Proton pumping by complex I (NADH : ubiquinone oxidoreductase) from Yarrowia lipolytica reconstituted into proteoliposomes

The mechanism of energy converting NADH:ubiquinone oxidoreductase (complex 1) is Still unknown. A current controversy centers around the question whether electron transport of complex I is always linked to vectorial proton translocation or whether in some organisms the enzyme pumps sodium ions instead. To develop better experimental tools to elucidate its mechanism, we have reconstituted the affinity purified enzyme into proteoliposomes and monitored the generation of Delta pH and Delta psi. We tested several detergents to solubilize the asolectin used for liposome formation. Tightly coupled proteoliposomes containing highly active complex I were obtained by detergent removal with BioBeads after total solubilization or the phospholipids with n-octyl-beta-D-glucopyranoside. We have used dyes to monitor the formation of the two components of the proton motive force, Delta pH and Delta psi, across the liposomal membrane, and analyzed the effects of inhibitors, uncouplers and ionophores on this process. We show that electron transfer of complex I of the lower eukaryote Y. lipolytica is clearly linked to proton translocation. While this study was not specifically designed to demonstrate possible additional sodium translocating properties of complex 1, we did not find indications for primary or secondary Na+ translocation by Y lipolytica complex I. (c) 2005 Elsevier B.V. All rights reserved.

A general framework for measuring inconsistency through minimal inconsistent sets

Hunter and Konieczny explored the relationships between measures of inconsistency for a belief base and the minimal inconsistent subsets of that belief base in several of their papers. In particular, an inconsistency value termed MIVC, defined from minimal inconsistent subsets, can be considered as a Shapley Inconsistency Value. Moreover, it can be axiomatized completely in terms of five simple axioms. MinInc, one of the five axioms, states that each minimal inconsistent set has the same amount of conflict. However, it conflicts with the intuition illustrated by the lottery paradox, which states that as the size of a minimal inconsistent belief base increases, the degree of inconsistency of that belief base becomes smaller. To address this, we present two kinds of revised inconsistency measures for a belief base from its minimal inconsistent subsets. Each of these measures considers the size of each minimal inconsistent subset as well as the number of minimal inconsistent subsets of a belief base. More specifically, we first present a vectorial measure to capture the inconsistency for a belief base, which is more discriminative than MIVC. Then we present a family of weighted inconsistency measures based on the vectorial inconsistency measure, which allow us to capture the inconsistency for a belief base in terms of a single numerical value as usual. We also show that each of the two kinds of revised inconsistency measures can be considered as a particular Shapley Inconsistency Value, and can be axiomatically characterized by the corresponding revised axioms presented in this paper.

Efficient excitation of dielectric-loaded surface plasmon-polariton waveguide modes at telecommunication wavelengths

The excitation of surface plasmon-polariton (SPP) waveguide modes in subwavelength dielectric ridges deposited on a thin gold film has been characterized and optimized at telecommunication wavelengths. The experimental data on the electromagnetic mode structure obtained using scanning near-field optical microscopy have been directly compared to full vectorial three-dimensional finite element method simulations. Two excitation geometries have been investigated where SPPs are excited outside or inside the dielectric tapered region adjoint to the waveguide. The dependence of the efficiency of the SPP guided mode excitation on the taper opening angle has been measured and modeled. Single-mode guiding and strong lateral mode confinement of dielectric-loaded SPP waveguide modes have been characterized with the near-field measurements and compared to the effective-index method model.

A simple and low-cost method for the preparation of self-supported TiO2-WO3 ceramic heterojunction wafers

Robust, bilayer heterojunction photodiodes of TiO₂-WO₃ were prepared successfully by a simple, low-cost powder pressing technique followed by heat-treatment. Exclusive photoirradiation of the TiO₂ side of the photodiode resulted in a rapid colour change (dark blue) on the WO₃ surface as a result of reduction of W⁶⁺ to W⁵⁺ (confirmed by X-ray photoelectron spectroscopy). This colour was long lived and shown to be stable in a dry environment in air for several hours. A similar photoirradiation experiment in the presence of a mask showed that charge transfer across the heterojunction occurred approximately normal to the TiO₂ surface, with little smearing out of the mask image. As a result of the highly efficient vectorial charge separation, the photodiodes showed a tremendous increase in photocatalytic activity for the degradation of stearic acid, compared to wafers of the respective individual materials when tested separately.