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Biomedical subjects

N A Zorin

Publications and source records attributed to N A Zorin.

At least 19 recordsLinked to original sources
PubMed2005

Hydrogenase electrodes for fuel cells.

Considering crucial problems that limit use of platinum-based fuel cells, i.e. cost and availability, poisoning by fuel impurities and low selectivity, we propose electrocatalysis by enzymes as a valuable alternative to noble metals. Hydrogenase electrodes in neutral media achieve hydrogen equilibrium potential (providing 100% energy conversion), and display high activity in H(2) electrooxidation, which is similar to that of Pt-based electrodes in sulphuric acid. In contrast with platinum, enzyme electrodes are highly selective for their substrates, and are not poisoned by fuel impurities. Hydrogenase electrodes are capable of consuming hydrogen directly from microbial media, which ensures their use as fuel electrodes in treatment of organic wastes.

Catalysis↗
PubMed2004

Properties of stable hydrogenase from the purple sulfur bacterium Lamprobacter modestohalophilus.

Some properties of a hydrogenase from the recently isolated phototrophic sulfur bacterium Lamprobacter modestohalophilus strain Syvash and its resistance to a number of inactivating factors have been investigated. The enzyme consists of two subunits, 64 and 30 kD; pI = 4.5. The optimal pH was 8.5-9.5 for hydrogen uptake and 4.0 for H2 evolution. Hydrogenase preparations were resistant to the effects of O2, CO, and temperature, revealing high stability under storage. A considerable inactivation of the enzyme was observed at temperatures above 80 degrees C; the temperature optimum of methyl viologen reduction by H2 was 85 degrees C. Inhibitory effects of Ni2+, Cd2+, and Mg2+ on the hydrogenase activity were shown to be reversible and competitive with respect to methyl viologen in the hydrogen oxidation reaction.

Bacterial Proteins↗
PubMed2002

Direct and electrically wired bioelectrocatalysis by hydrogenase from Thiocapsa roseopersicina.

Hydrogen enzyme electrodes based on direct and mediated bioelectrocatalysis were developed. Direct bioelectrocatalysis of hydrogen oxidation/evolution was observed for hydrogenase adsorbed on carbon filament material. The equilibrium hydrogen potential was achieved on mediatorless hydrogen enzyme electrodes in hydrogen atmosphere. The electrocatalytic activity of hydrogenase in direct bioelectrocatalysis of hydrogen oxidation was two orders of magnitude higher compared to platinum. The reported electrode remained 50% activity after 6 months of storage with periodical testing. Wired bioelectrocatalysis was achieved by adsorption of hydrogenase onto electropolymerized redox mediator N-methyl-N'-(12-pyrrol-1-yl-dodecyl)-4,4'-bipyridinium ditetrafluoroborate.

Catalysis↗
PubMed2000

Characterization of the hydrogen-deuterium exchange activities of the energy-transducing HupSL hydrogenase and H(2)-signaling HupUV hydrogenase in Rhodobacter capsulatus.

Rhodobacter capsulatus synthesizes two homologous protein complexes capable of activating molecular H(2), a membrane-bound [NiFe] hydrogenase (HupSL) linked to the respiratory chain, and an H(2) sensor encoded by the hupUV genes. The activities of hydrogen-deuterium (H-D) exchange catalyzed by the hupSL-encoded and the hupUV-encoded enzymes in the presence of D(2) and H(2)O were studied comparatively. Whereas HupSL is in the membranes, HupUV activity was localized in the soluble cytoplasmic fraction. Since the hydrogenase gene cluster of R. capsulatus contains a gene homologous to hoxH, which encodes the large subunit of NAD-linked tetrameric soluble hydrogenases, the chromosomal hoxH gene was inactivated and hoxH mutants were used to demonstrate the H-D exchange activity of the cytoplasmic HupUV protein complex. The H-D exchange reaction catalyzed by HupSL hydrogenase was maximal at pH 4. 5 and inhibited by acetylene and oxygen, whereas the H-D exchange catalyzed by the HupUV protein complex was insensitive to acetylene and oxygen and did not vary significantly between pH 4 and pH 11. Based on these properties, the product of the accessory hypD gene was shown to be necessary for the synthesis of active HupUV enzyme. The kinetics of HD and H(2) formed in exchange with D(2) by HupUV point to a restricted access of protons and gasses to the active site. Measurement of concentration changes in D(2), HD, and H(2) by mass spectrometry showed that, besides the H-D exchange reaction, HupUV oxidized H(2) with benzyl viologen, produced H(2) with reduced methyl viologen, and demonstrated true hydrogenase activity. Therefore, not only with respect to its H(2) signaling function in the cell, but also to its catalytic properties, the HupUV enzyme represents a distinct class of hydrogenases.

Acetylene↗
PubMed2000

Fabrication of an electrode-viologen-hydrogenase heterogeneous system and the electrochemical hydrogen evolution.

An indium tin oxide (ITO) electrode was chemically modified by one layer of viologen (VIO) derivative, which possessed a persistent and reproducible electrochemical response. A monolayer of a thermal stable hydrogenase from Thiocapsa roseopersicina was stabilized on a synthesized poly-L-lysine subphase surface and transferred onto the electrode for fabrication of an ITO-VIO-hydrogenase heterogeneous system. Electrochemical properties of both the ITO-VIO monolayer and the heterogeneous ITO-VIO-hydrogenase system have been investigated. Hydrogen evolution could be measured by potentiostating the VIO-hydrogenase-covered ITO electrode to "electroplate" [(VIO+)n]surf, and a large increase in hydrogen evolution was observed when using an electrolyte solution containing sodium dithionite. We discuss the possible electron transfer process.

Electrochemistry↗
PubMed2000

Influence of metal ions on hydrogenase from the purple sulfur bacterium Thiocapsa roseopersicina.

The effects of some metal ions on the activity and activation of Thiocapsa roseopersicina hydrogenase have been studied. Inhibitory effects of Ni2+ and Cd2+ on the catalytic activity of the enzyme were reversible and competitive with respect to methyl viologen (MV) in the reaction of hydrogen oxidation. The affinity of these metal ions to the enzyme increased significantly with increasing pH, suggesting that their interactions are determined by electrostatic forces. Cu2+ and Hg2+ irreversibly inhibited the hydrogenase activity. A decrease in absorption of hydrogenase at 400 nm in the presence of these metal ions is indicative of the destruction of the FeS cluster in the enzyme.

Catalysis↗
PubMed1999

In vitro and in vivo coupling of Thiocapsa hydrogenase with cyanobacterial and algal electron mediators.

H2 activation by the oxygen-tolerant hydrogenase from the purple sulfur bacterium Thiocapsa roseopersicina, using electron mediators of cyanobacterial and algal origin, has been demonstrated. Ferredoxins, either from the cyanobacterium Synechococcus PCC7942 or the green alga Scenedesmus obliquus, are capable of providing electrons for hydrogenase-mediated H2 evolution. The high-potential cytochrome c6 from Synechococcus PCC7942 proved to be capable of accepting electrons derived from hydrogenase-mediated H2 oxidation. In subsequent experiments, Thiocapsa hydrogenase was introduced into the cells of Synechococcus PCC7942 by electroporation, for enhanced H2 production.

Journal Article↗
PubMed1999

Tissue distribution of rat macroglobulins in tumour-bearing rats.

Rat macroglobulins were determined in blood sera and extracts of tissues of intact rats and rats with Walker carcinoma by rocket immunoelectrophoresis. The serum levels of alpha1-macroglobulin (alpha1MG) alpha2-macroglobulin (alpha2MG) and pregnancy-associated alpha1-glycoprotein (alpha1PAG) were 1.86 +/- 0.07 mg/ml, 0.12 +/- 0. 02 mg/ml and 18.32 +/- 4.07 AU/ml respectively in control rats. Maximum concentrations of alpha1MG were found in heart, lung and spleen and lesser quantities were in liver and thymus, while alpha2MG and alpha1PAG were not found at all in tissue extracts from control rats. Serum alpha2MG and alpha1PAG concentrations increased more than 30-fold in tumour-bearing rats compared to control animals, while alpha1MG serum concentration was little changed. Increases in all three macroglobulins occurred in the tissues of tumour-bearing rats, particularly alpha1PAG. The tissue concentrations of alpha1MG and alpha2MG were similar and the tissue distribution was also similar with highest concentrations in heart and lung. Considerable quantities of the proteins were found in the tumour and part of peritoneum which made contact with the tumour. Changes in the protein concentrations in serum and tissue extracts of tumour-bearing rats suggest that all members of rat macroglobulin family are disturbed during the development of the Walker carcinoma, though only alpha2MG and alpha1PAG were substantially elevated.

Animals↗
PubMed1998

Rhodobacter capsulatus HypF is involved in regulation of hydrogenase synthesis through the HupUV proteins.

The photosynthetic bacterium Rhodobacter capsulatus contains a membrane-bound [NiFe]hydrogenase encoded by the hupSL genes. We show in this study that hypF mutants are devoid of hydrogenase activity and lack the HupL protein. We also observed that, in contrast to the wild-type strain B10, transcription of the hupSL genes was not stimulated by H2 in the hypF mutants RS13 and BSE19. Complementation of the hypF mutants with the plasmid borne hypF gene restored hydrogenase activity to wild-type levels and inducibility by H2. The R. capsulatus hupU and hupV gene products share significant similarities with the small (HupS) and the large (HupL) hydrogenase subunits, respectively. Active HupUV proteins can catalyze the hydrogen-deuterium exchange reaction. In whole cells, this H-D exchange is distinguishable from the H-D exchange catalyzed by the membrane-bound HupSL proteins by its insensitivity to O2 and to acetylene. By measuring the formation of H2 and HD in exchange with D2 uptake, we demonstrated that the hypF mutants have no active HupUV nor HupSL proteins. H-D exchange activity, of both HupUV and HupSL, was restored by hypF gene complementation. These data indicate that the HypF protein participates not only in the maturation of HupSL, but also in the maturation of the HupUV proteins and that the latter are involved in the cellular response to H2.

Bacterial Proteins↗
PubMed1998

Effect of human alpha2-macroglobulin on proliferative activity of rat tumor cells.

The Walker carcinosarcoma cells were cultured in the medium with low concentration (0.25%) of fetal calf serum, in the presence of native or methylamine-treated (modified) human alpha 2-macroglobulin (alpha 2-MG) in vitro. The proliferative activity (3H-thymidine incorporation) of these cells increased in the presence of one or the other alpha 2-MG preparation. It allows to suppose that the human alpha 2-MG may serve as a growth-stimulating factor of tumour cells.

Animals↗