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991.
K Maskos 《Acta biochimica Polonica》1985,32(3):235-250
The copper (II)-inosine system in water-DMSO solutions was investigated as a function of pH and the molar ratio between the ligand and copper(II) ion by the EPR, NMR, CD and visible absorption spectrometric methods. It was concluded that a simple M.[-N]L copper(II)-inosine 1:1 complex is formed over the pH range 1.4-5.0, while M.[-N]L2 complexes are present in the solutions of pH 5.0-6.2. From pH 6.2 to 7.8 a diamagnetic, hydroxybridged complex M2.(OH)2.[-N]L4 dominates. At pH values of 7.8-9.2 an insoluble, oxybridged species (M.O.[-N]L)n is formed in addition to the soluble paramagnetic M.[-N-1)L4 complex. Above pH 9.1 the nitrogenbridged polymeric complex (M.[-N-1].M[-N-7] )n is formed which is stable up to pH 12.5, and above pH 12.5 the only species found is the M.[-OH]L2 chelate complex in which inosine is coordinated to copper through the two ionized hydroxyl groups. 相似文献
992.
In view of the importance of impedance plethysmography requirements are formulated for a modern impedance measuring device basing on a long experience with this method of measurement. The principle mode of action of the measuring equipment and the pneumatics with the timing element are described. A number of recordings is shown to illustrate the universality of the measuring equipment. 相似文献
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996.
Of the 1,972 deaths investigated by autopsy at the Los Angeles County Hospital in 1951, 64 were attributed to bronchogenic carcinoma. However, in some of these cases the protocols did not contain sufficient data to substantiate the diagnosis or the tissue specimens were not conclusive evidence. Although the survey left no doubt that the lung was the most common site of primary carcinoma in the series studied, a wider application of the findings is limited by the facts that patients with bronchogenic carcinoma are more likely than others to die in hospitals and that selection of cases for autopsy depends on the interest of the physician and the consent of the patient's survivors. 相似文献
997.
Free and derivatized aglycones and parent ascarosides of Ascaris lumbricoides and A. columnaris (Nematoda) were isolated by thin-layer and gas chromatography and analyzed by mass spectrometry and polarimetry. Results for monol aglycones confirmed previous chain-length assignments and the location of the l-hydroxyl group at C-2. The major monols of even carbon number possessed a methyl branch on the penultimate carbon (ω ? 1). Diol alycones were entirely unbranched homologues, mainly 31 and 33 carbons long, and had hydroxyl groups on C-2 and C-(ω ? 1). These aglycones were truly symmetrical, for they were optically inactive with the center bearing the glycone in diol ascaroside (C-2), being mostly or entirely the l configuration. Three major features of ascaroside structure—chain length composition of the aglycones, molecular weight of the unusual glycone (a dideoxyhexose), the kind and position of acyl groups—were clearly discernible in the spectra of intact ascarosides. 相似文献
998.
Further evidence for a cell surface proteinase essential to the growth of cultured fibroblasts 总被引:2,自引:0,他引:2
Specific antibodies and protein proteinase inhibitors will inhibit cell-surface proteinase activity on human fibroblasts and cause a concomitant inhibition of DNA synthesis and of cell multiplication. An insolubilized proteinase inhibitor also inhibits cell multiplication. The same reagents partially inhibit the multiplication of mouse L cells, both in monolayer and suspension culture, and inhibit the mitogenic effect of epidermal growth factor (EGF) on both types of cell. 相似文献
999.
Biocatalysis has ancient roots, yet it is developing into a key tool for synthesis in a wide range of applications. Important events in the history of enzyme technology from the 19th century onwards are highlighted. Considering the most relevant progress steps, the production of penicillanic acid and the impact of genetic engineering are traced in more detail. Applied biocatalysis has been defined as the application of a biocatalyst to achieve a desired conversion selectively, under controlled, mild conditions in a bioreactor. Biocatalysts are currently used to produce a wide range of products in the fields of food manufacture (such as bread, cheese, beer), fine chemicals (e.g., amino acids, vitamins), and pharmaceuticals (e.g., derivatives of antibiotics). They not only provide access to innovative products and processes, but also meet criteria of sustainability. In organic synthesis, recombinant technologies and biocatalysts have greatly widened the scope of application. Examples of current applications and processes are given. Recent developments and trends are presented as a survey, covering new methods for accessing biodiversity with new enzymes, directed evolution for improving enzymes, designed cells, and integrated downstream processing. 相似文献
1000.
Derivatives of human thrombin and antithrombin III with fluorescent labels covalently attached to their carbohydrate moieties were prepared by reaction of periodate-oxidized proteins with amino derivatives of dansyl, fluorescein and pyrene. The labeled derivatives retained full biological activity, including their ability to form stable enzyme-inhibitor complexes, a reaction whose rate could be monitored by the increase in fluorescence polarization. When the dansyl-labeled derivatives were heated, they exhibited sigmoidal increases in polarization with midpoints near 50 degrees C for thrombin and 60 degrees C for antithrombin III. By contrast, a complex between antithrombin III and dansyl-thrombin showed no change in polarization up to 70 degrees C, suggesting that the individual components are more stable in the complex. These studies show that fluorescent labels attached to carbohydrate moieties of glycoproteins provide convenient probes for monitoring conformational changes and protein-protein interactions with minimum interference by the probe. 相似文献