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61.
Applications of Gene Replacement Technology to Streptomyces clavuligerus Strain Development for Clavulanic Acid Production 总被引:2,自引:0,他引:2 下载免费PDF全文
A. S. Paradkar R. H. Mosher C. Anders A. Griffin J. Griffin C. Hughes P. Greaves B. Barton S. E. Jensen 《Applied microbiology》2001,67(5):2292-2297
Cephamycin C production was blocked in wild-type cultures of the clavulanic acid-producing organism Streptomyces clavuligerus by targeted disruption of the gene (lat) encoding lysine -aminotransferase. Specific production of clavulanic acid increased in the lat mutants derived from the wild-type strain by 2- to 2.5-fold. Similar beneficial effects on clavulanic acid production were noted in previous studies when gene disruption was used to block the production of the non-clavulanic acid clavams produced by S. clavuligerus. Therefore, mutations in lat and in cvm1, a gene involved in clavam production, were introduced into a high-titer industrial strain of S. clavuligerus to create a double mutant with defects in production of both cephamycin C and clavams. Production of both cephamycin C and non-clavulanic acid clavams was eliminated in the double mutant, and clavulanic acid titers increased about 10% relative to those of the parental strain. This represents the first report of the successful use of genetic engineering to eliminate undesirable metabolic pathways in an industrial strain used for the production of an antibiotic important in human medicine. 相似文献
62.
The aim of this study was to formulate a self-emulsifying system (SES) containing a lipophilic drug, loratadine, and to explore
the potential of preformed porous polystyrene beads (PPB) to act as carriers for such SES. Isotropic SES was formulated, which
comprised Captex 200 (63% wt/wt), Cremophore EL (16% wt/wt), Capmul MCM (16% wt/wt), and loratadine (5% wt/wt). SES was evaluated
for droplet size, drug content, and in vitro drug release. SES was loaded into preformed and characterized PPB using solvent
evaporation method. SES-loaded PPB were evaluated using scanning electron microscopy (SEM) for density, specific surface area
(SBET), loading efficiency, drug content, and in vitro drug release. After SES loading, specific surface area reduced drastically,
indicating filling of PPB micropores with SES. Loading efficiency was least for small size (SS) and comparable for medium
size (MS) and large size (LS) PPB fractions. In vitro drug release was rapid in case of SS beads due to the presence of SES
near to surface. LS fraction showed inadequate drug release owing to presence of deeper micropores that resisted outward diffusion
of entrapped SES. Leaching of SES from micropores was the rate-limiting step for drug release. Geometrical features such as
bead size and pore architecture of PPB were found to govern the loading efficiency and in vitro drug release from SES-loaded
PPB.
Published: March 24, 2006 相似文献
63.
Rohan A. Limaye Virendra B. Kumbhar Arun D. Natu Madhusudan V. Paradkar Varsha S. Honmore Rubia R. Chauhan Suwarna P. Gample Dhiman Sarkar 《Bioorganic & medicinal chemistry letters》2013,23(3):711-714
One pot synthesis of 3-Aracylphthalide was accomplished in good yield by reacting 2-carboxy benzaldehyde with various aromatic methyl ketones in presence of methane sulphonic acid. Various phthalides thus obtained were characterized with spectral techniques. These phthalides were subjected to in vitro antitubercular screening against Mycobacterium tuberculosis H37Ra (MTB) by using XRMA protocol. Among the phthalides screened, four exhibited half maximal inhibitory concentration (IC50) in the range of 0.81–1.24 μg/ml thereby providing potential lead compounds for future drug discovery studies. 相似文献
64.
Jacky Chung Sheila A. Anderson Babette Gwynn Kathryn M. Deck Michael J. Chen Nathaniel B. Langer George C. Shaw Nicholas C. Huston Leah F. Boyer Sumon Datta Prasad N. Paradkar Liangtao Li Zong Wei Amy J. Lambert Kenneth Sahr Johannes G. Wittig Wen Chen Wange Lu Bruno Galy Thorsten M. Schlaeger Matthias W. Hentze Diane M. Ward Jerry Kaplan Richard S. Eisenstein Luanne L. Peters Barry H. Paw 《The Journal of biological chemistry》2014,289(20):13707
65.
Hydrogen Storage: Hydrogen Flux through Size Selected Pd Nanoparticles into Underlying Mg Nanofilms (Adv. Energy Mater. 4/2018) 下载免费PDF全文
66.
Jacky Chung Sheila A. Anderson Babette Gwynn Kathryn M. Deck Michael J. Chen Nathaniel B. Langer George C. Shaw Nicholas C. Huston Leah F. Boyer Sumon Datta Prasad N. Paradkar Liangtao Li Zong Wei Amy J. Lambert Kenneth Sahr Johannes G. Wittig Wen Chen Wange Lu Bruno Galy Thorsten M. Schlaeger Matthias W. Hentze Diane M. Ward Jerry Kaplan Richard S. Eisenstein Luanne L. Peters Barry H. Paw 《The Journal of biological chemistry》2014,289(11):7835-7843
Mitochondrial iron is essential for the biosynthesis of heme and iron-sulfur ([Fe-S]) clusters in mammalian cells. In developing erythrocytes, iron is imported into the mitochondria by MFRN1 (mitoferrin-1, SLC25A37). Although loss of MFRN1 in zebrafish and mice leads to profound anemia, mutant animals showed no overt signs of porphyria, suggesting that mitochondrial iron deficiency does not result in an accumulation of protoporphyrins. Here, we developed a gene trap model to provide in vitro and in vivo evidence that iron regulatory protein-1 (IRP1) inhibits protoporphyrin accumulation. Mfrn1+/gt;Irp1−/− erythroid cells exhibit a significant increase in protoporphyrin levels. IRP1 attenuates protoporphyrin biosynthesis by binding to the 5′-iron response element (IRE) of alas2 mRNA, inhibiting its translation. Ectopic expression of alas2 harboring a mutant IRE, preventing IRP1 binding, in Mfrn1gt/gt cells mimics Irp1 deficiency. Together, our data support a model whereby impaired mitochondrial [Fe-S] cluster biogenesis in Mfrn1gt/gt cells results in elevated IRP1 RNA-binding that attenuates ALAS2 mRNA translation and protoporphyrin accumulation. 相似文献
67.
The purpose of this research was to investigate the potential use of anionick-carrageenan and nonionic hydroxypropyl-methylcellulose (HPMC, K4) to improve the matrix integrity of directly compressed
chitosan tablets containing naproxen sodium, an anionic drug. The influence of buffer pH and drug:polymer ratio on the water
uptake, matrix erosion, and drug release were studied. The rapid release of naproxen sodium was seen from matrices containing
100% chitosan due to loss in the matrix cohesiveness; whereas, it was relatively slow for matrices containing optimum concentration
ofk-carrageenan. In-situ interaction between oppositely charged moieties resulted in the formation of polyelectrolyte complexes
with stoichiometric charge ratios of unity. Fourier transform in frared (FTIR) spectroscopy and powder x-ray diffraction (PXRD)
data confirmed the importance of ionic bonds in polyelectrolyte complexation. The ionic interactions between polymers were
absent in matrices containing HPMC and the integrity of tablets was improved owing to the presence of viscous gel barrier.
The reasons for retarded release of naproxen sodium from the chitosan matrices at different pH include poor aqueous solubility
of drug, the formation of a rate-limiting polymer gel barrier along the periphery of matrices, the interaction of naproxen
sodium with protonated amino, groups of chitosan, and the interaction of ionized amino groups of chitosan with ionized sulfate
groups ofk-carrageenan.
Published: June 15, 2007 相似文献
68.
The basic objective of this work was to study the effect of model cationic drug metformin HCl on swelling and erosion and,
in turn, the release of KCl and drug itself, from the κ-carrageenan matrices. Water uptake by the matrix up to 2 hours was
found to increase with KCl concentration from the plain matrix. Erosion was not affected by concentration of KCl. Incorporation
of drug favors water uptake, but in presence of KCl it was found to be reduced. Drugcontaining matrices have shown higher
release of KCl as compared with plain batches. Drug release was retarded as KCl concentration increased up to 5%, above which
the reduced cohesivity of the matrix caused increase in drug release. 相似文献
69.
Fragments of genomic DNA from Streptomyces venezuelae ISP5230 were cloned in the Escherichia coli expression vector pTZ18R and the plasmids were used to transform E. coli JA194 (trpE). The transformants included a prototrophic strain containing a recombinant plasmid, pDQ181, with an approximately 6.8-kb insert. Subcloning located the trpE-complementing DNA in a 2.4-kb segment. Transformation of E. coli ED23 (lacking both trpE and trpG functions) with plasmids containing the 2.4-kb DNA segment gave prototrophic strains exhibiting both the ASI and ASII activities of anthranilate synthetase. The results indicated that trpE and trpG are clustered in S. venezuelae. Regions hybridizing to the pDQ181 insert were present in the genomic DNA of other streptomycetes. 相似文献
70.