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1.
2.
Characterization of the inhibitory effect of glucocorticoids on the DNA replication of adult rat hepatocytes growing at various cell densities 总被引:4,自引:0,他引:4
Dexamethasone inhibited the basal and EGF-stimulated DNA synthesis of adult rat hepatocytes in primary culture. The inhibition was glucocorticoid-specific: It was shown by dexamethasone and hydrocortisone, but not by progesterone, testosterone, or estradiol; and was counteracted by the glucocorticoid antagonist RU-38486 in a concentration-dependent manner. Dexamethasone acted by decreasing the rate of entry into S-phase (kG1/S), while cell cycle parameters were unaffected. The steroid was able to decrease the kG1/S severalfold even when added more than 20 hr after EGF, half-maximal effect occurring 11 hr after the addition of dexamethasone. Densely populated areas were much more sensitive to the inhibition by dexamethasone than sparsely populated areas within the same culture dish: A moderate (10 nM) concentration of dexamethasone nearly abolished the DNA synthesis in densely populated areas of hepatocyte cultures with only marginal effect on sparsely populated cells. 相似文献
3.
Evaluation of mass spectrometric techniques for charaterization of engineered proteins 总被引:7,自引:0,他引:7
Roepstorff Peter Schram Karl H. Andersen Jens S. Rafn Kate Baldursson Trausti Krøll Jenny Poulsen Kjeld Knudsen Jens Kristiansen Karsten 《Molecular biotechnology》1995,3(1):1-7
A simple and versatile method of in vitro site-specific mutagenesis based on polymerase chain reaction (PCR) is described.
The complete method required the use of three oligonucleotide primers and two PCRs. The product of the first PCR was used
as one of the primers (megaprimer) in the second PCR. Essentially 100% of the final product incorporated the desired mutation.
The various aspects of the procedure and its application is described in detail. 相似文献
4.
Uwe Karsten Gisela Papsdorf Annedore Pauly Borivoj Vojtesek Roland Moll E. Birgitte Lane Henrik Clausen Peter Stosiek Michael Kasper 《Differentiation; research in biological diversity》1993,54(1):55-66
Abstract. Normal (non-transformed) human mammary epithelial cell lines derived from reduction mammoplasties were analyzed by immunocytochemistry with more than 80 monoclonal antibodies (mAbs) and other specific reagents to tissue-specific and developmentally regulated antigens at different passage levels. A subpopulation of poorly differentiated, proliferating epithelial cells, corresponding to the 'selected' cell type of late passages, is shown to be characterized by a new marker, the histo-blood group antigen H type 2, probably carried on a membrane-bound glycolipid. These cells also express a number of other onco-developmental carbohydrate antigens [Ley , Lex , sialosyl-Lea , precursor of Thomsen Friedenreich antigen (Tn ), but not Thomsen-Friedenreich antigen and sialosyl-Tn ]. Their cytokeratin (CK) phenotype, as assessed by reactivity with monospecific mAbs and two-dimensional gel electrophoresis, is CK 5, 6, 14 and 17, with CK 19 being consistently absent, and varying minor amounts of CK 7, 8 and 18, as well as 15 and 16. The reactivity of these cells with a panel of 11 mAbs specific for CK 18 varies considerably even after cloning, indicating heterogeneity of epitope expression or accessibility. Our data strongly suggest that the H type 2+ cells develop from the basal cell layer of the mammary gland. 相似文献
5.
Hendrik Wunderlich Roque Augusto Castro Alvaro Holger Wenschuh Karsten Schnatbaum 《Journal of peptide science》2023,29(11):e3496
Peptide purification by high-performance liquid chromatography (HPLC) is associated with high solvent consumption, relatively large effort and lack of efficient parallelization. As an alternative, many catch-and-release (c&r) purification methods have been developed over the last decades to enable the efficient parallel purification of peptides originating from solid-phase peptide synthesis (SPPS). However, with one exception, none of the c&r systems has been widely established in industry and academia until today. Herein, we present an entirely new chromatography-free purification concept for peptides synthesized on a solid support, termed reactive capping purification (RCP). The RCP method relies on the capping of truncation peptides arising from incomplete coupling of amino acids during SPPS with a reactive tag. The reactive tag contains a masked functionality that, upon liberation during cleavage from the resin, enables straightforward purification of the peptide by incubation with a resin-bound reactive moiety. In this work, two different reactive tags based on masked thiols were developed. Capping with these reactive tags during SPPS led to effective modification of truncated sequences and subsequent removal of the latter by chemoselective reaction with a maleimide-functionalized solid support. By introducing a suitable protecting group strategy, the thiol-based RCP method described here could also be successfully applied to a thiol-containing peptide. Finally, the purification of a 15-meric peptide by the RCP method was demonstrated. The developed method has low solvent consumption, has the potential for efficient parallelization, uses readily available reagents, and is experimentally simple to perform. 相似文献
6.
Kiara Franke Lisa C. Matthes Angelika Graiff Ulf Karsten Inka Bartsch 《Journal of phycology》2023,59(3):518-537
Coastal kelp forests produce substantial marine carbon due to high annual net primary production (NPP) rates, but upscaling of NPP estimates over time and space remains difficult. We investigated the impact of variable underwater photosynthetically active radiation (PAR) and photosynthetic parameters on photosynthetic oxygen production of Laminaria hyperborea, the dominant NE-Atlantic kelp species, throughout summer 2014. Collection depth of kelp had no effect on chlorophyll a content, pointing to a high photoacclimation potential of L. hyperborea towards incident light. However, chlorophyll a and photosynthesis versus irradiance parameters differed significantly along the blade gradient when normalized to fresh mass, potentially introducing large uncertainties in NPP upscaling to whole thalli. Therefore, we recommend a normalization to kelp tissue area, which is stable over the blade gradient. Continuous PAR measurements revealed a highly variable underwater light climate at our study site (Helgoland, North Sea) in summer 2014, reflected by PAR attenuation coefficients (Kd) between 0.28 and 0.87 m−1. Our data highlight the importance of continuous underwater light measurements or representative average values using a weighted Kd to account for large PAR variability in NPP calculations. Strong winds in August increased turbidity, resulting in a negative carbon balance at depths >3–4 m over several weeks, considerably impacting kelp productivity. Estimated daily summer NPP over all four depths was 1.48 ± 0.97 g C · m−2 seafloor · d−1 for the Helgolandic kelp forest, which is in the range of other kelp forests along European coastlines. 相似文献
7.
8.
The N-terminal extension of the ADP/ATP translocator is not involved in targeting to plant mitochondria in vivo 总被引:4,自引:1,他引:3
Teresa Mozo Karsten Fischer Ulf Ingo Flügge Udo Klaus Schmitz 《The Plant journal : for cell and molecular biology》1995,7(6):1015-1020
The mitochondrial ADP/ATP translocator, also called adenine nucleotide translocase (ANT), is synthesized in plants with an N-terminal extension which is cleaved upon import into mitochondria. In contrast, the homologous proteins of mammals or fungi do not contain such a transient amino terminal presequence. To investigate whether the N-terminal extension is needed for correct intracellular sorting in vivo , translational fusions were constructed of the translocator cDNA—with and without presequence—with the β-glucuronidase ( gus ) reporter gene. The distribution of reporter enzymatic activity in the subcellular compartments of transgenic plants and transformed yeast cells was subsequently analysed. The results show that: (i) the plant translocator presequence is not necessary for the correct localization of the ANT to the mitochondria; (ii) the mitochondrial targeting information contained in the mature part of the protein is sufficient to overcome, to some extent, the presence of plastid transit peptides; and (iii) the presequence alone is not able to target a passenger protein to mitochondria in vivo . 相似文献
9.
The chemical and kinetic mechanisms of purified aspartate-beta-semialdehyde dehydrogenase from Escherichia coli have been determined. The kinetic mechanism of the enzyme, determined from initial velocity, product and dead end inhibition studies, is a random preferred order sequential mechanism. For the reaction examined in the phosphorylating direction L-aspartate-beta-semialdehyde binds preferentially to the E-NADP-Pi complex, and there is random release of the products L-beta-aspartyl phosphate and NADPH. Substrate inhibition is displayed by both Pi and NADP. Inhibition patterns versus the other substrates suggest that Pi inhibits by binding to the phosphate subsite in the NADP binding site, and the substrate inhibition by NADP results from the formation of a dead end E-beta-aspartyl phosphate-NADP complex. The chemical mechanism of the enzyme has been examined by pH profile and chemical modification studies. The proposed mechanism involves the attack of an active site cysteine sulfhydryl on the carbonyl carbon of aspartate-beta-semialdehyde, with general acid assistance by an enzyme lysine amino group. The resulting thiohemiacetal is oxidized by NADP to a thioester, with subsequent attack by the dianion of enzyme bound phosphate. The collapse of the resulting tetrahedral intermediate leads to the acyl-phosphate product and liberation of the active site cysteine. 相似文献
10.
Peng Sun Juan Huo Tibor Kurtán Attila Mándi Sándor Antus Hua Tang Siegfried Draeger Barbara Schulz Hidayat Hussain Karsten Krohn Weihua Pan Yanghua Yi Wen Zhang 《Chirality》2013,25(2):141-148
Four known hydroxyanthraquinones ( 1–4 ) together with four new derivatives having a tetralone moiety, namely coniothyrinones A–D ( 5–8 ), were isolated from the culture of Coniothyrium sp., an endophytic fungus isolated from Salsola oppostifolia from Gomera in the Canary Islands. The structures of the new compounds were elucidated by detailed spectroscopic analysis and comparison with reported data. The absolute configurations of coniothyrinones A ( 5 ), B ( 6 ), and D ( 8 ) were determined by TDDFT calculations of CD spectra, allowing the determination of the absolute configuration of coniothyrinone C ( 7 ) as well. Coniothyrinones A ( 5 ), B ( 6 ), and D ( 8 ) could be used as ECD reference compounds in the determination of absolute configuration for related tetralone derivatives. This is the first report of anthraquinones and derivatives from an isolate of the genus Coniothyrium sp. These compounds showed inhibitory effects against the fungus Microbotryum violaceum, the alga Chlorella fusca, and the bacteria Escherichia coli and Bacillus megaterium. Chirality 25:141–148, 2013. © 2012 Wiley Periodicals, Inc. 相似文献