title: Fast and reversible photoswitching of the fluorescent protein dronpa as evidenced by fluorescence correlation spectroscopy.
abstract: Controlling molecular properties through photoirradiation holds great promise for its potential for noninvasive and selective manipulation of matter. Photochromism has been observed for several different molecules, including green fluorescent proteins, and recently the discovery of a novel photoswitchable green fluorescent protein called Dronpa was reported. Dronpa displays reversible and highly efficient on/off photoswitching of its fluorescence emission, and reversible switching of immobilized single molecules of Dronpa with response times faster than 20 ms was demonstrated. In this Letter, we expand these observations to freely diffusing molecules by using fluorescence correlation spectroscopy with simultaneous excitation at 488 and 405 nm. By varying the intensity of irradiation at 405 nm, we demonstrate the reversible photoswitching of Dronpa under these conditions, and from the obtained autocorrelation functions we conclude that this photoswitching can occur within tens of microseconds.
authors.affiliation: Laboratory of Photochemistry and Spectroscopy, Department of Chemistry, Katholieke Universiteit Leuven, 3001 Heverlee, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Dedecker
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Hotta
authors.forename: Ryoko
authors.initials: R
authors.lastname: Ando
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyawaki
authors.forename: Yves
authors.initials: Y
authors.lastname: Engelborghs
authors.forename: Johan
authors.initials: J
authors.lastname: Hofkens
mesh_terms: D004307:Dose-Response Relationship, Radiation; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D008027:Light; D010777:Photochemistry / Q000379:methods*; D011829:Radiation Dosage; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D049452:Green Fluorescent Proteins