RIKEN/BNL Lunch Time Talk

The milieu of all biological activity is a complex electrolyte solution wherein inorganic ions play an important role. Classical electrolyte theory explains some of the activity of ionic species yet more interesting phenomena in biology such as the electrical activity of the heart and firing of neurons rely on the specific chemistry of the ions. We need a statistical mechanical theory to separately understand the role of physics and chemistry in the interaction of ions with biomaterials.
The excess free energy of ion hydration/binding contains all the information about the behavior of a given ion in solution. We develop a physically motivated framework to interrogate the different contributors to the excess free energy of an ion. We then apply the framework to the study of Na+(aq). We present a possible explanation for the disparate reports of experimentally determined coordination numbers for Na+(aq). We then apply the same framework and provide an explanation for the long standing puzzle of K+ over Na+ selectivity of the KcsA K+ channel, a membrane protein that excludes the smaller Na+ from the ionic current across neurons while allowing the larger K+ to pass.