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1.
Molecular analysis of a beta-lactam resistance gene encoded within the cephamycin gene cluster of Streptomyces clavuligerus. 下载免费PDF全文
A Streptomyces clavuligerus gene (designated pcbR) which is located immediately downstream from the gene encoding isopenicillin N synthase in the cephamycin gene cluster was characterized. Nucleotide sequence analysis and database searching of PcbR identified a significant similarity between PcbR and proteins belonging to the family of high-molecular-weight group B penicillin-binding proteins (PBPs). Eight of nine boxes (motifs) conserved within this family of proteins are present in the PcbR protein sequence in the same order and with approximately the same spacing between them. When a mutant disrupted in pcbR was constructed by gene replacement, the resulting pcbR mutant exhibited a significant decrease in its resistance to benzylpenicillin and cephalosporins, indicating that pcbR is involved in beta-lactam resistance in this organism. Western blot (immunoblot) analysis of S. clavuligerus cell membranes using PcbR-specific antibodies suggested that PcbR is a membrane protein. PcbR was also present in cell membranes when expressed in Escherichia coli and was able to bind radioactive penicillin in a PBP assay, suggesting that PcbR is a PBP. When genomic DNAs from several actinomycetes were probed with pcbR, hybridization was observed to some but not all beta-lactam-producing actinomycetes. 相似文献
2.
The purpose of this study was to formulate a gelled self-emulsifying drug delivery system (SEDDS) containing ketoprofen as
an intermediate in the development of sustained release solid dosage form. Captex 200 (an oil), Tween 80 (a surfactant), and
Capmul MCM (a cosurfactant) were used to formulate SEDDS. Silicon dioxide was used as a gelling agent, which may aid in solidification
and retardation of drug release. Effect of concentrations of cosurfactant and gelling agent on emulsification process and
in vitro drug diffusion was studied using 32 factorial design. Multiple regression analysis data and response surfaces obtained showed that liquid crystal phase viscosity
increased significantly with increasing amount of silicon dioxide, which in turn caused an increase in average droplet size
of resultant emulsion and slower drug diffusion. Drug release from the formulation increased with increasing amount of cosurfactant. 相似文献
3.
The purpose of this research was to obtain directly compressible agglomerates of ibuprofen-paracetamol containing a desired
ratio of drugs using a crystallo-co-agglomeration technique. Crystallo-co-agglomeration is an extension of the spherical crystallization
technique, which enables simultaneous crystallization and agglomeration of 2 or more drugs or crystallization of a drug and
its simultaneous agglomeration with another drug or excipient. Dichloromethane (DCM)-water system containing polyethylene
glycol (PEG) 6000, polyvinyl pyrollidone, and ethylcellulose was used as the crystallization system. DCM acted as a good solvent
for ibuprofen and bridging liquid for agglomeration. The process was performed at pH 5, considering the low solubility of
ibuprofen and the stability of paracetamol. Loss of paracetamol was reduced by maintaining a low process temperature and by
the addition of dextrose as a solubility suppressant. The agglomerates were characterized by differential scanning calorimetry,
powder x-ray diffraction (PXRD), and scanning electron microscopy and were evaluated for tableting properties. The spherical
agglomerates contained an ibuprofen-paracetamol ratio in the range of 1.23 to 1.36. Micromeritic, mechanical, and compressional
properties of the agglomerates were affected by incorporated polymer. The PXRD data showed reduction in intensities owing
to dilution and reduced crystallinity. Thermal data showed interaction between components at higher temperature. Ethylcellulose
imparted mechanical strength to the agglomerates as well as compacts. The agglomerates containing PEG have better comparessibility
but drug release in the initial stages was affected owing to asperity melting, yielding harder compacts. The agglomeration
and properties of agglomerates were influenced by the nature of polymer. 相似文献
4.
Conclusion Hydrolyzed gelatins (Byco-A, Byco-O and Byco-C), when used as binders, yielded soft, uniform granules with good flow properties.
As the molecular weight and viscosity of hydrolyzed gelatins increased, the compressibility of granules decreased and their
compactability increased. The balance between compressibility and compactability of granules may be achieved by careful monitoring
of the molecular weight of hydrolyzed gelatins that can serve as potential binders. 相似文献
5.
Amelt solidification technique has been developed to obtain sustained-release waxy beads of flurbiprofen. Low glass transition
temperature (t
g) and shear-induced crystallization of flurbiprofen made it a suitable candidate for melt solidification technique. The process
involved emulsification and solidification of flurbiprofen-cetyl alcohol melt at significantly low temperature (5°C). The
effect of variables, namely, the amount of cetyl alcohol and the speed of agitation, was studied using 32 factorial design. The technique and the beads were evaluated on the basis of process and desired yield, surface topography,
Fourier-transform infrared (FT-IR), differential scanning calorimetry (DSC), particle size distribution, crushing strength,
and drug release. Average values for process and desired yields were 97% wt/wt and 26% wt/wt, respectively. No interaction
was observed between drug and excipient. Multiple regression analysis was carried out, and response surfaces were obtained.
A curvilinear relationship was observed between percentage of desired yield and the amount of cetyl alcohol. Linear decrease
in crushing strength was observed with increase in the amount of cetyl alcohol. Drug released from the beads followed zero
order kinetics. Burst release was shown to a greater extent in beads containing a lower amount of cetyl alcohol. Response
surfaces of time required for certain percentage of drug (t
D%) showed that after critical concentration of about 20% of cetyl alcohol (400 mg/batch), no significant release retardant
effect was observed. 相似文献
6.
Russell DA Spatola LA Dian T Paradkar VM Dufield DR Carroll JA Schlittler MR 《Biotechnology and bioengineering》2005,89(7):775-782
Human growth hormone (hGH) is not only a valuable recombinant therapeutic protein for hormone deficiency indications, but is also an extensively characterized molecule both from recombinant bacterial systems and as circulating in humans. We describe the characterization of hGH produced in three different plant systems: tobacco cell culture, soy seed, and maize seed. The data indicate highest production in the maize seed system, with continued productivity over multiple generations, and when bred to a new host genotype for improved productivity. Purification indicated significant material of the correct structure from both plant cell culture and maize seed, with maize seed also showing correct activity relative to that produced by Escherichia coli. However, all systems showed some proteolyzed hGH, with data from gel electrophoresis, mass spectrometry, and peptide mapping localizing to a region of the protein also prone to cleavage in some other systems. Together, the data indicate the dependence of recombinant protein accumulation on posttranslational processes in different host systems. 相似文献
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8.
Buket Aksu Anant Paradkar Marcel de Matas ?zgen ?zer Tamer Güneri Peter York 《AAPS PharmSciTech》2012,13(4):1138-1146
The publication of the International Conference of Harmonization (ICH) Q8, Q9, and Q10 guidelines paved the way for the standardization of quality after the Food and Drug Administration issued current Good Manufacturing Practices guidelines in 2003. “Quality by Design”, mentioned in the ICH Q8 guideline, offers a better scientific understanding of critical process and product qualities using knowledge obtained during the life cycle of a product. In this scope, the “knowledge space” is a summary of all process knowledge obtained during product development, and the “design space” is the area in which a product can be manufactured within acceptable limits. To create the spaces, artificial neural networks (ANNs) can be used to emphasize the multidimensional interactions of input variables and to closely bind these variables to a design space. This helps guide the experimental design process to include interactions among the input variables, along with modeling and optimization of pharmaceutical formulations. The objective of this study was to develop an integrated multivariate approach to obtain a quality product based on an understanding of the cause–effect relationships between formulation ingredients and product properties with ANNs and genetic programming on the ramipril tablets prepared by the direct compression method. In this study, the data are generated through the systematic application of the design of experiments (DoE) principles and optimization studies using artificial neural networks and neurofuzzy logic programs.KEY WORDS: artificial neural networks (ANNs), gene expression programming (GEP), optimization, quality by design (QbD) 相似文献
9.
Pedro LC Pinheiro João CR Cardoso Ana S Gomes Juan Fuentes Deborah M Power Adelino VM Canário 《BMC evolutionary biology》2010,10(1):373
Background
Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) belong to a family of endocrine factors that share a highly conserved N-terminal region (amino acids 1-34) and play key roles in calcium homeostasis, bone formation and skeletal development. Recently, PTH-like peptide (PTH-L) was identified in teleost fish raising questions about the evolution of these proteins. Although PTH and PTHrP have been intensively studied in mammals their function in other vertebrates is poorly documented. Amphibians and birds occupy unique phylogenetic positions, the former at the transition of aquatic to terrestrial life and the latter at the transition to homeothermy. Moreover, both organisms have characteristics indicative of a complex system in calcium regulation. This study investigated PTH family evolution in vertebrates with special emphasis on Xenopus and chicken. 相似文献10.