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1.
Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect. 相似文献
2.
Genetic transfer of the pigment bacteriorhodopsin into the eukaryote Schizosaccharomyces pombe 总被引:9,自引:0,他引:9
V Hildebrandt M Ramezani-Rad U Swida P Wrede S Grzesiek M Primke G Büldt 《FEBS letters》1989,243(2):137-140
The gene encoding for bacterio-opsin (bop gene) from Halobacterium halobium has been introduced in a yeast expression vector. After transformation in Schizosaccharomyces pombe, bacterio-opsin (BO) is expressed and was detected by antisera. The precursor protein of BO (pre-BO) is processed by cleavage of amino acids at the N-terminal end as in H. halobium. Addition of the chromophore, retinal, to the culture medium results in a slight purple colour of the yeast cells indicating the in vivo regeneration of BO to bacteriorhodopsin (BR) and its incorporation into membranes. Therefore, in contrast to the expression in E. coli, isolation of the membrane protein and reconstitution in lipid vesicles is not necessary for functional analysis. The kinetics of the ground state signal of the photocycle BR in protoplasts is demonstrated by flash spectroscopy and is comparable to that of the natural system. The present investigation shows for the first time the transfer of an energy converting protein from archaebacteria to eukaryotes by genetic techniques. This is a basis for further studies on membrane biogenesis, genetics, and bioenergetics by analysis of in vivo active mutants. 相似文献
3.
Reinhard Lohmann Gisbert Schneider Dirk Behrens Paul Wrede 《Protein science : a publication of the Protein Society》1994,3(9):1597-1601
The architecture and weights of an artificial neural network model that predicts putative transmembrane sequences have been developed and optimized by the algorithm of structure evolution. The resulting filter is able to classify membrane/nonmembrane transition regions in sequences of integral human membrane proteins with high accuracy. Similar results have been obtained for both training and test set data, indicating that the network has focused on general features of transmembrane sequences rather than specializing on the training data. Seven physicochemical amino acid properties have been used for sequence encoding. The predictions are compared to hydrophobicity plots. 相似文献
4.
Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex 总被引:1,自引:0,他引:1
The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S
nuclear ribosomal DNA sequence and the intervening 5.8S region were
sequenced from three individuals in each of eight taxa of the Mimulus
guttatus species complex. Three discrete variants, or "types," of ITS
sequences were found, among which 30%-40% of sites differed, compared with
1%-2% within types. Dot plots indicate that these types were not related by
conspicuous rearrangements or inversions. More than one ITS type was often
found in the same taxon, and two of three ITS types span species
boundaries, indicating their presence prior to speciation. These ITS
sequences showed essentially no positional homology with the nearest
sequenced relative, tomato. In contrast, the 5.8S region was relatively
unvaried, with 8 of 162 sites varied in the sample among all eight taxa.
The phylogeny inferred by the most common ITS sequence type, rooted by the
two other ITS types, agreed with isozymes in showing the distinctness of M.
nudatus, M. laciniatus, and M. tilingii from the other five taxa.
相似文献
5.
Variation in heat shock proteins within tropical and desert species of poeciliid fishes 总被引:8,自引:0,他引:8
Norris CE; diIorio PJ; Schultz RJ; Hightower LE 《Molecular biology and evolution》1995,12(6):1048-1062
The 70-kilodalton heat shock protein (hsp70) family of molecular
chaperones, which contains both stress-inducible and normally abundant
constitutive members, is highly conserved across distantly related taxa.
Analysis of this protein family in individuals from an outbred population
of tropical topminnows, Poeciliopsis gracilis, showed that while
constitutive hsp70 family members showed no variation in protein isoforms,
inducibly synthesized hsp70 was polymorphic. Several species of
Poeciliopsis adapted to desert environments exhibited lower levels of
inducible hsp70 polymorphism than the tropical species, but constitutive
forms were identical to those in P. gracilis, as they were in the
confamilial species Gambusia affinis. These differences suggest that
inducible and constitutive members of this family are under different
evolutionary constraints and may indicate differences in their function
within the cell. Also, northern desert species of Poeciliopsis synthesize a
subset of the inducible hsp70 isoforms seen in tropical species. This
distribution supports the theory that ancestral tropical fish migrated
northward and colonized desert streams; the subsequent decrease in
variation of inducible hsp70 may have been due to genetic drift or a
consequence of adaptation to the desert environment. Higher levels of
variability were found when the 30- kilodalton heat shock protein (hsp30)
family was analyzed within different strains of two desert species of
Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In
both cases the distribution of hsp30 isoform diversity was similar to that
seen previously with allozyme polymorphisms.
相似文献
6.
Christoph Wrede Viola Krukenberg Anne Dreier Joachim Reitner Christina Heller Michael Hoppert 《Geomicrobiology journal》2013,30(3):214-227
In anoxic environments, methane oxidation is conducted in a syntrophic process between methanotrophic archaea (ANME) and sulfate reducing bacteria (SRB). Microbial mats consisting of ANME, SRB and other microorganisms form methane seep-related carbonate buildups in the anoxic bottom waters of the Black Sea Crimean shelf. To shed light on the localization of the biochemical processes at the level of single cells in the Black Sea microbial mats, we applied antibody-based markers for key enzymes of the relevant metabolic pathways. The dissimilatory adenosine-5′-phosphosulfate (APS) reductase, methyl-coenzyme M reductase (MCR) and methanol dehydrogenase (MDH) were selected to localize sulfate respiration, reverse methanogenesis and aerobic methane oxidation, respectively. The key enzymes could be localized by double immunofluorescence and immunocytochemistry at light- and electron microscopic levels. In this study we show that sulfate reduction is conducted synchronized and in direct proximity to reverse methanogenesis of ANME archaea. Microcolonies in interspaces between ANME/SRB express methanol dehydrogenase, which is indicative for oxidation of C1 compounds by methylotrophic or methanotrophic bacteria. Thus, in addition to syntrophic AOM, oxygen-dependent processes are also conducted by a small proportion of the microbial population. 相似文献
7.
Martin Lehnik-Habrink Leonie Rempeters ákos T. Kovács Christoph Wrede Claudia Baierlein Heike Krebber Oscar P. Kuipers J?rg Stülke 《Journal of bacteriology》2013,195(3):534-544
DEAD-box RNA helicases play important roles in remodeling RNA molecules and in facilitating a variety of RNA-protein interactions that are key to many essential cellular processes. In spite of the importance of RNA, our knowledge about RNA helicases is limited. In this study, we investigated the role of the four DEAD-box RNA helicases in the Gram-positive model organism Bacillus subtilis. A strain deleted of all RNA helicases is able to grow at 37°C but not at lower temperatures. The deletion of cshA, cshB, or yfmL in particular leads to cold-sensitive phenotypes. Moreover, these mutant strains exhibit unique defects in ribosome biogenesis, suggesting distinct functions for the individual enzymes in this process. Based on protein accumulation, severity of the cold-sensitive phenotype, and the interaction with components of the RNA degradosome, CshA is the major RNA helicase of B. subtilis. To unravel the functions of CshA in addition to ribosome biogenesis, we conducted microarray analysis and identified the ysbAB and frlBONMD mRNAs as targets that are strongly affected by the deletion of the cshA gene. Our findings suggest that the different helicases make distinct contributions to the physiology of B. subtilis. Ribosome biogenesis and RNA degradation are two of their major tasks in B. subtilis. 相似文献
8.
Protein kinase B/Akt prevents fatty acid-induced apoptosis in pancreatic beta-cells (INS-1) 总被引:30,自引:0,他引:30
Wrede CE Dickson LM Lingohr MK Briaud I Rhodes CJ 《The Journal of biological chemistry》2002,277(51):49676-49684
9.
Bredenbeck A Losch FO Sharav T Eichler-Mertens M Filter M Givehchi A Sterry W Wrede P Walden P 《Journal of immunology (Baltimore, Md. : 1950)》2005,174(11):6716-6724
The identification of tumor-associated T cell epitopes has contributed significantly to the understanding of the interrelationship of tumor and immune system and is instrumental in the development of therapeutic vaccines for the treatment of cancer. Most of the known epitopes have been identified with prediction algorithms that compute the potential capacity of a peptide to bind to HLA class I molecules. However, naturally expressed T cell epitopes need not necessarily be strong HLA binders. To overcome this limitation of the available prediction algorithms we established a strategy for the identification of T cell epitopes that include suboptimal HLA binders. To this end, an artificial neural network was developed that predicts HLA-binding peptides in protein sequences by taking the entire sequence context into consideration rather than computing the sum of the contribution of the individual amino acids. Using this algorithm, we predicted seven HLA A*0201-restricted potential T cell epitopes from known melanoma-associated Ags that do not conform to the canonical anchor motif for this HLA molecule. All seven epitopes were validated as T cell epitopes and three as naturally processed by melanoma tumor cells. T cells for four of the new epitopes were found at elevated frequencies in the peripheral blood of melanoma patients. Modification of the peptides to the canonical sequence motifs led to improved HLA binding and to improved capacity to stimulate T cells. 相似文献
10.
In several fields of cell biology, correlative microscopy is applied to compare the structure of objects at high resolution under the electron microscope with low resolution light microscopy images of the same sample. It is, however, difficult to prepare samples and marker systems that are applicable for both microscopic techniques for the same specimen at the same time. In our studies, we used microbial mats from Cold Seep communities for a simple and rapid correlative microscopy method. The mats consist of bacterial and archaeal microorganisms, coupling reverse methanogenesis to the reduction of sulfate. The reverse methanogenic pathway also generates carbonates that precipitate inside the mat and may be the main reason for the formation of a microbial reef. The mat shows highly differentiated aggregates of various organisms, tightly interconnected by extracellular polysaccharides. In order to investigate the role of EPS as adhesive mucilage for the biofilm and as a precipitation matrix for carbonate minerals, samples were embedded in a hydrophilic resin (Lowicryl K4 M). Sections were suitable for light as well as electron microscopy in combination with lectins, either labeled with a fluorescent marker or with colloidal gold. This allows lectin mapping at low resolution for light microscopy in direct comparison with a highly resolved electron microscopic image. 相似文献