title: Carbocyanine dyes as efficient reversible single-molecule optical switch.
abstract: We demonstrate that commercially available unmodified carbocyanine dyes such as Cy5 (usually excited at 633 nm) can be used as efficient reversible single-molecule optical switch, whose fluorescent state after apparent photobleaching can be restored at room temperature upon irradiation at shorter wavelengths. Ensemble photobleaching and recovery experiments of Cy5 in aqueous solution irradiating first at 633 nm, then at 337, 488, or 532 nm, demonstrate that restoration of absorption and fluorescence strongly depends on efficient oxygen removal and the addition of the triplet quencher beta-mercaptoethylamine. Single-molecule fluorescence experiments show that individual immobilized Cy5 molecules can be switched optically in milliseconds by applying alternating excitation at 633 and 488 nm between a fluorescent and nonfluorescent state up to 100 times with a reliability of >90% at room temperature. Because of their intriguing performance, carbocyanine dyes volunteer as a simple alternative for ultrahigh-density optical data storage. Measurements on single donor/acceptor (tetramethylrhodamine/Cy5) labeled oligonucleotides point out that the described light-driven switching behavior imposes fundamental limitations on the use of carbocyanine dyes as energy transfer acceptors for the study of biological processes.
authors.affiliation: Applied Laserphysics & Laserspectroscopy, Physics Faculty, University of Bielefeld, Universitätsstrasse 25, 33615 Bielefeld, Germany.
authors.forename: Mike
authors.initials: M
authors.lastname: Heilemann
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Margeat
authors.forename: Robert
authors.initials: R
authors.lastname: Kasper
authors.forename: Markus
authors.initials: M
authors.lastname: Sauer
authors.forename: Philip
authors.initials: P
authors.lastname: Tinnefeld
mesh_terms: D001710:Biotin / Q000737:chemistry; D002232:Carbocyanines / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer; D009841:Oligonucleotides / Q000737:chemistry; D055095:Optics and Photonics; D010777:Photochemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry; D019809:Streptavidin / Q000737:chemistry
chemical_list: D002232:Carbocyanines; D004396:Coloring Agents; D009841:Oligonucleotides; C085321:cyanine dye 5; D012710:Serum Albumin, Bovine; D001710:Biotin; D004247:DNA; D019809:Streptavidin