title: Excited state dynamics of the photoconvertible fluorescent protein Kaede revealed by ultrafast spectroscopy.
abstract: The ultrafast excited state dynamics of the fluorescent protein Kaede has been investigated by employing time resolved fluorescence and transient absorption. Upon irradiation of its neutral state, the protein undergoes an efficient conversion to a state that fluoresces at longer wavelengths. The molecular basis of the photoconversion involves an expansion of the chromophore π-conjugation by formal β-elimination but details of the reaction pathway remain subject to debate. Based on the kinetics observed in experiments on the protein sample in both H2O and D2O buffers, we suggest that a light-initiated cleavage mechanism (20 ps) could take place, forming the neutral red state in which the red chromophore resides. Excitation of the neutral red form results in the formation of the red anionic species via two Förster resonance energy transfer (FRET) channels. FRET between red neutral and red anionic forms occurs within the tetramer with time constants of 13.4 ps and 210 ps. In contrast to literature proposals no ESPT was observed.
authors.affiliation: Laboratory of Photochemistry and Spectroscopy, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium.
authors.forename: Eduard
authors.initials: E
authors.lastname: Fron
authors.forename: Michel
authors.initials: M
authors.lastname: Sliwa
authors.forename: Virgile
authors.initials: V
authors.lastname: Adam
authors.forename: Jan
authors.initials: J
authors.lastname: Michiels
authors.forename: Susana
authors.initials: S
authors.lastname: Rocha
authors.forename: Peter
authors.initials: P
authors.lastname: Dedecker
authors.forename: Johan
authors.initials: J
authors.lastname: Hofkens
authors.forename: Hideaki
authors.initials: H
authors.lastname: Mizuno
mesh_terms: D000042:Absorption; D000818:Animals; D017666:Deuterium Oxide; D005453:Fluorescence; D031541:Fluorescence Resonance Energy Transfer; D007700:Kinetics; D008164:Luminescent Proteins / Q000737:chemistry*; D013057:Spectrum Analysis; D013997:Time Factors; D014867:Water
chemical_list: C513582:Kaede protein, Trachyphyllia geoffroyi; D008164:Luminescent Proteins; D014867:Water; D017666:Deuterium Oxide