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1.
Defective transducing phages carrying aroG, the structural gene for phenylalanine (phe)-inhibitable phospho-2-keto-heptonate aldolase (EC 4.1.2.15; previously known as 3-deoxy-D-arabinoheptulosonate-7-phosphate synthetase[phe]), have been isolated, and DNA from two of these phages has been used to construct a restriction map of the region from att lambda to aroG. A 7.6-kb PstI-HindIII fragment from one of these phages was cloned into pBR322 and shown to contain aroG. The location of aroG within the 7.6 kb was established by subcloning and Tn3 transpositional mutagenesis. A fragment carrying the aroG promoter and operator has been cloned into a high copy number promoter-cloning vector (pMC489), and the resulting aroGpo-LacZ' (alpha) fusion subcloned in a low copy number vector. Strains with this fusion on the low copy number vector exhibit negative regulation of beta-galactosidase expression by both phenylalanine and tryptophan and positive regulation by tyrosine in a tyrR+ background. 相似文献
2.
Rupam Sarma 《Inorganica chimica acta》2009,362(6):1681-55
The coordination polymerization from lead(II) nitrate on reaction with 4-nitrobenzoic acid and pyridine N-oxide at room temperature passes through stepwise ligand substitution reaction. An intermediate polymer [Pb(NB)(PyO)2(NO3)]n (where NB = 4-nitrobenzoate, PyO = Pyridine N-oxide) is formed to give the final polymer [Pb(NB)2(PyO)]n. A hydrated mononuclear complex [Pb(NB)2(PyO)(H2O)] is also formed if rigorous anhydrous condition is not maintained. The reaction is extended to 4,4′-bipyridyl N-oxide (BPNO), which initially gives a coordination polymer [Pb2(NO3)(NB)3(BPNO)2]n which gets converted to another coordination polymer [Pb(NB)2(BPNO)2]n. All these complexes are structurally characterized. 相似文献
3.
In this paper the synthetic methods of three covalently linked porphyrin-phthalocyanine heteropentamers, containing four units of porphyrin linked to a central phthalocyanine (Mpor-LPc; M = 2H, Fe, L = Zn, Fe), are described. The synthetic strategy is on the basis of nucleophilic substitution reactions between [1,8,15,22-tetra nitro phthalocyanines] and [5-(4-hydroxy phenyl)-10,15,20-triphenyl porphyrins] as the phenolic alcohols. Porphyrins are linked with oxygen as spacer through meso position of phenyl group to phthalocyanines. These macromolecules were characterized by 1H NMR, UV-Vis, IR, fluorescence and mass spectroscopy. The electronic absorption spectrums of the hetero-dyad systems changed significantly upon coupling and showed a great red shift in the phthalocyanine Q-bands. These changes confirm the electron-donating effects of the porphyrin units and the extension of conjugated п-systems. The emission spectra of the products supports intramolecular energy and charge transfer between the sub-units. 相似文献
4.
5.
Pascal Griesmar Clément Sanchez Germain Puccetti Isabelle Ledoux Joseph Zyss 《Molecular Engineering》1991,1(3):205-220
Orientation of optically nonlinear organic molecules inside sol-gel matrices upon application of an external D.C. electrical field is demonstrated for the first time. The quadratic nonlinear response of silicon oxide or transition metal oxide based gels containing organic molecules has been determined from Electric Field Induced Second Harmonic (EFISH) measurements. Large concentrations of Optically Nonlinear Organic Molecules (ONOM) have been either incorporated inside the macromolecular network or chemically bonded to the oxide backbone of the gels. These results demonstrate the feasibility of permanently poled doped sol-gel matrices. Moreover, EFISH measurements performed on organic molecules appear to be a useful tool for monitoring the changes occurring during sol-gel transformations. 相似文献
6.
T. J. Lightfoot J. M. Coxhead B. C. Cupid S. Nicholson R. C. Garner 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2000,472(1-2)
Epidemiological evidence has suggested an association between meat consumption and the risk of breast cancer. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic amine found in cooked meat, has been implicated in the aetiology of breast cancer and has been shown to induce tumour formation in rodent mammary glands. In addition, polycyclic aromatic hydrocarbons, such as benzo[a]pyrene (B[a]P) which has also been shown to induce tumour formation at a number of sites in rodents including the breast, are produced during the cooking of meat through the pyrolysis of fats. The aim of this study was to examine the bioavailability of these compounds to human breast tissue and their ability to bind to DNA to form DNA adducts. Patients undergoing breast surgery at York District Hospital were orally administered prior to surgery a capsule containing 20 μg of 14C PhIP (182 kBq, specific activity 2.05 GBq/mmol) or 5 μg of 14C B[a]P (36 kBq, specific activity 1.81 GBq/mmol). At surgery, normal and tumour breast tissue was resected and tissue concentrations of carcinogen measured by liquid scintillation counting and DNA adduct levels by accelerator mass spectrometry (AMS) were subsequently determined. It was found that both 14C PhIP and 14C B[a]P were able to reach the target organ where they had the ability to form DNA adducts. The level of adducts ranged from 26.22–477.35 and 6.61–208.38 adducts/1012 nucleotides following administration of 14C PhIP and 14C B[a]P, respectively, with no significant difference observed between levels in normal or tumour tissue. In addition, the data obtained in this study were comparable to adduct levels previously found in colon samples following administration of the same compounds to individuals undergoing colorectal surgery. This is the first report that these two carcinogens bind to human breast DNA after administration of a defined low dose. 相似文献
7.
8.
Initial steps in the degradation of benzene sulfonic acid, 4-toluene sulfonic acids,and orthanilic acid in Alcaligenes sp. strain O-1 总被引:2,自引:0,他引:2
Thomas Thurnheer Daniel Zürrer Otmar Höglinger Thomas Leisinger Alasdair M. Cook 《Biodegradation》1990,1(1):55-64
Alcaligenes sp. strain O-1 grew with benzene sulfonate (BS) as sole carbon source for growth with either NH4
+ or NH4
+ plus orthanilate (2-aminobenzene sulfonate, OS) as the source(s) of nitrogen. The intracellular desulfonative enzyme did not degrade 3- or 4-aminobenzene sulfonates in the medium, although the enzyme in cell extracts degraded these compounds. We deduce the presence of a selective permeability barrier to sulfonates and conclude that the first step in sulfonate metabolism is transport into the cell. Cell-free desulfonation of BS in standard reaction mixtures required 2 mol of O2 per mol. One mol of O2 was required for a catechol 2,3-dioxygenase. When meta ring cleavage was inhibited with 3-chlorocatechol in desalted extracts, about 1 mol each of O2 and of NAD(P)H per mol of BS were required for the reaction, and SO3
2- and catechol were recovered in high yield. Catechol was shown to be formed by dioxygenation in an experiment involving 18O2. 4-Toluene sulfonate was subject to NAD(P)H-dependent dioxygenation to yield SO3
2- and 4-methylcatechol, which was subject to meta cleavage. OS also required 2 mol of O2 per mol and NAD(P)H for degradation, and SO3
2- and NH4
+ were recovered quantitatively. Inhibition of ring cleavage with 3-chrorocatechol reduced the oxygen requirement to 1 mol per mol of OS SO3
2- (1 mol) and an unidentified organic intermediate, but no NH4
+, were observed. 相似文献
9.
Summary The hyphal tip ofSclerotium rolfsii was examined after fixation by freeze substitution. The Spitzenkörper consisted of a dense mass of apical vesicles and microvesicles surrounding a vesicle-free zone. Linear arrangements of microvesicles were occasionally observed within the Spitzenkörper. Abundant microfilaments were seen within the Spitzenkörper region, often in close association with apical vesicles and microvesicles. Microtubules passed through the Spitzenkörper and terminated at the plasmalemma at the extreme hyphal apex. Filasomes were mostly observed within the apical region and were in close proximity to the plasmalemma. Rough ER, mitochondria, microtubules, and vacuoles were abundant in the subapical region and were usually oriented parallel to the long axis of the hypha. Ribosomes were aligned on the outer surfaces of mitochondria. Golgi body equivalents were observed throughout the subapical region and appeared as inflated cisternae of varying shapes and electron opacities. Relationships to other basidiomycetous hyphal tip cells are discussed.Abbreviations AV
apical vesicle
- C
Celsius
- diam
diameter
- f
filasome
- G
Golgi body equivalent
- h
hour
- nm
nanometer
- M
mitochondria
- ME
membranous elements; min minute
- MV
microvesicle
- MVB
multivesicular body
- N
nucleus
- OsO4
osmium tetroxide
- R
ribosome
- ER
endoplasmic reticulum
- S
Spitzenkörper
- Va
vacuole
- m
micrometer 相似文献
10.
Summary We have successfully localized fungal actin for the first time using immuno-electron microscopy and hyphal tips of the rice blast pathogenMagnaporthe grisea. Following ultrarapid freezing, samples were processed in a novel substitution fluid of 10% acrolein in anhydrous ethanol and embedded in LR White resin. A monoclonal anti-actin antibody, previously shown to recognizeM. grisea actin, bound specifically to filasomes concentrated in the peripheral cytoplasm of subapical regions, and to the core-region of the Spitzenkörper.Abbreviations IEM
immuno-electron microscopy
- TEM
transmission electron microscopy 相似文献