title: Specific ion binding to macromolecules: effects of hydrophobicity and ion pairing.
abstract: Using molecular dynamics simulations in an explicit aqueous solvent, we examine the binding of fluoride versus iodide to a spherical macromolecule with both hydrophobic and positively charged patches. Rationalizing our observations, we divide the ion association interaction into two mechanisms: (1) poorly solvated iodide ions are attracted to hydrophobic surface patches, while (2) the strongly solvated fluoride and to a minor extent also iodide bind via cation-anion interactions. Quantitatively, the binding affinities vary significantly with the accessibility of the charged groups as well as the surface potential; therefore, we expect the ion-macromolecule association to be modulated by the local surface characteristics of the (bio-)macromolecule. The observed cation-anion pairing preference is in excellent agreement with experimental data.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, and Center for Biomolecules and Complex Molecular Systems, Flamingovo nAm. 2, CZ-16610 Prague 6, Czech Republic. mikael.lund@uochb.cas.cz
authors.forename: Mikael
authors.initials: M
authors.lastname: Lund
authors.forename: Robert
authors.initials: R
authors.lastname: Vacha
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
mesh_terms: D003198:Computer Simulation; D005459:Fluorides; D057927:Hydrophobic and Hydrophilic Interactions; D007454:Iodides; D007477:Ions / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry*; D012997:Solvents; D055672:Static Electricity; D014867:Water
chemical_list: D007454:Iodides; D007477:Ions; D046911:Macromolecular Substances; D012997:Solvents; D014867:Water; D005459:Fluorides