G.B. Khomutov

Effect of electron transfer inhibitors on superoxide generation in the cytochrome bc1 site of the mitochondrial respiratory chain.

Antimycin, 2‐nonyl‐4‐hydroxyquinoline N‐oxide and funiculosin induce O·− 2 generation by submitochondrial particles oxidizing succinate, whereas KCN, mucidin, myxothiazol or 2,3‐dimercaptopropanol inhibit O·− 2 generation. Thenoyltrifluoroacetone does not induce superoxide production by itself but slightly stimulates the reaction initiated by antimycin. The results indicate that auto‐oxidation of unstable ubisemiquinone formed in centre o of the Q‐cycle generates most of the O·− 2 radicals in the cytochrome bc 1‐site of the mitochondrial respiratory chain.

Superoxide generation by the respiratory chain of tumor mitochondria.

O2-. generation by the succinate oxidase segment of the respiratory chain of mitochondria and submitochondrial particles from hepatoma 22a and hepatoma Zajdela has been studied with the use of the Tiron method. In the presence of succinate, superoxide generation is induced by antimycin, 2-n-4-hydroxyquinoline N-oxide or funiculosin, and is inhibited by mucidin, myxothiazol or cyanide. The rate of O2-. generation in the antimycin-inhibited state is maximal at the [succinate]/[fumarate] ratio of 1:10 and diminishes at more positive and more negative redox potentials. These characteristics of O2-.-generation are the same as observed earlier in submitochondrial particles from normal tissues. Accordingly, the mechanism of superoxide production is suggested to be the same in tumor and normal mitochondria, namely, autoxidation of the unstable ubisemiquinone in the ubiquinol-oxidizing centre o of cytochrome bc1 complex. With respect to the rate of O2-. generation, the hepatoma mitochondrial membranes are approximately twice as active as bovine heart submitochondrial particles and exceed those from rat liver by more than one order of magnitude.

Electron transport control in chloroplasts. Effects of photosynthetic control monitored by the intrathylakoid pH

Abstract (1) In isolated chloroplasts (class B) electron flow is controlled mainly by the intrathylakoid pH (pHin). A decrease in pHin due to the light-driven injection of protons inside the thylakoid leads to the retardation of electron flow between two photosystems. This effect can be abolished by uncouplers or under photophosphorylation conditions (addition of Mg2+-ADP with Pi); Mg2+-ATP does not influence the steady-state rate of electron flow, (2) The steady-state pH difference, ΔpH, across the thylakoid membrane was estimated from quantitative analysis of the rate of P-700+ reduction. In chloroplasts, without adding Mg2+-ADP, ΔpH increases from 1.6 to 3.2 as the external pH rises from 6 to 9.5. Under the photophosphorylation conditions, ΔpH decreases showing a minimum at the external pH 7.5 ( Δ pH ⋍ 0.5–1.0 ). (3) The value of photosynthetic control, K, measured as the ratio of the steady-state rates of P-700+ reduction in the presence of Mg2+-ADP (with Pi) and without adding Mg2+-ADP is dependent on external pH variations, showing a maximum value of K ⋍ 3.5 at pHout 7.5. This pH dependence coincides with that of the ADP-stimulated ΔpH decrease. (4) Experiments with spin labels provide evidence that the light-induced changes in the thylakoid membrane are sensitive to the addition of uncouplers and are affected only slightly by the addition of Mg2+-ADP and Pi.

Single-electron transistor based on a single cluster molecule at room temperature

A single-electron molecular transistor is implemented at room temperature on the basis of a stable Langmuir monomolecular film consisting of a mixture of stearic acid and carborane clusters. Control of the tunneling current with the aid of an independent voltage source is recorded at room temperature. The results are compared with the “orthodox” theory of single-charge electronics.

Molecular clusters as building blocks for nanoelectronics: the first demonstration of a cluster single-electron tunnelling transistor at room temperature

This work is the result of coherent effort of a multi-disciplinary research team working for a considerable number of years in the former USSR in the area of nanocluster molecular electronics. For the first time the successful demonstration of a single-electron tunnelling transistor working reliably at room temperature and based on a single molecular metallorganic cluster is presented. A broad spectrum of different molecular clusters was investigated. Our group has developed a complete cycle of custom-designed molecular cluster manufacturing, deposition, characterization and modification of nanoelectronic devices based on a single molecular cluster. It was shown that the atomic and electronic structure of nanoclusters containing from 3 up to 23 metal atoms had no crucial importance for the transistor fabrication. At the same time extensive research into characteristics of nanoelectronic devices based on single molecular clusters and their tunnelling properties is summarized.

Promising avenues of research in nanoscience : chemistry of semiconductor nanoparticles

The state-of-the-art in the field of research on semiconductor nanoparticles is analyzed; cadmium chalcogenide nanoparticles are considered in most detail. Emphasis is placed on the methods of synthesis and on control of the size, composition, and structure of semiconductor nanoparticles — “quantum dots”. The state of the surface plays a significant role in determining the properties of nanoparticles. Organized nanostructures comprised of quantum dots are considered. The properties of semiconductor nanoparticles are described. Prospects for applications of semiconductor nanomaterials are discussed.

STM study of morphology and electron transport features in cytochrome c and nanocluster molecule monolayers

The morphology and electron tunneling through single cytochrome c and nanocluster Pt(5)(CO)(7)[P(C(6)H(5))](4) molecules organized as monolayer Langmuir-Blodgett (LB) films on graphite substrate have been studied experimentally using scanning tunneling microscopy (STM) and spectroscopy techniques with sub-nanometer spatial resolution in a double barrier tunnel junction configuration STM tip-monomolecular film-conducting substrate at ambient conditions. STM images of the films revealed globular structures with characteristic diameters (approximately 3.5 nm for the protein molecule and approximately 1.2 nm for the nanocluster). The spectroscopic study by recording the tunneling current-bias voltage (I-V) curves revealed tunneling I-V characteristics with features as steps of different width and heights that are dependent on the STM tip position over the molecule in the monolayer, giving evidence for sequential discrete electron-tunneling effects with the combination of the single electron Coulomb-charging energy and the electronic energy level separation (molecular spectrum) in such immobilized metalloprotein and nanocluster structures that can be of interest for the development of bioelectronic and hybrid functional nanosystems.

Interfacial nanofabrication strategies in development of new functional nanomaterials and planar supramolecular nanostructures for nanoelectronics and nanotechnology

Clusters, nanoparticles, nanowires, long molecules as nanotubes and polynucleotides, and functional supramolecular nanostructures are currently considered as potential building blocks for nanotechnology and nanoelectronic devices and circuits, and development and introduction of new methods to control effectively their structure, composition and nanoscale organization are necessary. Here we describe a number of new nanofabrication methods which are based on the monolayer techniques, biomimetic principles, interfacial reactions and interactions. The methods allowed to produce new stable reproducible planar one-dimensional and two-dimensional arrays of ligand-stabilized nanoclusters and nanoparticles on solid substrates, ultrathin polymeric nanoscale-ordered mono- and multilayer quasi-crystalline and nanocomposite films, planar polymeric complex films with integrated DNA and inorganic building blocks as semiconductor and iron oxide nanoparticle quasi-linear arrays and nanowires. Transmission electron microscopy, STM and AFM techniques were used to characterize the fabricated nanostructures. Effects related to discrete electron tunneling were observed in the monolayers of nanoclusters and small gold nanoparticles at room temperature using STM.

Membrane lipid composition, fluidity, and surface charge changes in response to growth of the fresh water cyanobacterium Synechococcus 6311 under high salinity☆

The effect of adaptation to saline growth of a fresh water cyanobacterium Synechococcus 6311 on components of the cytoplasmic membranes and thylakoids was investigated. Significant changes in membrane surface charge, lipid, fatty acid, and carotenoid composition were observed upon transfer of the cells from a low salt (0.015 M NaCl) to a high salt (0.50 M NaCl) growth medium. Very similar changes in the polar lipid classes and fatty acid composition were observed in both membranes, but changes in fluidity and surface charge and a significant shift in the protein to lipid ratio were only apparent in the cytoplasmic membranes. The fluidity and surface charge data correlate well with functional studies and we can attribute the cytoplasmic membrane as the major site of interaction and adaptation to the saline environment.

Two-dimensional synthesis of anisotropic nanoparticles

Abstract A novel approach for the synthesis of nanoparticles has been introduced in which nanoparticles are fabricated via decomposition of an insoluble precursor compound in a monolayer at the gas/liquid interface, and nanoparticle growth is an example of a two-dimensional (2-D) process where true 2-D diffusion of precursor molecules, active intermediates, metal atoms and its complexes, nucleus and growing nanoparticles, surfactants and additives occurs only in the plain of the monolayer. In the present contribution, two possible example embodiments of the approach are described. First, magnetic iron-containing nanoparticles were photochemically generated by the ultraviolet decomposition of a volatile precursor compound iron pentacarbonyl in a mixed Langmuir monolayer. Secondly, nanoparticles were produced by the chemical reduction of palladium from Pd 3 (CH 3 COO) 6 molecules and of gold from Au(P(C 6 H 5 ) 3 )Cl in the mixed monolayers. Stearic acid, arachidic acid or octadecyl amine were used as surfactants to form Langmuir monolayers on the aqueous sub-phase surface and to stabilize the growing nanoparticles. Nanoparticles were formed in the 2-D gas phase of a monolayer (at very low or no surface pressure). The morphology of the nanoparticles synthesized was characterized by atomic force microscopy and transmission electron microscopy. It was established that the shape, size and crystallinity of the resulting nanoparticles were dependent substantially on the monolayer composition and state during the growth process. It was demonstrated that the shape of the magnetic nanoparticles can be changed from 2-D isotropic plate and ring-like to the field-aligned ellipsoidal and needle-like when external magnetic field parallel to the plane of particulate monolayer was applied during the synthesis. The effects of self-organization of nanoparticles and formation of 2-D nanostructures are also presented. It is shown that controlling the mixed monolayer composition and compression state opens wide possibilities for the growth regulation of the 2-D growth of nanoparticles and self-organization processes to obtain inorganic nanostructures with various and unique morphologies.