共查询到20条相似文献,搜索用时 320 毫秒
1.
J R Benemann K Miyamoto P C Hallenbeck M A Murry 《Biochemical and biophysical research communications》1982,106(4):1196-1202
Hydrogenase activity in the thermophilic cyanobacterium, was studied both and hydrogen consumption required oxygen but not light, was about ten-fold higher than in mesophilic cyanobacteria, and was relatively insensitive to carbon monoxide. H2-supported acetylene reduction in reductant-limited cultures was a light-dependent, but O2-independent reaction. hydrogen evolution was unaffected by carbon monoxide, and this activity could be partially purified using a procedure developed for . 相似文献
2.
A gas chromatography method for the determination of free and bound vanilmandelic acid (VMA) in pig urine and chicken feces has been developed. The method consisted of extraction of the free or bound acids by ethyl acetate under acidic conditions. The ethyl acetate extracts were dried under nitrogen, followed by complete silylation of the phenolic and carboxylic acid groups with BSA (N,O)-bis (trimethylsilyl) acetamid. The solution was distilled at 180°C in a sealed glass tube after which the sample was injected on a stainless steel column (6 ft × .125 in. o.d.) containing 4% SE-30 on mesh chromosorb GHP. The recovery of the urinary VMA was 82%, and the fecal VMA was 84% through the outlined procedures. Pigs ranging in age from 8 to 12 weeks were found to excrete with no significant difference between the free and bound. Commercial laying hens excreted bound VMA in a range of with a ratio of 1:3. 相似文献
3.
Squalene epoxidation by rat liver microsomes requires a supernatant protein factor and an acidic phospholipid in addition to NADPH and molecular oxygen. This study has shown that both the protein factor and the phospholipid lipid are necessary for externally added squalene to bind to the catalytic site on microsomal membranes. The epoxidation of squalene thus bound or biosynthesized from mevalonic acid proceeds effectively if the protein factor is present. Thus, the supernatant protein factor seems to play a dual function in both the binding and epoxidation of squalene in the assay system. The phospholipid is not required for the epoxidation of bound squalene. 相似文献
4.
Evidence is presented that water is the final product of electron donation to molecular oxygen by cytochrome from when ferrocytochrome acts as donor to . Negative evidence for the accumulation of superoxide and peroxide was obtained by rate effect experiments in the presence of superoxide dismutase, catalase, and peroxidase. Positive evidence for water was obtained by showing a 4 to 1 stoichiometric balance for rates of electron acceptance from ferrocytochrome to rates of donation to molecular oxygen. 相似文献
5.
M. Thirunavukkarasu Fergus G. Priest 《Biochemical and biophysical research communications》1983,114(2):677-683
α-Glucosidase was membrane bound during exponential growth of but was released into the medium during stationary phase. It could be partially removed from exponential phase cells by washing with NaCl (0.5 M). α-Amylase was exclusively extracellular and could not be detected in cells. Polysomes were prepared from exponential phase cells and separated into membrane bound and soluble fractions. chain completion and immunoprecipitation showed that α-glucosidase and α-amylase were synthesized by membrane bound and not by soluble ribosomes. 相似文献
6.
Cytoplasmic free and bound polysomes were isolated from bovine adrenal cortex, and used to program protein synthesis in rat liver cell sap and wheat germ lysate systems. Synthesis of adrenodoxin(Ad) and adrenodoxin reductase(AdR) in the cell-free systems was determined by immunoprecipitation using monospecific antibodies, and the sizes of the products were analyzed by SDS-polyacrylamide gel electrophoresis. Ad was synthesized by both free and bound polysomes as a putative large precursor having molecular weight of approximately 20,000 daltons, which was processed to mature size Ad (MW 12,000 daltons) by incubation with adrenal cortex mitochondria. On the other hand, AdR was synthesized only by free polysomes apparently as the mature size product. 相似文献
7.
M. Erecińska 《Biochemical and biophysical research communications》1977,76(2):495-501
Three lysine residues of horse heart cytochrome were modified by reaction with methyl-4-mercaptobutyrimidate hydrochloride and the free SH group of the latter was covalently linked to p-azidophenacyl bromide yielding a photoaffinity-labeled cytochrome . The photoaffinity-labeled cytochrome was bound by irradiation into a covalent complex with cytochrome oxidase. 相似文献
8.
The intracellular distribution of 115cadmium was determined following a pulsed exposure to the metal. The uptake and disappearance of label from rat liver nuclei was correlated with the appearance of a cytoplasmic Cd-binding protein. By coupling - experiments it was shown that unspecifically bound cadmium is free to enter the nucleus while specifically bound cadmium remains in the cytoplasm. 相似文献
9.
The model for rubredoxin based on X-ray diffraction data has been extensively refined with a 1.2 Å resolution data set. Water oxygen atoms were deleted from the model if B exceeded 50 Å2 and occupancy was less than 0.3 eÅ?3. The final water model consists of 127 sites with B values ranging from 15 to 0 Å2 and occupancies from unity down to 0.3, the most tightly bound water oxygen atoms being hydrogen bonded to two or more main-chain nitrogen or oxygen atoms. The water forms extensive hydrogen bond networks bridging the crevices on the molecular surfaces and between adjacent molecules. The minimum distances of the water sites from the protein surface are distributed about two distinct maxima, the major one at 2.5 to 3 Å and a minor one at 4 to 4.5 Å. Beyond to 6 Å from the protein surface, the discrete water merges into the aqueous continuum. 相似文献
10.
Wheat chloroplasts photochemically reduced molecular oxygen, as a Hill oxidant in the Mehler reaction, to superoxide anion which then oxidized added 1,2-dihydroxybenzene-3,5-disulfonate to its semiquinone, a comparatively stable free radical at pH 7. The last mentioned reaction was rapid in aqueous solution, but the rate of formation of 1,2-dihydroxybenzene-3,5-disulfonate semiquinone by the chloroplast system was calculated as a of 0.6 s. The Mehler reaction, or more specifically the univalent reduction of oxygen by Photosystem I, was rate-limiting so that the 1,2-dihydroxybenzene-3,5-disulfonate semiquinone was a useful spin probe for superoxide anion production at room temperature. The ESR signal of 1,2-dihydroxybenzene-3,5-disulfonate semiquinone was proportional to its steady state concentration and decayed in the dark with a of 5–6 s. This oxygen-dependent signal was enhanced by mediation of chloroplastic oxygen reduction through methyl viologen. The superoxide anion scavengers ascorbate and l-epinephrine competitively obscured 1,2-dihydroxybenzene-3,5-disulfonate semiquinone formation, but added superoxide dismutase was not as effective in this role. Partial inhibition by superoxide dismutase was achieved only by preincubation of Photosystem I enriched particles with ten times the endogenous concentration of superoxide dismutase. This and the persistence of a small amount of a 1,2-dihydroxybenzene-3,5-disulfonate (Tiron) oxidizing species in the dark supports the concept of Tiron accessibility but not the superoxide dismutase accessibility of superoxide anion bound in its formative enzyme complex. Benzoquinone and naphthoquinone disulfonate also reacted with superoxide anion, and supported both the Hill reaction and the Mehler reaction as final oxidants of both water and superoxide anion. 相似文献
11.
Identification of opiate receptor binding in intact animals. 总被引:1,自引:0,他引:1
After intravenous administration of 3H-naloxone to rats, particulate bound radioactivity accumulated in the brain is selectively associated with opiate receptor binding sites, providing a means of labeling the opiate receptor . The regional distribution of 3H-naloxone bound closely parallels regional differences in opiate receptor binding with highest levels in the corpus striatum, negligible receptor-associated binding in the cerebellum and intermediate levels in other regions. 3H-Naloxone binding is saturable with the same total number of binding sites determined as by procedures. Nalorphine is markedly more potent than morphine in inhibiting 3H-naloxone binding and non-opiates are ineffective. The half-life for dissociation of 3H-naloxone bound to particles is the same as its dissociation rate after binding occurs , and sodium stabilizes 3H-naloxone bound from initial rapid dissociation as predicted from the known properties of the opiate receptor . 相似文献
12.
M Erecińska R Oshino D F Wilson 《Biochemical and biophysical research communications》1980,92(3):743-748
[3H]-p-Azidophenacylbromide-(methyl-4-mercaptobutyrimidate)-cytochrome from was prepared and its properties determined. The radioactive photoaffinity-labeled cytochrome was linked by irradiation into a covalent complex with cytochrome oxidase. Analysis of the complex on SDS-polyacrylamide gels showed that cytochrome bound to one of the smaller subunits of cytochrome oxidase with an apparent molecular weight of 15,000. 相似文献
13.
Frank Gellerich Valdur A. Saks 《Biochemical and biophysical research communications》1982,105(4):1473-1481
The route of movement of ADP produced in the mitochondrial creatine kinase reaction was investigated by recording the rate of ADP-dependent oxygen consumption in the presence of phosphoenolpyruvate and pyruvate kinase. This pyruvate kinase system completely abolished activation of respiration by ADP added or by ADP produced in the hexokinase reaction in the medium, but was not able to inhibit the creatine kinase activated respiration when creatine kinase was bound to the inner mitochondrial membrane. These different responses of oxidative phosphorylation were observed at equal ratios in the medium. The data obtained evidence direct channeling of ADP from heart mitochondrial creatine kinase to the adenine nucleotide translocase without its prompt release into the medium. 相似文献
14.
O Brown F Yein D Boehme L Foudin C S Song 《Biochemical and biophysical research communications》1979,91(3):982-990
Quinolinate phosphoribosyl transferase was rapidly inactivated in exposed to hyperbaric oxygen. The enzyme is essential for de novo biosynthesis of NAD in and man. Because of its sensitivity and essentiality, inactivation of this enzyme is proposed as a significant mechanism of cellular oxygen toxicity. Niacin which enters the NAD biosynthetic pathway below the oxygen-poisoned enzyme provided significant protection against the decrease in pyridine nucleotides and the growth inhibition from hyperoxia in and could be useful in cases of human oxygen poisoning. 相似文献
15.
Zoltán Spolarics Jozsef Mandl Raymund Machovich Patrick Lambin Tamás Garzó Ferenc Antoni István Horváth 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1985,845(3):389-395
125I-labelled complexed with thrombin or plasmin bound to hepatocytes in a concentration-and time-dependent manner. The apparent values calculated from displacement experiments were 7.9 · 10?8 M for and 8.5 · 10?8 M for . Association of these complexes was only partially reversible; after a 180 min incubation period, 50–60% of the bound radioactivity was internalized by the cells. itself bound also to hepatocytes, but the affinity of the complexes was higher than that of the inhibitor alone, and was not internalized, either. 125I-labelled thrombin or plasmin bound to hepatocytes as well. These bindings were also concentration-dependent and could be decreased with an excess of unlabelled ligands. Binding rates and amounts of the bound proteinases were higher than those of their complexes. The complex competed with the complex in binding to hepatocytes, whereas there was no competition between these complexes and the antithrombin III-thrombin complex. These results suggest that the binding sites of hepatocytes for and antithrombin III-proteinase complexes are different. 相似文献
16.
Vesna Ivanovic Nicholas E. Geacintov I.Bernard Weinstein 《Biochemical and biophysical research communications》1976,70(4):1172-1179
A new approach has been developed to detect ultra low concentrations of benzo(a)pyrene products bound to nucleic acids . The binding to DNA of hamster embryo cell cultures was characterized by low temperature fluorescence spectroscopy. The method can detect less than one polycyclic hydrocarbon residue per 50,000 nucleotides. The fluorescence spectra indicate that the benzo(a)pyrene derivative bound to DNA has a pyrene-like chromophore and resembles that obtained when DNA is reacted with the 7,8-diol-9,10-oxide of benzo(a)pyrene. This confirms that metabolism of the 7,8,9,10 ring on benzo(a)pyrene precedes reaction with DNA. The method should be useful for detecting and characterizing the binding of other fluorescent carcinogens to nucleic acids. 相似文献
17.
Francis C. Knowles 《Biochemical and biophysical research communications》1980,92(3):1060-1065
The hemoglobin-oxygen equilibrium binding curve was found to be sensitive to the addition of inositol hexaphosphate at pH 9.1. A solution of hemoglobin A in 0.050 sodium borate was half-saturated with oxygen at a partial pressure of 0.55mm Hg. Hemoglobin A in 0.050 sodium borate, 0.001 inositol hexaphosphate, pH 9.1 was half-saturated with oxygen at a partial pressure of 0.95mm Hg. The Hill plot was linear with a slope of 2.0 in the absence of phosphates. In the presence of inositol hexaphosphate the slope of the Hill plot increased from 1.0 to 2.36. The dependence of fractional saturation of hemoglobin with oxygen on concentration of inositol hexaphosphate was determined at partial pressures of oxygen of 0.46 and 1.07mm Hg. 相似文献
18.
Rat heart mitochondria oxidizing pyruvate (in the presence of 20% as much malate) took up nearly the amount of oxygen required for complete oxidation to CO2. Thus pyruvate, a physiological substrate of the citrate cycle, is oxidized through the entire cycle in these mitochondria, and they seem suitable for study of regulation of integrated mitochondrial energy transduction. By addition of graded amounts of hexokinase or pyruvate kinase to the suspending medium (in the presence of excess glucose or phosphoenolpyruvate), a wide range of steady-state values of the concentration ratio was obtained. At a constant concentration of phosphate, the steady-state rate of oxygen uptake by rat heart mitochondria oxidizing pyruvate was a function of the adenylate energy charge or of the ratio, and relatively independent of the absolute concentrations of these nucleotides. The oxygen uptake rates typically spanned a range of about 20-fold. At very high values of the ratio, the rate of oxygen uptake is much lower than the “state 4” rate seen after added ADP has been phosphorylated. This result suggests that “state 4” respiration, at least in these freshly prepared mitochondria, measures the rate at which ADP is made available by ATPase activity, rather than indicating uncoupling of electron transport from phosphorylation. The concentration of orthophosphate affected the rate of oxygen uptake and the pattern of response to the ratio or the energy charge, but the effects did not seem interpretable in terms of the mass-action expression for hydrolysis of ATP, (Pi. 相似文献
19.
Affinity chromatography has been used to isolate and compare the peanut agglutinin receptors from neuraminidase-treated human, bovine and porcine erythrocyte membranes. Passage of Triton X-100-solubilised membrane material through either Sepharose- or acrylamide-based affinity columns resulted in the reversible binding of receptor molecules to the immobilised lectin. Elution with 0.2M galactose released specifically bound glycoprotein fractions, the composition and molecular weights of which were determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate.Carbohydrate analysis by gas chromatography identified these bound glycoprotein fractions as the major sources of the disaccharide in these membranes. It is suggested that these isolated fractions represent a discrete population of glycoproteins within the membranes studied, which possess both - and carbohydrates. 相似文献
20.
Michael D.P. Boyle 《Biochemical and biophysical research communications》1981,103(3):856-862
Zinc sulphate in the range of 10?4 to 2×10?5 M prevents the binding of to antigen antibody complexes, and the initation of the cascade of events in the classical complement pathway leading to cell lysis. Other heavy metals, Co++, Cd++, Cu++, or Mn++ were without effect in this concentration range. Zinc was ineffective when added after was bound and failed to displace which was already bound to antigen antibody complexes. The ability of zinc to regulate the binding of the zymogen or activated form of to antigen-antibody complexes represents a new method of controlling the initiation of the classical complement pathway. 相似文献