Search results for "PERFORMANCE."
showing 10 items of 4178 documents
Characterization of proteinaceous glues in old paintings by separation of the o-phtalaldehyde derivatives of their amino acids by liquid chromatograp…
2005
A HPLC-fluorescence method for characterization of proteinaceous glues from binding media used in pictorial works of art prior to conservation or restoration treatment is proposed. Fluorescence derivatization of amino acids released by acid hydrolysis of standard proteins is studied. The derivatization reagent was o-phtalaldehyde with 2-mercaptoethanol as catalyst. Mobile phase was a programmed gradient among two eluents (water buffered at pH 5.8 wit 5% THF, and methanol) and is able to satisfactorily resolve the amino acid derivatives in 45min. Peak area ratios among amino acid derivatives and the leucine derivative are useful to characterize the proteins. The method shows good sensitivity…
Peptide mapping by reversed-phase high-performance liquid chromatography employing silica rod monoliths.
2003
In this paper, a general procedure is described for the generation of peptide maps of proteins with monolithic silica-based columns. The peptide fragments were obtained by tryptic digestion of various cytochrome c species with purification of the tryptic fragments achieved by reversed-phase high-performance liquid chromatographic methods. Peak assignment of the various peptides was based on evaluation of the biophysical properties of the individual peptides and via mass spectrometric identification. The performance of several different monolithic sorbents prepared as columns of identical cross-sectional dimensions were investigated as part of these peptide mapping studies and the data evalu…
Calculation of the molecular masses of two newly synthesized thermostable enzymes isolated from thermophilic microorganisms
1995
Two thermostable enzymes synthesized by thermophilic microorganisms were isolated and purified. A thermostable beta-galactosidase was produced in a continuous fermentation process by Bacillus stearothermophilus TP 32 as an intracellular enzyme. After applying different concentration procedures the raw extract enzyme was prepurified on a Sephadex G-200 size exclusion column. The isolated beta-galactosidase fraction was then separated with HPLC on a TSK G 3000 SW size exclusion column to determine the molecular mass based on calibration curves of standard proteins. The other enzyme, a thermostable protease, was synthesized by Bacillus stearothermophilus TP 26 as an extracellular enzyme. After…
Interactions between 2-Aminobenzothiazole and Natural Organic Matter as Evidenced by CPMAS Nitrogen-15 NMR Spectroscopy
2009
Cross-polarization magic angle spinning (CPMAS) 15N nuclear magnetic resonance (NMR) spectroscopy was used to study the interactions between 2-aminobenzothiazole (ABT) and natural organic matter in the presence of the natural enzyme laccase and synthetic air. Through the use of synthesized model compounds, we were able to confirm previous findings by CPMAS 13C NMR spectroscopy that showed the formation of covalent amide bonds. We also provide evidence of the presence of two additional H bonds between ABT and the natural organic matter. Both H bonds involved the amino and thiazole groups of ABT.
Amino Acid Contents of Infant Formulas
1999
Abstract The amino acid supply in an infant's first month of life must be sufficient in quantity and quality to fulfil the needs of this period of life. Guidelines, recommendations and minimum and maximum values have been established regarding to amino acid composition of infant formulas. The aim of this study was to determine the amino acid profile of infant formulas of different types marketed in Spain in order to assess the compliance with the recommendations (ESPGAN) and to detect possible differences in the amino acid profiles depending on the protein source. Amino acids were determined by HPLC in ion-pair reversed phase after hydrolysis and derivatization with phenylisothiocyanate. Ne…
Size Exclusion Chromatography of Proteins on Improved Bonded Silica Columns
1985
Publisher Summary This chapter discusses the size exclusion chromatography (SEC) of proteins on improved bonded silica columns. Over the past few years, the use of high performance liquid chromatography (HPLC) has been extended to protein chemistry as a powerful separation and isolation technique. A spectrum of variants providing high resolution potential—ion exchange, reversed phase, hydrophobic interaction, affinity, and size exclusion—is available. Of these, SEC is the simplest with respect to method development and equipment design: proteins are separated according to their size in a short and predictable time span under isocratic conditions. The SEC columns are packed with micro-partic…
New high-performance liquid chromatography-based methodology for monitoring the conformational transitions of self-associating hydrophobic peptides, …
1988
A new high-performance size-exclusion chromatographic strategy is reported for the analysis of the hydrophobic self-associating peptide gramicidin A, incorporated into artificial phospholipid vesicles (liposomes). The method is based on the direct injection of a few microlitres of the gramicidin A-containing liposome suspension into the column, which is eluted with a non-polar solvent, such as tetrahydrofuran. The type and amount of information which can be derived from this methodology have been evaluated. Using this chromatographic approach, a correlation has been unambiguously shown to exist between the organization of the peptide in the vesicles and a number of variables involved in the…
The effect of pre-heating on monomer elution from bulk-fill resin composites
2020
Background The present study was aimed to evaluate the effect of pre-heating of bulk -fill resin composites on monomer elution from them. Material and Methods Three different types of resin composites were used including Tetric N-Ceram Bulk Fill, X-tra Fill and X-tra Base. 10 cylindrical samples were prepared from each resin composites. Before light curing, 5 samples were pre-heated until reaching 68˚C, then 5 other samples were polymerized at room temperature. After 24 hours, release of UDMA, TEGDMA and BIS-GMA monomers were measured by High-Performance Liquid Chromatography analysis. Data analysis was performed by two-way ANOVA test, Games-Howell and Sidak post hoc tests. Results Pre-heat…
Impact of operation condition on temperature distribution in single cell of polymer electrolyte fuel cell operated at higher temperature than usual
2016
For improving performance of the stationary Polymer Electrolyte Fuel Cell (PEFC) system, the cell operating temperature up to 90°C will be preferred in Japan during the period from 2020 to 2030. To understand the operation of the PEFC system under relatively high temperature conditions, detail heat and mass transfer analysis is required. The main focus of this study is to analyze the PEFC performance under operational conditions, such as initial operational temperature of cell (Tini), relative humidity of supply gas, and the cathode gas type, temperature distribution in a cell of PEFC (using Nafion membrane) under relatively higher operating temperature conditions. The in-plane temperature …
Tomographic and Topographic Investigation of Poly-D,L-Lactide-Co-Glycolide Microspheres Loaded with Prostaglandine E<sub>2</sub> for Exte…
2010
Polymeric, biodegradable microspheres represent a good reliable system to investigate the release of bioactive substances in both in vitro and in vivo applications. Common biomaterials for the synthesis of these microspheres are aliphatic polyesters of the poly(α-hydroxy)acids, especially poly-L-lactides (PLA) and polyglycolides (PGA) or their copolymers poly-D,L-lactide-co-glycolides (PLGA). In our own previous studies we have developed PLGA microspheres with integrated PGE2 as model substance for a wide range of biomedical applications, especially in angiogenesis, fracture healing and cartilage repair. The synthesis is based on a binary solvent in water emulsion approach, where two differ…