Electron transport system, composition

A second example of a membrane-bound arsenate reductase was isolated from Sulfurospirillum barnesii and was determined to be a aiPiyi-heterotrimic enzyme complex (Newman et al. 1998). The enzyme has a composite molecular mass of 100kDa, and a-, P-, and y-subunits have masses of 65, 31, and 22, respectively. This enzyme couples the reduction of As(V) to As(III) by oxidation of methyl viologen, with an apparent Kra of 0.2 mM. Preliminary compositional analysis suggests that iron-sulfur and molybdenum prosthetic groups are present. Associated with the membrane of S. barnesii is a h-type cytochrome, and the arsenate reductase is proposed to be linked to the electron-transport system of the plasma membrane. 

Electron transport chain see Respiratory chain. Eiectron transport particies, ETI fragments of mitochondria, obtained by ultrasonic or detergent treatment, which contain the complete electron transport system of the Respiratory chain (see). In the electron microscope, ETP appear as membrane-enclosed vesicles, which are thought by some authors to be a giant molecule of defined composition. Heavy... 

Conducting Polymer Blends, Composites, and Colloids. Incorporation of conducting polymers into multicomponent systems allows the preparation of materials that are electroactive and also possess specific properties contributed by the other components. Dispersion of a conducting polymer into an insulating matrix can be accompHshed as either a miscible or phase-separated blend, a heterogeneous composite, or a coUoidaHy dispersed latex. When the conductor is present in sufftcientiy high composition, electron transport is possible. 

Abstract The supramolecular composites containing fullerenes C60 immobilized at nanosilica were used for the design of the molecular systems that can be an effective agent in cancer photodynamic therapy (PDT). In particular, it was shown that photoexcited fullerene C60-containing composites decrease viability of transformed cells, intensify the process of lipid peroxidation (LPO) in cell membranes and accumulation of low-molecular weight DNA fragments, and also decrease the activity of electron-transport chain of mitochondria. 

Similar investigations have been carried out for the system LaCr xMnx03 [106]. A significant improvement in sinterability appears when Mn is substituted for Cr. For example, densities above 95% of theoretical were achieved at 1475 °C in air for La0.9Sr0 ]Cr03Mn07O3. Electrical conductivity and Seebeck coefficient results are interpreted by a small polaron mechanism for all compositions. This is illustrated for conductivity in Fig. 33. It was also demonstrated that the carrier (electron hole) mobility rather than carrier concentration governs the electronic transport. 

Most of these activities require both protein and lipid components of the membrane, as well as varying degrees of structural integrity of the membrane or cell. To obtain a chemical and physical understanding of membrane phenomena, it is necessary to isolate membranes and study their composition and structural arrangements. Ideally, you would reconstruct the phenomena of interest in isolated membranes or reconstituted systems made from membrane components. In some cases, this is difficult to carry out. An example of the study of biochemical functions in isolated membrane fractions is the characterization of electron transport performed in Experiment 14. 

Fujita, Y. and Murakami, A. 1987. Regulation of electron transport composition in cyano-bacterial photosynthetic system stoichiometry among PSI and PSII complexes and their light harvesting antenna and Cyt bt, f complex. Plant Cell Physiol. 28, 1547-1553. 

Thus, the reduced form of cytochrome P-450 functions as the oxygenactivating biocatalyst of a wide variety of mixed-function oxidations by vertebrate tissues effecting biosynthesis and catabolism of steroid hormones, bile acid formation, and the metabolism of drugs and other xeno-biotics (16). Since reduced pyridine nucleotides do not react directly with hemoproteins, the hydroxylase systems must include components that mediate the electron transport from TPNH to cytochrome P-450. There also must be distinctive diflFerences in composition causing the substrate specificity of the oxygenations. 

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