Search results for "pH dependence"
showing 5 items of 5 documents
Chromatographic retention–activity relationships for prediction of the toxicity pH-dependence of phenols
2007
Abstract An investigation of the use of the chromatographic retention (log k ) as an in vitro approach for modeling the pH-dependence of the toxicity to Guppy of phenols is developed. A data set of 19 phenols with available experimental toxicity–pH data was used. The importance of the mechanism of toxic action (MOA) of phenols was studied. log k data at three pH values were used for the phenols classification and two groups or ‘MODEs’ were identified. For one ‘MODE’ a quantitative retention–activity relationship (QRAR) model was calculated. Finally, the model was used to assess the toxicity to Guppy of phenols at different pH values. The results of this investigation suggest that chromato…
Introduction of histidine residues into avidin subunit interfaces allows pH-dependent regulation of quaternary structure and biotin binding
2003
AbstractIn order to turn the subunit association and biotin binding of avidin into pH-sensitive phenomena, we have replaced individually three amino acid residues in avidin (Met96, Val115 and Ile117) with histidines in the 1–3 interface, and in combination with a histidine conversion in the 1–2 interface (Trp110). The single replacements Met96His and Val115His in the 1–3 interface were found to have a clear effect on the quaternary structure of avidin, since subunit associations of these mutants became pH-dependent. The histidine replacement in the 1–2 interface affected the biotin-binding properties of the mutants, in particular reversibility of binding and protein–ligand complex formation…
Luminescence Efficiency of Si/SiO 2 Nanoparticles Produced by Laser Ablation
2019
Photoluminescence properties of Si(core)/SiO 2 (shell) nanoparticles produced by pulsed laser ablation in aqueous solution are investigated with the purpose to highlight the microscopic processes that govern the emission brightness and stability. Time resolved spectra evidence that these systems emit a µs decaying band centered around 1.95 eV, that is associated with the radiative recombination of quantum-confined excitons generated in the Si nanocrystalline core. Both the quantum efficiency and the stability of this emission are strongly dependent on the pH level of the solution, that is changed after the laser ablation is performed. They enhance in acid environment because of the H + pass…
Voltammetric Investigation on Uranyl Sorption by Alginate Based Material. Influence of Hydrolysis and pH Dependence
2015
The removal of U(VI) as uranyl (UO22+) from aqueous solutions was investigated by sorption onto alginate based material. The hydrolysis of uranyl ion was always taken into account in the calculations of free (22UO) ion in aqueous solution, in the experimental pH range considered, as well as the acid-base properties of alginate polymer. The sorption process follows a pseudo-second order kinetic model and the sorption rate decreases when the pH value increases. In addition to the classical Langmuir and Freundlich models, the equilibrium data were fitted by using a modified multi-component equilibrium model, never tested before. Differential Pulse Voltammetry (DPV) and Inductively Coupled Plas…
Temperature and pH Dependence of Gd-DOTA and Gd-DTPA Complexes Dissociation Studied by EXAFS
1997
The Gd L3-edge of Gd(DTPA) 2- and Gd(DOTA) - complexes, in crystalline state and aqueous solutions presenting various pH (0.15-8) at different temperatures (25-90 °C), are investigated by XAFS experiments. For the Gd(DTPA) 2- . complexes we observe a strong pH (0.15-1.5) dependence of XAFS signals. On the other hand, the XAFS signals of Gd(DOTA) - complexes exhibit a light pH (1-1.5) dependence and for pH<1 we observe a ligand decomposition. Conceming both complexes, we note just a light temperature dependence. To obtain information about the short and medium range order (up to 5 A), multiple scattering calculation is performed. For the first coordination shell, we apply multi-shell fitting…