|
| ||
|
|
||
Chromatography Techniques (chromatography + techniques)
Selected AbstractsPARTIAL PURIFICATION AND CHARACTERIZATION OF NEUTRAL TREHALASE FROM COMMERCIAL BAKER'S YEAST, SACCHAROMYCES CEREVISIAEJOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2000SANIYE YARAR ABSTRACT The neutral trehalase of a commercial baker's yeast (S. cerevisiae) strain has been partially purified using ammonium sidfate fractionation and DEAE-cellulose column chromatography techniques. Trehalase was precipitated between 35,50% ammonium sulfate saturation and approximately 5,8 fold purification was achieved. The yeast cAMP-dependent protein kinase was also precipitated in the same fraction and these two proteins were separated by DEAE-cellulose column chromatography. Trehalase became totally inactive after ion exchange chromatography, "cryptic trehalase" (tre-c), but was later activated with the addition of partially purified protem kinase together with cAMP and ATP. A 215 fold purification was obtained after DEAE-ceUulose column chromatography. One mM EDTA caused complete inhibition of the enzyme in crude extract, however the inhibition levels in ammonium sulfate and DEAE-cellulose fractions were 73.5% and 50%, respectively. Optimal pH range and temperature of the enzyme were determined as pH 6,6.8 and 30C, respectively. The kinetic parameters, Km and Vmax, were estimated as 11.78 mM trehalose and 12.47 ,mole glucose/min-mg protein, respectively. [source] An efficient synthetic route to well-defined theta-shaped copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2009Gang-Yin Shi Abstract A series of well-defined ,-shaped copolymers composed of polystyrene (PS) and poly(,-caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution have been successfully synthesized without any purification procedure by the combination of atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP), and the "click" chemistry. The synthetic process involves two steps: (1) synthesis of AB2 miktoarm star copolymers, which contain one PCL chain terminated with two acetylene groups and two PS chains with two azido groups at their one end, (,,,,-diacetylene-PCL) (,-azido-PS)2, by ROP, ATRP, and the terminal group transformation; (2) intramolecular cyclization of AB2 miktoarm star copolymers to produce well-defined pure ,-shaped copolymers using "click" chemistry under high dilution. The 1H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resultant intermediates and the target polymers. Their thermal behavior was investigated by DSC. The mobility decrease of PCL chain across PS ring in the theta-shaped copolymers restricts the crystallization ability of PCL segment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2620,2630, 2009 [source] Side-chain terpyridine polymers through atom transfer radical polymerization and their ruthenium complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2005Nikos P. Tzanetos Abstract Polymers containing side-chain terpyridine ligands of well-defined architectures and controllable molecular weights and molecular weight distributions are reported. These polymers were synthesized by the atom transfer radical polymerization (ATRP) of a newly synthesized terpyridine monomer with three functional initiators. The obtained polymers were characterized with 1H NMR and gel permeation chromatography techniques. The efficiency of the ATRP technique and the overall control of the molecular characteristics of the polymers were demonstrated by a kinetic study of the polymerization reaction. Subsequently, the ruthenium(III)/ruthenium(II) complexation chemistry was employed for the attachment of bis(dodecyloxy)-functionalized terpyridine moieties onto each side 2,2,:6,,2,-terpyridine unit of the main polymeric backbone. Thus, the grafting approach was successfully combined with the metal,ligand coordination chemistry for the preparation of highly soluble polymeric complexes. The resulting complexes were fully characterized by means of 1H NMR, gel permeation chromatography, and ultraviolet,visible spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4838,4848, 2005 [source] Effects of etomidate on free intracellular amino acid concentrations in polymorphonuclear leucocytes in vitroACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2000J. Mühling Background: Previous studies have shown the inhibitory effects of etomidate on polymorphonuclear leucocyte (PMN) function. No reports exist, however, regarding free intracellular amino acid metabolism, although physiological cell metabolism and basic cell functions rely upon a balanced intracellular amino acid content and the cell membrane-mediated separation of cellular amino acids from the extracellular plasma amino acid pool. Thus, in the current study, we evaluated the effects of etomidate on free intracellular amino acid metabolism in PMN. Methods: With ethics committee approval, blood was withdrawn from 35 healthy volunteers and incubated (1 h) either with 0 ,g/ml, 0.0156 ,g/ml, 0.0625 ,g/ml or 0.5 ,g/ml of etomidate as well as with its additives (propylene glycol and Lipofundin MCT® 10%). The PMN were separated using standardized Percoll® -gradient and centrifugation procedure before deep-freezing and lyophilization techniques were employed. All PMN samples were dissolved in methanol/H2O, and the concentrations of free intracellular amino acids were monitored using both novel advanced PMN-separation and high-performance liquid chromatography techniques. Results: Etomidate influenced important free amino acid profiles in PMN in a dose-dependent manner, indicating complex changes of cellular amino acid turnover. Neither propylene glycol nor Lipofundin MCT® 10% changed free amino acid concentrations in PMN. Conclusions: For the first time, the effects of etomidate on free intracellular amino acid metabolism in PMN have been investigated. Our results draw attention to the biochemical pathways which may be involved in etomidate-induced alterations in PMN function and cellular immunocompetence. [source] Unexpected Photolysis of the Sunscreen Octinoxate in the Presence of the Sunscreen Avobenzone,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Robert M. Sayre ABSTRACT A major concern raised about photostability studies of sunscreen products is that the photodegradation of sunscreens does not readily translate into changes in product performance. This study examines the correlation between photochemical degradation of sunscreen agents and changes in protection provided by sunscreen films. Films of a commercial sunscreen product containing avobenzone, oxybenzone and octinoxate were irradiated using a fluorescent UV-A phototherapy lamp with additional UV-B blocking filter. Periodically, during irradiation the transmittances of the films were measured and samples collected for chemical analysis of the sunscreen agents using high-performance liquid chromatography techniques. The results show that UV-induced changes in UV transmittance of sunscreen films correlate with changes in concentration of sunscreen agents. In a parallel experiment, we also irradiated a thin film of the same product in the cavity of an electron spin resonance (ESR) spectrometer. We report the concomitant photolysis of avobenzone and octinoxate that predominates over expected E/Z photoisomerization and that irradiation of a film of this product produced free radicals detected by ESR spectroscopy that persisted even after exposure had ended. [source] Application of electrochemically generated molybdenum-based catalyst system to the ring-opening metathesis polymerization of norbornene and a comparison with the tungsten analogueAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2005Okan Dereli Abstract This study describes the application of the electrochemically generated molybdenum-based catalyst system MoCl5e,AlCH2Cl2 to ring-opening metathesis polymerization of bicyclo[2.2.1]hept-2-ene (norbornene). The results are compared with those previously obtained by the WCl6e,AlCH2Cl2 system. The polymer product has been characterized by 1H and 13C NMR, IR and gel-permeation chromatography techniques. This molybdenum-based catalyst system has led to a mainly trans stereoconfiguration (ca 60%) of the double bonds, in contrast to the polymer obtained with the tungsten-based analogue, where the cis content is 60%. Analysis of the poly(1,3-cyclopentylenevinylene) microstructure by 13C NMR spectroscopy revealed that the polymer having ,c = 0.41 (fraction of double bonds with cis configuration) contains a slightly blocky distribution (rtrc > 1) of the double-bond dyads (rtrc = 1.44). In addition, the influence of reaction parameters, e.g. reaction time, electrolysis time and catalyst aging time, on conversion has been analysed in detail. Copyright © 2005 John Wiley & Sons, Ltd. [source] Purification, crystallization and preliminary X-ray analysis of urease from pigeon pea (Cajanus cajan)ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 7 2008Anuradha Balasubramanian Urease is a seed protein that is common to most Leguminosae. It also occurs in many bacteria, fungi and several species of yeast. Urease catalyzes the hydrolysis of urea to ammonia and carbon dioxide, thus allowing organisms to use exogenous and internally generated urea as a nitrogen source. Urease from pigeon pea seeds has been purified to electrophoretic homogeneity using a series of steps involving ammonium sulfate fractionation, acid precipitation, ion-exchange and size-exclusion chromatography techniques. The pigeon pea urease was crystallized and the resulting crystals diffracted to 2.5,Å resolution. The crystals belong to the rhombohedral space group R32, with unit-cell parameters a = b = 176.29, c = 346.44,Å. [source] | ||||||||||