title: Synthetic ion transporters: pore formation in bilayers via coupled activity of non-spanning cobalt-cage amphiphiles.
abstract: Three amphiphilic cobalt-cage congeners bearing a diaza-crown bridge and varying alkyl chains (1:2:3; n = 12, 16, 18) have been assessed for their ion transport across planar lipid bilayer membranes. In symmetrical electrolyte solutions, a range of ion transport activity is provoked: 1 disrupts painted (fluid) bilayers in a detergent-like mode of action; 2 forms conducting "pores" in folded (rigid) membranes with long open lifetimes (>2 min) while 3 requires the larger auxiliary solvent volume and lower lateral stress of painted membranes to effect ion transport via long-lived pores. Hill analysis of the conductance variation with monomer concentration yields coefficients (2:3; n = 2.3, 1.9) in support of dimeric (n = 2) membrane-active structures, for which the derived "pore" radii are correlated with charge-density of the transported cations and their affinity for the crown moiety. A toroidal-pore model is invoked to account for the flux of guest ions through planar bilayer membranes without a fast-diffusing intermediary or direct membrane-spanning structure.
authors: The Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago. Electronic address: lorale.lalgee@sta.uwi.edu.
authors: Lorale J
authors: LJ
authors: Lalgee
authors: The Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago. Electronic address: Lebert.grierson@sta.uwi.edu.
authors: Lebert
authors: L
authors: Grierson
authors: The Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago. Electronic address: Richard.fairman@sta.uwi.edu.
authors: Richard A
authors: RA
authors: Fairman
authors: The Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago. Electronic address: gina.jaggernauth@sta.uwi.edu.
authors: Gina E
authors: GE
authors: Jaggernauth
authors: The Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago. Electronic address: schulte@sut.ac.th.
authors: Albert
authors: A
authors: Schulte
authors: School of Engineering and Science, Jacobs University Bremen, Germany. Electronic address: r.benz@jacobs-university.de.
authors: Roland
authors: R
authors: Benz
authors: School of Engineering and Science, Jacobs University Bremen, Germany. Electronic address: m.winterhalter@jacobs-university.de.
authors: Mathias
authors: M
authors: Winterhalter
mesh_terms: D003035:Cobalt / Q000378:metabolism*; D017136:Ion Transport; D008051:Lipid Bilayers / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism; D008958:Models, Molecular; D018716:Molecular Mimicry; D013501:Surface-Active Agents / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D013501:Surface-Active Agents; D003035:Cobalt
keywords: Aza-crown spacer; Cobalt-cage metallosurfactant; Lipid bilayer membrane; Liposomes; Synthetic ion transporter