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Chromatography Methods (chromatography + methods)
Selected AbstractsTyrosinase inhibitors isolated from the roots of Paeonia suffruticosaINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 2 2010H. -Y. J. Cosmet. Sci., 60, 347,352 (May/June 2009) Accepted for publication November 6, 2008. Synopsis The inhibition of mushroom tyrosinase by Paeonia suffruticosa root-derived materials was evaluated. Six tyrosinase inhibitors were isolated by ethanol extraction, n -hexane, ethyl acetate, n -BuOH, and water partition, silica gel column chromatography, Sephadex LH-20, Lobar PR-8, and high-performance liquid chromatography methods, and they were identified as kaempferol (I), quercetin (II), mudanpioside B (III), benzoyloxypaeoniflorin (IV), mudanpioside H (V), and pentagalloyl-,-D-glucose (VI) on the basis of spectroscopic evidence. The inhibitory activities of compounds I to VI against mushroom tyrosinase were determined with IC50 values of 0.120, 0.108, 0.368, 0.453, 0.324, and 0.063 mM, respectively. The kinetic study indicated that all purified inhibitors acted competitively for the L-dopa binding site of the enzyme, with an exception of compound VI, which acted non-competitively. [source] Characterization of Ethylene Copolymers with Liquid Chromatography and Melt Rheology MethodsMACROMOLECULAR SYMPOSIA, Issue 1 2009Yefim Brun Abstract Summary: Melt rheology and polymer chromatography methods were applied to characterize molecular heterogeneities in products of free radical copolymerization of ethylene with methyl acrylate and vinyl acetate comonomers performed in continuously stirred tank and tubular reactors. We found that the ethylene,vinyl acetate copolymers made in both reactors had similar linear viscoelastic properties typical to branched products of the high pressure process. But the ethylene,methyl acrylate copolymers obtained in the tubular reactor had unusually high melt viscosity at low shear rate and much lower onset of shear thinning despite the narrower molecular weight distribution and the lower overall amount of long-chain branches compare to their autoclave counterparts with similar average molecular weight and chemical composition. Using interaction polymer chromatography method called gradient elution at critical point of adsorption we found that ethylene-acrylate copolymers from the tubular reactor had very broad chemical composition distribution, which was consistent with a significant difference in reactivity ratios between ethylene and acrylate comonomers. Such chemical composition heterogeneity can be a reason for the observed unusual rheological properties of these copolymers. [source] Stability and compatibility of drug mixtures in an implantable infusion systemANAESTHESIA, Issue 9 2008F. Bianchi Summary This study evaluated the stability and the compatibility of mixtures of morphine sulphate, bupivacaine, and clonidine hydrochloride and of hydromorphone, bupivacaine, and clonidine hydrochloride, when used in constant flow implantable pumps under simulated clinical use conditions. The pumps were filled with drug mixtures and incubated at 37 °C for a period of 90 days. Aliquots were sampled monthly from the reservoir and catheter outlet and the drug concentrations analysed using validated chromatography methods. Individual materials from the infusion system were immersed in the drug mixtures and stored at 37 °C for 60 weeks and evaluated for mechanical performance for compatibility testing. Both drug mixtures were found to be stable over 90 days in the pump at 37 °C. All device materials retained acceptable mechanical performance following exposure. These results demonstrate that both drug mixtures are stable when maintained at simulated body temperature in an implantable infusion system for 90 days. [source] Capturing of cell culture-derived modified Vaccinia Ankara virus by ion exchange and pseudo-affinity membrane adsorbersBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010Michael W. Wolff Abstract Smallpox is an acute, highly infectious viral disease unique to humans, and responsible for an estimated 300,500 million deaths in the 20th century. Following successful vaccination campaigns through the 19th and 20th centuries, smallpox was declared eradicated by the World Health Organization in 1980. However, the threat of using smallpox as a biological weapon prompted efforts of some governments to produce smallpox vaccines for emergency preparedness. An additional aspect for the interest in smallpox virus is its potential use as a platform technology for vector vaccines. In particular, the latter requires a high safety level for routine applications. IMVAMUNE®, a third generation smallpox vaccine based on the attenuated Modified Vaccinia Ankara (MVA) virus, demonstrates superior safety compared to earlier generations and represents therefore an interesting choice as viral vector. Current downstream production processes of Vaccinia virus and MVA are mainly based on labor-intensive centrifugation and filtration methods, requiring expensive nuclease treatment in order to achieve sufficient low host-cell DNA levels for human vaccines. This study compares different ion exchange and pseudo-affinity membrane adsorbers (MA) to capture chicken embryo fibroblast cell-derived MVA-BN® after cell homogenization and clarification. In parallel, the overall performance of classical bead-based resin chromatography (Cellufine® sulfate and Toyopearl® AF-Heparin) was investigated. The two tested pseudo-affinity MA (i.e., sulfated cellulose and heparin) were superior over the applied ion exchange MA in terms of virus yield and contaminant depletion. Furthermore, studies confirmed an expected increase in productivity resulting from the increased volume throughput of MA compared to classical bead-based column chromatography methods. Overall virus recovery was ,60% for both pseudo-affinity MA and the Cellufine® sulfate resin. Depletion of total protein ranged between 86% and 102% for all tested matrices. Remaining dsDNA in the product fraction varied between 24% and 7% for the pseudo-affinity chromatography materials. Cellufine® sulfate and the reinforced sulfated cellulose MA achieved the lowest dsDNA product contamination. Finally, by a combination of pseudo-affinity with anion exchange MA a further reduction of host-cell DNA was achieved. Biotechnol. Bioeng. 2010. 105: 761,769. © 2009 Wiley Periodicals, Inc. [source] | ||||||||||