Search results for "acids"

THERMO-CATALYTIC PROCESSES FOR BIOFUEL PRODUCTION

2017

Multilayer capsules: a promising microencapsulation system for transplantation of pancreatic islets

2001

In 1980, Lim and Sun introduced a microcapsule coated with an alginate/polylysine complex for encapsulation of pancreatic islets. Characteristic to this type of capsule is, that it consists of a plain membrane which is formed during a single procedural step. With such a simple process it is difficult to obtain instantly a membrane optimized with respect to all the properties requested for islet transplantation. To overcome these difficulties, it is recommended to build up the membrane in several consecutive steps, each optimized for a certain property. In this study, we have analysed such a multilayer microcapsule for the encapsulation of pancreatic islets. Therefore, empty and islet contai…

Occurrence of DBPs in Drinking Water of European Regions for Epidemiology Studies

2016

International audience; A three-year study was conducted on the occurrence of disinfection by-products (DBPs) - trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitriles - in drinking water of regions of Europe where epidemiology studies were being carried out. Thirteen systems in six countries (i.e., Italy, France, Greece, Lithuania, Spain, United Kingdom) were sampled. Typically chlorinated DBPs dominated. However, in most of Catalonia (Spain) and in Heraklion (Greece), brominated DBPs dominated. The degree of bromine incorporation into the DBP classes was in general similar among them. This is important, as brominated DBPs are a greater health concern. In parts of Catalonia,…

Enantioselective Synthesis of 5-Trifluoromethyl-2-oxazolines under Dual Silver/Organocatalysis.

2019

[EN] The first enantioselective formal [3 + 2] cycloaddition between ¿-isocyanoesters and trifluoromethylketones to give 5-trifluoromethyl-2-oxazolines bearing two contiguous stereogenic centers, one of them being a quaternary stereocenter substituted with a CF3 group, has been developed. The reaction is based upon a multicatalytic approach that combines a bifunctional Brønsted base-squaramide organocatalyst and Ag+ as Lewis acid. The reaction could be achieved with a range of aryl and heteroaryl trifluoromethyl ketones, and the resulting oxazolines were obtained with good to excellent diastereo- and enantioselectivity.

The (2-phenyl-2-trimethylsilyl)ethyl-(PTMSEL)-linker in the synthesis of glycopeptide partial structures of complex cell surface glycoproteins.

2003

The (2-phenyl-2-trimethylsilyl)ethyl-(PTMSEL) linker represents a novel fluoride-sensitive anchor for the solid-phase synthesis of protected peptides and glycopeptides. Its cleavage is achieved under almost neutral conditions using tetrabutylammonium fluoride trihydrate in dichloromethane thus allowing the construction of complex molecules sensitive to basic and acidic media commonly required for the cleavage of standard linker systems. The advantages of the PTMSEL linker are demonstrated in the synthesis of glycopeptides from the liver intestine (LI)-cadherin and the mucin MUC1, bearing carbohydrate moieties such as N-linked chitobiose or O-linked sialyl-T(N)-residues. The synthesis of the…

Effect of Chlorotriphenyl Derivatives of Sn and Pb upon Biophysical Properties of Membranes

2009

Biophysical activity of two twin organometallic compounds Triphenyltin chloride (TPhT) and Triphenyllead chloride (TPhL) in their interreaction with model membranes, as well as with yeast cellsSaccharomyces cerevisiae, was investigated. Four measurement methods were used in the experiments: two physical methods (spin probes method and the electric method); two biological methods (minimal inhibitory concentration /MIC/ and yeast survival test). It has been found that the activity of TPhT in interaction with model membranes and yeast cells is distinctly greater than that of TPhL. The activity manifests itself by considerable increase in the fluidity of the middle part of liposome bilayer, cha…

Rapid determination of sterols in vegetable oils by CEC using methacrylate ester-based monolithic columns

2008

A method for the determination of sterols in vegetable oils by CEC with UV-Vis detection, using methacrylate ester-based monolithic columns, has been developed. To prepare the columns, polymerization mixtures containing monomers of different hydrophobicities were tried. The influence of composition of polymerization mixture was optimized in terms of porogenic solvent, monomers/porogens and monomer/crosslinker ratios. The composition of the mobile phase was also studied. The optimum monolith was obtained with lauryl methacrylate monomer at 60:40% (wt:wt) lauryl methacrylate/ethylene dimethacrylate ratio and 60 wt% porogens with 20 wt% of 1,4-butanediol (12 wt% 1,4-butanediol in the polymeriz…

Capillary Electrophoresis of Free Fatty Acids by Indirect Ultraviolet Detection: Application to the Classification of Vegetable Oils According to The…

2011

A method for the determination of fatty acids in vegetable oils by capillary electrophoresis with indirect UV–vis detection has been developed. The separation of fatty acids was optimized in terms of Brij surfactant nature and concentration and organic modifier (2-propanol) percentage. The optimal background electrolyte consisted of 10 mM p-hydroxybenzoate, 5 mM Tris at pH 8.8, 80 mM Brij 98, 40% acetonitrile, and 10% 2-propanol. Under these conditions, vegetable oils from five botanical origins (avocado, corn, extra virgin olive, hazelnut, and soybean) were analyzed and the fatty acid contents established. Linear discriminant analysis (LDA) models were constructed using fatty acid peak are…

Synthesis, Characterization, and Properties of Weakly Coordinating Anions Based on tris-Perfluoro-tert-Butoxyborane

2017

A convenient method for the preparation of strongly Lewis acidic tris-perfluoro-tert-butoxyborane B(ORF)3 (1), (ORF = OC(CF3)3) was developed, and its X-ray structure was determined. 1 was used as a precursor, guided by density functional theory (DFT) calculations and volume-based thermodynamics, for the synthesis of [NEt4][NCB(ORF)3] (3) and [NMe4][FB(ORF)3] (5) and the novel large and weakly coordinating anion salts [Li 15-Crown-5][B(ORF)4] (2) and [NEt4][CN{B(ORF)3}2] (4). The stability of [B(ORF)4]− was compared with that of some related known weakly coordinating anions by appropriate DFT calculations.

Acidic Environment Leads to ROS-Induced MAPK Signaling in Cancer Cells

2011

Tumor micromilieu often shows pronounced acidosis forcing cells to adapt their phenotype towards enhanced tumorigenesis induced by altered cellular signalling and transcriptional regulation. In the presents study mechanisms and potential consequences of the crosstalk between extra- and intracellular pH (pH(e), pH(i)) and mitogen-activated-protein-kinases (ERK1/2, p38) was analyzed. Data were obtained mainly in AT1 R-3327 prostate carcinoma cells, but the principle importance was confirmed in 5 other cell types. Extracellular acidosis leads to a rapid and sustained decrease of pH(i) in parallel to p38 phosphorylation in all cell types and to ERK1/2 phosphorylation in 3 of 6 cell types. Furth…