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N J Oppenheimer M Singh C C Sweeley S J Sung P A Srere 《The Journal of biological chemistry》1979,254(4):1000-1002
The structure of the prosthetic group of citrate lyase (Klebsiella aerogenes) was studied by nuclear magnetic resonance and mass spectrometry. The spectra at 360 MHz of the nucleoside moiety (2'-ribosyladenosine) show the absence of 2'-hydroxyl proton, thus confirming the 2' position as the site of attachment of the second ribose moiety to the dephospho-CoA. This glycosidic linkage is found to be alpha(1" leads to 2') and is identical to that of poly(ADP-ribose). Studies of permethylation products by mass spectrometry support the above conclusion regarding the location of the ribosidic linkage. 相似文献
34.
Synthesis of 4-triazolopyrimidinone nucleotide and its application in synthesis of 5-methylcytosine-containing oligodeoxyribonucleotides. 总被引:7,自引:6,他引:1
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W L Sung 《Nucleic acids research》1981,9(22):6139-6151
5'-0-Dimethoxytritylthymidine (2) was phosphorylated and base-modified simultaneously to yield the 4-triazolopyrimidinone nucleotide (3). Coupling between (3) and other common deoxyribonucleotides gave a fully protected nonamer (4). Deblocking under different conditions yielded the nonamer as phosphodiester with concomitant conversion of 4-triazolopyrimidinone to 5-methylcytosine (aqueous ammonia) or thymine (N1,N1,N3,N3-tetramethyl-guanidinium syn-4-nitrobenzaldoximate solution). 相似文献
35.
Jane Smith Ian Furner Z. R. Sung 《In vitro cellular & developmental biology. Plant》1981,17(4):315-321
Summary The purpose of this study was to optimize growth conditions for a strain of haploid carrot callus and to follow its karyotypic
changes in a long span of time. The strain has been maintained in liquid suspension since September 1977. It has remained
predominantly haploid in its karyotype since that time. The original explant was initiated and subsequently subcultured in
Gamborg's B5 medium. The components of the B5 medium were omitted one at a time and sequentially added back to determine their
minimum, optimum, and maximum nontoxic concentrations. These changes were made in the original formula: the addition of an
organic buffering agent and an increase in the iron and other micronutrient concentrations. Using this slightly modified B5
medium, we assessed the effect on growth by single additions of amino acids, different carbon sources, growth regulators,
and vitamins. No improvement in plating efficiency resulted from addition of any of these compounds. We conclude that there
are factors limiting the plating efficiency of the haploid cells other than these tested, or that single additions will not
make a discernible difference, or that growth promoting factors cannot be exogenously supplemented to cultured cells. 相似文献
36.
Chicken brain choline acetyltransferase was purified to homogeneity using ammonium sulfate fractionation, followed by chromatography on DEAE-Sephadex (A-25), hydroxyapatite, Sephadex G-150, immunoabsorption and Sepharose-CoA columns. A purification of 3500-fold was achieved and the final preparation had a specific activity of 2:32 μmol acetylcholine formed per minute per milligram protein. The purified chicken choline acetyltransferase migrated as a single band on polyacrylamide gel electrophoresis in the presence and absence of sodium deodecyl sulfate. The native enzyme, with a molecular weight of 67,000 daltons, consists of two subunits of identical molecular weight. Chicken choline acetyltransferase has a sharp pH optimum of 7.4. It is activated by sodium chloride and potassium chloride but inhibited by cupric ion and N-ethylmaleimide. 相似文献
37.
Ultraviolet light induced preferential cross-linking of histone H3 to deoxyribonucleic acid in chromatin and nuclei of chicken erythrocytes 总被引:3,自引:0,他引:3
Histones have been cross-linked to DNA in chicken erythrocyte nuclei and chromatin by using ultraviolet light irradiation at 254 nm. Following irradiation, cross-linked histone-DNA adducts were isolated and purified by hydroxylapatite chromatography, and the DNA component was subjected to acid hydrolysis. Of several hydrolysis techniques investigated, trichloroacetic hydrolysis of the DNA component of the adducts was found to be most effective. Histones isolated from hydrolyzed histone-DNA adducts were characterized by gel electrophoresis and fingerprint analysis. No histone-histone protein adducts were observed. All histone fractions have been shown to cross-link DNA in nuclei or chromatin by utilizing the technique employed, but with different propensities. The order of observed cross-linking, deduced from kinetic experiments, is H1 + H5, H3 greater than H4 greater than H2A much greater than H2B. The preferential binding of the core histone H3, as compared to the other core histones, is discussed in light of recent data concerning histone-DNA interactions and nucleosome structure. The use of the ultraviolet light technique as a conformational probe to study chromatin is also discussed. 相似文献
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Micromanipulation of adhesion of a Jurkat cell to a planar bilayer membrane containing lymphocyte function-associated antigen 3 molecules
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A T?zeren K L Sung L A Sung M L Dustin P Y Chan T A Springer S Chien 《The Journal of cell biology》1992,116(4):997-1006
Cell adhesion plays a fundamental role in the organization of cells in differentiated organs, cell motility, and immune response. A novel micromanipulation method is employed to quantify the direct contribution of surface adhesion receptors to the physical strength of cell adhesion. In this technique, a cell is brought into contact with a glass-supported planar membrane reconstituted with a known concentration of a given type of adhesion molecules. After a period of incubation (5-10 min), the cell is detached from the planar bilayer by pulling away the pipette holding the cell in the direction perpendicular to the glass-supported planar bilayer. In particular, we investigated the adhesion between a Jurkat cell expressing CD2 and a glass-supported planar bilayer containing either the glycosyl-phosphatidylinositol (GPI) or the transmembrane (TM) isoform of the counter-receptor lymphocyte function-associated antigen 3 (LFA-3) at a concentration of 1,000 molecules/microns 2. In response to the pipette force the Jurkat cells that adhered to the planar bilayer containing the GPI isoform of LFA-3 underwent extensive elongation. When the contact radius was reduced by approximately 50%, the cell then detached quickly from its substrate. The aspiration pressure required to detach a Jurkat cell from its substrate was comparable to that required to detach a cytotoxic T cell from its target cell. Jurkat cells that had been separated from the substrate again adhered strongly to the planar bilayer when brought to proximity by micromanipulation. In experiments using the planar bilayer containing the TM isoform of LFA-3, Jurkat cells detached with little resistance to micromanipulation and without changing their round shape. 相似文献
40.