Conductance

About: Conductance is a research topic. Over the lifetime, 8088 publications have been published within this topic receiving 235961 citations.

Observation of microwave-induced zero-conductance state in Corbino rings of a two-dimensional electron system.

Abstract: Using Corbino samples we have observed oscillatory dc conductance in a high-mobility two-dimensional electron system when it is subjected to crossed microwave and magnetic fields. At the strongest of the oscillation minima the conductance is found to be vanishingly small, indicating a macroscopic insulating state associated with this minimum. With increasing voltage bias, a crossover from Ohmic to electron-heating regime is observed.

Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons

Abstract: Sodium pentobarbital and sodium thiopental decrease both the peak initial (Na) and late steady-state (K) currents and reduce the maximum sodium and potassium conductance increases in voltage-clamped lobster giant axons. These barbiturates also slow the rate at which the sodium conductance turns on, and shift the normalized sodium conductance vs. voltage curves in the direction of depolarization along the voltage axis. Since pentobarbital (pKa = 8.0) blocks the action potential more effectively at pH 8.5 than at pH 6.7, the anionic form of the drug appears to be active. The data suggest that these drugs affect the axon membrane directly, rather than secondarily through effects on intermediary metabolism. It is suggested that penetration of the lipid layer of the membrane by the nonpolar portion of the barbiturate molecules may cause the decrease in membrane conductances, while electrostatic interactions involving the anionic group on the barbiturate, divalent cations, and "fixed charges" in the membrane could account for the slowing of the rate of sodium conductance turn-on and the shift of the normalized conductance curves along the voltage axis.

Changes in the conductance of single peptide molecules upon metal-ion binding.

Abstract: As the field of silicon-based microelectronics attempts, with difficulty, to head towards the nanoscale, the construction of electronic devices with individual molecules becomes an attractive alternative and has stimulated a recent surge of interest in the study of the electronic properties of single molecules. As well as displaying excellent electronic properties, single molecules can also recognize other molecules through specific binding interactions, which is something that current silicon-based technology is unable to offer. This capability of molecular recognition is used with astonishing accuracy and efficiency in biological systems and serves as an important design principle for chemical and biological sensors. Various molecular recognition processes have been studied and applied to sensor applications, but most methods to date measure an optical, electrochemical, or mechanical signal that arises from a large number of molecules. Herein we demonstrate that the binding of a guest species onto a single host molecule can be studied electrically by wiring the host molecule to two electrodes. The measurement of electron-transport processes through a single molecule also allows the rectification properties of asymmetric host molecules and host–guest complexes to be studied. Peptides were chosen as the host molecules because of the unlimited choice of different sequences that can be tuned to obtain optimal binding strength and specificity for a metal ion—our chosen guest. Four peptides were studied, cysteamine-Cys, cysteamine-Gly-Cys, Cys-Gly-Cys, and cysteamine-Gly-Gly-Cys (Cys= cysteine, Gly= glycine), which each have two thiol termini that can form reproducible contact to Au electrodes for electrical measurement. These peptides were expected to bind transition-metal ions, such as Cu and Ni, specifically through deprotonated peptide bonds. The binding configuration and the binding constant are sensitive to the pH of the peptide local environment. To form the most stable metal–peptide complexes and also to avoid the precipitation of metal hydroxides on the Au electrodes, the pH of the solution was maintained at 8 and 9 for Cu and Ni, respectively. Under the experimental conditions, the metal ions and the peptides were expected to form mainly 1:1 metal-to-ligand complexes. For cysteamineCys, cysteamine-Gly-Cys, and Cys-Gly-Cys, the peptide bonds are completely deprotonated so the number of deprotonated