title: Cation-Selective Channel Regulated by Anions According to Their Hofmeister Ranking.
abstract: Specificity of small ions, the Hofmeister ranking, is long-known and has many applications including medicine. Yet it evades consistent theoretical description. Here we study the effect of Hofmeister anions on gramicidin A channels in lipid membranes. Counterintuitively, we find that conductance of this perfectly cation-selective channel increases about two-fold in the H2PO4-<Cl-≈Br-≈NO3-<ClO4-<SCN-series. Channel dissociation kinetics show even stronger dependence, with the dwell time increasing about 20-fold. While the conductance can be quantitatively explained by the changes in membrane surface potential due to exclusion of kosmotropes from (or accumulation of chaotropes at) the surface, the kinetics proved to be more difficult to treat. We estimate the effects of changes in the energetics at the bilayer surfaces on the channel dwell time, concluding that the change would have to be greater than typically observed for the Hofmeister effect outside the context of the lipid bilayer.
authors.affiliation: Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bldg. 9, Rm 1 N-124B, Bethesda, MD, 20892, USA.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Gurnev
authors.affiliation: Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bldg. 9, Rm 1 N-124B, Bethesda, MD, 20892, USA.|Department of Physics, Indiana University Purdue University Indianapolis, Indianapolis, IN, 46202, USA.
authors.forename: Torri C
authors.initials: TC
authors.lastname: Roark
authors.affiliation: Department of Physics, Indiana University Purdue University Indianapolis, Indianapolis, IN, 46202, USA.
authors.forename: Horia I
authors.initials: HI
authors.lastname: Petrache
authors.affiliation: Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bldg. 9, Rm 1 N-124B, Bethesda, MD, 20892, USA.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Sodt
authors.affiliation: Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bldg. 9, Rm 1 N-124B, Bethesda, MD, 20892, USA.
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Bezrukov
mesh_terms: D000838:Anions / Q000378:metabolism*; D001407:Bacillus / Q000378:metabolism; D002412:Cations / Q000378:metabolism*; D006096:Gramicidin / Q000378:metabolism*; D017136:Ion Transport; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism*; D013816:Thermodynamics; D053835:Unilamellar Liposomes / Q000378:metabolism
chemical_list: D000838:Anions; D002412:Cations; D008051:Lipid Bilayers; D053835:Unilamellar Liposomes; D006096:Gramicidin
keywords: interface phenomena; ion channels; ion specificity; membranes; nanopores