1,721,096 research outputs found
Silica-supported epoxide hydrolase from Aspergillus niger: properties and application in the enantioselective hydrolysis of racemic para-nitrostyrene oxide
No full textCircular dichroism as a detection method for the analysis of chiral products from biocatalysis
No full textEnzymes in Poly(Butylene-Succinate) Industry: An Overview on Synthesis Routes and Post-Processing Strategies
Full text linkThis paper will present some sectors in which enzymes can replace traditional catalysts in
poly(butylene-succinate) industry, emphasizing the green chemistry aspects associated with
these newer strategies
A comprehensive study for the validation of a LC/MS/MS method for the determination of free and total forms of urinary cortisol and its metabolites
No full textSeveral pathological conditions can be related to the alteration of the urinary levels of cortisol (F) and itsmetabolites. The determination of each of them in the free and free plus conjugated form can provide adeeper insight into the impaired activity of the cortisol metabolism enzymes, thus improving the diag-nosis protocol currently based only on the determination of total amount of urinary cortisol metabolites.In that view, an LC–MS/MS method for the determination of the free and total amount of urinary F, cor-tisone (E), tetrahydrocortisol (THF), allo-tetrahydrocortisol (A-THF) and tetrahydrocortisone (THE) wasthus developed and validated. Deconjugation of glucocorticoids was carried out by enzymatic hydroly-sis. Analytes were extracted by solid phase extraction, separated by liquid chromatography and analyzedvia electro-spray ionization (negative ion mode) triple-quadrupole mass spectrometry in the selectedreaction monitoring mode using a stable isotope-labeled internal standard.Baseline separation for all compounds, in particular the two stereoisomers A-THF and THF, wasobtained. Matrix effects, not reported so far, were observed and minimized for the determination ofurinary free E and THE. Validated range was 0.5–1000 ng/mL for A-THF and THF, 5–800 ng/mL for E andTHE and 1–1000 ng/mL for F, with R2values greater than 0.9981. The LOD and LOQ of the describedmethod ranged from 0.1 to 3.0 ng/mL, while the extraction recoveries resulted close to 100% for all theglucocorticoids determined. Precision and accuracy were well within ±10%. As suggested by the resultsobtained in the preliminary study on polycystic ovary syndrome (PCOS) urine samples, the method canbe used to support clinical diagnosis of pathologies related to cortisol metabolism. In fact, levels of freeand total glucocorticoids in control subjects were in agreement with previously reported data, as well asfree and total A-THF/THF ratio in PCOS patients. Conversely, in the latter free F/E and A-THF + THF/THEratios were lower than in control subjects (P < 0.01), suggesting a possible alteration of 11-HSD1 and11-HSD2 activity, to be further investigated
Heterogeneous Enantioselective Dihydroxylation of Alkenes by Osmium Tetroxide-Cinchona Alkaloid Complexes Supported on Polymeric Matrices
No full textCircular dichroism based detection system in HPLC: on line circular dichroism in analysis
No full textCovalent immobilization of chloroperoxidase on silica gel and properties of the immobilized biocatalyst
No full textImmobilization of chloroperoxidase (CPO) isolated from the mold Caldariomyces fumago on silica gel was performed. The support was derivatized with 3-glycidoxypropyltrimethoxysilane by using a reported method and the enzyme was covalently bound via reaction with epoxide groups under mild conditions. The enzyme was still active after the immobilization process. No leaching of the enzyme from the support was detectable after repeated washings. The halogenation reaction catalysed by the immobilized enzyme in buffer was compared to that catalysed by the free enzyme. The immobilization of CPO enhanced the stability of the enzyme with respect to the effect of pH and oxidizing agent concentration
In Defence of the Catalytic Asymmetric cis Dihydroxylation of Olefins Utilizing Insoluble Polymeric Ligands
No full textIn Defense of the Catalytic Asymmetric Cis
Dihydroxylation of Olefins Utilizing Insoluble
Polymeric Ligand
Silica-supported epoxide hydrolase from Aspergillus niger; a new biocatalyst for the enantioselective hydrolysis of epoxide
No full textInsoluble polymer-bound (IPB) approach to the catalytic asymmetric dihydroxylation of alkenes
No full textAsymmetric dihydroxylation induced by Insoluble Polymer-Bound (IPB approach) Cinchona alkaloid derivatives is reviewed. Reactivities and enantioselectivities comparable to those achieved with the soluble counterparts are obtained with polymers having structural properties compatible with the reaction conditions. By using a highly efficient polymer, olefins with different structures can be dihydroxylated at a synthetically useful level of enantioselectivity. Handling and recovery of the catalyst is very easy; recycling is performed with a small amount of metal
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