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Methyl 2-deoxy-3,5,6-tri-O-p-nitrobenzoyl-
-ribo-hexofuranoside was converted into the glycosyl halide which was then condensed with 2,4-bis(trimethylsilyloxy)-pyrimidine in the presence of mercuric chloride to give, after alkaline methanolysis, 1-(2-deoxy-β-
-ribo-hexofuranosyl)uracil, in a yield too low for the reaction to be applied to deuterated compounds. Methyl 2-deoxy-
-allofuranoside-2-d was degraded into methyl 2-deoxy-
-arabinofuranoside-2-d. Its di-p-nitrobenzoate was converted into the glycosyl halide which was coupled with 2,4-bis(trimethylsilyloxy)-pyrimidine to give, after alkaline hydrolysis, deuterated deoxyuridine. Thiationammonolysis of a mixture of the 3′,5′-di-p-nitrobenzoates of the latter compound and its anomer gave the corresponding deoxycytidines. Comparison of the n.m.r. spectra of these compounds to that of deuterated deoxycytidine, prepared by the enzymic reduction of cytidine 5′-pyrophosphate with the Escherichia coli system in the presence of deuterium oxide confirmed that the substitution of a hydroxyl group by a hydrogen atom proceeds with retention of configuration. 相似文献
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Commercial aqueous 25 per cent glutaraldehyde solutions contain no stable derivative of this aldehyde, but compounds of variable molecular weight which easily revert to glutaraldehyde. The effect of pH on the reaction of glutaraldehyde with amino acids and on the stability of the products under acid conditions, shows the importance of the structure modification of the dialdehyde which occurs when pH increases, and even leads to precipitation in highly alkaline solutions. This precipitate results from aldol condensation of glutaraldehyde molecules. It contains aldehyd groups conjugated with ethylenic double bonds. Such a structure reacts with amino groups to give an imino bond, stabilized by resonance with the ethylenic bond, and does not undergo Michael-type addition reactions.Therefore, glutaraldehyde does not react with proteins under its free form, but as an unsaturated polymer, which gives imino bonds stabilized by conjugation. 相似文献
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- 1. A glycoprotein: fucosyl-transferase activity was demonstrated in sheep cerebral cortex, using desialylated fetuin as exogenous acceptor and detergent Trition X 100 for solubilization.
- 2. Addition of Triton X 100 to the membrane suspension gave first an activation then a solubilization of the cerebral fucosyl-transferase.
- 3. Hydrophobic chromatography was investigated for purification of the enzyme. Binding was effective using alkyl-agarose chromatographic columns with two or more than two atoms of carbon, but elution was only possible with ethyl and butyl-agarose.
- 4. Combination of subcellular fractionation and hydrophobic chromatography on ethylagarose led to a 30 fold purification.
- 5. After ethyl-agarose chromatography, some properties of fucosyl-transferase were studied: the optimal temperature was 25°C. The optimum pH was about neutrality. Light activation was observed with Mn2+ concentration below 1 mM.
- 6. Homogeneity was tested using Ultrogel chromatography, polyacrylamide gel electrophoresis and ultracentrifugation.
- 7. It was concluded that ethyl-agarose hydrophobic chromatography easily bind a few solubilized proteins (about 20 per cent of the ST supernatant). When elution was performed, these proteins, including fucosyl-transferase, were released from ethyl-agarose columns as a stable aggregate, only dissociated with lower ionic strength.
- — with Ultrogel AcA 22 chromatography (Mw = 300.000).
- — with polyacrylamide gel electrophoresis without S.D.S.
- — with the analytical ultracentrifugo giving Mw = 280.000; S20 = 10.
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Degradation of Amino Acids at a Simulated Water-sediment Interface of a Mediterranean Lagoon Environment, Golfe du Lion The degradation of two 14C and 3H labelled amino acids at the simulated water-sediment interface of a Mediterranean lagoon was studied. The four day experiments included the respiratory activity measurement and the study of incorporation processes of the radioactivity in specific organic fractions of the 14C arginine. After active mineralization occurred during the first day, the radioactivity in the acid-soluble fraction decreased and polycondensed products were progressively incorporated. The radioactivity of the 3H lysine was included mainly in the acid soluble fraction. The nature of the substrate, and the reducing conditions in the environment affect the radioactivity distribution in the organic fractions. The identification of amino acids in the acid-soluble and base soluble fractions shows that the labelled arginine and lysine and other amino acids in the acid soluble and base soluble fractions shows that the labelled arginine and lysine released from the initial compounds are important quantitatively. 相似文献
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Louis-Marie Lalancette 《International Review of Hydrobiology》1987,72(2):205-223
The Comparative Productivity of Two Ponds in the Vicinity of Lake St-John, Québec In 1980 and 1981, the productivity of two ponds near Lake St. John were evaluated. One, the pond of Desbiens, did not communicate with Lake St. John and the other, the pond of St-Gédéon, was connected to the lake. The aim of this study was to evaluate the contribution that a pond could make to the increase in productivity of Lake St. John which is a reservoir. The pond of Desbiens is more productive than Lake St. John but two to three times less than the pond of St-Gédéon. The pond of Desbiens shows an advanced degree of eutrophication whereas the pond of St-Gédéon is similar to the northern lakes by its physico-chemistry, zooplankton, sediments and benthic fauna. If we want to create artificial ponds, for a better productivity of reservoirs, it is important that they be connected to each other. 相似文献
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Pure rabbit fibrinogen was prepared by a method involving two ammonium sulfate precipitations, one 2 M phosphate buffer precipitation, one DEAE cellulose chromatography and lastly one Sepharose 6 B chromatography. The aminoacid composition was determined and an immunonephelemetric assay was proposed. This assay allowed an accurate determination of fibrinogen concentration in a rabbit with inflammatory reaction. 相似文献
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9-cis-retinoids: biosynthesis of 9-cis-retinoic acid 总被引:5,自引:0,他引:5
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Caspase-9 总被引:4,自引:0,他引:4
Kuida K 《The international journal of biochemistry & cell biology》2000,32(2):121-124
Caspase-9 is a member of caspase family of cysteine proteases that have been implicated in apoptosis and cytokine processing. When cells receive apoptotic stimuli, mitochondria releases cytochrome c which then binds to Apaf-1, the mammalian Ced-4 homologue, together with dATP. The resultant complex recruits Caspase-9 leading to its activation. Activated Caspase-9 cleaves downstream caspases such as Caspase-3, -6 and -7 initiating the caspase cascade. The majority of homozygous Caspase-9 null mice die perinatally with a markedly enlarged and malformed cerebrum caused by a reduction of apoptosis during early brain development. Thus, Caspase-9 function is essential for apoptosis during normal development of the central nervous system. These data suggest that inhibition of Caspase-9 activity would render opportunity to treat patients suffering from neurological diseases such as stroke, neurodegenerative diseases or brain injury caused by hypoxia. 相似文献
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胱天蛋白酶-9 总被引:1,自引:0,他引:1
在哺乳动物细胞凋亡的过程中 ,需要一系列的半胱氨酰天冬氨酸特异性蛋白酶 (cys teinylaspartatespecificprotease) ,简称胱天蛋白酶 (caspase)。目前胱天蛋白酶家族中已有1 3个成员 ,根据其氨基端前域的不同 ,分为启动酶和执行酶。启动酶能通过其前域与信号分子结合 ,引起执行酶的活化 ,导致凋亡。胱天蛋白酶的激活途径 ,目前认为有两条 :其一是由细胞表面Fas和TNF等介导胱天蛋白酶 8活化 ,并依次活化下游分子胱天蛋白酶 3、6、7等 ;其二是由Cyt c/Apaf 1 /胱天蛋白酶 9/胱天蛋白… 相似文献
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