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排序方式: 共有161条查询结果,搜索用时 62 毫秒
61.
R Roy N Nasrin M F Ahmad N K Gupta 《Biochemical and biophysical research communications》1984,122(3):1418-1425
Under standard conditions, in the presence of GTP, highly purified eIF-2 and Co-eIF-2 factor preparations efficiently stimulated AUG-codon dependent but not physiological mRNA-dependent Met-tRNAf binding to 40S ribosomes. Replacement of GTP by a nonhydrolyzable GTP analog, GMP-PNP, in the above system, gave significant stimulation of Met-tRNAf binding to 40S ribosomes dependent on physiological mRNAs. Lower but significant stimulation of Met-tRNAf binding to 40S ribosomes was also observed when GTP was used in the presence of nucleoside 5'-diphosphate kinase (NDK) and ATP. ATP alone in the absence of NDK had no significant effect. This is the first report on the formation of a stable Met-tRNAf . 40S initiation complex dependent on physiological mRNAs and the factor requirements for such complex formation. 相似文献
62.
Mahdi Mohammadian Mehrnoosh Fathi-Roudsari Nasrin Mollania Arastoo Badoei-Dalfard Khosro Khajeh 《Journal of industrial microbiology & biotechnology》2010,37(8):863-869
Laccases (benzenediol oxygen oxidoreductase; EC 1.10.3.2) have many biotechnological applications because of their oxidation
ability towards a wide range of phenolic compounds. Within recent years, researchers have been highly interested in the identification
and characterization of laccases from bacterial sources. In this study, we have isolated and cloned a gene encoding laccase
(CotA) from Bacillus sp. HR03 and then expressed it under microaerobic conditions and decreased temperature in order to obtain high amounts of
soluble protein. The laccase was purified and its biochemical properties were investigated using three common laccase substrates,
2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), syringaldazine (SGZ) and 2,6-dimethoxyphenol (2,6-DMP). K
M and k
cat were calculated 535 μM and 127 s−1 for ABTS, 53 μM and 3 s−1 for 2, 6-DMP and 5 μM and 20 s−1 for SGZ when the whole reactions were carried out at room temperature. Laccase activity was also studied when the enzyme
was preincubated at 70 and 80°C. With SGZ as the substrate, the activity was increased three-fold after 50 min preincubation
at 70°C and 2.4-fold after 10 min preincubation at 80°C. Preincubation of the enzyme in 70°C for 30 min raised the activity
four-fold with ABTS as the substrate. Also, l-dopa was used as a substrate. The enzyme was able to oxidize l-dopa with the K
M and k
cat of 1,493 μM and 194 s−1, respectively. 相似文献
63.
Mandana Miri Bijan Bambai Fatemeh Tabandeh Majid Sadeghizadeh Nasrin Kamali 《Biotechnology letters》2010,32(4):497-502
Alcanivorax borkumensis is an oil-degrading marine bacterium. Its genome contains genes coding for three cytochrome P450s and two integral membrane
alkane hydroxylases (AlkB1 & AlkB2), all assumed to perform hydroxylation of different linear or branched alkanes. Although,
the sequence of alkB2 has been determined, the molecular characterization and the substrate specificity of AlkB2 require more precise investigation.
In this study, AlkB2 from A. borkumensis SK2 was expressed in Escherichia coli to examine the functionality of AlkB2 as a hydroxylating enzyme. Furthermore, the activity of the enzyme in the presence
of the accessory proteins, rubredoxin (RubA) and rubredoxin reductase (RubB), produced in E. coli BL21(DE3)plysS cells, was determined. Recombinant AlkB2 is produced in an active form and rubredoxin is the intermediate
electron donor to AlkB2 and can replace AlkG function, when NADH is the prime electron donor. 相似文献
64.
Foroumadi A Ghodsi S Emami S Najjari S Samadi N Faramarzi MA Beikmohammadi L Shirazi FH Shafiee A 《Bioorganic & medicinal chemistry letters》2006,16(13):3499-3503
N-(Phenethyl)piperazinyl quinolone derivatives that bear a methoxyimino-substituent have been synthesized and evaluated for antimicrobial activity against Gram-positive and Gram-negative microorganisms. In addition, to define structure-activity relationships, ciprofloxacin derivatives containing 2-oxo-2-phenylethyl or 2-hydroxyimino-2-phenylethyl moieties at N-4 position of piperazine ring were prepared and tested. Ciprofloxacin derivatives, containing a N-(chloro-substituted phenethyl) residue, showed in vitro Gram-positive and Gram-negative activity generally comparable or superior to that of reference quinolones. 相似文献
65.
Nasrin Jahan 《Journal of molecular biology》2009,392(3):763-1734
CqsA is an enzyme involved in the biosynthesis of cholerae autoinducer-1 (CAI-1), the major Vibrio cholerae autoinducer engaged in quorum sensing. The amino acid sequence of CqsA suggests that it belongs to the family of α-oxoamine synthases that catalyse the condensation of an amino acid to an acyl-CoA substrate. Here we present the apo- and PLP-bound crystal structures of CqsA and confirm that it shares structural homology with the dimeric α-oxoamine synthases, including a conserved PLP-binding site. The chemical structure of CAI-1 suggests that decanoyl-CoA may be one substrate of CqsA and that another substrate may be l-threonine or l-2-aminobutyric acid. A crystal structure of CqsA at 1.9-Å resolution obtained in the presence of PLP and l-threonine reveals an external aldimine that has lost the l-threonine side chain. Similarly, a 1.9-Å-resolution crystal structure of CqsA in the presence of PLP, l-threonine, and decanoyl-CoA shows a trapped external aldimine intermediate, suggesting that the condensation and decarboxylation steps have occurred, again with loss of the l-threonine side chain. It is suggested that this side-chain loss, an observation supported by mass spectrometry, is due to a retro-aldol reaction. Although no structural data have been obtained on CqsA using l-2-aminobutyric acid and decanoyl-CoA as substrates, mass spectrometry confirms the expected product of the enzyme reaction. It is proposed that a region of structure that is disordered in the apo structure is involved in the release of product. While not confirming if CqsA alone is able to synthesize CAI-1, these results suggest possible synthetic routes. 相似文献
66.
Nasrin Samadi Neda Abadian Reza Ahmadkhaniha Farzaneh Amini Dina Dalili Noushin Rastkari Eliyeh Safaripour Farzaneh Aziz Mohseni 《Folia microbiologica》2012,57(6):501-508
The aim of present work was to study chemical structures and biological activities of rhamnolipid biosurfactants produced by Pseudomonas aeruginosa MN1 isolated from oil-contaminated soil. The results of liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed that total rhamnolipids (RLs) contained 16 rhamnolipid homologues. Di-lipid RLs containing C10-C10 moieties were by far the most predominant congeners among mono-rhamnose (53.29?%) and di-rhamnose (23.52?%) homologues. Mono-rhamnolipids form 68.35?% of the total congeners in the RLs. Two major fractions were revealed in the thin layer chromatogram of produced RLs which were then purified by column chromatography. The retardation factors (R f) of the two rhamnolipid purple spots were 0.71 for RL1 and 0.46 for RL2. LC-MS/MS analysis proved that RL1 was composed of mono-RLs and RL2 consisted of di-RLs. RL1 was more surface-active with the critical micelle concentration (CMC) value of 15?mg/L and the surface tension of 25 mN/m at CMC. The results of biological assay showed that RL1 is a more potent antibacterial agent than RL2. All methicillin-resistant Staphylococcus aureus (MRSA) strains were inhibited by RLs that were independent of their antibiotic susceptibility patterns. RLs remarkably enhanced the activity of oxacillin against MRSA strains and lowered the minimum inhibitory concentrations of oxacillin to the range of 3.12?C6.25???g/mL. 相似文献
67.
Nargis Nasrin Xiaoping Wu Eric Fortier Yajun Feng Olivia Claire Bare' Sumiao Chen Xianglin Ren Zhidan Wu Ryan S. Streeper Laura Bordone 《The Journal of biological chemistry》2010,285(42):31995-32002
SIRT4, a member of the sirtuin family, has been implicated in the regulation of insulin secretion by modulation of glutamate dehydrogenase. However, the role of this enzyme in the regulation of metabolism in other tissues is unknown. In this study we investigated whether depletion of SIRT4 would enhance liver and muscle metabolic functions. To do this SIRT4 was knocked down using an adenoviral shRNA in mouse primary hepatocytes and myotubes. We observed a significant increase in gene expression of mitochondrial and fatty acid metabolism enzymes in hepatocytes with reduced SIRT4 levels. SIRT4 knockdown also increased SIRT1 mRNA and protein levels both in vitro and in vivo. In agreement with the increased fatty acid oxidation (FAO) gene expression, we showed a significant increase in FAO in SIRT4 knockdown primary hepatocytes compared with control, and this effect was dependent on SIRT1. In primary myotubes, knockdown of SIRT4 resulted in increased FAO, cellular respiration, and pAMPK levels. When SIRT4 was knocked down in vivo by tail vein injection of a shRNA adenovirus, we observed a significant increase in hepatic mitochondrial and FAO gene expression consistent with the findings in primary hepatocytes. Taken together these findings demonstrate that SIRT4 inhibition increases fat oxidative capacity in liver and mitochondrial function in muscle, which might provide therapeutic benefits for diseases associated with ectopic lipid storage such as type 2 diabetes. 相似文献
68.
Jan F. Gogarten Sbastien Calvignac‐Spencer Charles L. Nunn Markus Ulrich Nasrin Saiepour Henrik Vedel Nielsen Tobias Deschner Claudia Fichtel Peter M. Kappeler Sascha Knauf Nadine Müller‐Klein Julia Ostner Martha M. Robbins Somboon Sangmaneedet Oliver Schülke Martin Surbeck Roman M. Wittig Alexander Sliwa Christina Strube Fabian H. Leendertz Christian Roos Angela Noll 《Molecular ecology resources》2020,20(1):204-215
Despite their ubiquity, in most cases little is known about the impact of eukaryotic parasites on their mammalian hosts. Comparative approaches provide a powerful method to investigate the impact of parasites on host ecology and evolution, though two issues are critical for such efforts: controlling for variation in methods of identifying parasites and incorporating heterogeneity in sampling effort across host species. To address these issues, there is a need for standardized methods to catalogue eukaryotic parasite diversity across broad phylogenetic host ranges. We demonstrate the feasibility of a metabarcoding approach for describing parasite communities by analysing faecal samples from 11 nonhuman primate species representing divergent lineages of the primate phylogeny and the full range of sampling effort (i.e. from no parasites reported in the literature to the best‐studied primates). We detected a number of parasite families and regardless of prior sampling effort, metabarcoding of only ten faecal samples identified parasite families previously undescribed in each host (x? = 8.5 new families per species). We found more overlap between parasite families detected with metabarcoding and published literature when more research effort—measured as the number of publications—had been conducted on the host species' parasites. More closely related primates and those from the same continent had more similar parasite communities, highlighting the biological relevance of sampling even a small number of hosts. Collectively, results demonstrate that metabarcoding methods are sensitive and powerful enough to standardize studies of eukaryotic parasite communities across host species, providing essential new tools for macroecological studies of parasitism. 相似文献
69.
Juliane Bock Liliana H. Mochmann Cornelia Schlee Nasrin Farhadi-Sartangi Stefanie G?llner Carsten Müller-Tidow Claudia D. Baldus 《PloS one》2013,8(1)
High expression of the E26 transforming sequence related gene (ERG) is associated with poor prognosis in a subgroup of leukemia patients with acute myeloid (AML) and acute T-lymphoblastic leukemia (T-ALL). In a previous study we proposed that ERG overexpression may deregulate several signaling cascades in acute leukemia. Herein, we further expand those studies by identifying a consensus of biological targets in primary blasts of newly diagnosed acute leukemia patients. Our findings of chromatin immunoprecipitation-on-chip of primary samples revealed 48 significantly enriched single genes including DAAM1 and NUMB. Significantly enriched signaling pathways included WNT/β-catenin, p53, and PI3K/AKT with ERG overexpression inducing dephosphorylation of AKT(Ser473) relative to non ERG expressing K562 cells. Cell based ERG overexpression studies also revealed drug resistance to multi-kinase inhibitor, BAY 43-9006 (Sorafenib) and to the tyrosine kinase inhibitor TKI258. Thus in primary leukemic cells, ERG may contribute to the dysregulation of kinase signaling, which results in resistance to kinase inhibitors. 相似文献
70.
Tamer H. Farag Abu S. Faruque Yukun Wu Sumon K. Das Anowar Hossain Shahnawaz Ahmed Dilruba Ahmed Dilruba Nasrin Karen L. Kotloff Sandra Panchilangam James P. Nataro Dani Cohen William C. Blackwelder Myron M. Levine 《PLoS neglected tropical diseases》2013,7(6)