Several proton transfer systems were studied by quantum chemical calculations in the presence of further ligand waters. The calculated proton transfer barriers are fitted by an analytical expression, which allows for fast calculation of proton transfer rates between common donor–acceptor pairs in biological systems under the influence of surrounding chemical groups. The only information required is the chemical nature of the donor and acceptor, the distance between donor and acceptor, and the environmental influence in the acceptor and donor bound states. The quantum nature of the transferred proton is approximated at the level of an effective zero-point energy along the reaction coordinate. The approach presented allows efficient calculation of transfer rates and allows to include proton hopping events between titratable sites in classical molecular dynamics simulations.

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