脂肪胺的脂水分配系数与结构参数的关系

研究了脂肪胺的脂水分配系数实验值与半经验量子化学计算获得的理论计算参数值间的相关关系,结果表明:实验测定值与分子范德华体积及碳氮键长之间有良好的多元线性关系.     

Calculation of rotational partition functions by an efficient Monte Carlo importance sampling technique

The evaluation of the classical rotational partition function represented by a configuration integral over all external and internal rotational degrees of freedom of nonrigid chain polyatomic molecules is described. The method of Pitzer and Gwinn is used to correct the classical partition function for quantum mechanical effects at low temperatures. The internal rotor hindrance and all coupling arising from the external and internal rotational degrees of freedom are explicitly taken into account. Importance sampling Monte Carlo based on the adaptive VEGAS algorithm to perform multidimensional integration is implemented within the TINKER program package. A multidimensional potential energy hypersurface is calculated with the MM3(2000) molecular mechanics force field. Numerical tests are performed on a number of small n-alkanes (from ethane to octane), for which the absolute entropies calculated at three different temperatures are compared both with the experimental values and with the previous theoretical results. The application of a more efficient importance sampling technique developed here results in a substantial reduction of statistical errors in the evaluation of the configuration integral for a given number of Monte Carlo steps. Error estimates for the calculated entropies are given, and possible sources of systematic errors, and their importance for a reliable prediction of the absolute entropy, are discussed.     

Centrifugal partition chromatography: a survey of its history,and our recent advances in the field

Centrifugal partition chromatography (CPC) was introduced in 1982 by Sanki Eng. And for almost 20 years this company remained the only one manufacturing such an apparatus. A CPC instrument or a CPC column is a series of channels linked in cascade by ducts and aligned in cartridges or disks in a circle around a rotor; setting the rotor in motion submits this assembly to a constant centrifugal field. The originality of CPC is that it uses any biphasic liquid-liquid system as mobile and stationary phases. The United States branch of Sanki contributed greatly to the worldwide acceptance of the technique. Recent works performed in the Netherlands and in France have, by means of visualization of flow-patterns in CPC channels, contributed to a better knowledge of hydrodynamics and mass transfer phenomena. Nowadays research in our laboratory focuses on speediness and scale-up of the technique.     

Factors affecting adsorption of organic solutes on cellulose acetate in an aqueous solution system

Summary The adsorption properties of esters, aldehydes, ethers and amides on cellulose acetate, which is commonly used as a reverse osmosis membrane material, in an aqueous solution system were measured by high-performance liquid chromatography. The adsorption property was characterized with the specific retention volume. For a noncyclic homologous series the logarithm of the specific retention volume was linearly correlated with the logarithm of the partition coefficient between 1-octanol and water. The fact that the slopes of these regression lines are almost identical confirms that the dominant effect on adsorption is the hydrophobic interaction between cellulose acetate and the solute molecule. The intercept represents the effect of the polar groups on adsorption. The effect of the polar group decreases as follows: C(O)O, CO, HCON > CH₃CON > OH, O.     

Interfacial tension of alkylglucosides in different APG/oil/water systems

The interfacial performance of pure alkylglucosides (C₈G₁, C₁₀G₁ and C₁₂G₁) and of technical grade alkylpolyglucoside (APG) surfactants was investigated in three different water/oil systems (decane, isopropylmyristate and 2-octyldodecanol). From the dependence of the interfacial tension on the surfactant concentration below the CMC the cross-sectional area of the molecules at the decane/water interface was estimated. The plateau values of the interfacial tension at the CMC _c are independent of temperature and almost independent of added electrolyte in the decane/water system. The ability of the surfactants to lower the oil/water interfacial tension is most pronounced for the nonpolar oil. The partition coefficient of the surfactant between oil and water phase (k _c) was estimated from the CMC and the observed break point of the interfacial tension after equilibration of the two phases. In decane/water,k _c is nearly zero for all surfactants studied. For the polar oils,k _c increases with the chain length of the surfactant up tok _c10 for C₁₂G₁ in octyldodecanol/water. The values of _c in the different oil/water systems appear to be correlated withk _c and exhibit a minimum neark _c=1.     

Horseradish peroxidase extraction and purification by aqueous two-phase partition

The effect of poly(ethyleneglycol) (PEG) molecular weight, system pH, and sodium chloride concentration on the partitioning behavior of horseradish peroxidase fromArmomcia rusticana root extract was investigated in poly(ethyleneglycol)/sodium phosphate systems. PEG molecular weight strongly affects the enzyme partition coefficient, whereas pH variation from 5.5 to 8.0 has little effect. The addition of sodium chloride (8% w/w) to a PEG 1540/phosphate system, pH 7.0, raises the peroxidase partition coefficient 13.5-fold without important changes in that of total horseradish root proteins. Moreover, these conditions allow direct homogenization of theA. rusticana roots with the selected aqueous two-phase system with the clear top phase containing over 90% of the enzyme and the purification factor being 4.8.     

QSPR Study on Octanol/water Partition Coefficient （lgKow） of Substituted Naphthalin Compounds

Structural parameters of 24 substituted naphthalin compounds were computed at four levels using Hartree-Fock and DFT methods. Based on the experimental data of octanol/water partition coefficient (lgKow),three-parameter (energy of the highest occupied molecular orbital (EHOMO),the most positive atomic net charges of molecule (q+) and molecular average polari-zability (α)) dependent equations were developed using structural parameters as theoretical des-criptors. Especially,lgKow dependent equation calculated at the HF/6-311G** level is more advantageous than others in view of their correlation and predictive abilities. This dependent equation was validated by variance inflation factors (VIF) and t-test methods and used to predict lgKow of eight designed compounds. Upon comparison,the predictive abilities of our work are all more advantageous than those calculated from molecular property calculator program.     

一个新的连接性指数对脂肪醇的QSPR/QSAR研究

在分子拓扑理论的基础上 ,提出了一个新的连接性指数nχz,并用 nχz 研究了脂肪醇化合物在水中的溶解度 (Sw)、正辛醇 /水分配系数 (Kow)及对水生生物急性毒性 (-LC50 ) ,给出了相关方程 ,研究结果表明 ,相关性良好 ,新方法计算方便 ,物理意义明确 ,预测值与相应的实验值较吻合     

用外推容量因子法测定药物的疏水性

本文利用不同体积分数的甲醇-水作流动相,用外推容量因子法测定20种不同结构类型药物的疏水性,该法操作简便、快速、测定疏水性范围宽,相关性好。     

Taylor expansion of polymer chain dispersion relations and spectral densities to calculate thermodynamic functions

It is shown how to calculate exactly the derivatives of the dispersion relation and the spectral density for arbitrary regular polymer chains in harmonic approximation. The theory is based on a generalization of the characteristic polynomial. In the vibrational part of the free energy and other thermodynamic functions, the integral over normal modes is done approximately by Taylor expanding the density of states.Dedicated to Professor Dr. F. H. Müller.