Combination of RISM and Cheminformatics for Efficient Predictions of Hydration Free Energy of Polyfragment Molecules:Application to a Set of Organic Pollutants

摘要

Here, we discuss a new method for predicting the hydration free energy (HFE) of organic pollutants and illustrate theefficiency of the method on a set of 220 chlorinated aromatic hydrocarbons. The new model is computationally inexpensive,with one HFE calculation taking less than a minute on a PC. The method is based on a combination of a molecular integralequations theory, one-dimensional reference interaction site model (1D RISM), with the cheminformatics approach. We correctHFEs obtained by the 1D RISM with a set of empirical corrections. The corrections are associated with the partial molarvolume and structural descriptors of the molecules. We show that the introduced corrections can significantly improve thequality of the 1D RISM HFE predictions obtained by the partial wave free energy expression [Ten-no, S. J. Chem. Phys. 2001,115, 3724] and the Kovalenko-Hirata closure [Kovalenko, A.; Hirata, F. J. Chem. Phys. 1999, 110, 10095]. We also show thatthe quality of the model can be further improved by the reparametrization using QM-derived partial charges instead of theoriginally used OPLS-AA partial charges. The final model gives good results for polychlorinated benzenes (the mean andstandard deviation of the error are 0.02 and 0.36 kcal/mol, correspondingly). At the same time, the model gives somewhatworse results for polychlorobiphenyls (PCBs) with a systematic bias of -0.72 kcal/mol but a small standard deviation equal to0.55 kcal/mol. We note that the error remains the same for the whole set of PCBs, whereas errors of HFEs predicted withcontinuum solvation models (data were taken from Phillips, K. L. et al. Environ. Sci. Technol. 2008, 42, 8412) increasesignificantly for higher chlorinated PCB congeners. In conclusion, we discuss potential future applications of the model andseveral avenues for its further improvement.