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31.
The human cell surface receptor for transferrin is a transmembrane phosphoglycoprotein composed of two disulphide linked and apparently identical subunits of Mr 90 000. Using an affinity purified, polyclonal rabbit antibody, we have studied the in vitro biosynthesis of this receptor. The primary translation product, synthesised in a rabbit reticulocyte lysate programmed with human placental RNA, appears to have the same Mr (78 000) as the unglycosylated molecule immunoprecipitated from tunicamycin-treated cells. In the presence of a dog pancreatic microsomal system the cell free system accurately reproduces the glycosylation and the asymmetric transmembrane integration. 相似文献
32.
Ali Kazemi Seresht Per Nørgaard Eva Akke Palmqvist Asser Sloth Andersen Lisbeth Olsson 《Applied microbiology and biotechnology》2013,97(9):3939-3948
The use of auxotrophic Saccharomyces cerevisiae strains for improved production of a heterologous protein was examined. Two different marker genes were investigated, encoding key enzymes in the metabolic pathways for amino acid (LEU2) and pyrimidine (URA3) biosynthesis, respectively. Expression plasmids, carrying the partly defective selection markers LEU2d and URA3d, were constructed. Two CEN.PK-derived strains were chosen and insulin analogue precursor was selected as a model protein. Different truncations of the LEU2 and URA3 promoters were used as the mean to titrate the plasmid copy number and thus the recombinant gene dosage in order to improve insulin productivity. Experiments were initially carried out in batch mode to examine the stability of yeast transformants and to select high yielding mutants. Next, chemostat cultivations were run at high cell density to address industrial applicability and long-term expression stability of the transformants. We found that the choice of auxotrophic marker is crucial for developing a yeast expression system with stable heterologous protein production. The incremental truncation of the URA3 promoter led to higher plasmid copy numbers and IAP yields, whereas the truncation of the LEU2 promoter caused low plasmid stability. We show that the modification of the level of the recombinant gene dosage by varying the degree of promoter truncation can be a strong tool for optimization of productivity. The application of the URA3d-based expression systems showed a high potential for industrial protein production and for further academic studies. 相似文献
33.
Carles Pellicer‐Nàcher Stéphanie Franck Arda Gülay Maël Ruscalleda Akihiko Terada Waleed Abu Al‐Soud Martin Asser Hansen Søren J. Sørensen Barth F. Smets 《Microbial biotechnology》2014,7(1):32-43
Membrane‐aerated biofilm reactors performing autotrophic nitrogen removal can be successfully applied to treat concentrated nitrogen streams. However, their process performance is seriously hampered by the growth of nitrite oxidizing bacteria (NOB). In this work we document how sequential aeration can bring the rapid and long‐term suppression of NOB and the onset of the activity of anaerobic ammonium oxidizing bacteria (AnAOB). Real‐time quantitative polymerase chain reaction analyses confirmed that such shift in performance was mirrored by a change in population densities, with a very drastic reduction of the NOB Nitrospira and Nitrobacter and a 10‐fold increase in AnAOB numbers. The study of biofilm sections with relevant 16S rRNA fluorescent probes revealed strongly stratified biofilm structures fostering aerobic ammonium oxidizing bacteria (AOB) in biofilm areas close to the membrane surface (rich in oxygen) and AnAOB in regions neighbouring the liquid phase. Both communities were separated by a transition region potentially populated by denitrifying heterotrophic bacteria. AOB and AnAOB bacterial groups were more abundant and diverse than NOB, and dominated by the r‐strategists Nitrosomonas europaea and Ca. Brocadia anammoxidans, respectively. Taken together, the present work presents tools to better engineer, monitor and control the microbial communities that support robust, sustainable and efficient nitrogen removal. 相似文献
34.
Slaaby R Schäffer L Lautrup-Larsen I Andersen AS Shaw AC Mathiasen IS Brandt J 《The Journal of biological chemistry》2006,281(36):25869-25874
Insulin receptor (IR) and insulin-like growth factor I receptor (IGF-IR) are both from the same subgroup of receptor tyrosine kinases that exist as covalently bound receptor dimers at the cell surface. For both IR and IGF-IR, the most described forms are homodimer receptors. However, hybrid receptors consisting of one-half IR and one-half IGF-IR are also present at the cell surface. Two splice variants of IR are expressed that enable formation of two isoforms of the IGF-IR/IR hybrid receptor. In this study, these two splice variants of hybrid receptors were studied with respect to binding affinities of insulin, insulin-like growth factor I (IGF-I), and insulin-like growth factor II (IGF-II). Unlike previously published data, in which semipurified receptors have been studied, we found that the two hybrid receptor splice variants had similar binding characteristics with respect to insulin, IGF-I, and IGF-II binding. We studied both semipurified and purified hybrid receptors. In all cases we found that IGF-I had at least 50-fold higher affinity than insulin, irrespective of the splice variant. The binding characteristics of insulin and IGF-I to both splice variants of the hybrid receptors were similar to classical homodimer IGF-IR. 相似文献
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36.
Ian Whalley Asser Tantawi Malgorzata Steinder Mike Spreitzer Giovanni Pacifici Rajarshi Das David M. Chess 《Cluster computing》2006,9(4):401-416
This paper presents an autonomic system in which two managers with different responsibilities collaborate to achieve an overall
objective within a cluster of server computers. The first, a node group manager, uses modeling and optimization algorithms
to allocate server processes and individual requests among a set of server machines grouped into node groups, and also estimates
its ability to fulfill its service-level objectives as a function of the number of server machines available in each node
group. The second, a provisioning manager, consumes these estimates from one or more node group managers, and uses them to
allocate machines to node groups over a longer timescale. We describe the operation of both managers and the information that
flows between them, and present the results of some experiments demonstrating the effectiveness of our technique. Furthermore,
we relate our architecture to a general autonomic computing architecture based on self-managing resources and patterns of
inter-resource collaboration, and to emerging standards in the area of distributed manageability. We also discuss some of
the issues involved in incorporating our implementation into existing products in the short term, and describe a number of
further directions for this research. 相似文献