Search results for "partition coefficient"

New complex polycyclic compounds: Synthesis, antiproliferative activity and mechanism of action

2020

Abstract Polycyclic or O-glycoconiugate polycyclic compounds 1a-g were previously tested for their in vitro antiproliferative activity. In this series of compounds, activity increases as log P decreases. Specifically, compounds 1d and 1g showed lower log P values together with the best antiproliferative profiles. With the aim of extending our understanding of the structure–activity relationship (SAR) of this class of compounds, we prepared new polycyclic derivatives 2a-c, which bear on each of the two phenyl rings hydrophilic substituents (OH, SO2NH2 or NHCOCH3). These substituents are able to form hydrogen bonds and to decrease the partition coefficient value as compared with compound 1d. …

1980

A phenomenological theory of the Phase Distribution Chromatography (PDC)-separation effect is outlined and a theoretical equation for the measured PDC-calibration curves is given. Assuming a reversible-thermodynamical equilibrium in the polystyrene-PDC-column, only a relatively small part of the measured PDC-calibration curves could be explained: namely those running below their tangents. In order to explain the whole sigmoidal shape of the experimental curves, a theory of steady state in the system sol/gel was developed assuming deformation of the polymer coil near the gel front due to the stress related to the velocity gradient. The resulting dynamical flow-equilibrium differs highly from…

Controls on strontium and barium incorporation into freshwater bivalve shells ( Corbicula fluminea )

2017

Abstract Trace elements of bivalve shells can potentially serve as proxies of environmental change. However, to reconstruct past environments using the geochemical properties of the shells and determine the degree to which the element levels are biologically influenced, it is essential to experimentally determine the relationship between environmental variables and the element composition of the shells. To disentangle possible controls on the incorporation of strontium and barium into freshwater bivalve shells, we conducted controlled laboratory experiments using the extremely salinity and temperature tolerant Asian clam, Corbicula fluminea as a model species. Bivalves were reared for five …

Influence of the composition and the structure of different media on the release of aroma compounds

2004

International audience; The release of 2-nonanone and hexenol (hex-4-en-3-ol) was studied in model media with different structures and compositions: water, a gel of $\beta$-lactoglobulin, gelified or non-gelified emulsions (5.0% Miglyol, 6.9% $\beta$-lactoglobulin; the gelation was realized by heating) and milk. The aroma compounds were analyzed by gas chromatography. A strong influence of the nature of the volatile compound on its behavior towards the food matrix was observed: in the case of 2-nonanone, a hydrophobic compound (log P = 2.9) with a relatively high vapor-water partition coefficient (Kmol = 33.6), the release was greatly influenced by the composition and the structure of the m…

Fe-periclase reactivity at Earth's lower mantle conditions: Ab-initio geochemical modelling

2017

Intrinsic and extrinsic stability of the (Mg, Fe) O solid mixture in the Fe-Mg-Si-O system at high P, T conditions relevant to the Earth's mantle is investigated by the combination of quantum mechanical calculations (Hartree-26 Fock/DFT hybrid scheme), cluster expansion techniques and statistical thermodynamics. Iron in the (Mg, Fe) O binary mixture is assumed to be either in the low spin (LS) or in the high spin (HS) state. Un-mixing at solid state is observed only for the LS condition in the 23-42 GPa pressure range, whereas HS does not give rise to un-mixing. LS (Mg, Fe) O un-mixings are shown to be able to incorporate iron by subsolidus reactions with a reservoir of a virtual bridgmanit…

Cerebral toxicity of penicillins in relation to their hydrophobic character

1975

The neurotoxic effects of ticarcillin, methicillin, phenthicillin, oxacillin, cloxacillin and dicloxacillin were studied in the conscious rabbit. During and after intravenous administration of 1.2 and 2.4 g/kg, resp., over 50 min the blood concentrations of the drugs were determined and the neurotoxicity assessed by continuous recording of the electroencephalogram. The hydrophobia of the penicillins was characterized by determination of their partition coefficients between isobutanol and buffer solution pH 7.4. The penicillins showed quite different neurotoxic properties. A close correlation (r = 0.928) was found between the neurotoxic potency of the penicillins and their partition coeffici…

Separation of the azeotropic mixture 2-propanol + water employing different imidazolium ionic liquids as solvents

2020

Abstract The liquid-liquid equilibria of the ternary systems water (1) + 2-propanol (2) + [emim][Tf2N] (3) and water (1) + 2-propanol (2) + [hmim][Tf2N] (3) at 283.2, 303.2 and 323.2 K and atmospheric pressure were investigated, in order to achieve a better knowledge of the ternary mixture behaviour. The capability of [emim][Tf2N] and [hmim][Tf2N] as solvents in the separation of the azeotropic mixture water + 2-propanol was studied through the distribution coefficient and selectivity, and compared with the results obtained with other ionic liquids in the same azeotropic mixture studied before by our research group. The thermodynamic parameters of both ternary mixtures were calculated by th…

Capability study of 1-butyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide and trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phos…

2018

Abstract The liquid-liquid equilibria of the ternary systems water (1) + 1-propanol (2) + 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) (3) and water (1) + 1-propanol (2) + trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate ([TDTHP][Phosph]) (3) at 283.2, 303.2 and 323.2 K and atmospheric pressure were determined to study their behaviour, determine their thermodynamic parameters and know the capability as solvents of [bmim][Tf2N] and [TDTHP][Phosph] in the separation of the azeotropic mixture water + 1-propanol. The non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models were used in the calculation of the thermodynamic par…

Study of the capability of 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid as solvent in the separation of water from 1-pr…

2020

Abstract After the good behavior of different 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids (ILs) used as solvents in the separation of 1-propanol and 2-propanol from water, liquid-liquid equilibria data was measured from a system formed by a ternary mixture of water, 1-propanol or 2-propanol and 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([dmim][Tf2N]) at 283.2, 303.2 and 323.2 K and atmospheric pressure. The non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models were employed to obtain the thermodynamic parameters of both ternary mixtures, with good results in all cases. Finally, the capability of [dmim][Tf2N] to separate…

Negatively cooperative binding of melittin to neutral phospholipid vesicles

2007

Abstract The association of basic amphipathic peptides to neutral phospholipid membranes is investigated in terms of binding and partition models. The binding of native and modified melittin to egg-yolk phosphatidylcholine vesicles is studied by steady-state fluorescence spectroscopy. The effect of the ionic strength shows an enhancement of the association as the ionic strength increases. After correction for electrostatic effects by the Gouy–Chapman theory, the melittin binding isotherms could be described by a partition model. In terms of conventional binding mechanisms, which do not take into account electrostatic effects, this would correspond to a negative cooperativity. A plausible wa…