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991.
S C Lee J Y Shew F H Chang M J Chou C S Yang 《Proceedings of the National Science Council, Republic of China. Part B, Life sciences》1984,8(2):143-147
Protein kinase activity has been found in hepatitis B virions (Dane particles) purified from the plasma of hepatitis B surface antigen carriers [Albin, C., and Robinson, W.S. (1980) J. Virol. 34, 297-302]. Dane particles were purified from the pooled, HBeAg-positive plasma. When this preparation was incubated with [gamma 32P]ATP in the presence of 10mM MnCl2 and 0.5% NP-40 for 15 seconds at 30 degrees C, several phosphorylated polypeptides of 20,000, 42,000, 48,000, 50,000 and 56,000 daltons were detected in sodium dodecyl sulfate-polyacrylamide gels. When the Dane particles were incubated with [gamma 32P]ATP, 10 mM MnCl2, and 0.5% NP-40 in the presence of human hepatoma cell (J-5) particulate fraction at 30 degrees C, 15 seconds, the 42,000, 48,000 and 50,000 daltons phosphorylated polypeptides were not found. When human peripheral blood lymphocytes particulate fraction was incubated with Dane particles under the same conditions, no change of Dane particle phosphorylated polypeptides was detected. Previous publications [Albin, C., and Robinson, W.S. (1980) J. Virol. 34, 297-302; Gerlich, W.H. et al. (1982) J. Virol. 42, 761-766] showed that when hepatitis B core particles purified from hepatoma tissues contained protein kinase activity, only phosphorylated polypeptide was 20,000 daltons. Our data suggested that when Dane particles were put in an environment of hepatoma cells (or tissues), the protein kinase could only phosphorylate selected polypeptides in these particles. 相似文献
992.
The properties and conformational stability of the proteinaceous activator of fibrinolysis--native streptokinase--and its derivative obtained by modification with a linear hydrophilic copolymer based on N-vinylpyrrolidone, were studied by the circular dichroism method. It was shown that polymeric modification of streptokinase had no effect on the secondary structure, while the conformational stability of the modified protein to urea was higher than that of the native one. Studies on thermal stability of both native and modified forms of streptokinase showed that the inactivation rate was lower in the modified form as compared to the native one. 相似文献
993.
R. B. Flavell 《BioEssays : news and reviews in molecular, cellular and developmental biology》1984,1(1):21-22
Higher plant nuclear genomes contain many families of dispersed repeats that change during evolution. Recent evidence from studies on genetically defined transposable elements raises the possibility that many of the dispersed repeats are remnants of such elements. Transposition of DNA has also occurred between mitochondria, chloroplasts and nuclei, a fact that underlines the major role played by DNA transposition in determining the structure of plant genomes. 相似文献
994.
An NMR and nuclear Overhauser effect (NOE) analysis of Thermus thermophilus tRNAIle1a is presented. This species contains modifications including s2T54 and s4U8 [Horie, N., Hara-Yokoyama, M., Yokoyama, S., Watanabe, K., Kuchino, Y., Nishimura, S., & Miyazawa, T. (1985) Biochemistry 24, 5711-5715]. All the expected secondary and reverse Hoogsteen AU pairs were identified, with one possible exception. The general geometry of the T psi C loop is the same as the Escherichia coli species, and there is NOE evidence for an A9-UA12 triple. Preliminary measurements of solvent exchange rates of internally hydrogen-bonded bases suggest that this tRNA is more stable than previously studied E. coli and yeast tRNAs. 相似文献
995.
A simple enucleation technique that facilitates autoradiographic and electron microscopic examination of cytoplasms is described. Cells were grown on commercially available plastic Leighton coverslips and these were centrifuged in the presence of cytochalasin B. The centrifugation requires no special holders and only a high speed centrifuge. Enucleation frequencies of greater than 90% were obtained for Chinese hamster fibroblasts and mouse B-82 cells. 相似文献
996.
To determine whether histone genes are coordinately regulated, histone mRNA concentrations were measured in exponentially growing L6 myoblasts, S-phase synchronized myoblasts and in differentiating myoblasts. The levels of various histone mRNA subspecies declined rapidly and coordinately once myoblasts were given the signal to differentiate. mRNA levels were reduced on average to 1-5% of the amount observed in exponentially growing cells by 48 h after the signal to differentiate. The reductions occurred in concert with the cessation of DNA synthesis as the cells differentiated. Inhibition of DNA synthesis by treating myoblasts with Ara-C or hydroxyurea resulted in a histone mRNA half-life of 10-13 min for each of the histones examined. One example of non-coordinate regulation was observed however among the H4 mRNA subspecies in S-phase synchronized cells. The levels of two major subspecies of H4 mRNA increased coordinately in S-phase compared to levels observed in cells growing exponentially. A third subspecies of H4 mRNA on the other hand was found to decline by 50%. These studies suggest that the majority of histone mRNA subspecies are under coordinate control, although one exception has been noted among the subspecies of histone H4. 相似文献
997.
R.E. Jonkers B. Oosterhuis R.J.M. Ten Berge C.J. Van Boxtel 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1982,233(1):249-255
A relatively simple assay with improved reliability and sensitivity for measuring levels of 6-mercaptopurine in human plasma is presented. After extraction of the compound and the added internal standard with phenyl mercury acetate, samples were separated by ion-pair reversed-phase high-performance liquid chromatography. On-line the analytes were oxidized to fluorescent products and detected in a flow-fluorimeter. The within-day coefficient of variation was 3.8% at a concentration of 25 ng/ml. The lower detection limit was 2 ng/ml when 1.0 ml of plasma was used. Mercaptopurine concentration versus time curves of two subjects after a single oral dose of azathioprine are shown. 相似文献
998.
Interaction of hydrophobic bis (D-mannose) derivatives with adipocyte and erythrocyte sugar transport systems 总被引:2,自引:0,他引:2
The inhibition of sugar uptake by a series of hydrophobic bis(D-mannose) derivatives has been measured in rat adipocytes. When the D-mannose moieties of the bis compounds are separated by a hexane bridge the transport inhibition constant (Ki) is greater than for a decane-bridged molecule. This is probably due to the increased hydrophobicity of the bridge of the decane-bridged compound. The enhancement in affinity due to the second sugar in the bis(D-mannose) derivatives is probably only 2-fold, since half reduction of the bis(D-mannosyloxy)hexane increases Ki approx. 2-3-fold. N'-DNP-1,3-bis(D-mannos-4'-yloxy)propyl-2-amine has very high affinity in insulin-treated cells. The affinity is approx. 1000-fold higher than for D-mannose. This enhancement is probably due to the hydrophobicity of the DNP group. The distance from the sugar to the hydrophobic group is important because an increase in Ki occurs if an aminocaproyl spacer is introduced between the DNP group and 1,3-bis(D-mannos-4'-yloxy)propyl-2-amine. Aminocaproyl and glycyl spacers also increase the Ki for NAP derivatives of 1,3-bis(D-mannos-4'-yloxy)propyl-2-amine. Each of the hydrophobic bis(D-mannose) derivatives has a lower Ki in insulin-treated cells. This may be due to an insulin responsive hydrophobic interaction between the hydrophobic portion of the sugar and a hydrophobic domain in the transport system. The inhibition constants for the hydrophobic bis(D-mannose) compounds have also been measured in human erythrocytes. 相似文献
999.
1000.
Control of breathing in Sherpas at low and high altitude 总被引:2,自引:0,他引:2
Hackett P. H.; Reeves J. T.; Reeves C. D.; Grover R. F.; Rennie D. 《Journal of applied physiology》1980,49(3):374-379