Berlin 2012 – scientific programme
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BP: Fachverband Biologische Physik
BP 7: Posters: Proteins
BP 7.32: Poster
Monday, March 26, 2012, 17:30–19:30, Poster A
Divalent cation force field optimization based on thermodynamic properties
— •Shavkat Mamatkulov1, Maria Fyta2, and Roland R. Netz1 — 1Fachbereich Physik, Freie Universitat Berlin, 14195 Berlin, Germany
— 2Physik Department, Technische Universitat Munchen, 85748 Garching, Germany
In this work we develop force field parameters of the divalent cations Mg2+, Ca2+, Ba2+, and Sr2+. We perform Molecular Dynamics simulations with explicit water, using the SPC/E water model. The scheme we propose for the derivation of the ionic force fields is based on a simultaneous optimization of single-ion and ion-pair properties. The solvation free energy and the effective radius of the divalent cations are the single ion properties used in our approach. As a probe for the ion pair properties we compute the activity derivatives of salts in aqueous solutions. The optimization of the ionic force fields was done in two distinct steps. First, the solvation free energy and the first maximum in the ion-water radial distribution function (RDF) were determined as a function of the Lennard-Jones (LJ) parameters used in the simulations. Second, knowledge of the combinations of the LJ parameters which reproduce the exact solvation free energy and the first peak in the RDF of the divalent cations allowed us to compute the activity derivatives of the electrolytes such as MgY2, CaY2, BaY2, SrY2, where Y=Cl−, Br−,I−.