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排序方式: 共有222条查询结果,搜索用时 28 毫秒
91.
P T Wong D M Zahab S A Narang W L Sung 《Biochemical and biophysical research communications》1987,146(1):232-238
Infrared spectra of E. coli strain JM103 and transformants which overproduced recombinant proinsulin have been measured as a function of pressure up to 38 kbar. It is the first time that high-pressure infrared spectra of live bacteria have been successfully measured. In ambient conditions, spectra of the host strain JM103 and the transformants are generally identical. However, under pressure, distinct shifting pattern can be observed in specific spectral parameters of transformants, presumably due to accumulation of proinsulin in form of cytoplasmic inclusion bodies. In particular, the pressure-induced frequency shift of the amide III band (1235 cm-1) in the proinsulin-producing transformants is much smaller than in the host JM103. This pressure effect can potentially be an efficient approach to monitor maximum gene expression in microorganisms. Contrary to predictions based on model system, the pressure-induced denaturation and the sharp transition from disordered liquid crystalline state to the ordered gel state commonly observed in the aqueous solution of protein and aqueous bilayer dispersion of lipids, respectively, do not occur in the bacterial proteins and cell membrane of E. coli. 相似文献
92.
93.
S Chhabra R Narang LR Krishnan S Vasisht DP Agarwal LM Srivastava SC Manchanda N Das 《BMC genetics》2002,3(1):9-6
Background
A close association between Sst I polymorphism in the 3' untranslated region of the apolipoproteinC3 (APOC3 ) gene and levels of plasma triglycerides (TG) had been reported by different investigators. Hypertriglyceridemia(HTG) is a known risk factor for coronary artery disease (CAD) in the context of Asian Indians. We conducted a study on the relationship between APOC3 SstI polymorphism (S1S1, S1S2 and S2S2 genotypes) and plasma TG levels in a group of 139 male healthy volunteers from Northern India. 相似文献94.
Structure-function studies of murine epidermal growth factor: expression and site-directed mutagenesis of epidermal growth factor gene 总被引:3,自引:0,他引:3
P Ray F J Moy G T Montelione J F Liu S A Narang H A Scheraga R Wu 《Biochemistry》1988,27(19):7289-7295
Wild-type murine epidermal growth factor (mEGF) and mutants with Leu47 replaced by serine and valine, respectively, have been produced by recombinant DNA methodology. A synthetic gene for mEGF was fused to the coding sequence for the signal peptide of the outer membrane protein A (ompA) of Escherichia coli in the secretion vector pIN-III-ompA3, and the recombinant plasmid was used to transform E. coli. Upon induction of gene expression, mEGF and the mutants was expressed and secreted into the periplasmic space. Purification of the wild-type Leu47-mEGF and the mutants was carried out by reversed-phase and anion-exchange high-performance liquid chromatography (HPLC). Amino acid analysis and Western blot analysis further confirmed the identities of the proteins. Specific activities for wild-type and mutant proteins were measured in both mEGF receptor binding and autophosphorylation assays. The recombinant mEGF has specific activities identical with that of mEGF purified from mouse submaxillary glands, while both mutants have reduced specific activities in both bioassays. The data demonstrate the importance of the highly conserved Leu47 residue in mEGF for full biological activity. 相似文献
95.
Electrophoretic analysis of the developmental stages and tissues of Anopheles albimanus showed that qualitatively similar allozymes of aconitase (Acon-2) occur at all stages, and the enzyme is widespread in every larval and adult tissues. Relative heat stabilities of the allozymes were investigated by electrophoresis of heated aqueous extracts and by heating the enzyme in situ in acrylamide gels after electrophoretic separation in Tris-citrate and Tris-maleate buffer systems. The pupal aconitase in the crude extract is more stable to heat than the larval and adult enzyme. The presence of citrate ions in the gel increased the stability of aconitase to heat. Studies of substrate specificities indicated that cis-aconitic acid is the best substrate but citric acid can also serve as a substrate. Zymograms developed with isocitric acid as a substrate showed no aconitase electromorphs and produced only isocitrate dehydrogenase bands. Aconitase has a pH optimum of 8.0 and this enzyme is completely inhibited if treated in situ with ethylenediaminetetra-acetic acid (EDTA), p-chloromercuribenzoate (PCMB), and urea at concentrations higher than 5mm, 5×10–5
m, and 2 m, respectively. Acon-2100 and Acon-2105 do not respond differently to the above treatments. Genetic crosses involving a holandric translocation, pericentric inversions, visible mutants, and allozyme markers were analyzed to map the aconitase (Acon-2) locus on the left arm of chromosome 3. The gene sequence (and map distances) on 3L is centromere—esterase-8 (Est-8)—2—esterase-4 (Est-4)—25—esterase-2 (Est-2)—9—Acon-2—5—phosphoglucomutase (Pgm)—7—esterase-6 (Est-6). 相似文献
96.
Hyperexpression of a Bacillus circulans xylanase gene in Escherichia coli and characterization of the gene product. 总被引:2,自引:2,他引:0 下载免费PDF全文
A 4.0-kilobase (kb) fragment of Bacillus circulans genomic DNA inserted into pUC19 and encoding endoxylanase activity was subjected to a series of subclonings. A 1.0-kb HindIII-HincII subfragment was found to code for xylanase activity. Maximum expression levels were observed with a subclone that contained an additional 0.3-kb sequence upstream from the coding region. Enhancer sequences in the upstream region are thought to be responsible for these high expression levels. Southern hybridization analyses revealed that the cloned gene hybridized with genomic DNA from Bacillus subtilis and Bacillus polymyxa. Xylanase activity expressed by Escherichia coli harboring the cloned gene was located primarily in the intracellular fraction. Levels of up to 7 U/ml or 35 mg/liter were obtained. The protein product was purified by ion exchange and gel permeation chromatography. The xylanase had a molecular weight of 20,500 and an isoelectric point of 9.0. 相似文献
97.
Pranava S. Mishra Pratibha Narang Rahul Narang Bidhan Goswami Deepak K. Mendiratta 《Antonie van Leeuwenhoek》2018,111(1):73-87
During the last two decades, nontuberculous mycobacteria (NTM) have gained in importance but there is still a paucity of data, particularly for environmental isolates. We studied, over a period of two years, the spatio-temporal features of NTM isolates obtained from different environmental sources in Wardha district, India. A total of 1398 samples (699 each of soil and water) were tested and 170 (12.2%) yielded NTM isolates, including 123 from soil and 47 from water samples. Out of 170 NTM isolates, 107 (63%) belonged to potentially pathogenic mycobacteria (PPM) and 63 (37%) to the less pathogenic mycobacterial (LPM) group. Overall, maximum isolation was obtained in rainy season (20.3%) followed by winter (13.5%), post rainy (8.7%) and summer seasons (5.8%). Mycobacterium fortuitum, Mycobacterium gordonae and Mycobacterium avium complex (MAC) were common isolates followed by Mycobacterium flavescens, Mycobacterium scrofulaceum, Mycobacterium simiae and Mycobacterium marinum. From soil, isolation of NTM was highest from grounds used for community gatherings (42.8%) followed by soil from residential premises (27.7%) and near the wells (26.0%). From drinking water sources, highest NTM isolation was obtained from wells (15.4%) followed by treated water tanks (6.9%), household receptacles (6.3%), hand pumps (5.6%) and tap water supply (3.5%). Isolation from natural canal water was 6.6%, while from drainage and waste water ponds isolation was 8.3%. The results of the study revealed that in Wardha district, NTM are present both in the soil and drinking water. As NTM can be pathogenic, particularly in immune-compromised individuals, these can be of potential risk to the human population. 相似文献
98.
99.
The perception of toxicity to nitric oxide (NO) and irradiation (IR) by three different cell types has been studied. The three
cell types are the macrophage like RAW264.7 cells, EL4 lymphoma cells, and splenocytes, which represent the different components
of a tumor. These three cell types respond differently to NO donors (SNP and SNAP) and radiation treatment. The macrophages
were found to be most radio-resistant and insensitive to NO donors. The innate resistance of the macrophages was not due to
its antioxidant defense system since there was no significant activation of the enzymes (superoxide dismutases, catalase,
and glutathione peroxidase) in RAW264.7 cells after NO donor and irradiation. But the cell cycle arrest of the three cell
types was different from each other. The EL4 cells were found to arrest in the G2/M phase while the macrophages were found
arrested in the G1 phase of the cell cycle. Such specific killing of the tumor cell in response to NO donor while sparing
the macrophages can be of immense importance to radiotherapy. 相似文献
100.
Indra Narang Cedric Manlhiot Jolie Davies-Shaw Don Gibson Nita Chahal Karen Stearne Amanda Fisher Stafford Dobbin Brian W. McCrindle 《CMAJ》2012,184(17):E913-E920