Effect of temperature on excited-state proton tunneling in wt-green fluorescent protein.
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.
Leiderman
P
P
Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
Gepshtein
R
R
Tsimberov
I
I
Huppert
Dan
D
D049452:Green Fluorescent Proteins / Q000737:chemistry*; D007554:Isotopes / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D011522:Protons; D013050:Spectrometry, Fluorescence; D013696:Temperature
D007554:Isotopes; D011522:Protons; D049452:Green Fluorescent Proteins