共查询到20条相似文献,搜索用时 15 毫秒
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Philip A.J. Gorin 《Carbohydrate research》1982,101(1):13-20
The four isomers of methyl O-β-d-galactopyranosyl-β-d-galactopyranoside were prepared by condensation of 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide with appropriate, partially O-substituted derivatives of methyl β-d-galactopyranoside. Reaction of 3,4,6-tri-O-acetyl-1,2-O-(1-ethoxyethylidene)-α-d-galactopyranose with the same acceptors, in the presence of mercuric bromide, led to the formation of α and β linkages. Thus, it was possible to assign 13C-n.m.r. resonances of α and β anomers of methyl O-d-galactopyranosyl-β-d-galactopyranosides. In terms of application of these shift values and those of related d-galactobioses to the structural analysis of d-galactopyranans by shift comparisons, some generalizations can be made. For β-d-galactopyranans, the resonances of glycosyloxylated carbon atoms of methyl O-β-d-galactopyranosyl-β-d-galactopyranosides are sensitive to structure and appear to have typical values, whereas limited variation was observed with shifts of C-1′ signals. On the other hand, for assigning structures to d-galactopyranans containing α linkages, the C-1′ shifts (at higher field) of methyl O-α-d-galactopyranosyl-β-d-galactopyranosides are sensitive to linkage position, whereas those of glycosyloxylated carbon atoms vary only a little. 相似文献
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Karen B. Helle 《BBA》1971
1. Chromogranin A has been isolated from the washed membrane fraction of highly purified chromaffin granules after solubilization in Triton X-100. A hydrated molecular weight of 2.9·105 has been obtained for chromogranin AM which in its electrophoretic mobility and molecular volume appears very similar to chromogranin AI of the water-soluble fraction. 相似文献
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A new high-yield synthesis of 2-pyridylferrocene (1) without formation of the 1,1′-disubstituted product has been developed. Also the corresponding ruthenocene and cymantrene derivatives [C5H4(2-C5H4N)]MLn (MLn = Ru(C5H5) (2), Mn(CO)3 (3)) were prepared and fully characterized. Ortho-lithiation of 1 followed by electrophilic halogenation yielded [C5H3X(2-C5H4N)]Fe(C5H5) [X = F (4), Cl (5), Br (6), I (7)], with 4 only being the second reported and first fully characterized fluoroferrocene. The molecular structures of 1, 4 and 6 have been determined by X-ray crystallography. 相似文献
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Abstract Synthetic oligoribonucleotides (RNA) are efficiently prepared with 2′-O-tert-butyldimethylsilyl nucleoside 3′-O-phosphoramidites with labile base-protection; Admf or APac, Gdmf, Cibu, U. After cleavage from the polystyrene support, the exocyclic amine protecting groups are removed with conc. NH4OH: ethanol/3:1 by heating at 55°C for 3–5 h. The 2′-O- silyl protecting groups are removed with tetra-n-butylammonium fluoride in THF or more conveniently with neat triethylamine trihydrofluoride. To gain the advantages of increased capacity on reverse phase HPLC and the convenience of cartridge based purification (OPC, Oligonucleotide Purification Cartridge), the 5′ trityl was left on the RNA as the final protecting group to be removed. The mild conditions which are effective for trityl removal are shown to preserve 3′-5′ phosphate linkage integrity in RNA. The absence of phosphate migration is demonstrated by model studies, utilizing N4 -isobutyryl-5′-O-DMT-3′-O-TBDMS-2′-O-(2-cyanoethyl-N,N-diisopropylphosphoramidite) as a control monomer and digestion by 3′-5′ selective P1 nuclease and alkaline phosphatase and HPLC analysis. Oligoribonucleotides were analyzed by Microgel capillary electrophoresis, anion-exchange HPLC, and the enzymatic digest/HPLC method. 相似文献
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Yoji Kato Katsuhiro Iki Kazuo Matsuda 《Bioscience, biotechnology, and biochemistry》2013,77(12):2737-2744
A β-d-glucan was isolated on fractionation of a 4% potassium hydroxide extract (hemi-celluloses) of immature barley plants (Hordeum distichum L.). Most of the glucose residues in the extract were found to be derived from the glucan. Methylation analysis and enzyme degradation studies showed that the glucan had (l-→3)-and (1-→4)-linked d-glucopyranosyl residues in an approximate molar ratio of 1.0:2.3. The molecular weight of the glucan was estimated to be 1.8 x 105 by gel filtration on Sepharose CL-6B. 相似文献
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Atefeh Esmaeili Ahmad Ali Pourbabaee Hossein Ali Alikhani Farzin Shabani Lalit Kumar 《Bioremediation Journal》2014,18(3):213-226
The primary objective of this study was the isolation of low-density polyethylene (LDPE)-degrading microorganisms. Soil samples were obtained from an aged municipal landfill in Tehran, Iran, and enrichment culture procedures were performed using LDPE films and powder. Screening steps were conducted using linear paraffin, liquid ethylene oligomer, and LDPE powder as the sole source of carbon. Two landfill-source isolates, identified as Lysinibacillus xylanilyticus XDB9 (T) strain S7-10F and Aspergillus niger strain F1-16S, were selected as super strains. Photo-oxidation (25 days under ultraviolet [UV] irradiation) was used as a pretreatment of the LDPE samples without pro-oxidant additives. The PE biodegradation process was performed for 56 days in a liquid mineral medium using UV-irradiated pure LDPE films without pro-oxidant additives in the presence of the bacterial isolate, the fungal isolate, and the mixture of the two isolates. The process was monitored by measuring the fungal biomass, the bacterial growth, and the pH of the medium. During the process, the fungal biomass and the bacterial growth increased, and the pH of the medium decreased, which suggests the utilization of the preoxidized PE by the selected isolates as the sole source of carbon. Carbonyl and double bond indices exhibited the highest amount of decrement and increment, respectively, in the presence of the fungal isolate, and the lowest indices were obtained from the treatment of a mixture of both fungal and bacterial isolates. Fourier transform infrared (FT-IR), x-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses showed that the selected isolates modified and colonized preoxidized pure LDPE films without pro-oxidant additives. 相似文献
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Takayuki Uwajima Hitoshi Yagi Shizuko Nakamura Osamu Terada 《Bioscience, biotechnology, and biochemistry》2013,77(10):2345-2350
Among about 500 strains tested, a newly isolated soil bacterium, Brevibacterium sterolicum nov. sp. KY 3463 (ATCC 21387) showed the highest potency in production of 3β-hydroxysteroid oxidase in the culture fluid.The 3β-hydroxysteroid oxidase was purified from the culture filtrate by a procedure involving ammonium sulfate fractionation, DEAE-cellulose and hydroxyapatite column chromatographies and Sephadex G–75 gel filtration. Crystals of the enzyme were obtained from solutions of the purified preparation by the addition of ammonium sulfate. The crystals appeared as fine rods, with a bright yellow color.The enzyme is homogeneous by disc gel electrophoresis and ultracentrifugation. Sedimentation velocity yields a value of . It exhibits a typical flavoprotein spectrum of absorption maxima at 280, 390, and 470 mμ. 相似文献
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In the same year, 1961, Peter D. Mitchell and Robert R.J.P. Williams both put forward hypotheses for the mechanism of oxidative
phosphorylation in mitochondria and photophosphorylation in chloroplasts. Mitchell’s proposal was ultimately adopted and became
known as the chemiosmotic theory. Both hypotheses were based on protons and differed markedly from the then prevailing chemical
theory originally proposed by E.C. (Bill) Slater in 1953, which by 1961 was failing to account for a number of experimental
observations. Immediately following the publication of Williams’s hypothesis and before his own was published, Mitchell initiated
a correspondence. Examination of the letters shows the development of a dispute based on the validity of the proposals, who
should have priority and particularly whether Mitchell had drawn on Williams’s work without acknowledgement. We have concluded
that Mitchell’s proposals were original (a view still questioned by Williams) although it is evident that prior to the correspondence
Williams had considered and rejected a proposition similar to Mitchell’s theory. However, a major cause of the dispute was
the difference in disciplinary backgrounds of Mitchell, a microbial biochemist and Williams, a chemist. 相似文献
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A. P. Thomson 《BMJ (Clinical research ed.)》1949,2(4622):300-305