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排序方式: 共有3601条查询结果,搜索用时 15 毫秒
1.
Hong IS Kim YK Choi WS Seo DW Yoon JW Han JW Lee HY Lee HW 《FEMS microbiology letters》2003,225(2):177-182
We previously reported the presence of nitric oxide synthase (NOS) in Staphylococcus aureus ATCC6538P whose activity was induced by methanol. In the present study, the methanol-induced NOS was purified 900-fold from S. aureus by means of Mono Q ion exchange column, 2',5'-ADP-agarose affinity column, and Superdex 200HR gel permeation column chromatography. The purified bacterial NOS showed two protein bands with 67 and 64 kDa molecular mass on SDS-PAGE. However, the molecular mass of the NOS was 135 kDa on Superdex 200HR gel permeation column chromatography, indicating that the native enzyme exists as a heterodimer. This bacterial NOS had K(m) value of 13.4x10(-6) M for L-arginine and V(max) of 35.3 nmol min(-1) mg(-1) protein. In addition, reduced nicotinamide adenine dinucleotide phosphate, flavin adenine dinucleotide, flavin mononucleotide, tetrahydrobiopterin, calmodulin and Ca(2+) were required as cofactors in the conversion of L-arginine to L-citrulline, and NOS inhibitors selectively inhibited the activity of the purified NOS. 相似文献
2.
Kyo Seong Seo Kwang Ho Choo Ho Nam Chang Joong Kon Park 《Applied microbiology and biotechnology》2009,83(2):217-223
The biochemical oxygen demand (BOD) determination was studied using a novel flow injection analysis (FIA) system with encapsulated
Saccharomyces cerevisiae cells and an oxygen electrode and was compared with conventional 5-day BOD tests. S. cerevisiae cells were packed in a calcium alginate capsule at a dry cell weight of 250 g/l of capsule core. The level of dissolved oxygen
(DO) was reduced due to the enhanced respiratory activity of the microbial cells when the injected nutrient passed through
the bioreactor. The decrease in DO (ΔDO) was intensified with the amount of microbial cells packed in the bioreactor. However,
the specific ΔDO decreased as the amount of cells loaded in the bioreactor increased. The ΔDO value was dependent on the pH
and temperature of the mobile phase and reached its maximum value at 35°C and pH 7–8. Also, ΔDO became larger at longer response
times as the flow rate of the mobile phase decreased. The measurement of ΔDO was repeated more than six times consecutively
using a 20-ppm standard glucose and glutamic acid solution, which confirmed the reproducibility with a standard deviation
of 0.95%. A strong linear correlation between ΔDO and BOD was also observed. The 5-day BOD values of actual water and wastewater
samples were in accordance with the BOD values obtained by this FIA method using encapsulated S. cerevisiae cells. Unlike the cell-immobilized bead system, there was no contamination of the bioreactor resulting from any leak of yeast
cells from the sensor capsules during BOD measurements. 相似文献
3.
Kim Jong Deog Seo Hyo Jin Hayashi Kiyoshi 《Biotechnology and Bioprocess Engineering》2009,14(3):266-273
In order to create novel β-glucosidase constructs, 8 kinds of chimeric β-glucosidases were constructed using overlapping polymerase
chain reaction (PCR) based on Cellvibrio gilvus (CG) and Thermotoga maritima (TM) genes. Two kinds of novel chimeric β-glucosidases (No. 6 and No. 8 type) were selected and their properties characterized.
SDS-PAGE analysis showed that both constructs had a molecular mass of 80 kDa. The optimum pH of No. 6 chimeric β-glucosidase
was found to be 3.0 and 5.0, showing varying maximum activity according to the buffer used. No. 8 chimeric enzyme was found
to be optimally active at a pH of 4.5 and the optimum temperature of No.6 and No.8 chimeric β-glucosidases was reported to
be 60°C, respectively. The Km values of both novel chimeric enzymes were calculated to be 0.012 mM and 0.0082 mM, respectively
and the characteristics of the novel chimeric enzymes were to lie between those of the parental enzymes. 相似文献
4.
Tissue expression and cellular localization of phospholipid hydroperoxide glutathione peroxidase (PHGPx) mRNA in male mice 总被引:1,自引:0,他引:1
Baek IJ Seo DS Yon JM Lee SR Jin Y Nahm SS Jeong JH Choo YK Kang JK Lee BJ Yun YW Nam SY 《Journal of molecular histology》2007,38(3):237-244
Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is an ubiquitous antioxidant enzyme, but the exact expression pattern
in mammalian tissues is still unknown. The expression and cellular localization of PHGPx mRNA were examined in male mice using
real time-polymerase chain reaction and in situ hybridization techniques. The rank order of PHGPx mRNA expression across tissues exhibiting substantial levels of expression
was:testes ≫ heart > cerebrum ≥ ileum > stomach = liver = jejunum ≥ epididymis. In testes, PHGPx mRNA was highly expressed
in spermiogenic cells and Leydig cells. The signal was also expressed in the molecular layer, Purkinje cell layer, and white
matter of cerebellum, the pituicytes of neurohypophysis, the parafollicular cells and follicular basement membrane of thyroid,
the exocrine portion of pancreas, the tubular epithelium of kidney, the smooth muscle cells of arteries, and the red pulp
of spleen. In the gastrointestinal tract, PHGPx mRNA expression was mainly observed in the keratinized surface epithelium
of forestomach, the submucosal glands and serosa layers, and further the Paneth cells of intestines. PHGPx mRNA appeared to
be ubiquitously expressed in the parenchyma of heart, liver, and lung. These results indicate that PHGPx exhibits a cell-
and tissue-specific expression pattern in mice. 相似文献
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9.
Tokiha Masuda-Ozawa Trish Hoang Yeon-Soo Seo Lin-Feng Chen Maria Spies 《Nucleic acids research》2013,41(6):3576-3587
DNA repair helicases function in the cell to separate DNA duplexes or remodel nucleoprotein complexes. These functions are influenced by sensing and signaling; the cellular pool of a DNA helicase may contain subpopulations of enzymes carrying different post-translational modifications and performing distinct biochemical functions. Here, we report a novel experimental strategy, single-molecule sorting, which overcomes difficulties associated with comprehensive analysis of heterologously modified pool of proteins. This methodology was applied to visualize human DNA helicase F-box–containing DNA helicase (FBH1) acting on the DNA structures resembling a stalled or collapsed replication fork and its interactions with RAD51 nucleoprotein filament. Individual helicase molecules isolated from human cells with their native post-translational modifications were analyzed using total internal reflection fluorescence microscopy. Separation of the activity trajectories originated from ubiquitylated and non-ubiquitylated FBH1 molecules revealed that ubiquitylation affects FBH1 interaction with the RAD51 nucleoprotein filament, but not its translocase and helicase activities. 相似文献
10.
An SJ Park SK Hwang IK Kim HS Seo MO Suh JG Oh YS Bae JC Won MH Kang TC 《Neurochemistry international》2003,43(1):39-45
Considerable attention has been focused on the role of corticotropin-releasing factor (CRF) in neuropsychiatric disorders and neurodegenerative diseases including epilepsy. Therefore, in the present study, we investigated the temporal and spatial alteration of CRF receptor in the gerbil hippocampal complex in order to characterize the possible changes and associations with different sequelae of spontaneous seizure in these animals. Thirty minutes postictal, a decline in CRF receptor immunoreactivity was observed in the granule cells and hilar neurons. In the subiculum, CRF receptor immunoreactivity was also significantly decreased at this time point. Twenty-four hours after seizure onset, the immunoreactivity in these regions recovered to the pre-seizure level. Moreover, 30 min after seizure in the entorhinal cortex, the density of CRF receptor immunoreactivity began to decrease, particularly in the layers II and III, compared to pre-seizure group. Nevertheless, 24h after seizure onset, CRF receptor immunodensity had recovered to its seizure-sensitive (SS) level. These results suggest that altered CRF receptor expression in the hippocampal complex may affect tissue excitability and seizure activity in SS gerbils. 相似文献