全文获取类型
收费全文 | 160篇 |
免费 | 11篇 |
国内免费 | 1篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 4篇 |
2013年 | 10篇 |
2012年 | 14篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有172条查询结果,搜索用时 15 毫秒
1.
Konstantinos Papakostas Maria Botou Stathis Frillingos 《The Journal of biological chemistry》2013,288(52):36827-36840
The evolutionarily broad family nucleobase-cation symporter-2 (NCS2) encompasses transporters that are conserved in binding site architecture but diverse in substrate selectivity. Putative purine transporters of this family fall into one of two homology clusters: COG2233, represented by well studied xanthine and/or uric acid permeases, and COG2252, consisting of transporters for adenine, guanine, and/or hypoxanthine that remain unknown with respect to structure-function relationships. We analyzed the COG2252 genes of Escherichia coli K-12 with homology modeling, functional overexpression, and mutagenesis and showed that they encode high affinity permeases for the uptake of adenine (PurP and YicO) or guanine and hypoxanthine (YjcD and YgfQ). The two pairs of paralogs differ clearly in their substrate and ligand preferences. Of 25 putative inhibitors tested, PurP and YicO recognize with low micromolar affinity N6-benzoyladenine, 2,6-diaminopurine, and purine, whereas YjcD and YgfQ recognize 1-methylguanine, 8-azaguanine, 6-thioguanine, and 6-mercaptopurine and do not recognize any of the PurP ligands. Furthermore, the permeases PurP and YjcD were subjected to site-directed mutagenesis at highly conserved sites of transmembrane segments 1, 3, 8, 9, and 10, which have been studied also in COG2233 homologs. Residues irreplaceable for uptake activity or crucial for substrate selectivity were found at positions occupied by similar role amino acids in the Escherichia coli xanthine- and uric acid-transporting homologs (XanQ and UacT, respectively) and predicted to be at or around the binding site. Our results support the contention that the distantly related transporters of COG2233 and COG2252 use topologically similar side chain determinants to dictate their function and the distinct purine selectivity profiles. 相似文献
2.
Evaluation of monitoring approaches and effects of culture conditions on recombinant protein production in baculovirus-infected insect cells 总被引:2,自引:0,他引:2
The baculovirus infection process ofSpodoptera frugiperda (Sf9) insect cells in oxygen-controlled bioreactors in serum-free medium was investigated using a recombinantAutographa californica (AcNPV) virus expressing -galactosidase enzyme as a model system. A variety of monitoring techniques including trypan blue exclusion, fluorescent dye staining, oxygen uptake rate (OUR) measurements, and glucose consumption were applied to infected cells to determine the best way of evaluating cell integrity and assessing the course of baculovirus infection. The metabolism of newly-infected cells increased 90% during the first 24 hours, but as infection proceeded, and cells gradually succumbed to the baculovirus infection, the cytopathic effect of the baculovirus on the cells became evident. Oxygen and glucose uptake rate measurements appeared to more accurately assess the condition of infected cells than conventional trypan blue staining, which tended to overestimate cell viability in the mid stages of infection. The optimal harvest time varied, depending on which technique — SDS-PAGE, chromogenic (ONPG) or fluorometric (C12FDG) — was used to monitor -galactosidase production. Specific -galactosidase production was found to be insensitive to a wide range of culture dissolved oxygen tensions, whereas resuspending cells in fresh medium prior to infection increased volumetric productivity approximately two-fold (800,000 units -galactosidase/ml) compared to cultures infected in batch mode and allowed successful infections to occur at higher cell densities.Abbreviations ONPG
ortho-phenyl 2--D-galactopyranoside
- OUR
oxygen uptake rate (-mol O2/liter/hour)
- qglucose
specific glucose uptake rate (mg glucose/106cell/hour)
- qglutamine
specific glutamine uptake rate (mg glutamine/106cell/hour)
- qO2
specific oxygen uptake rate (-mol O2/106cell/hour)
- MOI
virus multiplicity of infection (viral plaque forming units/cell) 相似文献
3.
4.
5.
Emmanouil A. Fotakis Konstantinos Mavridis Anastasia Kampouraki Sofia Balaska Filianna Tanti George Vlachos Sandra Gewehr Spiros Mourelatos Antonios Papadakis Maria Kavalou Dimitrios Nikolakakis Maria Moisaki Nikolaos Kampanis Manolis Loumpounis John Vontas 《PLoS neglected tropical diseases》2022,16(2)
BackgroundIn Greece vector borne diseases (VBD) and foremost West Nile virus (WNV) pose an important threat to public health and the tourist industry, the primary sector of contribution to the national economy. The island of Crete, is one of Greece’s major tourist destinations receiving annually over 5 million tourists making regional VBD control both a public health and economic priority.MethodologyUnder the auspices of the Region of Crete, a systematic integrative surveillance network targeting mosquitoes and associated pathogens was established in Crete for the years 2018–2020. Using conventional and molecular diagnostic tools we investigated the mosquito species composition and population dynamics, pathogen infection occurrences in vector populations and in sentinel chickens, and the insecticide resistance status of the major vector species.Principal findingsImportant disease vectors were recorded across the island including Culex pipiens, Aedes albopictus, and Anopheles superpictus. Over 75% of the sampled specimens were collected in the western prefectures potentially attributed to the local precipitation patterns, with Cx. pipiens being the most dominant species. Although no pathogens (flaviviruses) were detected in the analysed mosquito specimens, chicken blood serum analyses recorded a 1.7% WNV antibody detection rate in the 2018 samples. Notably detection of the first WNV positive chicken preceded human WNV occurrence in the same region by approximately two weeks. The chitin synthase mutation I1043F (associated with high diflubenzuron resistance) was recorded at an 8% allelic frequency in Lasithi prefecture Cx. pipiens mosquitoes (sampled in 2020) for the first time in Greece. Markedly, Cx. pipiens populations in all four prefectures were found harboring the kdr mutations L1014F/C/S (associated with pyrethroid resistance) at a close to fixation rate, with mutation L1014C being the most commonly found allele (≥74% representation). Voltage gated sodium channel analyses in Ae. albopictus revealed the presence of the kdr mutations F1534C and I1532T (associated with putative mild pyrethroid resistance phenotypes) yet absence of V1016G. Allele F1534C was recorded in all prefectures (at an allelic frequency range of 25–46.6%) while I1532T was detected in populations from Chania, Rethymnon and Heraklion (at frequencies below 7.1%). Finally, no kdr mutations were detected in the Anopheles specimens included in the analyses.Conclusions/SignificanceThe findings of our study are of major concern for VBD control in Crete, highlighting (i) the necessity for establishing seasonal integrated entomological/pathogen surveillance programs, supporting the design of targeted vector control responses and; ii) the need for establishing appropriate insecticide resistance management programs ensuring the efficacy and sustainable use of DFB and pyrethroid based products in vector control. 相似文献
6.
Papaioannou A Manos M Karkabounas S Liasko R Evangelou AM Correia I Kalfakakou V Pessoa JC Kabanos T 《Journal of inorganic biochemistry》2004,98(6):959-968
Reaction of one equivalent of vanadium(III) chloride with three equivalents of l-cysteine(H2Cys) in methyl alcohol affords a VIII-Cys compound that is formulated as [VIII(Hcys)3].2HCl.2.5H2O 1. The solid state characterization of 1 was performed by microanalysis, circular dichroism (CD) and infrared studies as well as room temperature magnetic susceptibility. These studies have shown coordination of each HCys- ligand to the VIII atom through an amine nitrogen and a carboxylate oxygen atoms. Solution studies of 1 were carried out in water and methanol by UV-visible, CD and electron paramagnetic resonance (EPR) spectroscopies. According to these studies, it was evident that despite the progressive oxidation of 1 to oxovanadium(IV) species, some V(III) species were also present in solution after several hours. Compound 1, VIVOSO4.5H2O and l-cysteine were examined for their total antioxidant capacity (TAC) and lag time. Compound 1 exhibited significantly greater total antioxidant capacity and lag time values than l-cysteine. VIVOSO4.5H2O did not show any total antioxidant capacity or lag time. The inhibition of neutral endopeptidase (NEP) activity caused by 1, VIVOSO4.5H2O and thiorphan was also measured. Compound 1, at a concentration of 10(-3) M, showed inhibition of NEP activity as potent as thiorphan at 10(-6) M, while VIVOSO4.5H2O in the same concentration exhibited less than 50% inhibitory activity than that of thiorphan at 10(-6) M. Moreover, the antimetastatic effects of compound 1, l-cysteine and VIVOSO4.5H2O were examined on Wistar rats, treated with 3,4-benzopyrene. The results revealed that 1 prevents significantly lung metastases (only 9.5% of animals treated with 1 showed metastases), whereas 47-52% of the rats of the control group and those treated with l-cysteine and VIVOSO4.5H2O exhibited metastases. 相似文献
7.
Lazou A Gaitanaki C Vaxevanellis S Pehtelidou A 《The Journal of experimental zoology》2002,293(2):99-105
The aim of this study was to characterize alpha(1)-adrenergic receptors in frog heart and to examine their related signal transduction pathway. alpha(1)-Adrenergic binding sites were studied in purified heart membranes using the specific alpha(1)-adrenergic antagonist [(3)H]prazosin. Analysis of the binding data indicated one class of binding sites displaying a K(d) of 4.19 +/- 0.56 nM and a B(max) of 14.66 +/- 1.61 fmol/mg original wet weight. Adrenaline, noradrenaline, or phenylephrine, in the presence of propranolol, competed with [(3)H]prazosin binding with a similar potency and a K(i) value of about 10 microM. The kinetics of adrenaline binding was closely related to its biological effect. Adrenaline concentration dependently increased the production of inositol phosphates in the heart in the presence or absence of propranolol. Maximal stimulation was about 8.5-fold, and the half-maximum effective concentration was 30 and 21 microM in the absence and presence of propranolol, respectively. These data clearly show that alpha(1)-adrenergic receptors are coupled to the phosphoinositide hydrolysis in frog heart. To our knowledge, this is the first direct evidence supporting the presence of functional alpha(1)-adrenergic receptors in the frog heart. 相似文献
8.
An experimental simulation environment suitable for exploring the neuroinflammatory hypothesis of Alzheimer's disease (AD) has been developed. Using scientific literature, we have calculated parameters and rates and constructed an interactive model system. The simulation can be manipulated to explore competing hypotheses about AD pathology, i.e. can be used as an experimental "in silico" system. In this paper, we outline the assumptions and aspects of the model, and illustrate qualitative and quantitative findings. The interactions of amyloid beta deposits, glial cell dynamics, inflammation and secreted cytokines, and the stress, recovery, and death of neuronal tissue are investigated. The model leads to qualitative insights about relative roles of the cells and chemicals in the disease pathology. 相似文献
9.
10.
Immune and autoimmune disorders in HCV chronic liver disease: personal experience and commentary on literature 总被引:3,自引:0,他引:3
Giordano N Amendola A Papakostas P Cipolli F Agate VM Battisti E Marchi B Nuti R 《The new microbiologica》2005,28(4):311-317
HCV chronic liver disease can be associated with a plethora of immune and autoimmune perturbations and many authors claim that HCV chronic infection can play an important role in the pathogenesis of these disorders. To compare our experience with literature reports, we performed a retrospective study on the case histories of 265 patients with HCV chronic liver disease, evaluating the type and prevalence of the associated immune and autoimmune manifestations. We found that the patients with HCV chronic liver disease can present arthromyalgias (7.1% of the patients), Sj?rgen's syndrome (5.2%), thyroiditis (4.1%), rheumatoid arthritis (2.2%), autoimmune thrombocytopenia (2.6%), mixed cryoglobulinemia (1.5%), autoimmune anemia (0.3%) and oral lichen planus (0.3%). We claim that HCV liver infection is able to induce immune and autoimmune perturbations, without playing a significant role in the pathogenesis of a well-defined disorder. 相似文献