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1.
5-Bromo-UTP was found to replace UTP efficiently as a substrate for the virion-associated double-stranded RNA replicase of Penicilliumstoloniferum virus PsV-S. The double-stranded RNA product of the replication reaction with 5-bromo-UTP as a substrate gave in equilibrium caesium sulphate density gradient centrifugation a single band with a buoyant density of 1.647 g/ml, consistent with that of a hybrid double-stranded RNA consisting of one brominated and one unbrominated strand. After the reaction none of the original unbrominated double-stranded RNA (buoyant density 1.606 g/ml) could be detected. It is concluded that replication of double-stranded RNA in virions of PsV-S takes place by a semi-conservative mechanism.  相似文献   

2.
DNA from two rhizobial strains Cicer and Phaseolus and their bacteroids from root nodules have been isolated, purified and characterized for thermal denaturation temperature and buoyant density. Bacteroid DNA had a lower Tm value and buoyant density comparad to Rhizobium cell DNA. The calculated GC content of becteroid DNA was lower than the Rhizobium cell DNA.  相似文献   

3.
Insect yolk protein precursor, a juvenile hormone induced phosphoprotein   总被引:1,自引:0,他引:1  
The juvenile hormone induced vitellogenic female-specific protein of Leucophaeamaderae was isolated from hemolymph of egg maturing females on DEAE or QAE anion-exchange columns. Minor contaminants could be removed by centrifugation to equilibrium on CsCl gradients. The buoyant density of this purified protein is 1.344 g/ml. It is a lipophosphoprotein of low phosphorus (0.14%) content. Essentially all 32P label from in vivo labelled protein was recovered in phosphoserine. The amino acid residues of the vitellogenic protein compare well with the purified yolk protein.  相似文献   

4.
L(+)-threo-chloramphenicol induces reversion of His?Salmonella typhimurium strains TA100 and TA1535 in the conventional Ames' assay without microsomal activation. Any mutagenicity of D(?)-threo-chloramphenicol was masked by toxicity. Similarly, a sensitive fluctuation test showed mutagenesis with L(+)-threo-chloramphenicol at concentrations of 0.5 μM and above but the D(?) isomer proved to be toxic even at these low levels. The L(+) isomer caused single strand breaks in the DNA of Escherichia coliBr and Salmonella typhimurium strains TA1535, TA100 and TA1976. The D(?) isomer caused breaks in Escherichia coliBr and Salmonella typhimurium TA1976 although it was less effective and it did not produce DNA breaks in TA1535 or TA100.  相似文献   

5.
Microbodies isolated from sporangia of the aquatic fungus Blastocladiella emersonii have a mean buoyant density of 1.222 g/cm3 after centrifugation through a linear sucrose gradient, and contain catalase, isocitrate lyase and malate synthase. Microbodies fuse to produce one symphyomicrobody per zoospore at the time of sporogenesis. An increase in density accompanies this process. The symphyomicrobody has a mean buoyant density of 1.292 g/cm3 while the spore's single mitochondrion has a buoyant density of 1.219 g/cm3. Statistical data are also provided for both starting levels and purification of symphyomicrobody and mitochondrial enzyme markers.  相似文献   

6.
The metabolism of drobuline has been examined in the dog, rabbit, rat, guinea pig and hamster. In the dog, unlike the other species, glucuronide conjugation is the major route of metabolism. The structure of the conjugate has been established as an O-glucuronide by isolation using HPLC following by field desorption mass spectral analysis. When the separate d- and l-isomers of drobuline were administered to a series of dogs the l-isomer reached plasma levels approximately three time higher than those of the d-isomer. Deuterium labeled drobuline was synthesized and resolved by multiple crystallizations of the malate salts. Racemic mixtures containing d6-d and h6-l drobuline and d6-l and h6-d drobuline were prepared and analyzed by GC-MS as the pentafluoropropionate derivatives. When either racemic mixture was administered to dogs (10 mg/kg, p.o.) the plasma levels of the l-isomer were found to be approximately three times those of the d-isomer. Using these deuterium labeled mixtures the disposition of the two isomers has been examined in the isolated perfused dog liver, in hepatocytes and isolated microsomes. The results indicate that the difference in plasma levels of the d- and l-isomers is not dependent upon stereospecific absorption or excretion but rather it is caused by metabolism of the d-isomer at a faster rate than that of the l-isomer.  相似文献   

7.
The relationship between chromosome replication and the bacterial division cycle has been examined in three substrains of Escherichia coliBr obtained from different sources and designated Br A, Br F and Br K. At growth rates greater than 1.0 doubling per hour (μ > 1.0), the time for a round of chromosome replication (C) was 42 minutes in all three substrains, but the time between the end of a round and cell division (D) was 22 minutes in Br A, 16 minutes in Br F and 14 minutes in Br K. At slower growth rates C and D increased, but to significantly different extents in the three substrains. When μ = 0.5, C and D were approximately 80 and 40 minutes in Br A, 60 and 20 minutes in Br F, and 70 and 20 minutes in Br K.As a consequence of the lengths of the C and D periods in the three stocks of E. coliBr, the patterns of chromosome replication during the division cycle differed. The most obvious difference was that E. coliBr F and E. coliBr K possessed periods devoid of DNA synthesis at both the beginning and the end of the division cycle during slow growth, whereas E. coliBr A contained only one period devoid of DNA synthesis at the end of the cycle.  相似文献   

8.
Liver extracts (8000 × g for 10 min) from fasted rats contain about 4 times more phosphorylase phosphatase activity when the liver was homogenized in a hypotonic medium or frozen before homogenization. This increase is caused by: (i) release of partially latent phosphatases (Mr=60 000 and 45 000 in sucrose gradient centrifugation) from ruptured organelles; (ii) rapid activation of phosphatase in the ruptured pellet by endogenous protease(s) which can be blocked by p-tosyl-L-lysine chloromethyl ketone. Only the Mr=60 000 enzyme, associated with the nuclei, can be activated proteolytically, with conversion to an Mr=45 000.  相似文献   

9.
A procedure for production of N-acetyl-l-methionine (N-Ac-l-Met) from its racemic mixture by enzymatic continuous hydrolysis of the l-enantiomer of N-acetyl-dl-methioninamide (N-Ac-dl-Met · NH2) is described. For this hydrolysis, whole cells of Erwinia carotovora immobilized by κ-carrageenan gel were employed. The complete conversion of N-Ac-dl-Met · NH2 to N-Ac-l-Met was achieved by using a column packed with the immobilized cells. The half-life of the enzyme activity of the column was calculated to be ~100 days. Pure crystalline N-Ac-l-Met was readily isolated from the effluent with >87.5% yield. N-Ac-d-Met · NH2 was easily racemized by incubating in ethanol containing 0.1 m NaOH for 30 min at 80°C, and used again for substrate.  相似文献   

10.
2-Deoxy-D-glucoside-2-sulphamate sulphohydrolase was extracted from human liver and purified 40 000-fold by a simple four column procedure. The purification was followed using a specific substrate isolated from an acid hydrolysate of heparin, O-(α-2-sulphamino-2-deoxy-D-glucopyranosyl)-(1→3)-L-[6,3H]idonic acid. Only one form of the enzyme was seen on either ion exchange chromatography or isoelectric focussing, with a pI of 6.8. The apparent Mr of the haloenzyme as determined by gel filtration was 190 000 ± 20 000. Two other larger Mr protein peaks observed on gel filtration appear to be an inactive dimer of the 190 000 dalton peak and a larger aggregate near the exclusion limit of the column. On polyacrylamide disc gel electrophoresis in sodium dodecyl sulphate, with or without prior reduction, each protein peak from the gel filtration column electrophoreced as a single major band with an apparent Mr corresponding to 55 000 ± 6000.  相似文献   

11.
The plasma membrane of the hepatoma cell line, HTC cells, has been characterized and purified by cell fractionation techniques. In the absence of true 5′-nucleotidase in HTC cells, alkaline phosphodiesterase I has been used as a marker enzyme, following conclusions gained from differential and isopycnic centrifugation studies (Lopez Saura, P., Trouet A. and Tulkens P. (1978) Biochim. Biophys. Acta 543, 430–449). To confirm this localization, HTC cells were exposed to anti-plasma membrane IgG at 4°C and fractionated. Alkaline phosphodiesterase I and IgG showed super imposable distribution patterns in linear sucrose gradients. Alkaline phosphodiesterase I is, however, only poorly resolved from enzyme markers of other organelles, especially NADPH-cytochrome c reductase (endoplasmic reticulum) and galactosyltransferase (Golgi complex). Maximal purification from the homogenate is only 13-fold, on a protein basis, even when using a microsomal fraction (67 and 13% of alkaline phosphodiesterase I and protein, respectively) as the starting material. Improved resolution can be obtained after the addition of small quantities of digitonin (equimolar with respect to the cholesterol content). Digitonin increases the buoyant density of alkaline phosphodiesterase I by approx. 0.05 g/cm3, whereas the buoyant densities of galactosyltransferase and NADPH-cytochrome c reductase are increased only by 0.03 and 0.015 g/cm3, respectively. Accordingly, a procedure has been designed which yields a fraction containing 22.8% of alkaline phosphodiesterase I with a purification of 21-fold on a protein basis. The content of NADPH-cytochrome c reductase and galactosyltransferase is 1.2 and 2.1%, respectively. Electron microscopy shows smooth surface membrane elements and vesicles, with only occasional other recognizable elements.  相似文献   

12.
The effects of methylglyoxal bis(guanylhydrazone) on S-adenosyl-l-methionine decarboxylase (EC 4.1.1.50) activity were studied in the mouse kidney stimulated to growth by testosterone administration. The drug was found to be a potent inhibitor of the enzyme in vitro. Administration of methylglyoxal bis(guanylhydrazone) in vivo resulted in a transient inhibition followed by a strong enhancement of the enzyme activity. Dialysis of the kidney extract, to remove remaining methylglyoxal bis(guanylhydrazone), revealed a great and rapid increase in the activity of S-adenosyl-l-methionine decarboxylase. Injections of testosterone to castrated mice resulted in a marked increase in kidney weight and an accumulation of renal putrescine, spermidine and spermine. These effects of testosterone could not be blocked by simultaneous injections of methylglyoxal bis(guanylhydrazone). It appears that due to secondary effects by which the inhibition of methylglyoxal bis(guanylhydrazone) on S-adenosyl-l-methionine decarboxylase activity is circumvented the inhibitor seems to be of uncertain value in attempts to decrease selectively the in vivo levels of polyamines.  相似文献   

13.
Non-random segregation of DNA strands in Escherichia coli B-r   总被引:11,自引:0,他引:11  
The segregation of DNA strands during growth of Escherichia coliBr has been studied under conditions in which the chromosomal configuration and the ancestry of the cells during growth and division were known. Cells containing either one or two replicating chromosomes were pulse-labeled with [3H]thymidine, and the location of the radioactivity within chains of cells formed by growth in methylcellulose was determined by autoradiography. The locations of the radioactive cells within chains obtained after the second, third and fourth divisions were consistent with the co-segregation of only one of the replicating strands of each chromosome and a fixed region of the cell into daughter cells. The attachment of this strand to the region appeared to become permanent at the time the strand was used for the first time as a template. It is concluded that the segregation of DNA molecules into daughter cells is non-random in E. coli B/r.  相似文献   

14.
A chromatographic procedure utilizing common laboratory equipment and based on the batchwise adsorption of type C RNA virus onto hydroxyapatite for the concentration and partial purification of viruses from large volumes of tissue culture fluid has been developed. This procedure provides an alternative to the use of elaborate and expensive high-speed zonal ultracentrifuge equipment. The viruses obtained by this procedure have a buoyant density of 1.16 g/cm3, contain 70 S RNA, an RNA-directed DNA polymerase (reverse transeriptase), surface glycoproteins (GP6971), and the internal viral specific polypeptides p10 to 15 and p27 or p30.  相似文献   

15.
The metabolic conversion of α-l-acetylmethadol (LAM) to α-l-noracetylmethadol (NAM) and α-l-dinoracetylmethanol (NNAM), has been studied in three opiate addicts being maintained on 100 mg of LAM three times weekly. Plasma levels of NAM and NNAM were established shortly after the initial dose of LAM. The plasma level of NNAM was substantially higher following repeated dosing than following the initial dose. The combined daily urinary excretion of LAM, NAM and NNAM was 6–8 times greater after repeated dosing than after the initial dose. Since NAM and NNAM, which are formed by the sequential N-demethylation of LAM are both considerably more active morphine-like agonists than is LAM itself, it is likely that the pharmacological effects of LAM are due to NAe NAM and NNAM. Variations in the rates of formation and elimination of NAM and NNAM may partially explain the variability in response seen in LAM maintenance therapy.  相似文献   

16.
In the present study the effect of intracerebroventricularly (ICV) administered somatostatin on electroconvulsive shock- (ECS) induced retrograde amnesia was investigated in rats. The ECS significantly decreased foot shock-induced avoidance latency. Somatostatin in a dose of 1 μg4 μl (ICV) had no action on the ECS-induced retrograde amnesia, while in a dose of 4 μg4 μl it significantly increased the avoidance latency if the treatment was performed immediately, 4 hr, 20 hr or 23 hr after the ECS. The results suggest that ICV administered somatostatin has an antiamnesic effect.  相似文献   

17.
18.
A 0.5 × 106Mr RNA found in plastids of the aquatic angiosperm Spirodela, is synthesized at a much higher rate than any other rapidly labeling RNA species about 3–312 h after dark-grown plants are transferred to light. The pulse labeling kinetics of the 0.5 × 106Mr RNA after transfer to light, argue against its involvement in the biogenesis of plant rRNAs. Although poly(A) RNA is found in Spirodela, poly(A) sequences are not detected in the 0.5 × 106Mr RNA; yet a sucrose gradient fraction which includes RNA of this Mr stimulates amino acid incorporation by an E. coli cell free extract more than other RNA fractions. The possible involvement of the 0.5 × 106Mr RNA as a chloroplast messenger is discussed.  相似文献   

19.
20.
This paper presents an interpretation of fluorescence polarization measurements in lipid membranes which are labelled with the apolar probe 1,6-diphenyl-1,3,5-hexatriene. The steady-state fluorescence anisotropy, rS, is resolved into a fast decaying or kinetic component, rf, and an infinitely slow decaying or static component, r. The latter contribution, which predominates in biological membranes, is exclusively determined by the degree of molecular packing (order) in the apolar regions of the membrane; r is proportional to the square of the lipid order parameter. An empirical relation between rS and r is presented, which is in agreement with a prediction based on a theory of rotational dynamics in liquid crystals. This relation enabled us to estimate a lipid structural order parameter directly from simple steady-state fluorescence polarization measurements in a variety of isolated biological membranes. It is shown that major factors determining the order parameter in biomembranes are the temperature, the cholesterol and sphingomyelin content and (in a few systems) the membrane intrinsic proteins.  相似文献   

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