Water-Mediated Interactions

Purdue University, West Lafayette IN

Investigators

Abstract

In this award, funded by the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry, Professor Dor Ben-Amotz of Purdue University of Colorado and his graduate and undergraduate student colleagues are studying the way water influences the behavior of substances dissolved in it. Water-mediated interactions play a central role in biological, medicinal, environmental, and materials chemistry, and yet the magnitudes (and in some cases even the signs) of most such interactions have not been experimentally determined. Hydration-shell spectroscopic measurements are combined with theoretical and simulation analysis to quantify the free energy driving forces and the structural changes associated with the water-mediated aggregation of solutes such as dissolved alcohols, salts, gases, carboxylic acids, and surfactants. The quantitative experimental and theoretical studies of water-mediated interactions may advance the understanding of biochemical systems and of self-assembled devices. The research provides training and mentoring opportunities for graduate and undergraduate students, as they participate in the project. Prof. Ben-Amotz and his research group conducts combined Raman spectroscopy with multivariate curve resolution (Raman-MCR) to measure aggregation-induced changes in hydration-shells of aqueous solutes. A new sequential self-modeling curve resolution strategy is used to quantify changes in the concentrations of non-aggregated and aggregated solute species. Random mixing and molecular dynamics simulations, combined with finite lattice and weighted random mixing theoretical analysis strategies are used to separate direct and water-mediated, as well as energetic and entropic, contributions to the aggregation potential of mean force associated with both binary interactions between pairs of solutes and cooperative interactions between multiple solutes.