title: Photoionization and electron radical recombination dynamics in photoactive yellow protein investigated by ultrafast spectroscopy in the visible and near-infrared spectral region.
abstract: Photoinduced ionization of the chromophore inside photoactive yellow protein (PYP) was investigated by ultrafast spectroscopy in the visible and near-infrared spectral regions. An absorption band that extended from around 550 to 850 nm was observed and ascribed to solvated electrons, ejected from the p-hydroxycinnamic acid anion chromophore upon the absorption of two 400 nm photons. Global kinetic analysis showed that the solvated electron absorption decayed in two stages: a shorter phase of around 10 ps and a longer phase of more than 3 ns. From a simulation based on a diffusion model we conclude that the diffusion rate of the electron is about 0.8 Å(2)/ps in wild type PYP, and that the electron is ejected to a short distance of only several angstroms away from the chromophore. The chromophore-protein pocket appears to provide a water-similar local environment for the electron. Because mutations at different places around the chromophore have different effect on the electron recombination dynamics, we suggest that solvated electrons could provide a new method to investigate the local dielectric environment inside PYP and thus help to understand the role of the protein in the photoisomerization process.
authors.affiliation: Department of Physics and Astronomy, Faculty of Sciences, VU University , De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
authors.forename: Jingyi
authors.initials: J
authors.lastname: Zhu
authors.forename: Laura
authors.initials: L
authors.lastname: Paparelli
authors.forename: Marijke
authors.initials: M
authors.lastname: Hospes
authors.forename: Jos
authors.initials: J
authors.lastname: Arents
authors.forename: John T M
authors.initials: JT
authors.lastname: Kennis
authors.forename: Ivo H M
authors.initials: IH
authors.lastname: van Stokkum
authors.forename: Klaas J
authors.initials: KJ
authors.lastname: Hellingwerf
authors.forename: Marie Louise
authors.initials: ML
authors.lastname: Groot
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004058:Diffusion; D004583:Electrons; D020607:Halorhodospira halophila / Q000378:metabolism; D007700:Kinetics; D009154:Mutation; D020283:Photoreceptors, Microbial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013053:Spectrophotometry; D013055:Spectrophotometry, Infrared
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; C050162:photoactive yellow protein, Bacteria