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  • 1
    Electronic Resource
    Electronic Resource
    IONIC PROBES OF MEMBRANE STRUCTURES (1972)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 195 (1972), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: In this paper we have examined the possibility of identifying those membrane structural variables (polar head groups and the nature of hydrocarbon tails) that modulate membrane ionic permeability. Altering the bilayer lipid composition produces variations in physical parameters (surface potential, partition coefficient, and mobility) governing the conductance mediated by neutral carriers of anions and cations. Specifically, the effects of the charged polar head groups are shown to be understandable in terms of the surface potential they produce through the formation of a diffuse double layer, whereas the effects of the viscosity may be demonstrated by “freezing” the membrane. The effects of membrane composition on membrane conductance are illustrated by a third, less well understood, example of how cholesterol alters bilayer conductances. The results indicate the possibility of using positive and negative permeant species as probes of membrane structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1972.tb54807.x
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  • 2
    Electronic Resource
    Electronic Resource
    Na^+-dependent transport of tricarboxylic acid cycle intermediates by renal brush border membranes. Effects on fluorescence of a potential-sensitive cyanine dye
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 640 (1981), S. 767-778 
    Details
    ISSN: 0005-2736
    Keywords: Citrate ; Cyanine dye ; Fluorescence ; Na^+ dependence ; Succinate transport ; Tricarboxylic acid cycle
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(81)90107-3
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of molecular variations of ionophore and lipid on the selective ion permeability of membranes: I. Tetranactin and the methylation of nonactin-type carriers (1976)
    Springer
    The journal of membrane biology 30 (1976), S. 1-44 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The manner in which the molecular structure of the carrier and the lipid composition of the membrane modulate the membrane selectivity among monovalent cations has been investigated for nonactin, trinactin, and tetranactin, which differ only in their degrees of methylation, and for membranes made of two lipids, phosphatidyl ethanolamine and glyceryl dioleate, in which “equilibrium” and “kinetic” aspects of permeation, respectively, are emphasized. Bilayer permeability ratios for Li, Na, K, Rb, Cs, Tl, and NH4 have been characterized and resolved into “equilibrium” and “kinetic” components using a model for carrier-mediated membrane transport which includes both a trapezoidal energy barrier for translocation of the complex across the membrane interior and a potential-dependence of the loading and unloading of ions at the membrane-solution interfaces. The bilayer permeability properties due to tetranactin have been characterized in each of these lipids and found not only to be regular but to be systematically related to those of the less methylated homologues, trinactin and nonactin. This analysis has led to the following conclusions: (1) The change in lipid composition alters the relative contributions of “kinetic”vs. “equilibrium” components to the observed carrier-mediated selectivity. (2) Increased methylation of the carrier increases the contribution of the “kinetic” component to the selectivity relative to that of the “equilibrium” component and additionally alters the “equilibrium” component sufficiently that an inversion in Cs−Na selectivity occurs between trinactin and tetranactin. (3) For all ions and carriers examined, the “reaction plane” for ion-carrier complexation and the width for the “diffusion barrier” can be represented by the same two parameters, independent of the ion or carrier, so that in all cases the complexation reaction senses 10% of the applied potential and the plateau of the “diffusion barrier” extends across 70% of the membrane interior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869658
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  • 4
    Electronic Resource
    Electronic Resource
    A model for anomalous rectification: Electrochemical-potential-dependent gating of membrane channels (1978)
    Springer
    The journal of membrane biology 44 (1978), S. 103-134 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A model is presented for “anomalous rectification” based upon electrical measurements on the egg cell membrane of the starfish. The objective is to postulate a plausible molecular mechanism which yields an expression for the conductance similar to that deduced empirically by Hagiwara and Takahashi (1974), i.e., $$G_K = \frac{{Bc_K^{1/2} }}{{1 + \exp \left( {\frac{{\Delta V - \Delta V_h }}{v}} \right)}},$$ whereB, ΔV h andv are constant,c K is the external K+ concentration, and ΔV(=V−V 0) is the displacement of the membrane potential from its resting value. It is shown that a similar dependence of the conductance on ΔV is expected for a particular class of models in which the K+ ions are also implicated in “gating”. To give a specific example, we consider the case in which the formation of ion-permeable pores requires a voltage-induced orientation of membrane-bound, electrically-charged groups and subsequent complexation of these groups with the external cations. Furthermore, the proportionality betweenG K andc 1 2/K , when the internal K+ concentration is constant, is accounted for by conventional descriptions of the ionic fluxes using Eyring's rate reaction theory. In terms of the present model,B and ΔV h are explicit functions of the internal K+ concentrations and are thus constant only as long as this is unvaried. The particular value ofv required to fit the data (v≃8.4 mV) is rationalized by the assumption that each of the orientable groups carries three negative elementary charges. In addition, the predictions of the present model are compared with those deduced from an alternative viewpoint, which is related to Armstrong's “blocking particle hypothesis”, in that the probability for opening and closing of the pore is assumed to depend on whether the pore is occupied or empty. Differences and similarities between the two models, as well as ways to discriminate between them, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01976035
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