8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.20Thu 811:10-14:00Computer simulation study of the transfer of simple andcomposite ions through water /organic interface - anintrinsic approach -Mária Darvas 11 Eötvös Loránd University of Sciences, Pázmány Péter stny 1/A, H-1117, Budapest,HungaryThe transfer of small molecules and ions through various interfaces plays a decisive role in manybiochemical processes, such as the absorption of nutrients, anabolism and neural transmission ofstimuli. Preceding computational studies focused on the potential of mean force of the transferof ions and biochemically important molecules as well as on the distribution such particles inthe vicinity of interfaces. However, to best of our knowledge, the free energy profiles obtainedfrom such simulation were only presented with respect to the macroscopic imaginary plane ofthe interface. Within the framework of our present studies we introduce a novel intrinsic approachto the calculation of the free energy profile of transfer of various ions and molecules -namely thiocyanate- (SCN - ) and chloride ion, and additionally, methane - through a water/1,2-dichloroethane interface. Our method is based on the ITIM analysis from which we may obtainthe full list of interfacial molecules for an arbitrary, conveniently chosen number of frames, whichobviously allows us to calculate the intrinsic distance of the ion/molecule in question from thereal intrinsic molecularly rough interface. Thus, by merging the ITIM analysis with the existingmethods for PMF calculations, we may map the free energy of solvation with a higher accuracy,with respect to the true surface instead of the approximated molecularly flat macroscopic plane ofthe interface.20