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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)
Single myelinated nerve fibres of Rana esculenta were investigated under voltage clamp conditions at 13 degrees C. Fluctuations of steady-state membrane current were measured during the last 152 msec of 190-225 msec pulses depolarizing the membrane by 8-48 mV. Noise power spectral densities were calculated in the frequency range of 6-6-6757 Hz. 2. External(More)
Eine voltage-clamp-Methode für die Membran Ranvierscher Schnürringe wird beschrieben, ihre Fehlermöglichkeiten werden erörtert. Sie benutzt folgendes Prinzip: das Potential im Axoplasma des Schnürrings wird durch Gegenkopplung konstant gehalten und das Potential der Außenlösung so eingestellt, daß das gewünschte Membranpotential entsteht.(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)
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)
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 fibres of the frogRana esculenta. DPA (30nM-3 μM) enhances the current by a component that has the properties expected for a translocation current of DPA ion across the lipid membrane. Analysis(More)
The time course of the membrane currents in the node of Ranvier in which the sodium and potassium conductances have been blocked reveals asymmetries during and after the application of depolarizing and hyperpolarizing voltage-clamp pulses of identical size. Since 1. the integrals of the "on" and "off" current transients were found to be equal and opposite,(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)