Spiers Memorial Lecture Ions at aqueous interfaces

Studies of aqueous interfaces and of the behavior of ions therein have been profiting from a recent remarkable progress in surface selective spectroscopies, as well as from developments in molecular simulations. Here, we summerize and place in context our investigations of ions at aqueous interfaces employing molecular dynamics simulations and electronic structure methods, performed in close contact with experiment. This result is supported by surface-selective spectroscopic experiments and surface tension measurements. However, it contradicts the interpretation of electrophoretic and titration experiments in terms of strong surgace adsorption of hydroxidie; Simulations show that for alkali cations the dominant mechanism of specific interactions with the surface of hydrate proteins is via ion pairing with negatively charged amino acid residues and with the back bone amide groups. These finding, together with results for more complex molecular ions, allow us to formulate a local model of interactions of ions with proteins with the aim to rationalize at the molecular level ion-specific. Hofmeister effects, e.g. the salting out of proteins.