Search results for "partition coefficient"
showing 10 items of 146 documents
Interactions of benzodiazepines with human serum albumin. Circular dichroism studies.
1973
The circular dichroism spectra of 12 benzodiazepine derivatives studied in presence of human serum albumin are presented. Nearly all substances give biphasic extrinsic Cotton effects. At the CD maxima the molar ellipticities and the anisotropy factors are calculated. The influence of the chemical structure of the benzodiazepines on the induced Cotton effect is discussed. There is a linear correlation between the anisotropy factors and the logarithms of the partition coefficients of the substances. It is suggested that the phenyl ring of the benzodiazepine molecule is one of the essential groups for the binding of these substances to human serum albumin.
Quantitative structure-retention relationships for ionic and non-ionic compounds in biopartitioning micellar chromatography
2004
Quantitative structure–retention relationships, QSRRs, represent a powerful tool in chromatography. The objectives of QSRR studies are to predict the chromatographic retention behaviour of solutes based on their structural properties, to elucidate retention mechanisms, to optimize the separation of complex mixtures or to prepare experimental designs. In this paper, using the retention factors of 151 structurally unrelated solutes that cover a wide range of hydrophobicity, molecular size, hydrogen bonding properties and ionization degrees obtained in biopartitioning micellar chromatography (BMC) at different Brij35 micellar concentrations, several multivariate QSRR models are tested. It is d…
A density functional study of flavonoid compounds with anti-HIV activity.
2005
Abstract Quantum chemical calculations at the DFT/B3LYP theory level, with the 6-31G* basis set, was employed to calculate a set of molecular properties of 26 flavonoid compounds with anti-HIV activity. The correlation between biological activity and structural properties was obtained by using the multiple linear regression method. The model obtained showed not only statistical significance but also predictive ability. We demonstrate in this paper that the anti-HIV activity of compounds can be related with the molecular hydrophobicity (ClogP), the electronegativity ( χ ) and the charges on some key atoms, while that the toxicity can be related with the electronic affinities (EA), ClogP and …
Die Aufnahme von Promazin, Chlorpromazin und deren Desmethylmetaboliten in das isoliert perfundierte Rattenhirn
1971
The uptake of promazine, chlorpromazine, desmethylpromazine, and desmethylchlorpromazine into the isolated rat brain was determined in relation to their lipophilic character and their binding to albumin and erythroeytes in the perfusion media. The desmethylmetabolites showed about the same degree of binding as their parent compounds promazine and chlorpromazine. On the other hand the partition coefficients of promazine and chlorpromazine were about 10 times higher than those of their desmethylmetabolites. The more hydrophilic desmethyl-metabolites permeated more slowly into the rat brain, but in the distribution equilibrium they may obviously come up to the same concentration in the brain a…
Environmentally Relevant Properties of All 209 Polychlorinated Biphenyl Congeners for Modeling Their Fate in Different Natural and Climatic Conditions
2009
The temperature dependence of physical properties and degradation lifetimes in the environment of all polychlorinated biphenyl (PCB) congeners (N = 209) were determined. For physical properties, the coefficients A and B in equations log(property) = A(property) − B(property)/T(K) were determined by thermodynamic and QSPR methods and compared with the results of independent methods in the literature. The coefficients Apl and Bpl for liquid state vapor pressure PL, As and Bs for solubility in water SW, Ah and Bh for volatility kH (or kH = PL/SW), and Aow and Bow for lipophilicity (KOW), stored in the database of the fate model program, allowed automatic temperature corrections for realistic fa…
Estimation of vapor pressures, solubilities and Henry's law constants of selected persistent organic pollutants as functions of temperature
1999
Abstract An internally consistent set of temperature dependent physical-chemical property data was derived for 73 persistent organic pollutants, including polychlorinated biphenyls, diphenylethers, dibenzo-p-dioxins, and dibenzofurans, organochlorinated pesticides and polycyclic aromatic hydrocarbons. Measured data reported in the literature were expanded by different estimation and regression methods. Temperature dependent vapor pressures were estimated from relative gas chromatographic retention times and by a modified Watson equation. Temperature dependent water solubilities were estimated by equations based on mobile order theory modified from Ruelle and Kesselring. The temperature depe…
Proposed alternative phase ratio variation method for the calculation of liquid–vapour partition coefficients of volatiles
2012
International audience; The phase ratio variation PRV method is a classical way to determine the partition coefficients of volatile compounds between their solution and vapour phases in a variety of circumstances. However, some results obtained by this method can be disappointing. A new PRV equation in which the initial liquid-phase solute concentration is replaced by the liquid-phase solute concentration at equilibrium is proposed. This proposed PRV equation is a second-order polynomial equation. To thoroughly examine the possible modes of calculation, noisy dummy data were generated using both the classical, first-order PRV model (PRV1) and the proposed, second-order model (PRV2). Thus, p…
Reduction of the interfacial tension between ‘immiscible’ polymers: to which phase one should add a compatibilizer
2001
Abstract The reduction of interfacial tension σ between polyethylene oxide (PEO) and polypropylene oxide (PPO) by either a triblock copolymer EO–PO–EO or a diblock copolymer styrene–EO was studied by means of the pendant drop method from 70 to 120°C. Time independent data correspond to stationary states and do not represent equilibrium information. The addition of the compatibilizer to the PPO phase is approximately twice as efficient as the addition to the PEO phase for both block copolymers. Knowing the concentration dependence of σ for one of the coexisting phases it is possible to forecast the effects resulting from the addition of the other phase by means of model considerations based …
(Liquid + liquid) equilibria of polymer-salt aqueous two-phase systems for laccase partitioning : UCON 50-HB-5100 with potassium citrate and (sodium …
2012
Aqueous two-phase systems (ATPS) are recognized as very suitable techniques for the recovery of target solutes in biological applications. Three new phase diagrams of (UCON 50-HB-5100 + potassium citrate + water), (UCON 50-HB-5100 + sodium formate + water), and (UCON 50-HB-5100 + potassium formate + water) systems were measured at 23 C. The binodal curves were successfully described using the empirical equation suggested by Merchuk and co-workers. The reliability of the tie-line data experimentally determined was evaluated using the equations reported by Othmer–Tobias and Bancroft and satisfactory linearity was obtained for all ATPS. Among the salts studied, potassium citrate proved to be t…
Study of relationships between the structure of aroma compounds and their retention-release between vapour phase and dairy gels
2010
An integrated approach physicochemistry and structures activity relationships has been carried out to study the aroma compounds retention-release phenomenon in a fat free dairy gel added with pectin. This study aimed to identify the molecular properties that govern this phenomenon assuming that modifying the structure leads automatically to a change in the retention-release of aroma compounds. For this purpose, we have determined the partition coefficients of 28 aroma compounds in water, in pectin gels and in dairy gels supplemented or not supplemented with pectin, at equilibrium conditions using the PRV method (Phase Ratio Variation). Then, we have performed a structure-retention relations…