Search results for "Reagent"
showing 10 items of 699 documents
Synthesis of a polymer-bound galactosylamine and its application as an immobilized chiral auxiliary in stereoselective syntheses of piperidine and am…
2004
A 2,3,4-tri-O-pivaloylated beta-D-galactopyranosyl azide bearing a hydroxy-functionalized spacer unit at the C-6 position of the galactose was synthesized and immobilized on the solid phase by using a polymer-bound chlorosilane. The azide was reduced to the corresponding galactopyranosylamine, which served as a versatile chiral auxiliary in highly diastereoselective Ugi four-component condensation reactions at ambient temperature. Fluoride-induced cleavage from the polymeric support furnished N-glycosylated N-acylated alpha-amino acid amides. The reaction of the immobilized galactosylamine with aldehydes gave rise to the corresponding aldimines, which underwent a domino Mannich-Michael cond…
Synthesis of Soluble Donor-Acceptor Double-Cable polymers based on polythiophene and tetracyanoanthraquinodimethane (TCAQ).
2003
[structure: see text] Novel suitably functionalized tetracyanoanthraquinodimethane (TCAQ) derivatives covalently linked to thiophene moieties have been synthesized. The thiophene-based monomers have been chemically polymerized and copolymerized to yield new and soluble donor-acceptor double-cable polymers. The absorption and emission data reveal that the optical properties can be finely tuned by modifying the ratio of monomers in the copolymerization process.
Melatonin: Structural characterization of its non-enzymatic mono-oxygenate metabolite
2003
Oxidation of melatonin by Fenton reagents as well as with hypochlorous acid or oxoferryl hemoglobin has been investigated. Analysis of products by low resolution/mass spectra (MS), high resolution/MS, 1H-nuclear magnetic resonance (NMR), 13C-NMR, correlated spectroscopy (COSY) and heterocorrelated spectroscopy (HETCOR) 2D NMR reveals the formation of a single mono-oxygenated product under all conditions and unequivocally assigns the N-[2-(5-methoxy-2-oxo-2,3-dihydro-1H-indol-3-yl)-ethyl]-acetamide structure, which had not been previously considered.
Synthesis and evaluation of 2-tosylamino and 2-tosyliminopyrimidine derivatives as inhibitors of some leukocyte functions
2003
Abstract We have studied the potential anti-inflammatory effects of 20 2-tosylamino and 2-tosyliminopyrimidine new derivatives in human neutrophils. We have evaluated their interference with some leukocyte functions and 5-lipoxygenase activity. All the compounds reduced neutrophil degranulation process at concentrations in the μM range. Besides, compounds with a phenolic substitution inhibited leukotriene B 4 biosynthesis in neutrophils and decreased the cell-free 5-lipoxygenase activity. This study demonstrates that 2-tosylamino and 2-tosyliminopyrimidine derivatives can reduce the activation of neutrophil cells which may have relevance for the modulation of the inflammatory response.
Synthesis and antileukemic activity of new 3-(1-phenyl-3-methylpyrazol-5-yl)-2-styrylquinazolin-4(3H)-ones.
2004
Abstract 3-(1-Phenyl-3-methylpyrazol-5-yl)-2-styrylquinazolin-4(3H)-ones 14a–q and 15a–q were synthesized by refluxing in acetic acid the corresponding 2-methylquinazolinones 12 and 13 with the opportune benzoic aldehyde for 12 h. The synthesized styrylquinazolinones 14a–q and 15a–q were tested in vitro for their antileukemic activity against L1210 (murine leukemia), K562 (human chronic myelogenous leukemia) and HL60 (human leukemia) cell lines showing in some cases good activity.
Disulfide-crosslinked hyaluronan-gelatin hydrogel films: a covalent mimic of the extracellular matrix for in vitro cell growth
2003
A new disulfide crosslinking method was developed for the preparation of blended hyaluronan (HA)-gelatin hydrogels to form a synthetic, covalently linked mimic of the extracellular matrix (ECM). The HA and gelatin were chemically modified using 3,3′-dithiobis(propionic hydrazide) (DTP). After reduction with dithiothreitol (DTT), the thiol derivatives of HA (HA-DTPH) and gelatin (gelatin-DTPH) were obtained and characterized. To minimize interference with biological function, the degree of substitution of HA-DTPH and gelatin-DTPH was kept below 50%. Solutions of HA-DTPH and gelatin-DTPH in varying blends (20%, 40%, 60%, 80% gelatin) were prepared in 1% w/v NaCl and crosslinked by disulfide b…
Self-assembling and auto-crosslinkable hyaluronic acid hydrogels with a fibrillar structure
2008
Abstract A hyaluronic acid derivative bearing pendant l -benzoyl-cysteine portions (with a derivatization degree equal to 10 mol.%) was synthesized by linking N,N′-dibenzoyl- l -cystine to the polysaccharide and then reducing its disulfide bridge to thiol groups. The formation of π–π stacking interactions between the benzoyl moieties was studied by fluorescence spectroscopy as a function of polymer concentration and oxidation time. The efficiency of oxidation of thiol groups to disulfide bridges occurring in phosphate buffer pH 7.4, was determined by colorimetric assays. The hydrogel formed by means of oxidative crosslinking has shown the presence of fibrillar aggregates as detected by ligh…
Epstein-Barr virus DNA load kinetics analysis in allogeneic hematopoietic stem cell transplant recipients: Is it of any clinical usefulness?
2017
Abstract Background There is a lack of clinical information regarding the usefulness of plasma Epstein-Barr virus (EBV) DNA load kinetics analyses in the management of EBV infections in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Namely, it remains unknown whether this type of analysis can help physicians to anticipate the development of high-level EBV DNAemia episodes requiring rituximab treatment or predict the risk of recurrent EBV DNAemia or post-transplant lymphoproliferative disorders (PTLDs). Study design Unicentric, retrospective, observational study including 142 consecutive patients undergoing T-cell replete allo-HSCT. The plasma EBV DNA load was mon…
Effect of Riboflavin/UVA Collagen Cross-linking on Central Cornea, Limbus and Intraocular Pressure. Experimental Study in Rabbit Eyes
2016
The Purpose of present study was to investigate the effect of riboflavin/ultraviolet-A-induced collagen cross-linking (CXL) on central cornea, limbus and intraocular pressure (IOP). This was an animal experimental study. The right corneas of 10 rabbits were ultraviolet-A irradiated (3 mW/cm2 for 30 minutes) after de-epithelialization and instillation of 0.1% riboflavin / 20% Dextran drops. Left corneas served as controls. Samples were examined histologically one month postoperatively. Before and after treatment, IOP measurements were recorded bilaterally. At central cornea of eyes underwent CXL keratocyte repopulation, normal arrangement of collagen fibres and a statistically significant ch…
Influence of sample return time and ambient temperature on the performance of an immunochemical faecal occult blood test with a new buffer for colore…
2016
IF 2.415; International audience; The haemoglobin concentration measured by faecal immunochemical tests (FIT) may be decreased in cases of delayed sample return or high temperature. It is an issue of great importance. The aim of this study was to investigate the effects of sample return time and of season on the performance of an FIT (FOB-Gold) with a new buffer. The study included 20 371 participants involved in the French organized colorectal cancer (CRC) screening programme. The probability of a positive screening test, detection rates and positive predictive values for CRC and advanced adenoma were analysed according to sample return time and season of screening. A sample of positive FI…