Search results for "Titration"
showing 10 items of 312 documents
Supramolecular Assemblies Based on Complexes of Nonionic Amphiphilic Cyclodextrins and a meso-Tetra(4- sulfonatophenyl)porphine Tributyltin(IV) Deriv…
2013
Amphiphilic cyclodextrin (ACyD) provides water-soluble and adaptable nanovectors by modulating the balance between the hydrophobic and hydrophilic chains at both CyD sides. This work aimed to design nanoassemblies based on nonionic and hydrophilic ACyD (SC6OH) for the delivery of a poor-water-soluble organotin(IV)-porphyrin derivative [(Bu3Sn)4TPPS] to melanoma cancer cells. To characterize the porphyrin derivatives under simulated physiological conditions, a speciation was performed using complementary techniques. In aqueous solution (≤ 20 μM), (Bu3Sn)4TPPS primarily exists as a monomer (2 in Figure 1), as suggested by the low static anisotropy (ρ ≈ 0.02) with a negligible formation of por…
Heparin-Based Nanocapsules as Potential Drug Delivery Systems
2015
Herein, the synthesis and characterization of heparin-based nanocapsules (NCs) as potential drug delivery systems is described. For the synthesis of the heparin-based NCs, the versatile method of miniemulsion polymerization at the droplets interface was achieved resulting in narrowly distributed NCs with 180 nm in diameter. Scanning and transmission electron microscopy images showed clearly NC morphology. A highly negative charge density for the heparin-based NCs was determined by measuring the electro-kinetic potential. Measuring the activated clotting time demonstrated the biological intactness of the polymeric shell. The ability of heparin-based NCs to bind to antithrombin (AT III) was i…
Production and physicochemical characterization of a new amine derivative of gellan gum and rheological study of derived hydrogels
2020
The production of an amine derivative of gellan gum, named GG-EDA, was here obtained by functionalizing the polysaccharide backbone with pendant ethylenediamine moieties. The obtained derivative was characterized by spectroscopic, colorimetric, chromatographic and rheological analyses to study the effect of the free amino groups on the physicochemical properties of the macromolecule. A titration experiment was conducted to study the acid-base dissociation constants in aqueous media for the carboxylic and amino groups in the GG-EDA and to shed light on the possibility that the derivative shows a polyampholyte structure under physiological conditions. The rheological analysis conducted on bot…
ABC triblock polyampholytes containing a neutral hydrophobic block, a polyacid and a polybase
1997
Well defined ABC triblock copolymers of polystyrene-block-poly(2-vinylpyridine)-block-poly(tert-butyl methacrylate) and polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) were synthesized by sequential living anionic polymerization in tetrahydrofuran. Triblock copolymers with narrow molecular weight distribution were obtained. Hydrolysis of the poly(tert-butyl methacrylate) block yields polystyrene-block-polyvinylpyridine-block-poly(methacrylic acid) which demonstrates pH-dependent solution properties. Interpolymer complexation of the polyvinylpyridine and poly(methacrylic acid) blocks in the micellar solution is studied in dependence of the pH in solution by potent…
Analyse von Copolymeren aus Vinylestern und Acrylestern
1978
Die Copolymeren aus Vinyl- und Acrylestern werden in abgeschmolzenen Ampullen durch 2 M NaOH verseift. Die aus den Vinylester-Grundbausteinen gebildeten Sauren werden durch potentiometrische Titration bestimmt; liegen verschiedene Vinylester nebeneinander vor, so wird das Mengenverhaltnis der Sauren gaschromatographisch ermittelt. Die bei der Verseifung aus den Acrylester-Grundbausteinen entstehenden Alkohole werden gaschromatographisch identifiziert und gegen tert-Butanol als internen Standard quantitativ bestimmt. Ein besonderer Vorteil der Methode besteht darin, das auch wasrige Dispersionen ohne vorherige Abtrennung des Copolymeren eingesetzt werden konnen. The copolymers from vinyl est…
Thermodynamics of Surfactant, Block Copolymer and Their Mixtures in Water: The Role of the Isothermal Calorimetry
2009
The thermodynamics of conventional surfactants, block copolymers and their mixtures in water was described to the light of the enthalpy function. The two methodologies, i.e. the van't Hoff approach and the isothermal calorimetry, used to determine the enthalpy of micellization of pure surfactants and block copolymers were described. The van't Hoff method was critically discussed. The aqueous copolymer+surfactant mixtures were analyzed by means of the isothermal titration calorimetry and the enthalpy of transfer of the copolymer from the water to the aqueous surfactant solutions. Thermodynamic models were presented to show the procedure to extract straightforward molecular insights from the …
Synthesis and characterization of new polyamino-cyclodextrin materials.
2011
With the aim of the synthesis of chemically modified cyclodextrins bearing polyamine pendant groups, potentially useful as capping agents for the preparation of nanosized metal systems or as auxiliaries for gene transfection, the reaction between the heptakis-(6-iodo)-(6-deoxy)-b-cyclodextrin and various polyamines has been explored. This synthetic approach allows obtaining materials constituted by mixtures of cyclodextrins, having different degrees of substitution, which were satisfactorily characterized by means of various complementary techniques (ESI-MS, NMR, potentiometric titration). The products obtained were successfully subjected to preliminary tests for their binding abilities tow…
A hybrid catalyst for decontamination of organic pollutants based on a bifunctional dicopper(II) complex anchored over niobium oxyhydroxide
2017
Abstract This article describes the preparation and characterization of a hybrid oxidation catalyst for decontamination of organic pollutants which involves a bifunctional dicopper(II) complex and the niobium(V) oxyhydroxide as the active species, the later one being also a solid support. The pH range for the existence of the active species was determined by potentiometric and UV–vis spectroscopy at 25 °C and 0.15 M NaCl in a H 2 O/EtOH (70:30 v/v) solvent mixture containing copper(II) and the ligand N , N -2,2′-ethylenediphenylenebis(oxamic acid) (H 4 L). As far as the hybrid material is concerned, FTIR, FT-Raman, TEM and SEM images, surface area and TG/DTA analyses showed the occurrence o…
Examination of the least-squares method applied to the evaluation of physicochemical parameters with linearized equations
1989
Physicochemical parameters are frequently evaluated by the least-squares method after linearization of the equation which relates the experimental variables to the parameters of interest. When a given set of data is treated to evaluate (n+1) parameters. (n+2) nominally identical linearized equations are possible; each of these leads to different sets of values of the parameters which are also affected by different variances. These differences are also observed when statistical weights are used. Two methods for establishing which one of the (n+2) equations is best for fitting the data, i.e., simulation of experiments and propagation of errors, are discussed, compared and applied to a potenti…
Allosteric Models for Multimeric Proteins: Oxygen-Linked Effector Binding in Hemocyanin
2005
In many crustaceans, changing concentrations of several low molecular weight compounds modulates hemocyanin oxygen binding, resulting in lower or higher oxygen affinities of the pigment. The nonphysiological effector caffeine and the physiological modulator urate, the latter accumulating in the hemolymph of the lobster Homarus vulgaris during hypoxia, increase hemocyanin oxygen affinity and decrease cooperativity of oxygen binding. To derive a model that describes the mechanism of allosteric interaction between hemocyanin and oxygen in the presence of urate or caffeine, studies of oxygen, urate, and caffeine binding to hemocyanin were performed. Exposure of lobster hemocyanin to various pH …