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991.
Summary The immobilization of the mycelial-associated -glucosidase of Trichoderma E-58 has been carried out by encapsulating, in calcium alginate beads, the fungal mycelium obtained durinq liquid culture. The activity of this immobilized -glucosidase was found to vary with culture age and to be more thermally stable than the extracellular -glucosidase produced by this organism. The activity of the immobilized enzyme was successfully demonstrated in both static and shake-flask batch reaction mixtures at 50°C using both cellobiose and salicin as substrates. 相似文献
992.
Measurements are reported on μs delayed light emission, following a single 10 ns excitation flash, in Alaska pea thylakoids treated with hydroxylamine (NH2OH) or with silicomolybdate.
- In thylakoids treated with 2 mM NH2OH in the light, or in the dark, the quantum yield of delayed light emission is considerably enhanced. A 10 μs lifetime component of delayed light emission is not significantly changed, whereas a 50–70 μs lifetime component is increased. MnCl2 and diphenylcarbazide are unable to reverse the above effects of NH2OH treatment. Thus Mn2+ and diphenylcarbazide must not donate electrons directly to reaction center II but on the oxygen-evolution side of the NH2OH block.
- When the closed form of photosystem II reaction centers (P680Q-), where P680 is the reaction center chlorophyll and Q is a ‘stable’ electron acceptor, is generated by preillumination of NH2OH-treated thylakoids with diuron present, the μs delayed light emission is inhibited, but a low level residual delayed light emission remains. Possible origins of this emission are discussed. It is believed that the best explanation for residual DLE is the existence of another acceptor besides Q that partakes in charge separation and rapid dissipative recombination when the reaction center is in the P680Q- state.
- The quantum yield of delayed light emission from ‘closed’ reaction centers (P680 +Q-) that have all charge stabilization reactions (i.e., flow of electrons to P680 + and out of Q-) blocked by NH2OH treatment and addition of diuron is 1.1×10-3 for components measured in a range from 6 to 400 μs and extrapolated to zero time.
- The addition of silicomolybdate, which accepts electron from Q-, causes delayed light emission in the μs range to be greatly inhibited.
993.
Paul S. Agutter Keith E. Suckling 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,696(3):308-314
The effects of in vitro and in vivo modifications of nuclear envelope lipid on DNA leakage and on ATP-stimulated RNA release from isolated rat liver nuclei were investigated. The modifications included corn-oil feeding of the animals to alter the fatty acid composition of the lipids, phospholipase treatment of the isolated nuclei, and extraction of the total lipid with Triton X-100. Significant changes in lipid composition and approximate order parameter values of the spin-label 5-doxylstearate resulted, but there was no significant effect on RNA transport rate. It was concluded that the nuclear envelope lipid does not play any important part in nucleocytoplasmic RNA transport in mammalian liver. 相似文献
994.
Paul H. Weigel 《Biochemical and biophysical research communications》1981,101(4):1419-1425
Rat hepatocytes in the continuous presence of [3H]asialo-orosomucoid quickly establish a steady state number of free and occupied surface receptors and rate of endocytosis. These values do not change even though many times more glycoprotein is internalized than there are surface receptors per cell. However, when cells endocytose only one round of surface bound [3H]asialo-orosomucoid at 37°C the internalization of glycoprotein is about 5 times faster than the increase of functional receptors on the cell surface. At 18°C new surface receptors appear at only 6% of the rate of internalization of pre-bound asialoglycoprotein. The results suggest that reutilization of asialoglycoprotein receptors is preferentially inhibited at low temperature and that receptor-ligand complexes enter the cell. 相似文献
995.
Julia Bell-Quint Trudy Forte Paul Graham 《Biochemical and biophysical research communications》1981,99(2):700-706
Cultured rat hepatocytes were used to demonstrate that the liver can synthesize two forms of apolipoprotein B. Separation of apolipoprotein B by disc gel electrophoresis indicated that hepatocyte low density lipoprotein contains predominantly apolipoprotein B with an apparent molecular weight of 345,000 ± 5,055. In contrast, the major apolipoprotein B component of hepatocyte very low density lipoprotein is a variant form with a molecular weight of 242,000 ± 2,720. Hepatocyte high density lipoprotein, unlike plasma HDL, also contains apolipoprotein B with an apparent molecular weight of 244,000 ± 2,742. Incorporation of [3H] leucine into hepatocyte apolipoprotein B components suggested de novo synthesis. 相似文献
996.
Paul A. Price Sharon A. Baukol 《Biochemical and biophysical research communications》1981,99(3):928-935
1,25-dihydroxyvitamin D3 increases serum levels of bone Gla protein (BGP). The maximal increase occurs 12 h after injection and is given by 350 ng 1,25(OH)2D3 per 180 g body weight. In both 2 and 11 month-old male rats, the maximal increase is about 3 times the normal level, while in 2 month old female rats, the maximal increase is 2 times the normal level. These effects of 1,25(OH)2D3 in rats parallel the previously described effects of the vitamin on BGP secretion by rat osteosarcoma cells in culture.BGP is the first bone-specific protein whose synthesis in animals is dramatically increased by 1,25(OH)2D3. The possible functions of BGP in the biological actions of 1,25(OH)2D3 on bone are discussed. 相似文献
997.
Douglas L. Currell Bernice Law Michael Stevens Paul Murata Carmela Ioppolo Filippo Martini 《Biochemical and biophysical research communications》1981,102(1):348-354
Human hemoglobin reacts with 4-Isothiocyanatobenzene sulfonic acid at the four amino groups of the N-terminal valines. The modified protein shows a decreased oxygen affinity over a wide pH range, a reduced alkaline Bohr effect, decreased co-operativity, and a reduced effect of inositol hexasulfate on the oxygen affinity. 相似文献
998.
999.
Primary cell cultures derived from mutants in seventeen different genes were analyzed for their ability to excise pyrimidine
dimers from DNA. Five of these mutagen-sensitive mutants [mus(2)205A1, mus(3)302D1, mus(3) 304D3, mus(3)306D1, mus(3)308D2] display a significantly reduced excision capacity relative to control cultures. In addition, two of the five [mus(3)306D1, mus(3)308D2] are defective in the accumulation of single-strand breaks normally seen after ultraviolet irradiation. This study, therefore,
brings the total number of Drosophila mutants known to be defective in excision repair to seven. The results are discussed relative to other genetic and biochemical
properties of these mutants.
This work is dedicated to Professor W. Beermann whose own contributions were instrumental in focusing a modern analysis of
the eukaryotic genome on the diptera. Those of us who benefitted so much from his personal guidance recognize that we did
so as a result of some sacrifice on his part. One of Boyd's contemporaries in Tübingen once remarked: “It's terrifying to
think what Professor Beermann could do if he were in the lab full time.” 相似文献
1000.
Synthesis of histone H4 by mouse oocytes and unfertilized eggs has been examined by using a modified high-resolution two-dimensional gel electrophoresis procedure capable of resolving basic proteins (M. J. LaMarca and P. M. Wassarman, 1979, Develop. Biol.73, 103–119). Histones were separated on such gels and observed rates of incorporation of [35S]methionine into histone H4 were converted into absolute rates of synthesis by using previously determined values for the absolute rates of total protein synthesis in mouse oocytes and unfertilized eggs Schultz et al., 1979a, Schultz et al., 1979b. Histone H4 was synthesized at all stages of oogenesis examined, and accounted for 0.07, 0.05, and 0.04% of total protein synthesis in growing oocytes, fully grown oocytes, and unfertilized eggs, respectively. During oocyte maturation the absolute rate of histone H4 synthesis decreased by about 40%, as compared to a 23% decrease in the rate of total protein synthesis during the same period. These measurements indicate that enough histone is synthesized during oogenesis in the mouse to support two to three cell divisions. Examination of the intracellular location of newly synthesized proteins in fully grown oocytes revealed that histone H4 was highly concentrated in the nucleus (germinal vesicle), whereas total protein and tubulin were not. Nearly 50% of the histone H4 synthesized during a 5-hr period was located in the oocyte's germinal vesicle, as compared to 1.9 and 0.9% for total protein and tubulin, respectively. These results are compared with those obtained using oocytes and eggs from nonmammalian animal species. 相似文献