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31.
32.
The teuthids of the collection R. Stahlecker, 1929, from the Isle of Maio (Cape Verde Islands) are described.Neololigosepia stahleckeri n. gen. n. sp. andMaioteuthis morroensis n. gen. n. sp. are one of the first teuthids from the Lower Cretaceous (Barremian). 相似文献
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The activities of NADPH and NADH oxidase were determined in homogenates of isolated pure parenchymal and nonparenchymal rat liver cells at neutral (7.4) and acid (5.5) pH. The NADPH oxidase at pH 7.4 is about equally active in parenchymal and nonparenchymal cells and in both cell types is rather insensitive to KCN (1 mm) inhibition. By lowering the pH to 5.5, the NADPH oxidase of the nonparenchymal cells is stimulated (twofold) while the activity in parenchymal cells is decreased. The NADH consumption at neutral pH in parenchymal cells is 75% inhibited by KCN, while this activity in nonparenchymal cells is relatively insensitive to KCN. The NADH oxidase in both parenchymal and nonparenchymal liver cells is less active when the pH is lowered from 7.4 to 5.5. The distribution of NAD(P)H oxidases between parenchymal and nonparenchymal liver cells and the effect of pH on their activities suggest that in the nonparenchymal cells, the NADPH oxidase might play a role in the synthesis of H2O2 within the phagocytic vacuole. A scheme is proposed which describes the metabolic events involved in H2O2 formation and catabolism of endo(phago)cytosed particles in nonparenchymal liver cells. 相似文献
35.
Complexation of M+=Li+, Na+, Ag+ and TI+ by the cryptands 4, 7, 13, 18-tetraoxa-l, 10-diazabicyclo[8.5.5]eicosane (C211) and 4,7,13-trioxa-1,10-diazabicyclo[8.5.5]eicosane (C21C5) to form the cryptates [M.C211]+ and [M.C21C5]+ has been studied in trimethyl phosphate by potentiometric titration and 7Li and 23Na NMR spectroscopy. For [M.C211]+ the logarithm of the apparent stability constants, log K (dm3 mol-1)=6.98±0.05, 5.38±0.05, 9.82±0.02 and 3.95±0.02 for M+ =Li+, Na+, Ag+ and TI+, respectively; and for [M.C21C5]+ log K (dm3 mol-1)=2.40±0.10, 1.90±0.05, 6.04±0.02 and 2.42±0.10 for M+=Li+, Na+, Ag+ and Tl+, respectively. The decomplexation kinetic parameters for [Na.C211]+ are: kd (298.2 K)=6.924±0.50 s-l, ΔHd≠=62.2±0.9 kJ mol-1, and ΔSd≠= -20.3±2.7 J K-1 mol-1; and those for [Li.C21C5]+ are: kd (298.2 K)=23.3±0.4 s-1, ΔHd≠ =61.2±1.1 kJ mol-1, and ΔSd≠= -13.6±3.6 J K-1 mol-1. Metal ion exchange on [Li.C211]+ is in the very slow extreme of the NMR timescale up to 390 K and kd « 4 s-1 at 298.2 K, while in contrast exchange on [Na.C21C5]+ is in the fast extreme of the NMR timescale at 298.2 K (kd≈ 104 s-1). These data are compared with those obtained in other solvents. 相似文献
36.
Eric P. Krenning Roel Docter Bert Bernard Theo Visser Georg Hennemann 《FEBS letters》1982,140(2):229-233
37.
Virginia Brothers Barbara ONeill Rowley Theo Gerritsen 《Archives of biochemistry and biophysics》1975,166(2):475-482
The effects of vitamin B12 deficiency in rats and dietary supplementation with vitamin B12 and/or l-methionine plus folate on the oxidation of compounds metabolized through folate coenzyme pathways were investigated. Rats fed a vitamin B12-deficient diet oxidized significantly lower amounts in 60 min of l-histidine, glycine, sarcosine, formate, and l-serine to CO2 than vitamin B12-supplemented controls. Supplementation of the deficient diet with l-methionine plus folate restored the ability to oxidize the ring-2-carbon of l-histidine, the methyl group of sarcosine, and formate to the same level as that observed in animals receiving vitamin B12. In contrast, oxidation of the 1-carbon of glycine and the 3-carbon of l-serine was not restored to control levels by addition of methionine plus folate to the vitamin B12-deficient diet. Inhibition of the metabolism of the 2-carbon of glycine to CO2 was partially overcome by additional dietary methionine and folate. Glycine synthase activity in homogenates paralleled the in vivo pattern of oxidation of the 1-carbon of glycine to CO2, whereas sarcosine dehydrogenase activity appeared to increase 2-fold in vitamin B12 deficiency. 相似文献
38.
David C. Turner Rudolf Gmür Herbert G. Lebherz Marianne Siegrist Theo Wallimann Hans M. Eppenberger 《Developmental biology》1976,48(2):284-307
The presence or absence of five proteins (glycogen phosphorylase, aldolase A, aldolase C, creatine kinase M, creatine kinase B) in the various classes of cells found in primary cultures derived from embryonic chick breast muscle was investigated using cytological staining methods. Histochemical staining for phosphorylase and indirect fluorescent antibody staining for aldolase A and C as well as for creatine kinases M and B showed the following: All five proteins were found in the many myotubes present in standard medium cultures and in the very few myotubes found in cultures containing 5-bromodeoxyuridine (10?5M). The elongated bipolar cells prevented from fusing in medium containing EGTA also contain all five proteins. The flattened myogenic cells that predominate in the 5-bromodeoxyuridine-treated cultures contain no phosphorylase or creatine kinase M, though many of them contain creatine kinase B and aldolases A and C. These results are interpreted as indicating that: (1) phosphorylase and creatine kinase M, but not aldolase A, are suitable all-or-none markers for terminal muscle differentiation; (2) the small amounts of creatine kinase M detected in electrophoreses of 5-bromodeoxyruridine-treated cultures can be accounted for by the few myotubes present and are not due to “protodifferentiation” of large numbers of cells; (3) proteins typical of differentiated muscle are produced only in cells that have passed through the last step in myogenesis that is susceptible to 5-bromodeoxyuridine inhibition, and (4) if fusion is blocked by reducing the concentration of calcium ions, accumulation of characteristic muscle proteins can continue in those cells that have initiated terminal differentiation. 相似文献
39.
40.
Bert van Loo Jaap Kingma Gertjan Heyman Alex Wittenaar Jeffrey H. Lutje Spelberg Theo Sonke Dick B. Janssen 《Enzyme and microbial technology》2009,44(3):145-153
In epoxide hydrolase from Agrobacterium radiobacter (EchA), phenylalanine 108 flanks the nucleophilic aspartate and forms part of the substrate-binding pocket. The influence of mutations at this position on the activity and enantioselectivity of the enzyme was investigated. Screening for improved enantioselectivity towards para-nitrophenyl glycidyl ether (pNPGE) using spectrophotometric progress curve analysis yielded five different mutants with 3- to 7-fold improved enantioselectivity. The increase in enantioselectivity was in most cases the result of an enhanced catalytic efficiency toward the preferred enantiomer. Several mutations at position F108 resulted in a higher activity toward cis-disubstituted meso-epoxides, which were converted to a single product enantiomer. Mutant F108C converted cis-2,3-epoxybutane to (2R,3R)-2,3-butanediol of >99% ee with a 7-fold improved activity, and mutant F108A hydrolyzed cyclohexene oxide to (1R,2R)-1,2-cyclohexanediol of >99% ee with a more than 150-fold higher activity than wild-type enzyme. It is concluded that single amino acid substitutions in the active site of epoxide hydrolase can result in enzyme variants with catalytic properties that are suitable for preparative scale production of (S)-epoxides and chiral vicinal diols in high yield and with excellent ee. 相似文献