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Summary A selection method has been developed for the isolation of recombinant strains of Trichoderma reesei QM 9414. The method is based on somatic hybridization via anastomosis or protoplast fusion, and on the difference in growth rate of the resulting heterokaryons and synkaryons. The more intensive growth of the synkaryons as due to allelic complementation of adenine-requiring auxotrophic strains mutated in the adenylosuccinate synthetase gene. The synkaryons appeared is energetically growing spots in the heterokaryotic background. Stable diploids could not be isolated, which points to the transient nature of the diploid state in this species. 相似文献
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Polyethylenimine selectivity precipitates a large fraction of the proteins present in a crude Drosophila embryonic extract. While the free catalytic subunit of the cAMP dependent protein kinase is quantitatively retained in the soluble fraction after polyethylenimine precipitation, the rest of the abundant and highly active protein kinases present in the embryo are quantitatively precipitated. The catalytic subunit of the cAMP dependent protein kinase was purified until apparent homogeneity from the soluble protein fraction after polyethylenimine precipitation. The pH optimum of the purified enzyme is 6.3. While magnesium is the preferred divalent cation for all the cAMP dependent protein kinases described previously, the Drosophila enzyme is three times more active if manganese is present as divalent cation compared with magnesium. The enzyme is tost active between 50–100 mM monovalent ion concentration. Heparin can selectively modulate the phosphorylation of different substrate proteins. 相似文献
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Bradykinin (BK) is a peptide hormone with sequence Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9 and has been implicated in a multitude of pathophysiological processes such as the ability to lower systemic blood pressure and stimulate pain. BK analogues having bulky, β-branched D -aliphatic residues at position 7 combined with bulky L -aliphatic residues at position 8 have now been observed to be strong antagonists. Conformational studies based on two-dimensional nmr experiments in methanol/water (80/20 v/v) were carried out on several such active antagonists in a polar solvent. Included in this study were the very active antagonists, [D -Arg0, Hyp3, Thi5, D -Cpg7, Cpg8]-BK [Cpg: α-cyclo-pentyl-glycine; Hyp: trans-4-hydroxy-L -proline; Thi: β-(2-thienyl)-L -alanine] ( I ), [D -Arg0, Hyp3, D -Cpg7, Cpg8] -BK ( II ), as well as its variant with D -Cpg7 replaced by Cpg7, namely [D -Arg0, Hyp3, Cpg7, Cpg8]-BK ( III ). A turn-like structure, which coexists with the extended conformation, was observed between residues 2 and 5 for the most active antagonists I and II , in direct correlation with the peptide activities. No turn-like structure was found for residues 6–9. In peptide III , a turn-like structure was not identified. The existence of a turn at the C-terminal end of bradykinin and its analogues has been predicted by empirical calculations and supported by nmr measurements. But the present nmr study on the most active antagonists ( I , II ) does not support this hypothesis. Instead, the data suggest that a turn-like structure between residues 2 and 5 could be important for antagonist activity. Finally, one weak inhibitor [D -Cpg7]-BK ( IV ) showed no defined secondary structure. © 1993 John Wiley & Sons, Inc. 相似文献
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Eszter Gács-Baitz Lajos Radics G.B. Oganessian Vilen A. Mnatsakanian 《Phytochemistry》1978,17(11):1967-1973
The structure and stereochemistry of teucrins H1, H2, H3 and H4, four novel diterpenes from Teucrium hyrcanicum have been established by detailed studies of the PMR and 13C NMR spectra, CD results and chemical transformations. Teucrin H4, a minor constituent is shown to possess a unique stereochemistry hitherto not reported for related diterpenoids. 相似文献
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Based on 388 parallel data of phytoplankton biomass and chlorophyll-a of two shallow lakes and two ponds, the following results were obtained:
- Relative chlorophyll-a content of phytoplankton biomass varied between 0.08–1.88%; chlorophyll-a concentration showed great differences among lakes.
- Significant correlations (r = 0.68–0.92) were established between phytoplankton biomass and chlorophyll-a concentration. The regression in the artificial ponds was non-linear.
- In parallel with the increase of average cell volume, a decrease in relative chlorophyll-a content was observed. A significant correlation (r = + 0.83) between the two variables was found. Relative chlorophyll-a content of phytoplankton is a log-function of average cell volume.
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A number of commercially available enzymes were used to modify the cell surface of human erythrocytes to varying degrees. In protease-treated erythrocytes the decrease in surface charge (determined by cell electrophoresis or analysis of sialic acid content) correlates with an increase in agglutinability with concanavalin A (ConA) and wheat germ agglutinin (WGA). On the other hand, treatment with neuraminidase leads to very large decrease in surface charge with only an intermediate increase in agglutinability with both lectins. Subsequent protease treatment of these cells enhances their agglutinability appreciably without further altering their surface charge. It is concluded that the increased agglutinability following protease treatment is due both to a decrease in the net negative charge and a removal of peptides and glycopeptides from the cell surface that may sterically hinder the agglutination reaction. 相似文献
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H G Durkin S M Chice E Gaetjens H Bazin L Tarcsay P Dukor 《Journal of immunology (Baltimore, Md. : 1950)》1989,143(6):1777-1783
Mechanisms regulating the appearance of sIgE+ B lymphocytes appear to be lacking in adult germfree (GF) rats in that their Peyer's patches (PP) contain high numbers of cells with sIgE (approximately 15% of total cells), one-half of which simultaneously express sIgA, whereas sIgE+ cells are absent from PP of conventional rats (less than 1%). GF rat PP also contain elevated numbers of sIgA+ cells and decreased numbers of sIgM+ cells, with elevated numbers of sThy-1+ RT 7.1+ Ig- T cells, and reduced numbers of sThy-1- RT 7.1+ Ig- T cells. The cellular composition of PP of GF rats was converted to that resembling a conventional rat within 18 h after either 1) use of standard (unautoclaved) food; 2) feeding with certain bacteria (Clostridium difficile, Corynebacterium pseudodiphtheriticum, Mycobacterium tuberculosis, and Klebsiella pneumoniae), in either live or heat-killed, but not autoclaved form; or with certain bacterial cell wall components: murein (peptidoglycan), and its synthetic derivatives, muramyltripeptide phosphatidylethanolamine and desmethyl-muramyldipeptide, but not with LPS, core lipid A or lipoprotein; there was no effect if any bacterial cell wall component was injected i.v.; or 3) thymectomy. Each procedure resulted in elimination of sIgE+ B cells and normalization of the other surface isotypes, and loss of sThy-1+ RT 7.1+ Ig- T cells and normalization of sThy-1- RT 7.1+ Ig- T cells. Irrespective of treatment, no sIgE+ cells were detected in bone marrow, thymus, other lymphoid organs or blood, excluding the possibility that the elimination of these cells from PP was associated with their redistribution to other sites. Thus, exposure to gut flora and bacterial peptidoglycan components may have resulted in IgE isotype switching, either directly or through the mediation of accessory and/or sThy-1+ RT 7.1+ regulatory T cells. The sites in which sIgE+ B cells are down-regulated appear to be PP. 相似文献
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