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L-type Ca channels contain a cluster of four charged glutamate residues (EEEE locus), which seem essential for high Ca specificity. To understand how this highly charged structure might produce the currents and selectivity observed in this channel, a theory is needed that relates charge to current. We use an extended Poisson-Nernst-Planck (PNP2) theory to(More)
The ionic permeability of a voltage-dependent Cl channel of rat hippocampal neurons was studied with the patch-clamp method. The unitary conductance of this channel was approximately 30 pS in symmetrical 150 mM NaCl saline. Reversal potentials interpreted in terms of the Goldman-Hodgkin-Katz voltage equation indicate a Cl:Na permeability ratio of(More)
Motor endplates of frog semitendinosus muscles were studied under voltage clamp. Current fluctuations induced by iontophoretic application of acetylcholine were analyzed to give the elementary conductance, gamma , and mean open time, tau , of endplate channels. Total replacement of the external Na+ ion by several other metal ions and by many permeant(More)
Asymmetrical displacement currents are measured in the absence and in the presence of the lipophilic anion dipicrylamine (DPA) in the extracellular solution of nerve fibers of the frog Rana esculenta. DPA (30 nM--3 microM) enhances the current by a component that has the properties expected for a translocation current of DPA ion across the lipid membrane.(More)
L-type calcium channels are Ca(2+) binding proteins of great biological importance. They generate an essential intracellular signal of living cells by allowing Ca(2+) ions to move across the lipid membrane into the cell, thereby selecting an ion that is in low extracellular abundance. Their mechanism of selection involves four carboxylate groups, containing(More)
Ionic channels bathed in mixed solutions of two permeant electrolytes often conduct less current than channels bathed in pure solutions of either. For many years, this anomalous mole fraction effect (AMFE) has been thought to occur only in single-file pores containing two or more ions at a time. Most thinking about channels incorporates this view. We show(More)
Background Cl channels in neurons and skeletal muscle are significantly permeable for alkali cations when tested with asymmetrical concentrations of the same salt. Both anion and cation permeation were proposed to require binding of an alkali cation with the pore (Franciolini, F., and W. Nonner. 1987. Journal of General Physiology. 90:453-478). We tested(More)
An approximate electrostatic (ES) excess free energy functional for charged, hard sphere fluids is presented. This functional is designed for systems with large density variations, but may also be applied to systems without such variations. Based on the Rosenfeld method of perturbation about a bulk (homogeneous) reference fluid [Y. Rosenfeld, J. Chem. Phys.(More)
1. Sodium currents (INa) and asymmetrical displacement currents (ID) were measured in the same nerve fibres from Rana esculenta under similar conditions. 2. For exploring possible kinetic and steady state relations between INa and ID the following quantities were compared: (i) the activation of the sodium channels and (ii) the charge displacement of ID. 3.(More)
1. Single, voltage-clamped nerve fibres of Rana esculenta were stimulated with ;P/2' pulse patterns for measuring Na and gating currents at 13 degrees C.2. Gating currents during test pulses to - 122 or + 10 mV were measured after 45 msec conditioning steps to voltages between - 122 and - 18 mV. As the conditioning voltage was made more positive than - 80(More)