title: Effect of temperature on excited-state proton tunneling in wt-green fluorescent protein.
abstract: Steady-state emission and time-correlated single-photon counting (TCSPC) are used to measure the temperature dependence of the proton-transfer rate of wt-GFP in H2O and D2O. As the temperature decreases, the proton-transfer rate from the protonated form slows down. At about 80 K, the rate is about 10-fold slower than the rate at room temperature. At lower temperatures of 70 K down to 13 K (the lowest temperature studied), the rate of proton transfer is almost temperature independent. We explain the temperature dependence of the proton-transfer rate by an intermolecular vibration assisted tunneling mechanism. We attribute the specific intermolecular vibration to the oscillation of two oxygen atoms: the chromophore's phenol ring and the nearby water molecule. The kinetic isotope effect is about 5 and is almost temperature independent.
authors.affiliation: Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: P
authors.initials: P
authors.lastname: Leiderman
authors.forename: R
authors.initials: R
authors.lastname: Gepshtein
authors.forename: I
authors.initials: I
authors.lastname: Tsimberov
authors.forename: Dan
authors.initials: D
authors.lastname: Huppert
mesh_terms: D049452:Green Fluorescent Proteins / Q000737:chemistry*; D007554:Isotopes / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D011522:Protons; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D007554:Isotopes; D011522:Protons; D049452:Green Fluorescent Proteins