We present three methods for obtaining infinitely dilute partial molar quantities (volume, enthalpy, isothermal compressibility, heat capacity, etc.) from molecular dynamics simulations. Two approaches for obtaining fluctuating quantities, which both require simulations across a range of compositions, are also compared. The first uses fluctuations in the bulk properties of the system, while the second obtains the fluctuations from simulations over a variety of temperatures and pressures. These methods both work by fitting the molar property of interest as a function of composition, taking partial derivatives to obtain the partial molar quantities, and then interpolating the infinitely dilute partial molar quantities. We show how these methods can be used to determine changes to peptide or protein thermodynamic properties upon undergoing a conformational change. A third approach, which theoretically requires only one simulation, is also introduced. This last method is based upon fluctuations in a local, grand-canonical region within a closed simulation system using the Fluctuation Theory of solutions.

Obtaining infinitely dilute partial molar quantities from computer simulations

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.