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61.
62.
DNA-dependent in vitro synthesis of enzymes of the galactose operon of Escherichia coli 总被引:19,自引:0,他引:19
Summary Two active enzymes of the galactose operon of Escherichia coli, uridyl transferase and galactokinase have been synthesized with high yields in a DNA dependent system for protein synthesis. The unspecific blank values amount to less than two percent of the rate obtained under optimal conditions and permit the accurate determination of even a small fraction of the maximum synthesis rate. Therefore this system provides a sensitive assay for the biological activity of DNA that contains the intact galactose operon of Escherichia coli.The synthesis of these galactose enzymes is to a high extent dependent on the presence of cyclic adenosine-3:5-monophosphate.D-fucose, known as an inducer of the galactose operon in vivo, stimulates the synthesis of galactokinase, indicating that the repressor of the galactose operon in active under these conditions. This stimulation is not observed, if the bacterial extract is prepared from a strain defective for the galactose repressor or if the DNA carries an operator constitutive mutation in the galactose operon. Therefore the stimulation by D-fucose is true derepression. 相似文献
63.
Fifteen species of freshwater blue-green algae, including unicellular, filamentous, and colonial forms, were subjected to a variety of fixatives, fixation conditions, and stains for comparison of the preservation of phycobilisomes. Absorption spectra of the corresponding in vivo and released photosynthetic pigments, in 10 of the species that were maintained in culture, demonstrated the presence of phycocyanin in all 10 species and phycoerythrin in only 2 of them. Spectroscope and electron microscope evidence was obtained for localization of phycobiliproteins in phycobilisomes of Nostoc muscorum. Phycobilisomes were observed in all species examined in situ, strenghening the hypothesis that phycobilisomes are common to all phycobiliprotein-containing photosynthetic blue-green algae. 相似文献
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65.
The reaction of alkylating agents with bacteriophage R17. Biological effects of phosphotriester formation 总被引:4,自引:2,他引:2
The extent of biological inactivation and of the degradation of the RNA after reaction of bacteriophage R17 with ethyl methanesulphonate, isopropyl methanesulphonate and N-ethyl-N-nitrosourea was studied. Formation of breaks in the RNA chain probably results from hydrolysis of phosphotriesters formed in the alkylation reactions. Near neutral pH the ethyl and isopropyl phosphotriesters are sufficiently stable for the kinetics of the hydrolysis reaction to be followed. Results indicate that the rate of hydrolysis increases rapidly as the pH is raised. The evidence shows that a phosphotriester group does not itself constitute a lethal lesion. The extent of phosphotriester formation by the different agents is discussed in terms of reaction mechanism. 相似文献
66.
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68.
Ruth Van Heyningen 《The Biochemical journal》1969,112(2):211-220
1. The metabolism of d-glyceraldehyde by the lens was examined. 2. When low concentrations of d-[U-(14)C]glyceraldehyde were incubated with lens extracts there was no incorporation of the label into protein; more than two-thirds of the labelled metabolites consisted of glyceric acid and glycerol, their relative proportions depending on the species. Lactic acid, a phosphate, glutathione-glyceraldehyde compounds and a neutral compound were also formed. 3. When high concentrations of d-[U-(14)C]glyceraldehyde were incubated with lens, extensive incorporation of the label into protein occurred and the protein became yellow-brown. This coloured protein did not exhibit the fluorescent properties shown by the brown proteins of human cataractous senile lens, or of naphthaquinone-treated lens. 4. Evidence that d-glyceraldehyde is formed by the lens was sought but not found. 相似文献
69.
70.
Ruth Lotmar W. R. Ranscht-Froemsdorff H. Weise 《International journal of biometeorology》1969,13(3-4):231-238
Zusammenfassung In einem gegen die natürliche Langwellenstrahlung abgeschirmten Versuchsraum wurde die Atmung von Mäuselebergewebe in künstlich erzeugten elektromagnetischen Feldern gemessen. Unter der Einwirkung von zyklonale Wetterlagen simulierenden Programmen (30–100 pulses sec–1, > 100 mV m–1, 10–100 kHz) ergab sich im Vergleich zu den Kontroll-QO2-Werten eine signifikante Dämpfung der Gewebeatmung um 42% ± 2,8% (p<0,001). Die Applikation eines H-Feld-Programms blieb ohne Wirkung. Programme mit Simulierung antizyklonaler Wetterlagen(1–3 pulses sec–1, <10 mV m–1, 10 kHz) hatten ebenfalls keinen Einfluss auf die Atmungsgeschwindigkeit der Mäuseleber.
In a room completely shielded against long wave radiation, liver tissue of mice in a Warburg apparatus was exposed to artificial electromagnetic radiation simulating cyclonic and anticyclonic weather. Under the influence of simulated cyclonic weather programs (30–100 pulses sec–1, > 100 mV m–1 10–100 kHz) a significant decrease (42% ± 2,8%) of the respiration rate of the liver tissue was found, compared with the control QO2 (p < 0,001). The application of a cyclonic weather H-field program had no effect. Simulated anticyclonic weather (1–3 pulses sec–1, < 10 mV m–1, 10 kHz) also failed to produce a demonstrable effect on the respiration rate of mouse liver tissue.
Resume Dans un local absolument protégé contre l'irradiation naturelle par ondes longues, des tissus de foie de souris ont été exposés, dans un appareil de Warburg, à des impulsions électromagnétiques artificielles, correspondant à celles de temps cyclonal et anticyclonal. Sous l'influence des programmes artificiels simulant le temps cyclonal(30–100 pulses sec–1, > 100 mV m–1, 10–100 kHz), il a été constaté une inhibitation significative de la respiration tissulaire de 42% ± 2,8% comparée aux valeurs du QO2 de contrôle (p < 0.001). L'application d'un temps cyclonal-"H-field"-programme séparé, est demeuré sans effet. De même. les signaux de temps anticyclonal(1–3 pulses sec–1, < 10 mV m–1, 10 kHz), n'ont eu aucune influence démonstrable sur la vitesse de respiration du fois de souris.相似文献