We present a study on the excited state proton transfer in the Green Fluorescent Protein (GFP).The reaction path was followed both in the ground and the first singlet excited state by integrating the intrinsic reaction coordinate.1,2 Previously validated DFT methods were adopted to define the potential energy surfaces of a GFP model, including essential protein effects.3 The analysis of the results revealed that 1) the movement of the protons is attributable to a concerted but asynchronous mechanism, and 2) in the excited state the barrier is lower, and the product is more stable. The role of residues close to the GFP chromophore was also analyzed.As main result, this study supports the hypothesis formulated on the basis of VIS/midIR pump probe spectra,4 suggesting that the electronic excitation favors the proton transfer mostly for changes in the structural arrangement in proximity of the chromophore, leading to a conversion from a short ionic to low barrier hydrogen bond network. References[1] K. Fukui, Acc. Chem. Res. 14, 363 (1981).[2] H.P. Hratchian, and B. Schlegel, J. Chem. Phys. 120, 9918 (2004).[3] A. Petrone et al., Phys. Chem. Chem. Phys., 15, 20536 (2013).[4] M. Di Donato et al., Phys. Chem. Chem. Phys. , 13, 16295 (2011).

Exploring the reactivity by integrating the intrinsic reaction coordinate: The excited state proton transfer in the Green Fluorescent Protein

248th National Meeting (2014)

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