排序方式: 共有102条查询结果,搜索用时 109 毫秒
21.
High-level production of amorpha-4,11-diene in a two-phase partitioning bioreactor of metabolically engineered Escherichia coli 总被引:1,自引:0,他引:1
Newman JD Marshall J Chang M Nowroozi F Paradise E Pitera D Newman KL Keasling JD 《Biotechnology and bioengineering》2006,95(4):684-691
Reconstructing synthetic metabolic pathways in microbes holds great promise for the production of pharmaceuticals in large-scale fermentations. By recreating biosynthetic pathways in bacteria, complex molecules traditionally harvested from scarce natural resources can be produced in microbial cultures. Here we report on a strain of Escherichia coli containing a heterologous, nine-gene biosynthetic pathway for the production of the terpene amorpha-4,11-diene, a precursor to the anti-malarial drug artemisinin. Previous reports have underestimated the productivity of this strain due to the volatility of amorphadiene. Here we show that amorphadiene evaporates from a fermentor with a half-life of about 50 min. Using a condenser, we take advantage of this volatility by trapping the amorphadiene in the off-gas. Amorphadiene was positively identified using nuclear magnetic resonance spectroscopy and determined to be 89% pure as collected. We captured amorphadiene as it was produced in situ by employing a two-phase partitioning bioreactor with a dodecane organic phase. Using a previously characterized caryophyllene standard to calibrate amorphadiene production and capture, the concentration of amorphadiene produced was determined to be 0.5 g/L of culture medium. A standard of amorphadiene collected from the off-gas showed that the caryophyllene standard overestimated amorphadiene production by approximately 30%. 相似文献
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Peter C.K. Lau Farnaz Forghani Diane Labbé Hélène Bergeron Roland Brousseau H. Joachim Höltke 《Molecular genetics and genomics : MGG》1994,243(1):24-31
The genes encoding the Neisseria lactamica restriction endonuclease IV (R.NIaIV) and its cognate DNA methyltransferase (M.NlaIV), both of which recognize the sequence GGNNCC, have been cloned in Escherichia coli and overexpressed using the T7 polymerase/promoter system. Analysis of a sequenced 3.58 kb fragment established the gene order, leuD-M.NlaIV-R.NlaIV-leuB. The predicted primary sequence of M.NlaIV (423 amino acids) shows the highest degree of identity to a pair of cytosine-specific methyltransferases, M.BanI (44.9%) and M.HgiCI (44.3%), which recognize the sequence GGYRCC (Y, pyrimidines; R, purines). In contrast, the R.NlaIV protein sequence (243 amino acids) is unique in the existing database, a situation that holds for most endonucleases. Flanking the NlaIV modification and restriction genes are homologues of the leuD and leuB genes of enteric bacteria, which code for enzymes in the leucine biosynthesis pathway. This gene context implies a possible new mode of gene regulation for the RM.NlaIV system, which would involve a mechanism similar to the recently discovered leucine/Lrp regulon in E. coli. 相似文献
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Krishnaprasad G Nandanan Sagar Salim Ajith V Pankajam Miki Shinohara Gen Lin Parijat Chakraborty Amamah Farnaz Lars M Steinmetz Akira Shinohara Koodali T Nishant 《Genetics》2021,219(2)
In the baker’s yeast Saccharomyces cerevisiae, most of the meiotic crossovers are generated through a pathway involving the highly conserved mismatch repair related Msh4-Msh5 complex. To understand the role of Msh4-Msh5 in meiotic crossing over, we determined its genome wide in vivo binding sites in meiotic cells. We show that Msh5 specifically associates with DSB hotspots, chromosome axes, and centromeres on chromosomes. A basal level of Msh5 association with these chromosomal features is observed even in the absence of DSB formation (spo11Δ mutant) at the early stages of meiosis. But efficient binding to DSB hotspots and chromosome axes requires DSB formation and resection and is enhanced by double Holliday junction structures. Msh5 binding is also correlated to DSB frequency and enhanced on small chromosomes with higher DSB and crossover density. The axis protein Red1 is required for Msh5 association with the chromosome axes and DSB hotspots but not centromeres. Although binding sites of Msh5 and other pro-crossover factors like Zip3 show extensive overlap, Msh5 associates with centromeres independent of Zip3. These results on Msh5 localization in wild type and meiotic mutants have implications for how Msh4-Msh5 works with other pro-crossover factors to ensure crossover formation. 相似文献
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Shariftabrizi A Khorramizadeh MR Saadat F Alimoghadam K Safavifar F Ebrahimkhani MR 《Molecular and cellular biochemistry》2005,273(1-2):109-116
Background: The level of activity of the telomerase has been shown to correlate with the degree of invasiveness in several tumor types. In addition, cellular redox state is believed to regulate the secretion of matrix metalloproteinase-2 (MMP-2).Aims: To determine the effect of anti-sense telomerase treatment of prostate cancer cells on MMP-2 activity, and the reactive oxygen and nitrogen species (two effectors of cellular redox state).Methods: Anti-sense oligonucleotide against RNA component of human telomerase (hTR) was introduced into the cells using Fugene-6 transfection reagent. The activity of telomerase was assessed using Telomere Repeat Amplification Protocol (TRAP assay). Activity of matrix metalloproteinase-2 (MMP-2) was determined by zymography. Levels of intracellular reactive oxygen species (ROS) and nitric oxide metabolites were measured by dichlorofluorescein diacetate (DCFH-DA) staining and Griess reagent, respectively. The level of apoptosis was determined using TUNEL assay.Results: TRAP assay showed more than 90% inhibition of telomerase activity after 72 h of transfection. Pro-MMP-2 activity was decreased down to 50% of the control levels. Intracellular reactive oxygen species were also significantly decreased. Neither apoptosis rate nor the level of nitric oxide metabolites was significantly different between anti-sense treated and control cells.Conclusions: Concomitant reduction of the pro-MMP-2 secretion and ROS in PC-3 cells following hTR inhibition suggests that over-activity of telomerase in cancer cells might increase the level of matrix metalloproteinase-2 and thus, be directly involved in the invasion process through enhancement of intracellular oxidative stress. 相似文献
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Siahi MR Barzegar-Jalali M Monajjemzadeh F Ghaffari F Azarmi S 《AAPS PharmSciTech》2005,6(4):E626-E632
The present study was performed to design oral controlled delivery systems for the water-soluble drug, verapamil hydrochloride,
using natural and semisynthetic polymers as carriers in the forms of 1- and 3-layer matrix tablets. Verapamil hydrochloride
1-layer matrix tablets containing hydroxypropylmethylcellulose, tragacanth, and acacia either alone or mixed were prepared
by direct compression technique. 3-layer matrix tablets were prepared by compressing the polymers as release retardant layers
on both sides of the core containing the drug. The prepared tablets were subjected to in vitro drug release studies. Tragacanth
when used as the carrier in the formulation of 1- and 3-layer matrices produced satisfactory release prolongation either alone
or in combination with the other 2 polymers. On the other hand, acacia did not show enough prolonging efficiency in 1- and
3-layer matrix tablets. The results also showed that the location of the polymers in the 3-layer tablets has a pronounced
effect on the drug release. Kinetic analysis of drug release from matrices exhibiting sustained release indicated that release
was predominantly attributable to the contribution made by Fickian diffusion, while the erosion/relaxation mechanisms had
a minor role in the release.
Published: December 7, 2005 相似文献
26.
Xi-Lin Chen Daniel Serrano Farnaz Ghobadi Marian Mayhue Kasper Hoebe Subburaj Ilangumaran Sheela Ramanathan 《PloS one》2016,11(3)
GTPase of the immune associated nucleotide binding protein (GIMAP) family of proteins are expressed essentially in cells of the hematopoietic system. Mutation in the founding member of this gene family, Gimap5, results in the lymphopenic phenotype in Bio-Breeding diabetes prone rats. In mice, deletion of functional Gimap5 gene affects the survival and renewal of hematopoietic stem cells in addition to the defects observed in T cells. Here we show that T cells from OTII TCR-transgenic Gimap5sph/sph mice do not proliferate in response to its cognate antigen. Furthermore, T cells from Gimap5 mutant rats and mice show decreased phosphorylation of STAT5 following stimulation with IL-7. Our results suggest that functional Gimap5 is required for optimal signaling through TCR and IL-7R in T cells. 相似文献
27.
Abbas Nasehi Jugah Bin Kadir Farnaz Abed Ashtiani Mehdi Nasr-Esfahani Mui Yun Wong Siti Khadijah Rambe Hajar Ghadirian Farshid Mahmodi Elham Golkhandan 《Mycological Progress》2014,13(4):1041-1048
A new species of Alternaria causing leaf spot of pepper (Capsicum annuum) obtained from the Cameron highlands, Pahang, Malaysia, was determined based on phylogenetic analyses, morphological characteristics, and pathogenicity assays. Phylogenetic analyses of combined dataset of the glyceraldehyde-3-phosphate dehydrogenase (gpd), Alternaria allergen a 1 (Alt a1) and calmodulin genes revealed that the new isolates clustered into a subclade distinct from the closely related Alternaria species A. tomato and A. burnsii. The solitary or short chains of conidia resemble those of A. burnsii. However, conidia with long beaks are morphologically similar to A. tomato. Hence, the pathogenic fungus is proposed as Alternaria capsicicola sp. nov. Pathogenicity assays indicated that A. capsicicola causes leaf spot on pepper. 相似文献
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Seyed N Zahedifard F Safaiyan S Gholami E Doustdari F Azadmanesh K Mirzaei M Saeedi Eslami N Khadem Sadegh A Eslami Far A Sharifi I Rafati S 《PLoS neglected tropical diseases》2011,5(9):e1295