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Conductance
About: Conductance is a research topic. Over the lifetime, 8088 publications have been published within this topic receiving 235961 citations.
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TL;DR: In this paper, the authors measured conductance distribution for single molecule benzenediamine-gold junctions, based on 59,000 individual conductance traces recorded while breaking a gold point contact in solution, has a clear peak at 0.0064 G$_{0}$ with a width of 40%.
Abstract: The measured conductance distribution for single molecule benzenediamine-gold junctions, based on 59,000 individual conductance traces recorded while breaking a gold point contact in solution, has a clear peak at 0.0064 G$_{0}$ with a width of $\pm$ 40%. Conductance calculations based on density functional theory (DFT) for 15 distinct junction geometries show a similar spread. Differences in local structure have a limited influence on conductance because the amine-Au bonding motif is well-defined and flexible. The average calculated conductance (0.046 G$_{0}$) is seven times larger than experiment, suggesting the importance of many-electron corrections beyond DFT.
358 citations
TL;DR: It is found that junctions formed with dimethyl phosphine terminated alkanes have the highest conductance and this allows a detailed analysis of the single-molecule junction elongation properties which correlate well with calculations based on density functional theory.
Abstract: We compare the low bias conductance of a series of alkanes terminated on their ends with dimethyl phosphines, methyl sulfides, and amines and find that junctions formed with dimethyl phosphine terminated alkanes have the highest conductance. We see unambiguous conductance signatures with these link groups, indicating that the binding is well-defined and electronically selective. This allows a detailed analysis of the single-molecule junction elongation properties which correlate well with calculations based on density functional theory.
355 citations
TL;DR: A phenomenological theory considering the output characteristics of oxidative phosphorylation has been worked out by adopting the formalism of linear nonequilibrium thermodynamics and in isolated rat livers perfused in a metabolic resting state, the condition of conductance matching is fulfilled.
Abstract: A phenomenological theory considering the output characteristics of oxidative phosphorylation has been worked out by adopting the formalism of linear nonequilibrium thermodynamics. The linearity of oxidative phosphorylation in the range of the output forces of practical interest has been experimentally verified.
The efficiency of oxidative phosphorylation is zero if either a load with a zero conductance (open-circuited situation) or a load with an infinite conductance (short-circuited situation) is attached to oxidative phosphorylation. In between these extreme conductances there exists a finite load conductance permitting oxidative phosphorylation to operate with optimal efficiency. The necessary and sufficient condition for optimal efficiency was found to be L33/L11=√1−q2 where L11 is the phenomenological conductance of phosphorylation, L33 the phenomenological conductance of the load and q the degree of coupling of oxidative phosphorylation driven by respiration. This condition was called conductance matching.
Under the condition of conductance matching, four output functions of oxidative phosphorylation of practical interest were optimized. A maximal net rate of oxidative phosphorylation occurs at a degree of coupling qf= 0.78. A maximal output power of oxidative phosphorylation, i.e. net rate times established phosphate potential, results at qp= 0.91. The maximization of the function net rate times efficiency yielded an economic degree of coupling qecp= 0.95 for maximal ATP flow. Finally, maximization of the function output power times efficiency led to a degree of coupling qecp= 0.97. This last function simultaneously maximizes net rate of ATP production, developed phosphate potential and efficiency and reflects therefore the most economic solution to the output problem under the condition of conductance matching.
In isolated rat livers perfused in a metabolic resting state, the condition of conductance matching is fulfilled. In addition, the degree of coupling of oxidative phosphorylation under these conditions corresponds to the economic degree of coupling qecp.
354 citations
TL;DR: A voltage-gated inactivation mechanism is proposed which involves the binding of two polyvalent cations to the channel, one in the open and one in a closed configuration, and which can explain voltage, dose and time dependence of the inactivation.
Abstract: The interaction of Staphylococcus aureus alpha-toxin with planar lipid membranes results in the formation of ionic channels whose conductance can be directly measured in voltage-clamp experiments. Single-channel conductance depends linearly on the solution conductivity suggesting that the pores are filled with aqueous solution; a rough diameter of 11.4 +/- 0.4 A can be estimated for the pore. The conductance depends asymmetrically on voltage and it is slightly anion selective at pH 7.0, which implies that the channels are asymmetrically oriented into the bilayer and that ion motion is restricted at least in a region of the pore. The pores are usually open in a KCl solution but undergo a dose- and voltage-dependent inactivation in the presence of di- and trivalent cations, which is mediated by open-closed fluctuations at the single-channel level. Hill plots indicate that each channel can bind two to three inactivating cations. The inhibiting efficiency follows the sequence Zn2+ greater than Tb3+ greater than Ca2+ greater than Mg2+ greater than Ba2+, suggesting that carboxyl groups of the protein may be involved in the binding step. A voltage-gated inactivation mechanism is proposed which involves the binding of two polyvalent cations to the channel, one in the open and one in the closed configuration, and which can explain voltage, dose and time dependence of the inactivation.
348 citations
TL;DR: The results demonstrate the major role of anatomy in constraining mesophyll diffusion conductance and, consequently, in determining the variability in photosynthetic capacity among species.
Abstract: Abbreviations: α, leaf absorptance; β, fraction of absorbed light that reaches photosystem II; Γ*, CO2 compensation point in the absence of mitochondrial respiration; ФPSII, effective quantum efficiency of the PSII photochemistry; Δ Lias, effective diffusion path length in the gas phase; ϵPSII, fraction of electrons absorbed by PSII; ς, diffusion path tortuosity; Amass, photosynthetic capacity per dry mass; AN, net CO2 assimilation rate; Ca, atmospheric CO2 concentration; Cc, chloroplastic CO2 concentration; Ci, substomatal CO2 concentration; Ci-Cc, CO2 drawdown from intercellular airspace to chloroplasts; Da, diffusion coefficient for CO 2 in the gas phase; DL, leaf density; Dw, aqueous phase diffusion coefficient for CO 2; fias, volume fraction of intercellular air spaces; Fm’, maximum fluorescence in lightadapted state; Fs, steady-state fluorescence emission; g cel, partial liquid phase conductance for different portions along cell walls; gcyt, cytosol conductance; genv, chloroplast envelope conductance; gias, intercellular air space conductance to CO2 (gas phase conductance); gliq, sum of liquid and lipid phase conductances; gm, mesophyll diffusion conductance; gpl, plasma membrane conductance; gs, stomatal conductance to CO2; gtot, total conductance to CO2 from ambient air to chloroplasts; H/(RTk), dimensionless form of Henry’s law constant; JF, linear electron transport rate from chlorophyll fluorescence; J max, maximum photosynthetic electron transport rate; Kc, Michaelis–Menten constant for the carboxylation activity of Rubisco; Ko, Michaelis–Menten constant for the oxygenation activity of Rubisco; lb, biochemical limitation; Lchl, length of chloroplasts exposed to intercellular air spaces; Lcyt, diffusion pathway length in the cytoplasm; lias, gas-phase limitation; lm, mesophyll limitation; ls, stomatal limitation; MA, leaf mass per area; O, leaf internal oxygen concentration; pi, effective porosity in the given part of the diffusion pathway; Q, incident quantum flux density; R, gas constant; R d, leaf respiration in the dark; rf,i, proportional reduction of Dw in the cytosol and in the stroma compared with free diffusion in water; RL, leaf respiration in the light; SC/O, Rubisco specificity factor; S c/S, chloroplast surface area exposed to intercellular air spaces per unit of leaf area; Sc/Sm, ratio of exposed chloroplasts to mesophyll surface areas; Sm/S, mesophyll surface area exposed to intercellular air spaces per unit of leaf area; Ss, cross-sectional area of mesophyll cells in micrograph; SE, standard error; Tchl, chloroplast thickness; Tcw, cell wall thickness; Tcyt, cytoplasm thickness; Tk, absolute temperature; TL, leaf thickness; tmes, mesophyll thickness; Vcmax, maximum rates for the carboxylation activity of Rubisco; W, width of the leaf anatomical section.
346 citations