title: Ground-state proton transfer in the photoswitching reactions of the fluorescent protein Dronpa.
abstract: The reversible photoswitching between the 'on' and 'off' states of the fluorescent protein Dronpa involves photoisomerization as well as protein side-chain rearrangements, but the process of interconversion remains poorly characterized. Here we use time-resolved infrared measurements to monitor the sequence of these structural changes, but also of proton transfer events, which are crucial to the development of spectroscopic contrast. Light-induced deprotonation of the chromophore phenolic oxygen in the off state is a thermal ground-state process, which follows ultrafast (9 ps) trans-cis photoisomerization, and so does not involve excited-state proton transfer. Steady-state infrared difference measurements exclude protonation of the imidazolinone nitrogen in both the on and off states. Pump-probe infrared measurements of the on state reveal a weakening of the hydrogen bonding between Arg66 and the chromophore C=O, which could be central to initiating structural rearrangement of Arg66 and His193 coinciding with the low quantum yield cis-trans photoisomerization.
authors: Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
authors: Mark M
authors: MM
authors: Warren
authors: Marius
authors: M
authors: Kaucikas
authors: Ann
authors: A
authors: Fitzpatrick
authors: Paul
authors: P
authors: Champion
authors: J Timothy
authors: JT
authors: Sage
authors: Jasper J
authors: JJ
authors: van Thor
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D008027:Light; D008164:Luminescent Proteins / Q000378:metabolism*; D008958:Models, Molecular; D010777:Photochemistry; D011522:Protons; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry
chemical_list: D000596:Amino Acids; D008164:Luminescent Proteins; D011522:Protons; D014867:Water
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