title: Octa-Coordination and the Aqueous Ba(2+) Ion.
abstract: The hydration structure of Ba(2+) ion is important for understanding blocking mechanisms in potassium ion channels. Here, we combine statistical mechanical theory, ab initio molecular dynamics simulations, and electronic structure methods to calculate the hydration free energy and local hydration structure of Ba(2+)(aq). The predicted hydration free energy (-304 ± 1 kcal/mol) agrees with the experimental value (-303 kcal/mol) when a maximally occupied, unimodal inner solvation shell is treated. In the local environment defined by the first shell of hydrating waters, Ba(2+) is directly and stably coordinated by eight (8) waters. Octa-coordination resembles the crystal structure of Ba(2+) and K(+) bound in potassium ion channels, but differs from the local hydration structure of K(+)(aq) determined earlier.
authors.affiliation: †Center for Biological and Engineering Sciences, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States.
authors.forename: Mangesh I
authors.initials: MI
authors.lastname: Chaudhari
authors.affiliation: ‡Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148, United States.
authors.forename: Marielle
authors.initials: M
authors.lastname: Soniat
authors.affiliation: †Center for Biological and Engineering Sciences, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States.
authors.forename: Susan B
authors.initials: SB
authors.lastname: Rempe
mesh_terms: D001464:Barium / Q000737:chemistry*; D002413:Cations, Divalent; D056004:Molecular Dynamics Simulation; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D002413:Cations, Divalent; D014867:Water; D001464:Barium