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  • 机译 枯草芽孢杆菌中的孢子形成。形态变化
    摘要:1. When Bacillus subtilis was grown in a medium in which sporulation occurred well-defined morphological changes were seen in thin sections of the cells. 2. Over a period of 7·5hr. beginning 2hr. after the initiation of sporulation the following major stages were observed: axial nuclear-filament formation, spore-septum formation, release of the fore-spore within the cell, development of the cortex around the fore-spore, the laying down of the spore coat and the completion of the corrugated spore coat before release of the spore from the mother cell. 3. The appearance of refractile bodies and 2,6-dipicolinic acid and the development of heat-resistance began between 5 and 6·5hr. after initiation of sporulation. 4. The appearance of 2,6-dipicolinic acid and the onset of refractility appeared to coincide with a diminution of electron density in the spore core and cortex. 5. Heat-resistance was associated with the terminal stage, the completion of the spore coat. 6. The spore coat was composed of an inner and an outer layer, each of which consisted of three or four electron-dense laminae. 7. Serial sections through cells at an early stage of sporulation showed that the membranes of each spore septum were always continuous with the membranes of a mesosome, which was itself in close contact with the bacterial or spore nucleoid. 8. These changes were correlated with biochemical events occurring during sporulation.
  • 机译 十二烷基硫酸钠与各种蛋白质的结合
    摘要:1. The binding of sodium dodecyl sulphate to proteins by equilibrium dialysis was investigated. 2. Most of the proteins studied bound 90–100% of their weight of sodium dodecyl sulphate. 3. The glycoproteins studied bound 70–100% of their weight of sodium dodecyl sulphate, calculated in terms of the polypeptide moiety of the molecule. 4. Proteins not containing S·S groups bound about 140% of their weight of sodium dodecyl sulphate. 5. Reduction of four proteins containing S·S groups caused a rise in sodium dodecyl sulphate binding to 140% of the weight of protein. 6. The apparent micellar molecular weights of the protein–sodium dodecyl sulphate complexes were measured by the dye-solubilization method; they were all found to have approximately the same micellar molecular weight (34000–41000) irrespective of the molecular weight of the protein to which they were attached.
  • 机译 血浆和组织提取物中绵羊,山羊和牛催乳激素的放射免疫分析
    摘要:1. A radioimmunoassay for ovine prolactin is described based on the inhibition of the reaction between 131I-labelled ovine prolactin and guinea-pig or rabbit antiserum to ovine prolactin. The extent of the reaction after a 4-day incubation period is determined by chromatoelectrophoresis or by adsorption of unchanged 131I-labelled ovine prolactin on charcoal. The sensitivity is equal to 5·9ng. of prolactin/ml. of plasma with chromatoelectrophoresis, or 0·2ng. of prolactin/ml. of tissue extracts with the charcoal separation. 2. A complete cross-reaction demonstrated between ovine prolactin and caprine pituitary extracts allows the assay to be used to measure caprine prolactin. The partial cross-reactions between ovine prolactin and bovine prolactin and between ovine prolactin and bovine pituitary extract differ, and an alteration in the immunological activity of bovine prolactin during its isolation is suggested. Bovine prolactin in plasma may be measured against a bovine pituitary extract as standard. No cross-reactions were demonstrated with pituitary extracts from a number of other species. The extent of the contamination of ovine and bovine growth hormone preparations by their respective prolactins is shown. 3. Dilutions of ovine and caprine plasma inhibit the reaction between 131I-labelled ovine prolactin and antiserum with the same characteristics as ovine prolactin. 4. The immunoreactive material in plasma fractionates on Sephadex G-200 and in sucrose density gradients as a single peak similar to that shown by freshly dissolved ovine prolactin. There is no evidence that ovine prolactin is bound to a plasma protein. 5. By suppressing prolactin secretion and assaying serial samples of plasma thereafter it is shown that the immunological activity of the surviving hormone becomes progressively altered with time. It is suggested that this alteration is usually not detected but introduces an element of uncertainty into the quantitative but not the qualitative value of the measurements obtained by reference to standard ovine prolactin.
  • 机译 脂肪组织中的清除因子脂肪酶。腺苷3',5'-(环状)-单磷酸在调节其活性中的可能作用
    摘要:1. The rise in clearing-factor lipase activity that occurs when epididymal fat bodies from starved rats are incubated in appropriate media in vitro is inhibited in the presence of 6-N-2′-O-dibutyryl-3′,5′-(cyclic)-AMP (1mm). 2. Inhibition occurs at a concentration of glucose in the incubation medium of 1·3mg./ml. or less, but not at a glucose concentration of 2·4mg./ml., unless caffeine (1mm), an inhibitor of 3′,5′-(cyclic)-nucleotide phosphodiesterase, is also present. Caffeine (5mm) alone inhibits the rise in clearing-factor lipase activity at a glucose concentration of 2·4mg./ml. of medium. 3. The concentration of free fatty acids in the epididymal fat bodies normally falls during incubations in vitro as the rise in clearing-factor lipase activity occurs. In the presence of 1mm-6-N-2′-O-dibutyryl-3′,5′-(cyclic)-AMP, however, either the tissue free fatty acid concentration is increased or it does not fall to the same extent. The concentration of glucose in the incubation medium is important in determining the direction and extent of the changes in tissue free fatty acid concentration that occur in the presence of 6-N-2′-O-dibutyryl-3′,5′-(cyclic)-AMP. 4. Free fatty acid concentrations in epididymal fat bodies in vivo rise as the clearing-factor lipase activity of the tissue falls during starvation. 5. The possibility that the concentration of 3′,5′-(cyclic)-AMP in adipose tissue may regulate clearing-factor lipase activity, and that the regulation may occur through effects of the nucleotide on tissue free fatty acid concentrations, is discussed.
  • 机译 磺胺二甲嘧啶代谢的物种差异
    摘要:1. The fate of sulphadimethoxine (2,4-dimethoxy-6-sulphanilamidopyrimidine) was studied in man, rhesus monkey, dog, rat, guinea pig and rabbit. 2. About 20–46% of the dose (0·1g./kg.) of the drug is excreted in the urine in 24hr. in these species, except the rat, in which only 13% is excreted. 3. In man and the monkey sulphadimethoxine N1-glucuronide is the major metabolite in the urine. In the rabbit and guinea pig N4-acetylsulphadimethoxine is the main metabolite. In the dog the drug is excreted mainly unchanged. In the rat equal amounts of the unchanged drug and its N4-acetyl derivative are the main products. 4. Small amounts of sulphadimethoxine N4-glucuronide are found in the urine of all the species. Sulphadimethoxine N1-glucuronide occurs in small amounts in the urine of rat, dog and guinea pig; none is found in rabbit urine. 5. Sulphadimethoxine N4-sulphate was synthesized and found to occur in small amounts in rat urine. 6. Monkey liver homogenates fortified with UDP-glucuronic acid are able to synthesize sulphadimethoxine N1-glucuronide with the drug as substrate. Rat liver has also this ability to a slight extent, but rabbit liver is unable to do so. 7. Sulphadimethoxine N4-glucuronide is formed spontaneously when the drug is added to human urine. 8. The biliary excretion of the drug and its metabolites was examined in rats. The drug is excreted in rat bile mainly as the N1-glucuronide. The N1- and N4-glucuronides administered as such are extensively excreted in the bile by rats.
  • 机译 硫酸软骨素蛋白对体外胶原原纤维形成的影响
    摘要:1. It was found that the precipitation of collagen fibrils at 37° from mixtures of chondroitin sulphate–protein and tropocollagen at physiological ionic strength and pH takes place in two distinct phases. The first occurs immediately on mixing either at 4° or at 37°, and the second occurs only at 37° and after a lag phase whose magnitude depends on the proportions of components. 2. When the second stage of precipitation was inhibited by mixing the reactants at 4°, the initial precipitate was found to contain `native-type' collagen fibrils and chondroitin sulphate–protein. 3. On the basis of kinetic experiments it was concluded that aggregates of chondroitin sulphate–protein and tropocollagen form instantaneously and that these act as sites for the second stage of precipitation of fibrils. 4. The gels that result after continued incubation at 37° are fibrous in appearance if formed in the presence of the initial precipitate of chondroitin sulphate–protein and tropocollagen. 5. On the basis of these experiments in vitro the authors propose a sequence of events for collagen fibrogenesis in vivo.
  • 机译 肝脏切片中某些磷酸化中间体浓度的变化和糖酵解的刺激
    摘要:1. The concentrations of some phosphorylated glycolytic intermediates and of NADH were measured in glycolysing rat liver slices. 2. In anaerobically incubated liver slices the concentration of hexose monophosphates decreases during the first 20min. of incubation, whereas the concentrations of fructose diphosphate and triose phosphates increase progressively. 3. In liver slices from fed rats, previously exposed to oxygen, the stimulated anaerobic glycolysis is accompanied by an increase in the concentration of hexose monophosphates; fructose diphosphate and triose phosphates maintain the concentrations reached at the end of the aerobic preincubation. 4. The same pattern in the concentration of glycolytic phosphorylated intermediates is seen under all conditions where aerobic preincubation brings about a stimulation of anaerobic glycolysis. A similar pattern is also found in liver slices from fed rats incubated anaerobically in the presence of fructose; these slices display a high glycolytic activity, which is not further affected by previous aerobic incubation. 5. The concentration of NADH decreases in liver slices during exposure to oxygen; during the subsequent anaerobic glycolysis the concentration increases but is always lower in preincubated than in non-preincubated liver slices. 6. The results of the present experiments suggest that the limiting step mainly affected by the preliminary exposure to oxygen might be at the level of the utilization of triose phosphates.
  • 机译 烟曲霉培养物中六氢聚异戊二烯基酯的表征和分布
    摘要:The total mycelial lipid of Aspergillus fumigatus was analysed and over half of its hexahydropolyprenol was shown to be esterified with fatty acids. Comparison of the fatty acid content of the prenyl esters with the sterol ester and the total lipid indicated a marked predominance of saturated fatty acids in the polyprenyl esters. The predominant acids esterified to the prenols were palmitic acid, linoleic acid, oleic acid, lignoceric acid, stearic acid and palmitoleic acid. Most of the unesterified polyprenol was found in the mitochondrial fraction, but the esterified prenol was equally distributed throughout the cell fractions. This distribution was unlike that found for ergosteryl ester in the same tissue.
  • 机译 人胸主动脉中糖蛋白的分离与鉴定
    摘要:1. A glycoprotein extracted by cold alkali from the walls of human aorta was purified by chromatography on DEAE-cellulose. 2. The compound was electrophoretically homogeneous and essentially so by chromatography on DEAE-cellulose. Ultracentrifugal examination revealed two components, and it is suggested that the faster-sedimenting component represents an aggregated form of the glycoprotein. 3. Glycoprotein preparations contained approx. 8% of carbohydrate. Digestion with Pronase yielded a glycopeptide fraction containing all the carbohydrate of the glycoprotein. The glycopeptide, of molecular weight about 7800, contained sialic acid, galactose, mannose, fucose and hexosamine in the approximate molar proportions 5:10:5:2:11. Sialic acid was terminal with respect to the polysaccharide chains. 4. Both elastase and elastomucoproteinases exhibited proteolytic activity towards the glycoprotein. Studies by other investigators have led to the conclusion that elastomucoproteinases attack protein–carbohydrate complexes occurring in intimate association with elastin in aorta and other tissues, and it is suggested that the glycoprotein may be identified with one of these compounds.
  • 机译 鞭毛盲蛾的丙酸同化。诱导型线粒体酶系统
    摘要:1. The assimilation of propionate by Polytomella caeca involves the β-oxidation of this fatty acid. 2. Propionate-grown cells immediately oxidize propionate, β-hydroxypropionate, malonic semialdehyde and acetate; acetate-grown cells oxidize propionate rapidly only after a lag of 2hr., and this adaptation of resting cells to propionate involves the formation of the enzymes of β-oxidation. 3. The β-hydroxypropionate dehydrogenase and malonic semialdehyde dehydrogenase activities of both propionate-grown and propionate-adapted cells are partly located in mitochondrial fractions. 4. Mitochondria isolated from propionate-grown cells, and also those from acetate-grown cells fully adapted to propionate, oxidize succinate, α-oxoglutarate, β-hydroxypropionate and malonic semialdehyde; oxidation of these substrates is tightly coupled to the phosphorylation of ADP. 5. Mitochondria from acetate-grown cells exhibit ADP-dependent oxidation of succinate and α-oxoglutarate, but do not oxidize β-hydroxypropionate or malonic semialdehyde. Mitochondria isolated from acetate-grown cells adapted to propionate for 5hr. slowly oxidize β-hydroxypropionate and malonic semialdehyde, but no tightly coupled phosphorylation is detectable. 6. Two of the inducible enzymes of propionate oxidation are located within the NAD-impermeable barrier and appear to be membrane-bound. 7. The formation of the inducible enzymes is inhibited by cycloheximide and actinomycin D, but not by chloramphenicol.
  • 机译 药理活性和其他有机碱置换磷脂单层中的钙离子
    摘要:1. The binding of 45Ca2+ to a monolayer of phosphatidylinositol at the air–water interface was maximal when the separation of the phospholipid head groups approximated to the diameter of a hydrated Ca2+ ion. 2. The displacement of Ca2+ adsorbed on monomolecular films of phosphatidylinositol by a series of drugs (both narcotic and excitatory) and other organic bases was related to the ability of the bases to penetrate into the film. 3. With films of phosphatidylinositol at constant area, and at an initial surface pressure of 10dynes/cm., the displacement of Ca2+ by increasing concentrations of the local anaesthetic, tetracaine, was linearly related to the change in surface pressure (Δπ) caused by the penetration of the drug. 4. Δπ and the displacement of Ca2+ showed a related fall when the initial surface pressure of the phosphatidylinositol film was increased from 4 to 40dynes/cm. both at a constant bulk tetracaine concentration and when this latter concentration was adjusted to keep it at a constant ratio to the surface density of phosphatidylinositol molecules. 5. The displacement of Ca2+ from phosphatidylinositol films by cetyltri-methylammonium ions was directly compared with the surface concentration of the base in the film, measured by using labelled base and a surface-radioactivity technique. 6. The ability of a series of straight-chain aliphatic amines to displace Ca2+ from phosphatidylinositol films increased with the number of carbon atoms up to C12. However, there was a marked jump in the displacing activity after hexylamine, and this could probably be correlated with the carbon chain's being of sufficient length to just reach the hydrophobic fatty acid chains of the orientated phospholipid molecules with the charges on both substances in juxtaposition.
  • 机译 C57小鼠中邻氨基偶氮甲苯与脱氧核糖核酸,核糖核酸和蛋白质的结合
    • 作者:T. A. Lawson
    • 刊名:Biochemical Journal
    • 2014年第5期
    摘要:1. 3H-labelled o-aminoazotoluene was synthesized from [G-3H]o-toluidine on a semi-micro scale. 2. An association of 3H with DNA, RNA and protein from the liver, kidney and spleen of female C57b mice was demonstrated after the administration of a single dose of [3H]o-aminoazotoluene. 3. This association is judged to represent covalent binding as a result of experiments involving solvent extraction, examination of the acid hydrolysates of the DNA and RNA and administration of [3H]water with unlabelled o-aminoazotoluene. 4. Examination of the extents of binding at various times after the administration of a single dose of [3H]o-aminoazotoluene showed that there was a peak of binding to liver DNA in the female mice at about 16hr. that was not present in the male mice. 5. The extent of binding to DNA, RNA and protein at 16hr. in the female C57b mouse liver was greater than that in the spleen and kidney.
  • 机译 草酰乙酸和l-苹果酸向大鼠肝线粒体易位的影响因素
    摘要:1. The rates of translocation of oxaloacetate and l-malate into rat liver mitochondria were measured by a direct spectrophotometric assay. 2. Penetration obeyed Michaelis–Menten kinetics, and apparent Km values were 40μm for oxaloacetate and 0·13mm for l-malate. 3. Arrhenius plots of the temperature-dependence of rates of penetration gave activation energies of +10kcal./mole for oxaloacetate and +8kcal./mole for l-malate. 4. The translocation of both oxaloacetate and l-malate was competitively inhibited by d-malate, succinate, malonate, meso-tartrate, maleate and citraconate. The Ki values of these inhibitors were similar for the penetration of both oxaloacetate and l-malate. 5. Rates of penetration were stimulated by NNN′N′-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate under aerobic conditions or by ATP under anaerobic conditions. 6. The energy-dependent stimulation of translocation was abolished by uncouplers of oxidative phosphorylation. Oligomycin A, aurovertin, octyl-guanidine and atractyloside prevented the stimulation by ATP, but did not inhibit the stimulation by NNN′N′-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate. 7. Mitochondria prepared in the presence of ethylene-dioxybis(ethyleneamino)tetra-acetic acid did not exhibit the energy-dependent translocation, but this could be restored by the addition of 50μm-calcium chloride. 8. Valinomycin or gramicidin plus potassium chloride enhanced the energy-dependent translocation of oxaloacetate and l-malate. 9. Addition of oxaloacetate stimulated the adenosine triphosphatase activity of the mitochondria, and the ratio of `extra' oxaloacetate translocation to `extra' adenosine triphosphatase activity was 1·6:1. 10. Possible mechanisms for the energy-dependent entry of oxaloacetate and l-malate into mitochondria are discussed in relation to the above results.
  • 机译 通过硝酸银-硅胶薄层色谱法纯化叶提取物。
    摘要:
  • 机译 四氢香豆素的体外生物合成。
    摘要:
  • 机译 兔免疫球蛋白G重链的异型相关序列变异
    • 作者:
    • 刊名:Biochemical Journal
    • 2014年第5期
    摘要:
  • 机译 过氧化氢酶-过氧化氢系统在没有底物的情况下,亚基在细菌过氧化氢酶的热失活中的作用
    • 作者:
    • 刊名:Biochemical Journal
    • 2014年第5期
    摘要:
  • 机译 MptpB是结核分枝杆菌的一种致病因子,具有三特异性磷酸酶活性
    摘要:Bacterial pathogens have developed sophisticated mechanisms of evading the immune system to survive in infected host cells. Central to the pathogenesis of Mycobacterium tuberculosis is the arrest of phagosome maturation, partly through interference with PtdIns signalling. The protein phosphatase MptpB is an essential secreted virulence factor in M. tuberculosis. A combination of bioinformatics analysis, enzyme kinetics and substrate-specificity characterization revealed that MptpB exhibits both dual-specificity protein phosphatase activity and, importantly, phosphoinositide phosphatase activity. Mutagenesis of conserved residues in the active site signature indicates a cysteine-based mechanism of dephosphorylation and identifies two new catalytic residues, Asp165, essential in catalysis, and Lys164, apparently involved in substrate specificity. Sequence similarities with mammalian lipid phosphatases and a preference for phosphoinositide substrates suggests a potential novel role of MptpB in PtdIns metabolism in the host and reveals new perspectives for the role of this phosphatase in mycobacteria pathogenicity.
  • 机译 五海藻c型细胞色素NrfB的晶体结构及其与五海亚硝酸盐还原酶NrfA的溶液状态相互作用的表征
    摘要:NrfB is a small pentahaem electron-transfer protein widely involved in the respiratory reduction of nitrite or nitric oxide to ammonia, processes that provide energy for anaerobic metabolism in many enteric bacteria and also serve to detoxify these reactive nitrogen species. The X-ray crystal structure of Escherichia coli NrfB is presented at 1.74 Å (1 Å=0.1 nm) resolution. The architecture of the protein is that of a 40 Å ‘nanowire’ in which the five haems are positioned within 6 Å of each other along a polypeptide scaffold. During nitrite reduction, the physiological role of NrfB is to mediate electron transfer to another pentahaem protein, NrfA, the enzyme that catalyses periplasmic nitrite or nitric oxide reduction. Protein–protein interaction studies suggest NrfA and NrfB can form a 20-haem NrfA2–NrfB2 heterotetrameric complex.
  • 机译 多药耐药相关蛋白9(ABCC12)存在于小鼠和公猪的精子中
    摘要:The human and murine genes for MRP9 (multidrug resistance-associated protein 9; ABCC12) yield many alternatively spliced RNAs. Using a panel of monoclonal antibodies, we detected full-length Mrp9 only in testicular germ cells and mouse sperm; we obtained no evidence for the existence of the truncated 100 kDa MRP9 protein reported previously. In contrast with other MRPs, neither murine Mrp9 nor the human MRP9 produced in MRP9-transfected HEK-293 cells (human embryonic kidney cells) appears to contain N-linked carbohydrates. In mouse and boar sperm, Mrp9 localizes to the midpiece, a structure containing all sperm mitochondria. However, immunolocalization microscopy and cell fractionation studies with transfected HEK-293 cells and mouse testis show that MRP9/Mrp9 does not localize to mitochondria. In HEK-293 cells, it is predominantly localized in the endoplasmic reticulum. We have been unable to demonstrate transport by MRP9 of substrates transported by other MRPs, such as drug conjugates and other organic anions.

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