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51.
Analysis of lambda receptor and beta-lactamase synthesis and export using cloned genes in a minicell system 总被引:8,自引:0,他引:8
Jean-Marie Clement David Perrin Joe Hedgpeth 《Molecular & general genetics : MGG》1982,185(2):302-310
Summary We have cloned lamB, the gene for receptor (an outer membrane protein), on a small plasmid which also carries the gene for -lactamase (a periplasmic protein). We have identified a promoter in the region of malK, the gene immediately preceding lamB, which is active in minicells but relatively inactive in vitro. Using a minicell system, we have found that both receptor and -lactamase are made as full length precursors which are subsequently processed. We also show that the receptor precursor can be exported to the outer membrane before it is processed. Mature -lactamase is found only in the periplasm, suggesting that processing may be a requirement for export to the periplasm. 相似文献
52.
The use of spectrofluorimeter coupled to a reverse phase high performance liquid chromatography column permits selective detection of indole-3-acetic acid at the low picogram level. The value of the technique is demonstrated by the analysis of endogenous IAA in elongating shoots, xylem sap and callus of Douglas-fir. The data are also used to illustrate a procedure whereby the accuracy of chromatographic analyses can be verified within definable probability limits.Abbreviations GC-MS
combined gas chromatography-mass spectrometry
- HPLC
high performance liquid chromatography
- IAA
indole-3-acetic acid
- SEC
steric exclusion chromatography
- SICM
selected ion current monitoring
Technical Paper No. 5379 from the Oregon State University Agricultural Experiment Station 相似文献
53.
In an automobile accident, a young man sustained blunt trauma to the chest that caused injury to the fibrous skeleton of the heart. The mitral and tricuspid valves and their annuli were lacerated, the aortic annulus was separated from the ventricular septum, and the ventricular septum was disrupted; however, with surgical management, the patient survived. 相似文献
54.
A developmental change in dolichyl phosphate mannose synthase activity in pig brain 总被引:8,自引:3,他引:5 下载免费PDF全文
The initial rate of dolichyl phosphate mannose biosynthesis was measured in white-matter membranes from pig brain at various ages from before birth throughout the period of most rapid brain development. Dolichyl phosphate mannose synthase activity increased from prenatal values to a maximum in 3 week-old animals, and gradually decreased to adult values after 8 weeks of age. The nature of the developmental change was investigated by enzymic and biochemical comparisons of the membrane preparations from the most active age (3 weeks) and adult controls. The specific activity of dolichyl phosphate mannose synthase in preparations from actively myelinating animals was approx. 3-fold higher than adults when mannolipid formation was assayed with saturating concentrations of GDP-[14C]mannose and utilizing only endogenous acceptor lipid. No major variations were found in the apparent Km values for GDP-mannose or exogenous dolichyl monophosphate. However, the ratio of dolichyl phosphate mannose synthase activity for myelinating animals/adult animals decreased significantly when large amounts of exogenous dolichyl monophosphate were added to the incubation mixtures. Dolichyl phosphate mannose synthase activity was also compared in white-matter membranes depleted of endogenous dolichyl monophosphate by enzymic mannosylation or treatment with butanol. When these preparations were assayed with identical amounts of exogenous dolichyl monophosphate, the dolichyl monophosphate-depleted membranes from actively myelinating animals contained only 20–30% more dolichyl phosphate mannose synthase activity. Overall, these studies strongly suggest that the developmental change in dolichyl phosphate mannose synthase activity is due primarily to the presence of a relatively lower amount of endogenous dolichyl monophosphate being accessible to the mannosyltransferase in the white-matter membranes from adult animals. 相似文献
55.
Joe Murphy Roger Rowlett Susan B. Smith James Hoeferlin 《Archives of biochemistry and biophysics》1980,202(2):405-413
The KI values for inhibition of thermolysin activity by N-β-phenylpropionyl-aliphatic amino acids (Gly, Ala, Val, Leu, Ile) are correlated by π, the hydrophobic substituent parameter for the amino acid side chain (log KI = ?0.73π ?1.80, correlation coefficient = 0.990). By contrast, the KI values for the corresponding benzyloxycarbonyl amino acids are poorly correlated by π, but show a good correlation with the steric parameter Es(log KI = 0.880Es ? 3.086, correlation coefficient = 0.985). Binding of β-phenylpropionyl-l-alanine is associated with an acidic residue of pK 7.3 and a basic residue of pK 8.0 in the E · I complex, and appears to raise the pK of Glu-143 by 2 units. Binding of benzyloxycarbonyl-Ala and -Phe is associated with an acidic residue of pK 8.0 and two basic residues, both with pK 8.3. Three similar pK values are observed with benzyloxycarbonyl-Phe. These results are interpreted in terms of different modes of binding of β-phenylpropionyl and benzyloxycarbonyl inhibitors. 相似文献
56.
Winfrid Liebrich Sabine Gonser Silke Brüderlein Peter Schlag 《In vitro cellular & developmental biology. Animal》1991,27(5):345-346
Supported by the “Tumorzentrum Heidelberg-Mannheim”. 相似文献
57.
Silke Ruppel Charlotte Hecht-Buchholz Rainer Remus Ursula Ortmann Rita Schmelzer 《Plant and Soil》1992,145(2):261-273
The aim of this study was to investigate the ability of Pantoea agglomerans, a plant growth-promoting bacterium, to colonize various regions and tissues of the wheat plant (Triticum aestivum L.) by using different inoculation methods and inoculum concentrations. In addition, the enzyme-linked immunosorbent assay
(ELISA) and transmission electron microscopy (TEM) were used to determine: (a) the ability of the bacterial cells to grow
and survive both on the surface and within internal tissue of the plant and (b) the response of the plant to bacterial infection.
After inoculation, cells of the diazotrophic bacterial strain P. agglomerans were found to be located in roots, stems and leaves. Colony development of bacterial cells was only detected within intercellular
spaces of the root and on the root surface. However, single bacterial cells were observed in leaves and stems on the surface
of the epidermis, in the vicinity to stomatal cells, within intercellular spaces of the mesophyll and within xylem vessels.
Inoculated bacterial cells were found to be able to enter host tissues, to multiply in the plant and to maintain a delicate
relationship between endophyte and host. The density of bacterial settlement in the plant in all experiments was about 106 to 107 cells per mL root or shoot sap. Establishment was confirmed by a low coefficient of variation of ELISA means at these concentrations. 相似文献
58.
An experimental investigation of the low hydration phase properties of phospholipid mixtures is described. 2H (D2O) NMR, X-ray diffraction and differential scanning calorimetry have been used to elucidate the phase properties of mixtures of the mixed chain phospholipids palmitoyloleoylphosphatidylcholine (POPC) and palmitoyloleoylphosphatidylethanolamine (POPE). At 10% hydration pure POPE exhibited a HII phase above 330 K, a fluid lamellar phase below 315 K, and a minimally hydrated crystalline phase below 300 K. For the 1:1 mixture, the samples exhibited only gel or fluid phases between 270 K and 360 K for hydrations in the range 15% to 30%. Below 15% hydration the mixture exhibited two fluid phases with different repeat spacings, as predicted previously. 相似文献
59.
Effect of Hydrogenase and Mixed Sulfate-Reducing Bacterial Populations on the Corrosion of Steel 总被引:4,自引:2,他引:2 下载免费PDF全文
Richard D. Bryant Wayne Jansen Joe Boivin Edward J. Laishley J. William Costerton 《Applied microbiology》1991,57(10):2804-2809
The importance of hydrogenase activity to corrosion of steel was assessed by using mixed populations of sulfate-reducing bacteria isolated from corroded and noncorroded oil pipelines. Biofilms which developed on the steel studs contained detectable numbers of sulfate-reducing bacteria (104 increasing to 107/0.5 cm2). However, the biofilm with active hydrogenase activity (i.e., corrosion pipeline organisms), as measured by a semiquantitative commercial kit, was associated with a significantly higher corrosion rate (7.79 mm/year) relative to noncorrosive biofilm (0.48 mm/year) with 105 sulfate-reducing bacteria per 0.5 cm2 but no measurable hydrogenase activity. The importance of hydrogenase and the microbial sulfate-reducing bacterial population making up the biofilm are discussed relative to biocorrosion. 相似文献
60.
Productivity and longevity decreased in a laboratory colony of the parasitoid wasp Microplitis croceipes (Cresson) (Hymenoptera: Braconidae). Using light microscopy, it was determined that the colony was free of microsporidia. However, samples of the colony examined for pathogens by electron microscopy revealed three types of viruses: a nonpathogenic polydnavirus which is produced by all female wasps; a nonoccluded baculovirus which is pathogenic to late-stage pupae and adults; and a picorna-like virus which is present in larvae, pupae, and adults. The nonoccluded baculovirus was eliminated from the laboratory colony of M. croceipes by selection of progeny from wasps which had oviposited within 2 to 3 days after emergence from the cocoons and which had lived for at least 14 days post-emergence. Upon death, the wasps were examined by negative stain electron microscopy and only progeny from baculovirus-free wasps were retained. Parasitoid colonies should be systematically examined for pathogenic viruses that may reduce their productivity and efficacy as biological control agents. In addition, exotic parasitoids and predators should be evaluated for viruses and other pathogens while in quarantine. 相似文献