Search results for " stability."
showing 10 items of 1315 documents
Binding properties of mono-(6-deoxy-6-amino)-β-cyclodextrin towards p-nitroaniline derivatives: a polarimetric study
2009
Abstract Polarimetry was used in order to investigate the formation of supramolecular complexes between mono-6-amino-β-cyclodextrin and various p-nitroaniline derivatives at two different pH values. Comparison with the behaviour of native β-cyclodextrin gave us the opportunity to consider the effect exerted by the presence of charged groups, having different solvation requirements, on the binding equilibrium. Data offer some support to the hypothesis of ‘dynamic co-inclusion’ of solvent molecules within the host–guest complex.
Computational Study of Nanosized Drug Delivery from Cyclodextrins, Crown Ethers and Hyaluronan in Pharmaceutical Formulations
2015
Abstract The problem in this work is the computational characterization of cyclodextrins, crown ethers and hyaluronan (HA) as hosts of inclusion complexes for nanosized drug delivery vehicles in pharmaceutical formulations. The difficulty is addressed through a computational study of some thermodynamic, geometric and topological properties of the hosts. The calculated properties of oligosaccharides of D-glucopyranoses allow these to act as co-solvents of polyanions in water. In crown ethers, the central channel is computed. Mucoadhesive polymer HA in formulations releases drugs in mucosas. Geometric, topological and fractal analyses are carried out with code TOPO. Reference calculations are…
Thermal, glass-forming, nonlinear optical and holographic properties of "push-pull" type azochromophores with triphenyl moieties containing isophoren…
2013
Molecular organic compounds with electron donating fragment bounded through π-conjugated system with electron acceptor fragment, as well as with incorporated triphenyl groups in their molecules show potential for creating cheap and simple solution processable materials with nonlinear optical properties. Additional insertion of azobenzene fragment in their structures makes them also possible to form holographic volume and surface relief gratings (SRG) after exposure to laser radiation, which could be useful for holographic data storage. For these purposes polymers are generally used. However, their application is complicated and challenging task as in every attempt to obtain the same polymer…
Degradation Behavior of Nanocomposite Polymer Blends
2014
The usefulness of any material, including nanocomposite polymer blends, depends on its degradability and durability. Thus, this chapter reviews the status of the research on degradation of nanocomposite polymer blends and, in particular, on clay-nanocomposite polymer blends, paying particular attention to both the role of the filler and the role of the blend morphology and composition. The results of recent research indicate that the clay has two opposing effects on the thermal stability of a nanocomposite polymer blend: (1) a promoter effect of the polymer matrix degradation, which decreases the thermal stability, and (2) a barrier effect, which improves the thermal stability. Moreover, th…
Biochemical characterization of two functional human liver acyl-CoA oxidase isoforms 1a and 1b encoded by a single gene
2007
Abstract Human acyl-CoA oxidase 1 (ACOX1) is a rate-limiting enzyme in peroxisomal fatty acids β-oxidation and its deficiency is associated with a lethal, autosomal recessive disease, called pseudoneonatal-adrenoleukodystrophy. Two mRNA variants, transcribed from a single gene encode ACOX1a or ACOX1b isoforms, respectively. Recently, a mutation in a splice site has been reported [H. Rosewich, H.R. Waterham, R.J. Wanders, S. Ferdinandusse, M. Henneke, D. Hunneman, J. Gartner, Pitfall in metabolic screening in a patient with fatal peroxisomal β-oxidation defect, Neuropediatrics 37 (2006) 95–98.], which results in the defective peroxisomal fatty acids β-oxidation. Here, we show that these mRNA…
Transport of amino acids through liquid membranes supported on novel poly(vinylidenefluoride) porous flat-sheet matrix
1997
Flat-sheet membranes from poly(vinylidenefluoride) (PVDF) were prepared by the phase inversion process. LiCl was used as a modifying agent. The porosity, maximum pore size and LEPW (liquid entry pressure of water) were determined. Three types of these membranes were tested as a support for n-decanol supported liquid membranes (SLM). Transport of eight amino acids, selected to cover a wide variety of side chains, and of phenylalanine methyl ester through n-decanol SLM were studied. The ability of amino acids to permeates through these membranes depends on the type of flat-sheet PVDF used as a support. An increase in porosity and pore size of the microporous matrix resulted in an increase of …
Insights into the Formation and Structures of Molecular Gels by Diimidazolium Salt Gelators in Ionic Liquids or “Normal” Solvents
2016
Insights are provided into the properties of molecular gels formed by diimidazolium salts both in “normal” solvents and ionic liquids. These materials can be interesting for applications in green and sustainable chemistry in which ionic liquids play a significant role, like catalysis and energy. In particular, two positional isomers of a diimidazolium cation have been examined with a wide range of anions for their ability to form gel phases. In particular, di-, tri-, and tetravalent anions bearing aliphatic or aromatic spacers were paired with the divalent cations. The properties of the organo- and ionogels formed have been analyzed by means of several different techniques, including calori…
Kinetic properties of a nucleoside phosphotransferase of chick embryo
1981
1. A nonspecific nucleoside phosphotransferase (nucleotide : 3'-deoxynucleotide 5'-phosphotransferase, EC 2.7.1.77), purified from chick embryos, catalyzes the transfer of phosphate ester from a nucleotide donor to a nucleoside acceptor. 2. The enzyme exhibits sigmoidal kinetics with respect to nucleoside monophosphate donors, but with respect to nucleoside di- or triphosphate donors and nucleoside acceptors hyperbolic kinetics were obtained. 3. The nucleoside phosphotransferase of chick embryo is unstable to heat and is protected from inactivation by a large number of nucleosides. 4. Nucleoside di- and triphosphates lower both the concentration of nucleoside monophosphates required for hal…
Effect of Heating Time and Temperature on the Chemical Characteristics of Biochar from Poultry Manure
2014
Poultry manure (PM) chars were obtained at different temperatures and charring times. Chemical-physical characterization of the different PM chars was conducted by cross-polarization magic angle spinning (CPMAS) (13)C NMR spectroscopy and thermal analysis. CPMAS (13)C NMR spectra showed that the chemical composition of PM char is dependent on production temperature rather than on production duration. Aromatic and alkyl domains in the PM chars obtained at the lowest temperatures remained unchanged at all heating times applied for their production. The PM char obtained at the highest temperature consisted only of aromatic structures having chemical nature that also appeared invariant with hea…
Calculation of the molecular masses of two newly synthesized thermostable enzymes isolated from thermophilic microorganisms
1995
Two thermostable enzymes synthesized by thermophilic microorganisms were isolated and purified. A thermostable beta-galactosidase was produced in a continuous fermentation process by Bacillus stearothermophilus TP 32 as an intracellular enzyme. After applying different concentration procedures the raw extract enzyme was prepurified on a Sephadex G-200 size exclusion column. The isolated beta-galactosidase fraction was then separated with HPLC on a TSK G 3000 SW size exclusion column to determine the molecular mass based on calibration curves of standard proteins. The other enzyme, a thermostable protease, was synthesized by Bacillus stearothermophilus TP 26 as an extracellular enzyme. After…