A New Atom-Additive Method for Calculating Partition Coefficients

1997 ◽  
Vol 37 (3) ◽  
pp. 615-621 ◽  
Author(s):  
Renxiao Wang ◽  
Ying Fu ◽  
Luhua Lai
Keyword(s):  
Partition Coefficients ◽  
Additive Method

Partition Coefficient Ratios and Tumour Perfusion Studied with 85mKr and 133Xe

1987 ◽  
Vol 26 (06) ◽  
pp. 253-257
Author(s):  
M. Mäntylä ◽  
J. Perkkiö ◽  
J. Heikkonen
Keyword(s):  
Partition Coefficient ◽  
Partition Coefficients ◽  
Regional Blood Flow ◽  
Blood Perfusion ◽  
Compartmental Analysis ◽  
Malignant Tumour ◽  
Mean Value ◽  
Perfusion Rate ◽  
Biological Variables ◽  
The Mean

The relative partition coefficients of krypton and xenon, and the regional blood flow in 27 superficial malignant tumour nodules in 22 patients with diagnosed tumours were measured using the 85mKr- and 133Xe-clearance method. In order to minimize the effect of biological variables on the measurements the radionuclides were injected simultaneously into the tumour. The distribution of the radiotracers was assumed to be in equilibrium at the beginning of the experiment. The blood perfusion was calculated by fitting a two-exponential function to the measuring points. The mean value of the perfusion rate calculated from the xenon results was 13 ± 10 ml/(100 g-min) [range 3 to 38 ml/(100 g-min)] and from the krypton results 19 ± 11 ml/(100 g-min) [range 5 to 45 ml/(100 g-min)]. These values were obtained, if the partition coefficients are equal to one. The equations obtained by using compartmental analysis were used for the calculation of the relative partition coefficient of krypton and xenon. The partition coefficient of krypton was found to be slightly smaller than that of xenon, which may be due to its smaller molecular weight.

Temperature Dependence of the Self-Assembled Styrene Based Random Ionomers in Aqueous Solution

2003 ◽  
Vol 775 ◽  
Author(s):  
Sung-Hwa Oh ◽  
Ju-Myung Song ◽  
Joon-Seop Kim ◽  
Hyang-Rim Oh ◽  
Jeong-A Yu
Keyword(s):  
Partition Coefficients ◽  
Room Temperature ◽  
Aqueous Media ◽  
The Self ◽  
Spectroscopic Methods ◽  
Ion Content ◽  
Repeat Units ◽  
Notable Effect ◽  
Order Of Magnitude ◽  
Experimental Errors

AbstractSolution behaviors of poly(styrene-co-sodium methacrylate) were studied by fluorescence spectroscopic methods using pyrene as a probe. The mol% of methacrylate was in the range 3.6–9.4. Water and N,N-dimethylforamide(DMF) mixture was used as a solvent (DMF/water = 0.2 mol %). The critical micelle (or aggregation) concentrations of ionomers and the partition coefficients of pyrene were obtained the temperature range 10–80°C. At room temperature, the values of CMCs (or CACs) were in the range 4.7 ×10-6 5.3 ×10-6 g/mL and we could not find any notable effect of the content of ionic repeat units within the experimental errors. Unlike CMCs, as the ion content increased, partitioning of pyrene between the hydrophobic aggregates and an aqueous media decreased from 1.5 ×105 to 9.4 ×104. As the temperature increased from 10 to 80 °C, the values of CMCs increased less than one order of magnitude. While, the partition coefficients of pyrene decreased one order of magnitude and the effect of the ion content became negligible.

Fatty Liver and Impaired Hepatic Metabolism Alters the Congener-Specific Distribution of Polychlorinated Biphenyls (PCBs) in Mice with a Liver-Specific Deletion of Cytochrome P450 Reductase

2020 ◽  
Author(s):  
Xueshu Li ◽  
Chun-Yun Zhang ◽  
Hans-Joachim Lehmler
Keyword(s):  
Cytochrome P450 ◽  
Polychlorinated Biphenyls ◽  
Fatty Liver ◽  
Partition Coefficients ◽  
Hepatic Metabolism ◽  
Gas Chromatography Mass Spectrometry ◽  
Cytochrome P450 Reductase ◽  
P450 Reductase ◽  
Specific Distribution ◽  
Specific Deletion

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are linked to adverse health outcomes. PCB tissue levels are determinants of PCB toxicity; however, it is unclear how factors, such as an altered metabolism and/or a fatty liver, affect PCB distribution in vivo. We determined the congener-specific disposition of PCBs in mice with a liver specific deletion of cytochrome P450 reductase (KO), a model of fatty liver with impaired hepatic metabolism, and wildtype (WT) mice. Male and female KO and WT mice were exposed orally to Aroclor 1254, a technical PCB mixture. PCBs were quantified in adipose, blood, brain and liver tissues by gas chromatography-mass spectrometry. PCB profiles and levels in tissues were genotype and sex dependent. PCB levels were higher in the liver from KO compared to WT mice. PCB profiles showed clear differences between tissues from the same exposure group. While experimental tissue : blood partition coefficients in KO and WT mice did not follow the trends predicted using a composition-based model, the agreement between experimental and calculated partition coefficients was still reasonable. Thus, a fatty liver and/or an impaired hepatic metabolism alter the distribution of PCBs in mice and the magnitude of the partitioning of PCBs from blood into tissues can be approximated using composition-based models.<br>

Partition Coefficients of Methylated DNA Bases Obtained from Free Energy Calculations with Molecular Electron Density Derived Atomic Charges.

2018 ◽  
Author(s):  
Alejandro Lara ◽  
Maximiliano Riquelme ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Electron Density ◽  
Partition Coefficients ◽  
Dna Bases ◽  
Atomic Charges ◽  
Free Energies ◽  
Solvation Model ◽  
Minimal Basis ◽  
Methylated Dna ◽  
Implicit Solvation Model ◽  
Good Agreement

<div> <div> <div> <p>Partition coefficients serve in various areas as pharmacology and environmental sciences to predict the hydrophobicity of different substances. Recently, they have been also used to address the accuracy of force fields for various organic compounds and specifically the methylated DNA bases. In this study atomic charges were derived by different partitioning methods (Hirshfeld and Minimal Basis Iterative Stockholder) directly from the electron density obtained by electronic structure calculations in vac- uum, with an implicit solvation model or with explicit solvation taking the dynamics of the solute and the solvent into account. To test the ability of these charges to describe electrostatic interactions in force fields for condensed phases the original atomic charges of the AMBER99 force field were replaced with the new atomic charges and combined with different solvent models to obtain the hydration and chloroform solvation free energies by molecular dynamics simulations. Chloroform-water partition coefficients derived from the obtained free energies were compared to experimental and previously reported values obtained with the GAFF or the AMBER-99 force field. The results show that good agreement with experimental data is obtained when the polarization of the electron density by the solvent has been taken into account deriving the atomic charges of polar DNA bases and when the energy needed to polarize the electron den- sity of the solute has been considered in the transfer free energy. These results were further confirmed by hydration free energies of polar and aromatic amino acid side chain analogues. Comparison of the two partitioning methods Hirsheld-I and Minimal Basis Iterative Stockholder (MBIS) revealed some deficiencies in the Hirshfeld-I method related to nonexistent isolated anionic nitrogen pro-atoms used in the method. Hydration free energies and partitioning coefficients obtained with atomic charges from the MBIS partitioning method accounting for polarization by the implicit solvation model are in good agreement with the experimental values. </p> </div> </div> </div>

Short Communication: A Note of Caution to Users of ECOSAR

1999 ◽  
Vol 34 (1) ◽  
pp. 179-182 ◽  
Author(s):  
Klaus L.E. Kaiser ◽  
John C. Dearden ◽  
Werner Klein ◽  
T. Wayne Schultz
Keyword(s):  
Environmental Protection Agency ◽  
Partition Coefficients ◽  
Short Communication ◽  
Computer Software ◽  
Aquatic Organisms ◽  
Protection Agency ◽  
Personal Computer Software ◽  
Linear Correlations ◽  
Class Representative ◽  
Chemical Class

Abstract ECOSAR (1998), a personal computer software program available from the U.S. Environmental Protection Agency (EPA) and affiliated vendors, is used to estimate the toxicity of chemicals to aquatic organisms, particularly fish, daphnid and algae species. It relies on approximately 150 equations, each for a chemical class of substances (Clements et al. 1996), which are linear correlations (SARs) of measured toxicity values of class-representative compounds with their octanol/water partition coefficients, with the latter taken from a database or computed by a companion program.

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