhotochemistry and Photobiology
Issue number1
Publication statusPublished - Jan 2012
Externally publishedYes


FundersFunder number
NIH Office of the DirectorDP2OD007428


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