Search results for "Kinetic"
showing 10 items of 3064 documents
Micellar electrokinetic chromatography of polyamines and monoacetylpolyamines
2001
A selective procedure for qualitative and quantitative analysis of ten polyamines by micellar electrokinetic chromatography (MEKC) was developed. Benzoylated polyamines and acetylpolyamines in micellar phase of SDS (10 mM) were separated at 25 degrees C by 20 mM borate buffer pH 8.5, containing 8% ethanol, with an applied voltage of 25 kV (5 microA) and then detected at 198 nm. The experimental factors and operational parameters were optimized by performing analysis at different surfactant concentrations, pH, voltage and temperature with and without ethanol. The repeatibility of migration times and peak heights is a peculiarity of the method here described.
Effect of ethanol on membrane fluidity of protoplasts fromSaccharomyces cerevisiae andKloeckera apiculata grown with or without ethanol, measured by …
1994
Direct measurements of membrane fluidity by fluorescence anisotropy of protoplasts fromKloeckera apiculata andSaccharomyces cerevisiae, a low and a high ethanol tolerant strain respectively, are presented. The comparison of the behaviour of the two strains grown with or without ethanol enabled us to demonstrate the existing relationship between ethanol tolerance and membrane fluidity.
An ethoxylated surfactant enhances the penetration of the sulfated laminarin through leaf cuticle and stomata, leading to increased induced resistanc…
2016
International audience; Some β-1,3-glucans and particularly sulfated laminarin (PS3) are known as resistance inducers (RIs) in grapevine against the downy mildew. However, their efficacy in vineyard is still often too low, which might be caused by a limited penetration through the leaf cuticle following spray application. We used (14) C-sucrose uptake experiments with grapevine leaves in order to select a surfactant as saccharide penetration enhancer. Our results showed that though sucrose foliar uptake was low, it was strongly enhanced by Dehscofix CO125 (DE), a highly ethoxylated surfactant. Fluorescent saccharides were then produced and laser scanning microscopy was used to analyze their…
Evidence of chloroethylene oxide being the reactive metabolite of vinyl chloride towards DNA: comparative studies with 2,2′ -dichloro-diethylether
1983
The roles of chloroethylene oxide (CEO) and chloroacetaldehyde (CAA) in carcinogenicity of vinyl chloride (VC) have been studied by comparing biological effects of VC exposure with those of 2,2'-dichlorodiethylether (bis(chloroethyl)ether, BCEE) as a metabolic precursor of CAA. Biological end-points investigated were covalent protein binding, nucleic acid (RNA and DNA) alkylation and the potency of the two chemicals to induce preneoplastic ATPase-deficient foci in rat liver. After exposure of rats to [1-14C]BCEE, BCEE derived radioactivity was bound to liver proteins. Analysis of hydrolysates of liver RNA and DNA gave no indication for the formation of either 7-N-(2-oxoethyl)guanine, 1,N6-e…
“Dumb” pH-Independent and Biocompatible Hydrogels Formed by Copolymers of Long-Chain Alkyl Glycidyl Ethers and Ethylene Oxide
2020
The formation and rheological properties of hydrogels based on amphiphilic ABA triblock polyether copolymers are described, relying solely on the hydrophobic interaction of long-chain alkyl glycidyl ether (AlkGE)- based A-blocks that are combined with a hydrophilic poly(ethylene glycol) (PEG) midblock. Via anionic ring-opening copolymerization (AROP), ethylene oxide (EO) and long-chain alkyl glycidyl ethers (AlkGEs) were copolymerized, using deprotonated poly(ethylene glycol) (PEG) macroinitiators (Mn of 10, 20 kg mol-1). The polymerization afforded amphiphilic ABA triblock copolymers with molar masses in the range of 21-32 kg mol-1 and dispersities (Đ) of Đ = 1.07-1.17. Kinetic studies rev…
Reactions at Interfaces: Oxygenation of n-Butyl Ligands Anchored on Silica Surfaces with Methyl(trifluoromethyl)dioxirane
2011
The oxygenation of n-butyl and n-butoxy chains bonded to silica with methyl(trifluoromethyl)dioxirane (1) revealed the ability of the silica matrix to release electron density toward the reacting C(2)-H σ-bond through the Si-C(1) and Si-O(1) σ-bonds connecting the alkyl chain to the surface (silicon β-effect). The silica surface impedes neither the alkyl chain adopting the conformation required for the silicon β-effect nor dioxirane 1 approaching the reactive C(2) methylene group. Reaction regioselectivity is insensitive to changes in the solvation of the reacting system, the location of organic ligands on the silica surface, and the H-bonding character of the silica surface. Reaction rates…
Sol–gel material as a support of organometallic catalyst for ethylene polymerization
2008
Abstract The sol–gel procedure was applied to obtain powdery materials with different structures and morphology. It was possible to produce almost non-porous silica powder, with an extremely low surface area (ca. 4 m 2 /g) and very high uniformity of spherical particles as well as materials with various uniformity of particles and different porosity, most likely associated with increasing pore volume. Dependent on the properties of the carrier, the resulting supported vanadium catalysts (VOCl 3 /AlEt 2 Cl) showed significant differences concerning activity and stability. It was confirmed that improved hydrophobicity of the carrier’s surface may be useful and improve the activity of the syst…
Competition between α and γ phases in isotactic polypropylene: effects of ethylene content and nucleating agents at different cooling rates
2001
Abstract The influence of ethylene content, nucleating agents and cooling rate upon the formation of γ phase in isotactic polypropylene is investigated. Detailed analysis of wide angle X-ray diffraction shows that some γ phase can appear even in copolymers of very low ethylene content (0.5 mol.%). Differential scanning calorimetry shows a double melting peak. Nucleating agents of different types are found to enhance γ phase crystallization, even in high molecular weight homopolymers. In any of the materials studied the amount of γ phase decreases with increasing cooling rate, going to zero at a cooling rate of about 10°C s−1. We interpret the observations in terms of the kinetics of growth …
Elimination kinetics of synthetic interferon inducer tilorone in experimental animals
2017
Objective. A comparative investigation was carried out on the kinetics of [3H]-tilorone ([3H]-I) excretion in rats and mice. Materials and method. Kinetics of urinary and biliary excretion of [3H]-I in rats and mice was studied following a single oral and intravenous administration. The excretion mass balance was monitored in the faeces and urine of rats and mice for 5 and 10 days, respectively. Radioactivity was determined in the samples of excreta using a liquid scintillation counter. Results. In rats, [3H]-I were nearly fully (~80%) eliminated with excreta in 5 days, indicating a lack of any significant accumulation of the drug in the body. Faecal excretion of tilorone predominated (69.0…
Control of Enzymic Hydrolysis of Polyadenylate Segment of Messenger RNA: Role of Polyadenylate-Associated Proteins
1978
The role of poly(A)-associated proteins in the breakdown of poly(A) sequences in both mammalian polyribosomes and in isolated poly(A) · protein complexes has been studied on an enzymic level. Two nucleases (alkaline exoribonuclease and endoribonuclease IV; both isolated from eukaryotic tissue), which preferentially hydrolyze poly(A) sequences, have been applied to determine the susceptibility of poly(A) in dependence on the presence of poly(A) · protein(s). Polysomes, isolated from L5178y mouse lymphoma cells, do not contain endogenous poly(A) nuclease activity. The poly(A) segment in polysomes is hydrolyzed by the exoribonuclease, irrespective of the preincubation conditions used. Pretreat…