Search results for "Hydrogen"

Succinate dehydrogenase functioning by a reverse redox loop mechanism and fumarate reductase in sulphate-reducing bacteria.

2006

Sulphate- or sulphur-reducing bacteria with known or draft genome sequences (Desulfovibrio vulgaris, Desulfovibrio desulfuricans G20, Desulfobacterium autotrophicum [draft], Desulfotalea psychrophila and Geobacter sulfurreducens) all contain sdhCAB or frdCAB gene clusters encoding succinate : quinone oxidoreductases. frdD or sdhD genes are missing. The presence and function of succinate dehydrogenase versus fumarate reductase was studied. Desulfovibrio desulfuricans (strain Essex 6) grew by fumarate respiration or by fumarate disproportionation, and contained fumarate reductase activity. Desulfovibrio vulgaris lacked fumarate respiration and contained succinate dehydrogenase activity. Succi…

Über den Abbau von L-Äpfelsäure durch Hefen verschiedener Gattungen mit Malatenzym

1974

Summary (1) The aerobic assimilation of malic acid is not a character of certain yeast genera or species as was shown by testing more than 300 different strains. Single strains of the following-species were found to grow on malic acid as the only carbon source: Candida pulcherrima, C. utilis, C. mycoderma, Torulopsis famata, Pichia membranaefaciens, P. wickerhamii, Hansenula capsulata, Trigonopsis variabilis , and Zygosaccharomyces chevalieri . (2) During fermentation C. pulcherrima and T. famata decompose up to 40% and C. utilis up to 80% of the L-malic acid that is present in the medium. (3) L-Malic acid is decomposed to CO 2 and the corresponding amounts of ethanol or pyruvate by cell fr…

Structural characterization in solution of multifunctional nucleotide coordination systems

2000

The interaction in aqueous solution of the cyclophane receptors 2,6,10,13,17,21-hexaaza[22]orthocyclophane (L11) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L22) with the nucleotides ATP, ADP and AMP has been studied by pH titration and NMR. The obtained results are compared with those previously reported for the analogous meta-substituted receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L). All the experimental data support the actuation of these cyclophane molecules as multi-point binders of nucleotides through electrostatic, hydrogen bonding and π-stacking interactions. The combined use of NMR and molecular dynamics permits us to get a rather reliable picture of the way in which th…

Dihydrodiol Dehydrogenase: An Important Enzyme in Dihydrodiol-Epoxide Pathway — Mediated Benzo(A)Pyrene Mutagenicity

1978

Benzo(a)pyrene is metabolized to two major groups of mutagenically reactive metabolites: Monofunctional epoxides and dihydrodiol-epoxides. Various monooxygenase forms catalyze the various pathways at very different rates. In metabolic situations where the contribution by dihydrodiol-epoxides is small, epoxide hydratase represents a very efficient protective system. However, in situations where the mutagenic effect is predominately due to dihydrodiol-epoxide, the effect of epoxide hydratase is complicated and weak. We have now obtained evidence that a dihydrodiol dehydrogenase represents an efficient protective system in the latter situation. The enyzme was purified to homogeneity and the pu…

Dihydrodiol Dehydrogenase: Substrate Specificity, Inducibility and Tissue Distribution

1982

The present study shows that: Dihydrodiol dehydrogenase activity is present in the 100,000 g supernatant fraction of extrahepatic tissues. Dihydrodiol dehydrogenase is able to oxidize the hydroxy group and to reduce the keto group of a number of xenobiotics including quinones derived from polycyclic aromatic hydrocarbons. Dihydrodiol dehydrogenase was not inducible by various substances including hormones, polycyclic aromatic hydrocarbons, substrates of the enzyme and potent inducers of monooxygenases, epoxide hydrolase and glutathione S-transferases. Only in the case of thyroxine was a weak induction with a high dose of the hormone observed.

A novel synthesis of 2-aryl-4-piperidones by mannich cyclization of iminoketals

1983

2-Aryl-4-piperidones have been synthesized by condensation between an aromatic aldehyde and a β-aminoketone ethylene ketal, and further cyclization of the resulting iminoketal with dry hydrogen chloride or anhydrous p-toluensulfonic acid. Alternatively, reaction of the above iminoketals with methyl fluorosulfonate followed by dry hydrogen chloride treatment and acid hydrolysis gives directly N-methyl-4-piperidones. The application of these reactions to the synthesis of some 2-aryl-3-acetylpyrrolidine systems is also described.

Elucidation of the Conformational Freedom of Ferrocene Amino Acid (Bio)Conjugates: A Complementary Theoretical and Experimental Approach

2011

Molecularly imprinted polymers (MIPs) against uracils: Functional monomer design, monomer-template interactions in solution and MIP performance in ch…

2002

AbstractThe interaction of N1-substituted uracils (cyclohexyl (1) and benzyl (2)) with three polymerisable recognition elements, the novel monomers 9-(3/4-vinylbenzyl)adenine (3) and 2,6-diamino-9-(3/4-vinylbenzyl)purine (4) and the previously synthesised monomer 2,6-bis(acrylamido)pyridine (5), has been studied via1H NMR in deuterio-chloroform solution. MIPs against (2) have been prepared using each of the monomers and tested in the chromatographic mode. The effect of the number and type of hydrogen bonds formed between the templates and the functional monomers is reflected in the values of the apparent association constants obtained from the solution study and by the performance of the su…

Enantioselective Ester Hydrolysis Catalyzed by Imprinted Polymers. 2,

2000

Highly cross-linked network polymers prepared by molecular imprinting catalyzed enantioselectively the hydrolysis of N-tert-butoxycarbonyl phenylalanine-p-nitrophenyl ester (BOCPheONP). The templates were designed to allow incorporation of the key catalytic elements, found in the proteolytic enzyme chymotrypsin, into the polymer active sites. Three model systems were evaluated. These were constructed from a chiral phosphonate analogue of phenylalanine (series A, C) or L-phenylalanine (series B) attached by a labile ester linkage to an imidazole-containing vinyl monomer. Free radical copolymerization of the template with methacrylic acid (MAA) and ethylene glycol dimethacrylate (EDMA) gave a…

β-(3,6,9-Trimethyl-9-xanthenyl)propionic acid

2007

The title compound, C19H20O3, was obtained, among other condensation products, from the reaction of meta-cresol and levulinic acid. The pyrane ring closure does not alter significantly the environment of the ethereal linkage in comparison with diaryl ethers. The deformations of the endocyclic valence angles in the benzene rings, centred on the C atoms substituted with alkyl groups, is greater than expected. The mol­ecular packing is influenced by O—H⋯O hydrogen bonds, leading to centrosymmetric dimers.