title: Photoinduced transformations in bacteriorhodopsin membrane monitored with optical microcavities.
abstract: Photoinduced molecular transformations in a self-assembled bacteriorhodopsin (bR) monolayer are monitored by observing shifts in the near-infrared resonant wavelengths of linearly polarized modes circulating in a microsphere cavity. We quantify the molecular polarizability change upon all-trans to 13-cis isomerization and deprotonation of the chromophore retinal ( approximately -57 A(3)) and determine its orientation relative to the bR membrane ( approximately 61 degrees ). Our observations establish optical microcavities as a sensitive off-resonant spectroscopic tool for probing conformations and orientations of molecular self-assemblies and for measuring changes of molecular polarizability at optical frequencies. We provide a general estimate of the sensitivity of the technique and discuss possible applications.
authors.affiliation: Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts 02142, USA.
authors.forename: Juraj
authors.initials: J
authors.lastname: Topolancik
authors.forename: Frank
authors.initials: F
authors.lastname: Vollmer
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000528:radiation effects*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D008027:Light; D008567:Membranes, Artificial; D010775:Photic Stimulation / Q000295:instrumentation* / Q000379:methods; D010777:Photochemistry / Q000295:instrumentation* / Q000379:methods
chemical_list: D008567:Membranes, Artificial; D001436:Bacteriorhodopsins