Search results for "kinetics"

Die oxydation von polyepoxiden mit molekularem sauerstoff

1966

Polypropylenoxid, Polybutylen-1-oxid und Polystyroloxid wurden dargestellt und mit Hilfe von Losungsmitteln in verschiedene taktische Fraktionen getrennt. Diese Fraktionen und Polyathylenoxide mit verschiedenem Molekulargewicht wurden in Substanz autoxydiert und die fluchtigen Reaktionsprodukte gaschromatographisch identifiziert. Die Autoxydation dieser Polymeren in Losung wurde durch Messung der Sauerstoffaufnahme verfolgt. Die Bruttoaktivierungsenergien der taktischen Fraktionen der Polymeren sind groser als die der ataktischen Fraktionen. Die Kinetik der Autoxydation des Polybutylen-1-oxides wurde aufgeklart. Polypropyleneoxide, polybutene-1-oxide, and polystyreneoxide were prepared and …

3'-Arylazido-beta-alanyl-2-azido ATP, a cross-linking photoaffinity label for F1ATPases.

1989

Abstract The synthesis of the 3′-arylazido-2-azido ATP derivative 3′-O-{3-[N-(4-azido-2-nitrophenyl)-amino]propionyl}2-azido-adenosine 5′-triphosphate (2,3′-DiN3ATP) is described. The bifunc­ tional photoreactive ATP analog is characterized spectroscopically. Photoaffinity labeling of F, ATPase from Micrococcus luteus by this analog results in the inactivation of the enzyme and in the formation of higher molecular weight cross-links,

Proteolytic cleavage of soybean Bowman-Birk inhibitor monitored by means of high-performance capillary electrophoresis. Implications for the mechanis…

1996

The hydrolysis of the soybean Bowman-Birk inhibitor in the presence of catalytic amounts of bovine trypsin and the formation of the non-covalent enzyme-inhibitor complex with an equimolar amount of enzyme are monitored by means of high-performance capillary electrophoresis (HPCE). The inhibitor is cleaved in the trypsin-reactive and more slowly in the chymotrypsin-reactive subdomain. HPCE proves itself as the only reliable analytical tool to monitor these reactions in clear contrast to classical electrophoretic, chromatographic and enzymatic methods. The most efficient separation of the intact and the two active site cleaved forms of the inhibitor was achieved in borate buffer at pH 10.0. T…

Biophysical approaches for the study of metal-protein interactions

2019

Protein-protein interactions play important roles for a variety of cell functions, often involving metal ions; in fact, metal-ion binding mediates and regulates the activity of a wide range of biomolecules. Enlightening all of the specific features of metal-protein and metal-mediated protein-protein interactions can be a very challenging task; a detailed knowledge of the thermodynamic and spectroscopic parameters and the structural changes of the protein is normally required. For this purpose, many experimental techniques are employed, embracing all fields of Analytical and Bioinorganic Chemistry. In addition, the use of peptide models, reproducing the primary sequence of the metal-binding …

2003

Resting cells of the yeast Rhodosporidium toruloides (UOFS Y-0471) were immobilised in calcium alginate beads for the enantioselective kinetic resolution of racemic-1,2-epoxyoctane. The initial activity exhibited by immobilised cells was almost 50% lower than that of the free counterpart but was extremely stable when compared to the free cells. The concentration of the immobilised biomass had no effect on apparent enzyme activity but did lead to a decrease in single cell activity. An increase in both the alginate and CaCl2 concentrations used for bead preparation led to a decrease in enzyme stability. An increase in the alginate concentration led to an increase in bead diameter. The stoichi…

On the applicability of [18F]FBPA to predict L-BPA concentration after amino acid preloading in HuH-7 liver tumor model and the implication for liver…

2017

Abstract Introduction In recent years extra-corporal application of boron neutron capture therapy (BNCT) was evaluated for liver primary tumors or liver metastases. A prerequisite for such a high-risk procedure is proof of preferential delivery and high uptake of a 10 B-pharmaceutical in liver malignancies. In this work we evaluated in a preclinical tumor model if [ 18 F]FBPA tissue distribution measured with PET is able to predict the tissue distribution of [ 10 B]L-BPA. Methods Tumor bearing mice (hepatocellular carcinoma cell line, HuH-7) were either subject of a [ 18 F]FBPA-PET scan with subsequent measurement of radioactivity content in extracted organs using a gamma counter or injecte…

The role of pH on instability and aggregation of sickle hemoglobin solutions

2004

Understanding the physical basis of protein aggregation covers strong physical and biomedical interests. Sickle hemoglobin (HbS) is a point-mutant form of normal human adult hemoglobin (HbA). It is responsible for the first identified "molecular disease," as its propensity to aggregation is responsible for sickle cell disease. At moderately higher than physiological pH value, this propensity is inhibited: The rate of aggregate nucleation becomes exceedingly small and solubility after polymerization increases. These order-of-magnitude effects on polymer nucleation rates and concurrent relatively modest changes of solubility after polymerization are here shown to be related to both pH-induced…

Controlling the Polymer Microstructure in Anionic Polymerization by Compartmentalization.

2018

An ideal random anionic copolymerization is forced to produce gradient structures by physical separation of two monomers in emulsion compartments. One monomer (M) is preferably soluble in the droplets, while the other one (D) prefers the continuous phase of a DMSO-in-cyclohexane emulsion. The living anionic copolymerization of two activated aziridines is thus confined to the DMSO compartments as polymerization occurs selectively in the droplets. Dilution of the continuous phase adjusts the local concentration of monomer D in the droplets and thus the gradient of the resulting copolymer. The copolymerizations in emulsion are monitored by real-time 1 H NMR kinetics, proving a change of the re…

Organo-phosphorus compounds—LXVI

1970

Abstract The recemization kinetics of (+)-methyl-n-propylphenylphosphine were studied in several solvents of widely varying polarity. The recemization followed first order kinetics in every solvent with approximately equal activation energies of 30 ±3 kcal/mole. The rate of racemization showed no dependence on solvent polarity and could not be correlated with any known solvent parameters. The unusually slow racemization in caproic acid and in tributyl borate were attributed to partial salt and adduct formation respectively.

Synthesis and Cu(II) coordination of two new hexaamines containing alternated propylenic and ethylenic chains: Kinetic studies on pH-driven metal ion…

2006

Abstract The synthesis of the open-chain and cyclic polyamines, 1,5,8,12,15,19-hexaazaheptadecane (L1) and 2,6,9,13,16,20-hexaaza[21]-(2,6)-pyridinophane (L2), are described. The protonation constants and interaction constants with Cu(II) have been determined by potentiometric measurements carried out at 298.1 K in 0.15 mol dm −3 NaClO 4 . The values obtained are discussed as a function of the open-chain or cyclic nature of the ligands and compared with analogous polyamines containing different sets of hydrocarbon chains between the nitrogen donors. Kinetic studies on the acid-promoted dissociation of the Cu(II) complexes indicate that the mono and binuclear complexes of L1 decompose with d…