Search results for "partition coefficient"
showing 6 items of 146 documents
Stationary–mobile phase distribution coefficient for polystyrene standards
2002
The measured shifts of the retention volume V R of polystyrene (PS) towards lower values in benzene–methanol (Bz–MeOH), and towards higher values in butanone–heptane (But–Hep) are in agreement with our theoretical model, in which both MeOH and But are adsorbed on Lichrospher. This paved way for us to model the chromatographic stationary (s)-phase as MeOH and the mobile (m)-phase as Bz–MeOH, and to calculate the distribution coefficients for PS. For But–Hep, the s-phase has been modeled as But, and the m-phase as But–Hep. A linear relation for the experimental equilibrium distribution P sm of PS is shown between the s- and m- phases in Bz–MeOH and But–Hep vs. the logarithm of the molecular m…
Thermodynamic Study of Small Hydrophobic Ions at the Water–Lipid Interface
2001
Abstract The thermodynamics of binding of two small hydrophobic ions such as norharman and tryptophan to neutral and negatively charged small unilamellar vesicles was investigated at pH 7.4 using fluorescence spectroscopy. Vesicles were formed at room temperature from dimyristoyl phosphatidylcholine (DMPC) or DMPC/dimyristoylphosphatidic acid and DMPC/dimyristoylphosphatidylglycerol. The changes in fluorescence properties were used to obtain association isotherms at variable membrane surface negative charge and at different ionic strengths. The binding of both ions was found to be quantitatively enhanced as the percentage of negative phospholipid increases in the membrane. Also, a decrease …
Macromolecules in ordered media III. A fluorescence study on the association of poly-2-vinylpyridine with a phospholipid bilayer
2007
Association of low molecular weight poly-2-vinylpyridine taken as a polycation model with unilamellar vesicles based on dimirystoylphosphatidic acid has been experimentally investigated by means of fluorescence energy transfer experiments. The conventional profiles for the binding isotherms were obtained, confirming strong deviations from the ideality of these complex fluid composites. Two approaches, named binding and partitioning equilibrium, respectively, were used to obtain the association constant, K A; the number of phospholipids that form a binding site, N; the partition coefficient, Λ; the activity coefficient, γ; and the effective charge, v. Analysis of these parameters as a functi…
Calculation of organic solvent–water partition coefficients of iron–sulfur protein models
2002
Abstract A method is presented that permits semiquantitative estimation of the partitioning of many solutes between many pairs of media. As an example, the organic solvent–water partition coefficients P are calculated. The only needed parameters are the dielectric constant and molecular volume of the organic solvent. Fe 4 S 4 Cys n models of high-potential FeS proteins are studied. The Gibbs free energies of solvation and partition coefficients for Fe 4 S 4 Cys n are calculated. The organic solvent–water partition coefficients for 1-octanol P o , cyclohexane P ch and chloroform P cf decrease 4.41, 6.22 and 4.60 log units per cysteine (Cys) ligand, respectively. P o results are compared with…
Low-pressure synthesis and Bridgman growth of Hg1−xMnxTe
1999
To reduce Hg high pressure related to the high-temperature synthesis reaction between the components in elemental form, Hg 1-x Mn x Te bulk crystals were produced by a two-step procedure including (I) the alloy synthesis using HgTe crystals grown by the cold travelling heater method and elemental Mn and Te to complete the desired composition, followed by (II) the Bridgman growth. The growth was carried out at temperature in the range of 700-850°C and rate of 1 mm/h. The Hg 1-x Mn x Te crystals have been characterised by X-ray diffractometry, energy dispersive X-ray analysis, Fourier transformed infrared spectroscopy and Hall effect techniques. Although the distribution coefficient of Mn was…
Microfungal Alkylation and Volatilization of Selenium Adsorbed by Goethite
2009
Selenium adsorbed in the oxyanionic form by Fe-oxides like goethite is considered of benefit for long-term stabilization of (79)Se under near field conditions of radionuclide waste disposal sites. However, microbe-mediated volatilization of the uranium fission product (79)Se has not yet been considered for risk assessment based on the use of the water-solid distribution coefficient K(D). We have performed incubation experiments in a ternary system selenium-microbe-goethite and show that mycobiota including the common black microfungi genera Alternaria alternata are capable of volatilizing the Se even if immobilized by goethite. The microfungi were incubated in a standardized nutrient broth …