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排序方式: 共有70条查询结果,搜索用时 15 毫秒
41.
Low KO Mahadi NM Abdul Rahim R Rabu A Abu Bakar FD Abdul Murad AM Illias RM 《Journal of biotechnology》2010,150(4):453-459
The hemolysin transport system was found to mediate the release of cyclodextrin glucanotransferase (CGTase) into the extracellular medium when it was fused to the C-terminal 61 amino acids of HlyA (HlyAs(61)). To produce an improved-secretion variant, the hly components (hlyAs, hlyB and hlyD) were engineered by directed evolution using error-prone PCR. Hly mutants were screened on solid LB-starch plate for halo zone larger than the parent strain. Through screening of about 1 × 10(4) Escherichia coli BL21(DE3) transformants, we succeeded in isolating five mutants that showed a 35-217% increase in the secretion level of CGTase-HlyAs(61) relative to the wild-type strain. The mutation sites of each mutant were located at HlyB, primarily along the transmembrane domain, implying that the corresponding region was important for the improved secretion of the target protein. In this study we describe the finding of novel site(s) of HlyB responsible for enhancing secretion of CGTase in E. coli. 相似文献
42.
Kheng Oon Low Nor Muhammad Mahadi Rosli Md. Illias 《Applied microbiology and biotechnology》2013,97(9):3811-3826
Escherichia coli—the powerhouse for recombinant protein production—is rapidly gaining status as a reliable and efficient host for secretory expression. An improved understanding of protein translocation processes and its mechanisms has inspired and accelerated the development of new tools and applications in this field and, in particular, a more efficient secretion signal. Several important characteristics and requirements are summarised for the design of a more efficient signal peptide for the production of recombinant proteins in E. coli. General approaches and strategies to optimise the signal peptide, including the selection and modification of the signal peptide components, are included. Several challenges in the secretory production of recombinant proteins are discussed, and research approaches designed to meet these challenges are proposed. 相似文献
43.
Hamsters show a preference for Polycose, a mixture of starch-derived
glucose polymers, that is as strong as their preference for sucrose.
However, in the hamster, taste aversions to Polycose may be less easily
acquired than taste aversions to sucrose and the qualitative aspects of
Polycose are unknown in this species. In order to examine the taste of
Polycose in the hamster, we utilized a taste-aversion protocol with two
conditioning trials. Animals were trained to avoid one of three different
conditioning stimuli: 50 mM sucrose, 100 mM Polycose and a mixture of 50 mM
sucrose with 100 mM Polycose. Control animals were conditioned with
deionized water. After the second conditioning trial, generalization
testing began for the three conditioning stimuli plus 3 mM citric acid, 300
mM KCI and 30 mM NaCl. The results showed that aversions to Polycose,
sucrose or the Polycose/sucrose mixture cross- generalized, demonstrating
that Polycose and sucrose share a common taste percept in the hamster. None
of the aversions generalized to NaCl, citric acid or KCI. In addition,
comparisons among the patterns of taste generalizations indicated that the
tastes of Polycose and sucrose also had distinct qualitative components.
Finally, although the taste of 100 mM Polycose was more salient than the
taste of 50 mM sucrose, the taste of sucrose could still be detected in a
mixture with Polycose.
相似文献
44.
Purification of galectin-3 from ovine placenta: developmentally regulated expression and immunological relevance 总被引:1,自引:1,他引:1
Iglesias MM; Rabinovich GA; Ambrosio AL; Castagna LF; Sotomayor CE; Wolfenstein-Todel C 《Glycobiology》1998,8(1):59-65
Galectins, beta-galactoside-binding lectins, are extensively distributed in
the animal kingdom and share some basic molecular properties. Galectin-3, a
member of this family, is generally associated with differentiation,
morphogenesis, and metastasis. In this study, galectin-3 was isolated from
ovine placental cotyledons round the middle of the gestation period by
lactose extraction followed by affinity chromatography on lactosyl-agarose,
and separated from galectin-1 by size exclusion chromatography on a
Superose 12 column. Under native conditions this lectin behaved as a
monomer with an apparent molecular weight of approximately 29,000 and an
isoelectric point of 9.0. The partial amino acid sequence of the peptides
obtained by tryptic digestion of this protein followed by HPLC separation
showed striking homology with other members of the galectin-3 subfamily.
Furthermore, ovine placental galectin-3 exhibited specific mitogenic
activity toward rat spleen mononuclear cells. Besides, this protein
strongly reacted with a rabbit antiserum raised against a chicken galectin.
Results obtained by Western blot analysis showed that its expression was
greatly decreased in term placenta with respect to the middle of the
gestation period, suggesting a regulated expression throughout development.
相似文献
45.
46.
47.
Placental transfer of lactate, glucose and 2-deoxyglucose
was examined employing the in situ perfused
placenta. Control and streptozotocin induced diabetic
Wistar rats were infused with [U14C]-glucose and
[3H]-2-deoxyglucose (2DG). The fetal side of the placenta
was perfuseci with a cell free medium and glucose
uptake was calculated in the adjacent fetuses.
Despite the 5-fold higher maternal plasma glucose
concentration in the diabetic dams the calculated
fetal glucose metabolic index was not significantly
different between the 2 groups. Placental blood flow
was reduced in the diabetic animals compared with
controls but reduction of transfer of [U14C]-glucose and [3H]-2-deoxyglucose and endogenously derived
[14C]-Lactate to the fetal compartment, could not be
accounted for by reduced placental blood flow
alone. There was no significant net production or
uptake of lactate into the perfusion medium that
had perfused the fetal side of the placenta in either
group. The plasma lactate levels in the fetuses adjacent
to the perfused placenta were found to be higher
than in the maternal plasma and significantly
higher in the fetuses of the diabetic group compared
with control group. In this model the in situ perfused
placenta does not secrete significant quantities
of lactate into the fetal compartment in either
the control or diabetic group. 相似文献
48.
Expression of integrated hepatitis B virus X variants in human hepatocellular carcinomas and its significance 总被引:10,自引:0,他引:10
Chen WN Oon CJ Leong AL Koh S Teng SW 《Biochemical and biophysical research communications》2000,276(3):885-892
Hepatitis B virus X protein (HBX) has been implicated in the transactivation of diverse cellular genes and possibly also the pathogenesis of human hepatocellular carcinoma (HCC). We report the characterization of HBX variants from HBV-related human hepatocellular carcinoma (HCC). These HBX variants were integrated into the host chromosomes and also expressed in the HCC tissues. In addition, we report a novel in vitro HBX activity assay based on color changes that were indicative of the beta-galactosidase enzyme activity. Conducted in wheat germ lysates, the transactivating function of either wild type or mutant HBX protein was measured through their interaction with the Early Growth Response factor 1 (Egr-1) that controls the beta-galactosidase gene. Further analysis of these HBX deletion mutants using this assay may shed new insights on the significance of various mutations occurring in HCC-associated HBX. 相似文献
49.
Oon Han H Kim SH Kim KH Hur GC Joo Yim H Chung HK Ho Woo S Dong Koo K Lee CS Sung Koh J Kim GT 《Bioorganic & medicinal chemistry letters》2007,17(4):937-941
Oxime ethers of alpha-acyl-beta-phenylpropanoic acids were prepared to apply as PPARalpha and gamma dual agonists. Among them, compound 11l proved to exhibit potent in vitro activities with EC(50) of 19 and 13nM in PPARalpha and gamma, respectively. It showed better glucose lowering effects than rosiglitazone 1 and ameliorated the lipid profile like plasma triglyceride in db/db mice model. 相似文献
50.
Yoong-Sin Oon Soon-An Ong Li-Ngee Ho Yee-Shian Wong Yoong-Ling Oon Harvinder Kaur Lehl Wei-Eng Thung 《Bioprocess and biosystems engineering》2016,39(6):893-900
The main aim of this study is to investigate the performance of organic oxidation and denitrification of the system under long-term operation. The MFC reactor was operated in continuous mode for 180 days. Nitrate was successfully demonstrated as terminal electron acceptor, where nitrate was reduced at the cathode using electron provided by acetate oxidation at the anode. The removal efficiencies of chemical oxygen demand (COD) and nitrate were higher in the closed circuit system than in open circuit system. Both COD and nitrate reduction improved with the increase of organic loading and subsequently contributed to higher power output. The maximum nitrate removal efficiency was 88 ± 4 % (influent of 141 ± 14 mg/L). The internal resistant was 50 Ω, which was found to be low for a double chambered MFC. The maximum power density was 669 mW/m3 with current density of 3487 mA/m3. 相似文献