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71.
Two novel gene orders and the role of light-strand replication in rearrangement of the vertebrate mitochondrial genome 总被引:22,自引:8,他引:14
Macey JR; Larson A; Ananjeva NB; Fang Z; Papenfuss TJ 《Molecular biology and evolution》1997,14(1):91-104
Two novel mitochondrial gene arrangements are identified in an agamid
lizard and a ranid frog. Statistical tests incorporating phylogeny indicate
a link between novel vertebrate mitochondrial gene orders and movement of
the origin of light-strand replication. A mechanism involving errors in
light-strand replication and tandem duplication of genes is proposed for
rearrangement of vertebrate mitochondrial genes. A second mechanism
involving small direct repeats also is identified. These mechanisms
implicate gene order as a reliable phylogenetic character. Shifts in gene
order define major lineages without evidence of parallelism or reversal.
The loss of the origin of light-strand replication from its typical
vertebrate position evolves in parallel and, therefore, is a less reliable
phylogenetic character. Gene junctions also evolve in parallel. Sequencing
across multigenic regions, in particular transfer RNA genes, should be a
major focus of future systematic studies to locate novel gene orders and to
provide a better understanding of the evolution of the vertebrate
mitochondrial genome.
相似文献
72.
Evolutionary relationships among the male and female mitochondrial DNA lineages in the Mytilus edulis species complex 总被引:1,自引:0,他引:1
A novel form of mitochondrial DNA (mtDNA) inheritance has previously been
documented for the blue mussel (Mytilus edulis). Female mussels inherit
their mtDNA solely from their mother while males inherit mtDNA from both
their mother and their father. In males, the paternal mtDNA is
preferentially amplified so that the male gonad is highly enriched for the
paternal mtDNA that is then transmitted from fathers to sons. We
demonstrate that this mode of mtDNA inheritance also operates in the
closely related species M. galloprovincialis and M. trossulus. The
evolutionary relationship between the male and female mtDNA lineages is
estimated by phylogenetic analysis of 455 nucleotides from the large
subunit ribosomal RNA gene. We have found that the male and female lineages
are highly divergent; the divergence of these lineages began prior to the
speciation of the three species of blue mussels. Further, the separation
between the male and female lineages is estimated to have occurred between
5.3 and 5.7 MYA.
相似文献
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76.
A novel system for continuous protein refolding and on-line capture by expanded bed adsorption 总被引:2,自引:0,他引:2
Ferré H Ruffet E Nielsen LL Nissen MH Hobley TJ Thomas OR Buus S 《Protein science : a publication of the Protein Society》2005,14(8):2141-2153
A novel two-step protein refolding strategy has been developed, where continuous renaturation-bydilution is followed by direct capture on an expanded bed adsorption (EBA) column. The performance of the overall process was tested on a N-terminally tagged version of human beta2-microglobulin (HAT-hbeta2m) both at analytical, small, and preparative scale. In a single scalable operation, extracted and denatured inclusion body proteins from Escherichia coli were continuously diluted into refolding buffer, using a short pipe reactor, allowing for a defined retention and refolding time, and then fed directly to an EBA column, where the protein was captured, washed, and finally eluted as soluble folded protein. Not only was the eluted protein in a correctly folded state, the purity of the HAThbeta2m was increased from 34% to 94%, and the product was concentrated sevenfold. The yield of the overall process was 45%, and the product loss was primarily a consequence of the refolding reaction rather than the EBA step. Full biological activity of HAT-hbeta2m was demonstrated after removal of the HAT-tag. In contrast to batch refolding, a continuous refolding strategy allows the conditions to be controlled and maintained throughout the process, irrespective of the batch size; i.e., it is readily scalable. Furthermore, the procedure is fast and tolerant toward aggregate formation, a common complication of in vitro protein refolding. In conclusion, this system represents a novel approach to small and preparative scale protein refolding, which should be applicable to many other proteins. 相似文献
77.
Purification of correctly oxidized MHC class I heavy-chain molecules under denaturing conditions: a novel strategy exploiting disulfide assisted protein folding 总被引:4,自引:0,他引:4
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Ferré H Ruffet E Blicher T Sylvester-Hvid C Nielsen LL Hobley TJ Thomas OR Buus S 《Protein science : a publication of the Protein Society》2003,12(3):551-559
The aim of this study has been to develop a strategy for purifying correctly oxidized denatured major histocompability complex class I (MHC-I) heavy-chain molecules, which on dilution, fold efficiently and become functional. Expression of heavy-chain molecules in bacteria results in the formation of insoluble cellular inclusion bodies, which must be solubilized under denaturing conditions. Their subsequent purification and refolding is complicated by the fact that (1). correct folding can only take place in combined presence of beta(2)-microglobulin and a binding peptide; and (2). optimal in vitro conditions for disulfide bond formation ( approximately pH 8) and peptide binding ( approximately pH 6.6) are far from complementary. Here we present a two-step strategy, which relies on uncoupling the events of disulfide bond formation and peptide binding. In the first phase, heavy-chain molecules with correct disulfide bonding are formed under non-reducing denaturing conditions and separated from scrambled disulfide bond forms by hydrophobic interaction chromatography. In the second step, rapid refolding of the oxidized heavy chains is afforded by disulfide bond-assisted folding in the presence of beta(2)-microglobulin and a specific peptide. Under conditions optimized for peptide binding, refolding and simultaneous peptide binding of the correctly oxidized heavy chain was much more efficient than that of the fully reduced molecule. 相似文献
78.
Jürgen J. Hubbuch Dennis B. Matthiesen Timothy J. Hobley Owen R.T. Thomas 《Bioseparation》2001,10(1-3):99-112
A robust new adsorptive separation technique specifically designed for direct product capture from crude bioprocess feedstreams is introduced and compared with the current bench mark technique, expanded bed adsorption. The method employs product adsorption onto sub-micron sized non-porous superparamagnetic supports followed by rapid separation of the loaded adsorbents from the feedstock using high gradient magnetic separation technology. For the recovery of Savinase® from a cell-free Bacillus clausii fermentation liquor using bacitracin-linked adsorbents, the integrated magnetic separation system exhibited substantially enhanced productivity over expanded bed adsorption when operated at processing velocities greater than 48 m h–1. Use of the bacitracin-linked magnetic supports for a single cycle of batch adsorption and subsequent capture by high gradient magnetic separation at a processing rate of 12 m h–1 resulted in a 2.2-fold higher productivity relative to expanded bed adsorption, while an increase in adsorbent collection rate to 72 m h–1 raised the productivity to 10.7 times that of expanded bed adsorption. When the number of batch adsorption cycles was then increased to three, significant drops in both magnetic adsorbent consumption (3.6 fold) and filter volume required (1.3 fold) could be achieved at the expense of a reduction in productivity from 10.7 to 4.4 times that of expanded bed adsorption. 相似文献
79.
Braunstein M Griffin TJ IV Kriakov JI Friedman ST Grindley ND Jacobs WR 《Journal of bacteriology》2000,182(10):2732-2740
Secreted and cell envelope-associated proteins are important to both Mycobacterium tuberculosis pathogenesis and the generation of protective immunity to M. tuberculosis. We used an in vitro Tn552'phoA transposition system to identify exported proteins of M. tuberculosis. The system is simple and efficient, and the transposon inserts randomly into target DNA. M. tuberculosis genomic libraries were targeted with Tn552'phoA transposons, and these libraries were screened in M. smegmatis for active PhoA translational fusions. Thirty-two different M. tuberculosis open reading frames were identified; eight contain standard signal peptides, six contain lipoprotein signal peptides, and seventeen contain one or more transmembrane domains. Four of these proteins had not yet been assigned as exported proteins in the M. tuberculosis databases. This collection of exported proteins includes factors that are known to participate in the immune response of M. tuberculosis and proteins with homologies, suggesting a role in pathogenesis. Nine of the proteins appear to be unique to mycobacteria and represent promising candidates for factors that participate in protective immunity and virulence. This technology of creating comprehensive fusion libraries should be applicable to other organisms. 相似文献
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