Resolving the problem of trapped water in binding cavities: prediction of host–guest binding free energies in the SAMPL5 challenge by funnel metadynamics

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• 作者：Soumendranath Bhakat ; Pär Söderhjelm
• 关键词：SAMPL5 ; Host–guest complex ; Metadynamics ; Binding free energy ; MD simulation
• 刊名：Journal of Computer-Aided Molecular Design
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：31
• 期：1
• 页码：119-132
• 全文大小：1588KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Physical Chemistry; Computer Applications in Chemistry; Animal Anatomy / Morphology / Histology;
• 出版者：Springer International Publishing
• ISSN：1573-4951
• 卷排序：31

文摘

The funnel metadynamics method enables rigorous calculation of the potential of mean force along an arbitrary binding path and thereby evaluation of the absolute binding free energy. A problem of such physical paths is that the mechanism characterizing the binding process is not always obvious. In particular, it might involve reorganization of the solvent in the binding site, which is not easily captured with a few geometrically defined collective variables that can be used for biasing. In this paper, we propose and test a simple method to resolve this trapped-water problem by dividing the process into an artificial host-desolvation step and an actual binding step. We show that, under certain circumstances, the contribution from the desolvation step can be calculated without introducing further statistical errors. We apply the method to the problem of predicting host–guest binding free energies in the SAMPL5 blind challenge, using two octa-acid hosts and six guest molecules. For one of the hosts, well-converged results are obtained and the prediction of relative binding free energies is the best among all the SAMPL5 submissions. For the other host, which has a narrower binding pocket, the statistical uncertainties are slightly higher; longer simulations would therefore be needed to obtain conclusive results.