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Phenylalkyl modified phosphoramidites (alkyl chain length n = 1,2,3,5; Fig. 1) were synthesised and incorporated into a DNA hexamer (5′-d(GCCp-GCG); p = place of modification). The obtained diastereomeres were separated by RP-HPLC. After hybridisation with the complementary DNA strand Tm-value and thermodynamic data were measured. The stability of duplexes depends on the linker length and the absolute configuration of the backbone modified oligodeoxynucleotides (Rp, Sp).

Figure 1. Structure of Rp- and Sp-configurated oligomers; synthesised phosphoramidites.  相似文献   

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The intra- and intermolecular hydrogen bonding (ΔGº298K ≈ 2, kcal mol?1) of 2′-OH in nucleos(t)ides has been reported by the temperature- and concentration-dependent NMR study in conjunction with dihedral dependence of the NMR derived both endo (3 J H,H)- and exocyclic (3 JH,OH) coupling constants, nOe contacts and lineshape analyses of hydroxyl protons for EtpA (1), 3′-dA (2), rA (3), 2′-dA (4) [Fig. 1] in DMSO-d 6 at 500 MHz.

Figure 1. The schematic representation of the bias of the dymanic two-state pseudorotational equilibrium between the North-type (N, C2′-exo -C3′-endo) and the South-type (S, C3′-exo-C2′-endo) [3a] Thibaudeau, C. and Chattopadhyaya, J. 1999. Stereoelectronic Effects in Nucleosides and Nucleotides and their Structural Implications Sweden: (ISBN 91-506-1351-0), Department of Bioorganic Chemistry, Uppsala University Press (fax: +4618554495). For review see: and references therein [Google Scholar] pseudorotamers of the sugar moeity for EtpA (1), 3′-dA (2), rA (3), 2′-dA (4) and torsion (Φ) around C2′/3′-O bond viz. Φ1 = ΦH2′?C2′?O?H and Φ2 = ΦH3′?C3′?O?H except in 1 where the torsion across C3′-O3′ bond is actually ?? [C4′-C3′-O3′-P].  相似文献   

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Neutral and acidic polysaccharides and their protein complexes were fractionated and purified from the brown seaweed umitoranoo (Sargassum thunbergii) by fractional extraction, iron-exchange chromatography, and gel filtration. Thirty-one polysaccharide fractions were obtained and tested for antitumor activity in mice with Ehrlich carcinoma transplanted i.p. Two of the fractions, GIV-A ( – 127° and mol. wt., 19,000) and GIV-B ( – 110° and mol. wt., 13,500) had such activity. On the basis of chemical and spectral analyses, these compounds were found to be a fucoidan or L-fucan containing approx. 30% sulfate ester groups per fucose residue, about 10% uronic acid, and less than 2% protein.  相似文献   

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(See Color Plate V)  相似文献   

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The effects of 7-ketocholesterol on rat hepatocytes prepared by collagenase perfusion were examined. The viability of cells incubated with 100 μm 7-ketocholesterol was significantly lower than those with cholesterol, although the LDH activity in the cultured medium remained unchanged during the incubation. Hepatocytes treated with 7-ketocholesterol produced large amounts of ·NO and in the early stage of incubation. Treatment of the hepatocytes with Carboxy-PTIO, which selectively scavenged ·NO, or with l-NMMA, an inhibitor of ·NO synthase, increased the cell viability. The addition of 7-ketocholesterol to the culture medium tended to increase the ratio of total sterol to phospholipid of the hepatocytes in a time-dependent manner without changing the content of phospholipid. No lipid peroxidation or oxidation of the cellular SH groups, protein SH and glutathione, was apparent. Vitamin E added 1 h before the addition of 7-ketocholesterol prevented the hepatocytes from cell death by suppressing the incorporation of 7-ketocholesterol into the hepatocytes and by scavenging .  相似文献   

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Abstract

«Pinus mugo» Turra and «Pinus uncinata» Miller in Piedmont. Critical notes and distribution. — The Authors have carried on a research on the distribution of Pinus mugo Turra (sensu Fl. Eur.) and Pinus uncinata Miller in all Piedmont Alpes and, having observed the extreme variability of the characters which are employed in the keys of determination to differentiate these two species, they suggest other and more constant characters. These are:

Table  相似文献   


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The substrate specificity of rice α-glucosidase II was studied. The enzyme was active especially on nigerose, phenyl-α-maltoside and maltooligosaccharides. The actions on isomaltose and phenyl-α-glucoside were weak, and on sucrose and methyl-α-glucoside, negligible. The α-glucans, such as soluble starch, amylopectin, β-limit dextrin, glycogen and amylose, were also hydrolyzed.

The ratio of the maximum velocities for hydrolyses of maltose (G2), nigerose (N), kojibiose (K), isomaltose (I), phenyl-α-maltoside (?M) and soluble starch (SS) was estimated to be 100: 94.4: 14.2: 7.1: 89.5: 103.1 in this order, and that for hydrolyses of malto-triose (G3), -tetraose (G4), -pentaose (G5), -hexaose (G6), -heptaose (G7), -octaose (G8), and amyloses ( and ), 113: 113: 113: 106: 113: 100: 106: 106. The Km values for N, K, I, ?M and SS were 2.4 mm, 0.58 mm, 20 mm, 1.6 mm and 5.0 mg/ml, respectively; those for G2, G3, G4, G5, G6, G7, G8, and , 2.4 mm, 2.2 mm, 2.1 mm, 1.5 mm, 1.0 mm, 1.1 mm, 0.95 mm, 1.5 mm and 1.1 mm.

Rice α-glucosidase II is considered an enzyme with a preferential activity on maltooligosaccharides.  相似文献   

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