Determination of the partition coefficient for yeast invertase between microwater droplets in air in contact with liquid water

Applied Biochemistry and Biotechnology - The experiments carried out in the separatory funnel provide a simple technique for concentrating proteins up to 30 times. From a feed concentration of 0.1...     

ClogPalk: a method for predicting alkane/water partition coefficient

Alkane/water partition coefficients (P_alk) are less familiar to the molecular design community than their 1-octanol/water equivalents and access to both data and prediction tools is much more limited. A method for predicting alkane/water partition coefficient from molecular structure is introduced. The basis for the ClogP_alk model is the strong (R² = 0.987) relationship between alkane/water partition coefficient and molecular surface area (MSA) that was observed for saturated hydrocarbons. The model treats a molecule as a perturbation of a saturated hydrocarbon molecule with the same MSA and uses increments defined for functional groups to quantify the extent to which logP_alk is perturbed by the introduction each functional group. Interactions between functional groups, such as intramolecular hydrogen bonds are also parameterized within a perturbation framework. The functional groups and interactions between them are specified substructurally in a transparent and reproducible manner using SMARTS notation. The ClogP_alk model was parameterized using data measured for structurally prototypical compounds that dominate the literature on alkane/water partition coefficients and then validated using an external test set of 100 alkane/water logP measurements, the majority of which were for drugs.     

Determination of octanol-water partition coefficient for terpenoids using reversed-phase high-performance liquid chromatography

Octanol-water partition coefficients (Kow) for 57 terpenoids were measured using a RP-HPLC method. Sample detection was achieved with standard UV and refractive index detectors and required no special column treatment. Measured log Kow values for the terpenoids ranged from 1.81 to 4.48 with a standard error of between 0.03 and 0.08 over the entire range. Partition coefficients determined by the RP-HPLC method were compared against shake flask, atom/fragment contribution, fragment and atomistic methods. The HPLC values were found to give the best correlation with shake flask results. Log Kow values calculated by the atom/fragment contribution method gave the best correlation with the HPLC values when compared to fragment and atomistic methods.     

Determination of the radon diffusion coefficient and radon exhalation rate in Moroccan quaternary samples using the SSNTD technique

Measurements have been made of radon (²²²Rn), release from diverse quaternary samples collected from different sediment deposits in the Errachidia and Beni-Mellal areas (Morocco). The radon diffusion coefficient as one of some important parameters of radon transport in the soil has been measured using solid state nuclear track detectors (SSNTD). Radon -activity, uranium content and radon exhalation rate have been determined in the studied samples. Uranium concentrations were found to vary from 0.14 to 9.52 ppm whereas the radon exhalation rate varied from 0.003 to 0.145 Bq^.m^-2.h^-1. A positive correlation has been found between radon exhalation rate and uranium content in the studied samples. The average radon diffusion coefficients were found to vary from (1.26±0.09)^.10^-6 m^2.s^-1 to (4.3±0.36)^.10^-6 m^2.s^-1. Furthermore, the correlation between ²²²Rn diffusion coefficient and porosity are also discussed.     

胆固醇基键合相-反相高效液相色谱法测定正辛醇/水分配系数

通过反相高效液相色谱法系统地考察了中性和弱酸性化合物在新型胆固醇基键合相色谱柱（Cholester柱）上的保留行为。以甲醇和乙腈为有机调节剂,建立了保留因子（k）与有机调节剂比例（φ）间的关系,并外推获取100%水相为流动相时的log k_w;同时进一步建立并验证了不同流动相下正辛醇/水分配系数的对数（log K_ow）和log k_φ（log k_w）间的模型,并预测了部分化合物的log K_ow。结果表明,使用Cholester柱测定log K_ow时,甲醇比乙腈更适合作为有机调节剂;对中性化合物和中性状态的酸性化合物,可以用任意甲醇比例下获取的log k_φ预测log K_ow;对存在离解的酸性化合物,依然用外推方式获取的log k_w预测log K_ow。将采用Cholester柱与文献中采用C₁₈柱、C₈柱建立的log K_ow-log k_φ模型进行对比,结果表明化合物与胆固醇基键合相存在特别的作用。     

Determination of partition coefficient of spin probe between different lipid membrane phases

Model lipid membranes made from binary mixtures of dimyristoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DMPC/DPPC) and dimyristoylphosphatidylcholine/cholesterol (DMPC/Chol) exhibit coexistence of diverse lipid phases at appropriate temperature and composition. Since lipids in different phases show different structural and motional properties, it is expected that the corresponding spin probe electron paramagnetic resonance (EPR) spectra will be superposition of several spectral components. From comparison of proportions of spectral components of the EPR spectrum with the fractions of the corresponding lipid phases obtained from known phase diagrams the partition coefficient of spin probe methyl ester of 5-doxyl palmitate between different lipid phases was determined. The results indicate that the used spin probe partitions approximately equally between different phases.     

Calibration coefficient of the SSNTD and equilibrium factor for radon

Disintegration, ventilation and deposition were considered as removal processes of the radon and its short-lived daughters in air and the respective concentration equations were applied. Calibration coefficient (K_F) of the solid state nuclear track detector (SSNTD) LR-115 for radon and the equilibrium factor (F) were related to track densities of the bare detector (D) and the filtered one (D_o). A useful relationship between K_F, F and detector sensitivity coefficient (k) was derived. Using the calibrated value k=3.29×10^–3 m, the exposed detectors gave the average values of the equilibrium factor, calibration coefficient and indoor radon concentration of a single house living room in Osijek 0.46, 142.3 m^–1 and 37.8 Bq m^–3, respectively.     

用密度泛函理论预测酚类化合物的正辛醇/水分配系数

利用密度泛函理论(DFT),基于B3LYP/6-31G(d,p)和B3LYP/6-311G(d,p)两种水平计算了36种酚类化合物的分子结构参数和热力学参数,建立了两种水平的正辛醇/水分配系数(Kow)的定量结构-性质关系模型;确定相关系数(R)分别为0.988和0.988,交叉验证系数(q2)分别为0.94和0.96...     

A rapid determination method of the air/water partition coefficient and its application

The air/water partition coefficient (K_aw) and Henry's constant (H) were measured by our own modified EPICS (Equilibrium Partitioning in Closed System) method, which uses two bubble columns. This method gives accurate K_aw data much more rapidly than other methods. In order to establish this method, the influence of airflow rate and the volume ratios of water in two columns to partition coefficient were carefully examined. Then we have measured K_aw for some n-alkanes, aromatic and chlorinated compounds. The experimental results of our modified EPICS method agreed very well with literature values. Besides the relationships between K_aw and molar volume, vapor pressure and water solubility were also analyzed.     

Dependence of chymosin and pepsin partition coefficient with phase volume and polymer pausidispersity in polyethyleneglycol-phosphate aqueous two-phase system

The influence of the phase volume ratio and polymer pausidispersity on chymosin and pepsin partition in polyethylenglycol-phosphate aqueous two-phase systems was studied. Both proteins showed a high affinity for the polyethylenglycol rich phase with a partition coefficient from 20 to 100 for chymosin and from 20 to 180 for pepsin, when the polyethyleneglycol molecular mass in the system varied between 1450 and 8000. The partition coefficient of chymosin was not affected by the volume phase ratio, while the pepsin coefficient showed a significant decrease in its partition coefficient with the increase in the top/bottom phase volume ratio.     

Determination of attenuation coefficient for self-absorption correction in routine gamma ray spectrometry of environmental bulk sample

A simple method to determine -ray attenuation coefficients using Ba-133 -rays has been developed and applied to self-absorption correction in routine -ray spectrometry for environmental samples composed of unknown matrix elements. Experimental values of the mass attenuation coefficient obtained by the method agree well with calculated values for samples of known elemental composition which was determined by means of chemical analysis.     

Comparison of two ICP-MS set-ups for measuring 99Tc in large volume water samples

Large volume fjord and seawater samples have been radiochemically prepared for ICP-MS analysis in order to test the robustness of the procedure and to carry out a comparison of two ICP-MS set-ups. A sector field instrument (MicroMass PT2) coupled with an ultrasonic nebuliser and a quadrupole ICP-MS (Perkin-Elmer Elan 6000) coupled with an electrothermal vaporisation (ETV) unit were used. The results showed that the radiochemical procedure was robust, removing Ru and Mo to acceptable levels, and that the two set-ups gave results that were in agreement. The correlation coefficient between the sets of 11 results was 1.0 +/- 0.05. The importance of establishing the matrix effect when using an ETV is discussed.