Search results for "Constants"

Acid-base properties of halloysite clay nanotubes in NaCl medium

2014

Modelling of protonation constants of halloysite clay nanotubes in various aqueous media, at different ionic strengths

2015

In the last decade nanoparticles have assumed more and more importance because of their particular properties mainly due to the nanometer-scale dimensions that confer them a large surface/volume ratio. Among nanomaterials one of the most studied is the halloysite that, as well as the other natural clay minerals is safe for human and environmental friendly. Halloysite is abundant and cheap and is present in large deposits worldwide like those in New Zealand, France, Belgium and China [1,2]. It is similar to kaolin but has a hollow tubular structure that can be attributable to particular crystallization conditions. Typically, halloysite nanotubes (HNTs) are formed by 15 – 20 aluminosilicate l…

Advances in the study of phytate-cation interactions

2008

On the G‐quadruplex binding of a new class of Ni(II), Cu(II) and Zn(II) salphen‐like complexes

2021

The involvement of non-canonical DNA structures, such as Gquadruplex (G4) DNA, in cancer development and progression has set the pace towards the renaissance of DNA-binding metal complexes. In this work, we report the DNA-binding of three Ni(II), Cu(II), Zn(II) complexes of a salphen-like N4-donor ligand, bearing two imidazole groups condensed with a phenylenediamine moiety. Both duplex and G4 DNAs derived from human telomeres (hTelo), and a sequence mimicking the promoter of the oncogene myc (c-myc) were studied. UV-Vis and circular dichroism spectroscopic binding studies pointed out that, while all the three complexes bind the selected oligonucleotides, the Cu(II) derivative is the strong…

Interaction of UO2(2+) with ATP in aqueous ionic media.

2005

Interaction of dioxouranium(VI) (uranyl) ion with ATP was studied by ligand/proton and metal/hydroxide displacement technique, at very low ionic strength and at I=0.15 mol L(-1), in aqueous Me4NCl and NaCl solutions, at t=25 degrees C. Measurements were carried out in the pH range 3-8.5, before the formation of precipitate. Computer analysis allowed us to find the quite stable species UO2(ATP)H2(0), UO2(ATP)H-, UO2(ATP)2-, UO2(ATP)2(6-), UO2(ATP)2H2(4-) and UO2(ATP)(OH)3- whose formation constants are (at I=0 mol L(-1)) logbeta(112)=18.21, logbeta(111)=14.70, logbeta(110)=9.14, logbeta(120)=12.84, logbeta(122)=24.82, and logbeta(11-1)=2.09, respectively. Different values were obtained in th…

Thermodynamic and kinetic properties of water–oil–surfactant mixtures

1998

Abstract We present experimental data on thermodynamic and kinetic properties of the emulsification failure of a droplet-phase microemulsion, and model them by a bending free energy. In contrast to most other models used to describe water–oil–surfactant mixtures no entropic contributions are included in the present description. Still, there is quantitative agreement between theory and measurements, even though there are no free parameters in our model – only experimentally accessible material constants appear.

Quantum correlations in generalized spin star system

2006

The problem of detecting quantum signatures in the correlations formed in dynamical evolution of quantum bipartite systems receives a lot of attention in current literature. Generally speaking, the occurrence of correlations between two observables of a system does not necessarily reflect nonclassical behaviour. In this paper, the exact dynamics of a pair of uncoupled spins 1/2 interacting with a common spin 1/2 bath is investigated. Starting from a separable initial condition, the ability of the system to develop purely quantum correlations is brought to light. Physical interpretation of the concurrence function as well as a suggestion on how to measure it are given.

Interaction of the Dioxouranium(VI) Ion with Aspartate and Glutamate in NaCl(aq) at Different Ionic Strengths

2005

The formation of complexes species of the dioxouranium(VI) ion with aspartic and glutamic acids was studied in the pH range of 3 to 6 at 25 °C by potentiometric measurements (H+−glass electrode). R...

Tungsten(VI)-gluconic acid complexes: Polarimetric and13C-N.m.r. Studies in an excess of tungsten(VI)

1986

A polarimetric study of the tungsten (VI)-gluconic acid system in an excess of metal reveals the formation of four stable complexes: two monomers with 1 : 2 and 2: 1 stoichiometries and two dimers of 2:2 composition. The pH ranges of these species, the amount of acid equivalents their formation requires, and their conditional stability constants have also been calculated.

Determination of equilibrium constants and computational interaction energies for adducts of [Rh2(RCO2)(4-n)(PC)n] (n = 0-2) with Lewis bases.

2007

Properties of dirhodium catalysts with cyclometalated aryl phosphine ligands have been studied. We report here the study of the acid−base reaction of Rh2(RCO2)2(PC)2(H2O)2 catalysts (PC = cyclometalated aryl phosphine) with different Lewis bases. The determination of the equilibrium constants of these reactions can be used to study to which extent the properties of the axial coordination site of the catalyst, considered the active site, are affected by modification of the metalated phosphines, the carboxylate ligands, or the incoming axial ligand. The trends in the computational density functional theory interaction energies show good agreement with the major trends in the equilibrium const…