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排序方式: 共有406条查询结果,搜索用时 31 毫秒
71.
Muhammad Altaf Khan Saima Sadaf Muhammad Sajjad M. Waheed Akhtar 《Protein expression and purification》2009,68(1):85-89
This study describes comparison between IPTG and lactose induction on expression of caprine growth hormone (cGH), enhancing cell densities of Escherichia coli cultures and refolding the recombinant cGH, produced as inclusion bodies, to biologically active state. 2–3 times higher cell densities were obtained in shake flask cultures when induction was done with lactose showing almost same level of expression as in case of IPTG induction. With lactose induction highest cell densities were achieved in TB (OD600 16.3) and M9NG (OD600 16.1) media, producing 885 and 892 mg cGH per liter of the culture, respectively. Lactose induction done at mid-exponential stage resulted in a higher cell density and thus higher product yield. cGH over-expressed as inclusion bodies was solubilized in 50 mM Tris–Cl buffer (pH 12.5) containing 2 M urea, followed by dilution and lowering the pH in a step-wise manner to obtain the final solution in 50 mM Tris–Cl (pH 9.5). The cGH was purified by Q-Sepharose chromatography followed by gel filtration with a recovery yield of 39% on the basis of total cell proteins. The product thus obtained showed a single band by SDS–PAGE analysis. MALDI-TOF analysis showed a single peak with a mass of 21,851 dalton, which is very close to its calculated molecular weight. A bioassay based on proliferation of Nb2 rat lymphoma cells showed that the purified cGH was biologically active. 相似文献
72.
Khalid Mohammed Khan Momin Khan Muhammad Ali Muhammad Taha Saima Rasheed Shahnaz Perveen M. Iqbal Choudhary 《Bioorganic & medicinal chemistry》2009,17(22):7795-7801
Bis-Schiff bases 1–27 have been synthesized and their in vitro antiglycation potential has been evaluated. Compounds 21 (IC50 = 243.95 ± 4.59 μM), 20 (IC50 = 257.61 ± 5.63 μM), and 7 (IC50 = 291.14 ± 2.53 μM) showed an excellent antiglycation activity better than the standard (rutin, IC50 = 294.46 ± 1.50 μM). This study has identified a series of potential molecules as antiglycation agents. A structure–activity relationship has been studied, and all the compounds were characterized by spectroscopic techniques. 相似文献
73.
Rajakumar P Mohammed Abdul Rasheed A Iman Rabia A Chamundeeswari D 《Bioorganic & medicinal chemistry letters》2006,16(23):6019-6023
Macrocyclic di- and tetra-amides with thia- and oxylinkages were synthesized and screened for in vitro anti-inflammatory activity. Cyclophane diamide 15 showed a dose-dependent activity, while the other cyclophane amides 16-20 exhibited mild activity. 相似文献
74.
Saima Chaudhry Muhammad Idrees Mateen Izhar Arshad Kamal Butt Ayyaz Ali Khan 《Current microbiology》2011,62(1):78-83
Polymerase Chain reaction (PCR) assay is considered superior to other methods for detection of Helicobacter pylori (H. pylori) in oral cavity; however, it also has limitations when sample under study is microbial rich dental plaque. The type of gene
targeted and number of primers used for bacterial detection in dental plaque samples can have a significant effect on the
results obtained as there are a number of closely related bacterial species residing in plaque biofilm. Also due to high recombination
rate of H. pylori some of the genes might be down regulated or absent. The present study was conducted to determine the frequency of H. pylori colonization of dental plaque by simultaneously amplifying two genes of the bacterium. One hundred dental plaque specimens
were collected from dyspeptic patients before their upper gastrointestinal endoscopy and presence of H. pylori was determined through PCR assay using primers targeting two different genes of the bacterium. Eighty-nine of the 100 samples
were included in final analysis. With simultaneous amplification of two bacterial genes 51.6% of the dental plaque samples
were positive for H. pylori while this prevalence increased to 73% when only one gene amplification was used for bacterial identification. Detection
of H. pylori in dental plaque samples is more reliable when two genes of the bacterium are simultaneously amplified as compared to one
gene amplification only. 相似文献
75.
Rizwan Rasheed A. Wahid M. Farooq Iqbal Hussain Shahzad M. A. Basra 《Plant Growth Regulation》2011,65(1):35-45
High temperature strongly hampers the plant growth particularly at early growth stages. In this study, changes in some physiological
and anatomical characteristics and possibility of mitigating the adversities of heat stress by soaking sugarcane nodal buds
in 20 mM proline and glycinebetaine (GB) solutions have been explored. Heat stress reduced the rate of bud sprouting nonetheless
soaking the setts in proline followed by GB was beneficial. In addition, heat stress reduced the bud fresh and dry weights,
generated H2O2, reduced the tissue levels of K+ and Ca2+, while increased the osmolytes synthesis in a time course manner. Heat stress also delayed the emergence and expansion of
new bud leaves, by restricting the number and area of mesophyll cells. It also caused poor and aberrant development and diffused
appearance of mesophyll cells and vascular bundles in the bud leaves. However, soaking of buds in proline and GB solutions
substantially reduced the H2O2 production, improved the accumulation of soluble sugars and protected the developing tissues from heat stress effects; although
proline was more effective than GB. Correlations of various attributes indicated that soaking in GB and proline restricted
the H2O2 generation, improved K+ and Ca2+ contents, and increased the concentrations of free proline, GB and soluble sugars eventually improving the heat tolerance
of buds. Cost-benefit analysis showed that, considering increase in sprouting of buds, soaking in 20 mM solution of both osmoprotectants
is economical. 相似文献
76.
Salin-Cantegrel A Rivière JB Shekarabi M Rasheed S Dacal S Laganière J Gaudet R Rochefort D Lesca G Gaspar C Dion PA Lapointe JY Rouleau GA 《The Journal of biological chemistry》2011,286(32):28456-28465
Missense and protein-truncating mutations of the human potassium-chloride co-transporter 3 gene (KCC3) cause hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC), which is a severe neurodegenerative disease characterized by axonal dysfunction and neurodevelopmental defects. We previously reported that KCC3-truncating mutations disrupt brain-type creatine kinase-dependent activation of the co-transporter through the loss of its last 140 amino acids. Here, we report a novel and more distal HMSN/ACC-truncating mutation (3402C → T; R1134X) that eliminates only the last 17 residues of the protein. This small truncation disrupts the interaction with brain-type creatine kinase in mammalian cells but also affects plasma membrane localization of the mutant transporter. Although it is not truncated, the previously reported HMSN/ACC-causing 619C → T (R207C) missense mutation also leads to KCC3 loss of function in Xenopus oocyte flux assay. Immunodetection in Xenopus oocytes and in mammalian cultured cells revealed a decreased amount of R207C at the plasma membrane, with significant retention of the mutant proteins in the endoplasmic reticulum. In mammalian cells, curcumin partially corrected these mutant protein mislocalizations, with more protein reaching the plasma membrane. These findings suggest that mis-trafficking of mutant protein is an important pathophysiological feature of HMSN/ACC causative KCC3 mutations. 相似文献
77.
This study describes a simple approach for enhanced secretory expression of bubaline somatotropin (BbST) in the methylotropic yeast Pichia pastoris. A Muts Pichia transformant carrying multi-copy, non-codon optimized BbST cDNA sequence, expressed and secreted the recombinant protein into the culture medium to a level of 25 % of the total proteins in the culture supernatant, after 120 h of induction. Inclusion of polysorbate-80 in the inducing medium resulted in a significant improvement in the BbST expression (up to 45 % of the total culture supernatant proteins) with concomitant reduction in the induction time to 48 h. The amount of BbST obtained was 148 mg/L, which was around fivefold higher than that obtained without the surfactant. BbST was purified to near homogeneity by FPLC on Q-sepharose FF anion-exchange column. Protein authenticity was judged by SDS-PAGE and western blot analyses. A bioassay based on proliferation of Nb2 rat lymphoma cell lines confirmed that the purified, recombinant BbST is biologically active. Use of polysorbate-80 in combination with methanol, during the induction phase, is likely to have general applicability in lowering the induction time and enhancing the secretory expression of other commercially important proteins in Muts strains of P. pastoris. 相似文献
78.
Iqbal Ahmad Kiran Qadeer Saima Zahid Muhammad Ali Sheraz Tehmina Ismail Waqar Hussain Izhar Ahmad Ansari 《AAPS PharmSciTech》2014,15(5):1324-1333
The degradation kinetics of 5 × 10−5 M cyanocobalamin (B12) and hydroxocobalamin (B12b) in the presence of ascorbic acid (AH2) was studied in the pH range of 1.0–8.0. B12 is degraded to B12b which undergoes oxidation to corrin ring cleavage products. B12b alone is directly oxidized to the ring cleavage products. B12 and B12b in degraded solutions were simultaneously assayed by a two-component spectrometric method at 525 and 550 nm without interference from AH2. Both degrade by first-order kinetics and the values of the rate constants at pH 1.0–8.0 range from 0.08 to 1.05 × 10−5 s−1 and 0.22–7.62 × 10−5 s−1, respectively, in the presence of 0.25 × 10−3 M AH2. The t1/2 values of B12 and B12b range from 13.7 to 137.5 h and 2.5–87.5 h, respectively. The second-order rate constants for the interaction of AH2 with B12 and B12b are 0.05–0.28 × 10−2 and 1.10–30.08 × 10−2 M−1 s−1, respectively, indicating a greater effect of AH2 on B12b compared to that of B12. The kobs–pH profiles for both B12 and B12b show the highest rates of degradation around pH 5. The degradation of B12 and B12b by AH2 is affected by the catalytic effect of phosphate ions on the oxidation of AH2 in the pH range 6.0–8.0.KEY WORDS: ascorbic acid, cyanocobalamin, degradation, hydroxocobalamin, kinetics, two-component spectrometry 相似文献
79.