Impact assessment of the rational selection of training and test sets on the predictive ability of QSAR models

This study performed an analysis of the influence of the training and test set rational selection on the quality and predictively of the quantitative structure–activity relationship (QSAR) model. The study was carried out on three different datasets of Influenza Neuraminidase (H1N1) inhibitors. The three datasets were divided into training and test sets using three rational selection methods: based on k-means, Kennard–Stone algorithm and Activity and the results were compared with Random selection. Then, a total of 31,490 mathematical models were developed and those models that presented a determination coefficient higher than: r²_train > 0.8, r²_loo > 0.7, r²_test > 0.5 and minimum standard deviation (SD) and minimum root-mean square error (RMS) were selected. The selected models were validated using the internal leave-one-out method and the predictive capacity was evaluated by the external test set. The results indicate that random selection could lead to erroneous results. In return, a rational selection allows for obtaining more reliable conclusions. The QSAR models with major predictive power were found using the k-means algorithm and selection by activity.     

离子液体的定量结构-性质/活性研究

本文系统介绍了离子液体定量结构-性质/活性相关(QSPR/QSAR)的研究方法和步骤,综述了QSPR/QSAR在离子液体的熔点、有机物在离子液体中的无限稀释活度系数、离子液体的表面张力、离子液体的电导率、有机物在离子液体中的溶解度、离子液体的黏度以及离子液体的生物毒性和降解性等方面的最新研究进展,总结了该方法的优缺点,并对未来的研究趋势进行了展望。     

表面活性剂的QSAR/QSPR研究进展*

本文综述了表面活性剂定量结构-活性/性质相关(QSAR/QSPR)研究的最新进展,以及相关结构描述符在表面活性剂QSAR/QSPR研究中的应用.重点介绍了表面活性剂的cmc和表面张力γ与分子结构的定量关系、离子型表面活性剂电荷分布的定量计算及其对胶体结构与性质的影响.对表面活性剂分子结构与活性/性质的定量相关研究的发展趋势进行了展望.     

A Lu index for QSAR/QSPR studies

A novel topological index based on Wiener index, named Lu index, is proposed and can be used for modeling properties of heteroatom-containing and multiple bond organic compounds. The usefulness of the Lu index was demonstrated by modeling normal boiling points and molar refractions of aldehydes and ketones, and the retention indices of gas chromatography of hydrocarbons and halogenated hydrocarbons. The high correlation coefficients (>0.99) for all constructed models indicate the need of such an index, and show the potential of the Lu index for QSAR/QSPR studies.     

离子液体的QSPR/QSAR研究

离子液体以其独特的性质广受关注,人们对其潜在的应用价值做了大量的研究,但对离子液体特性和结构与性质/活性相关的研究却很少。本文综述了离子液体定量结构-性质/活性相关(QSPR/QSAR)研究的最新进展,重点介绍了QSPR/QSAR的基本原理和离子液体的熔点、有机化合物在离子液体中的无限稀释活度系数、离子液体的界面张力、有机物在离子液体中的溶解系数和分配系数、离子液体的电导率和黏度以及离子液体的毒性等性质与分子结构的定量关系,并对离子液体分子结构与性质/活性的定量相关研究的发展趋势进行了展望。     

A new strategy of outlier detection for QSAR/QSPR

The crucial step of building a high performance QSAR/QSPR model is the detection of outliers in the model. Detecting outliers in a multivariate point cloud is not trivial, especially when several outliers coexist in the model. The classical identification methods do not always identify them, because they are based on the sample mean and covariance matrix influenced by the outliers. Moreover, existing methods only lay stress on some type of outliers but not all the outliers. To avoid these problems and detect all kinds of outliers simultaneously, we provide a new strategy based on Monte‐Carlo cross‐validation, which was termed as the MC method. The MC method inherently provides a feasible way to detect different kinds of outliers by establishment of many cross‐predictive models. With the help of the distribution of predictive residuals such obtained, it seems to be able to reduce the risk caused by the masking effect. In addition, a new display is proposed, in which the absolute values of mean value of predictive residuals are plotted versus standard deviations of predictive residuals. The plot divides the data into normal samples, y direction outliers and X direction outliers. Several examples are used to demonstrate the detection ability of MC method through the comparison of different diagnostic methods. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

多氯联苯的定量结构－性质(活性)关系

多氯联苯(PCBs)是一类重要的持久性环境污染物.首先对所有209个PCB分子进行了HF/6-31G*水平上的结构优化, 在优化结构上获得了分子的表面静电势分布, 并在此基础上对其统计导出的参数进行了计算．其后, 运用多元线性回归方法对PCBs的水溶性、正辛醇/水分配系数、正辛醇/空气分配系数、土壤吸附性、水溶液活度系数、298 K超冷流体蒸汽压、总分子表面积、色谱保留指数、升华焓、蒸发焓、熔融焓、PCB结合芳烃受体活性数据、生物降解度以及生物降解速率参数等理化性质和生物活性与分子的结构参数进行了关联．结果表明:分子静电势参数结合分子表面积和常规的量子化学参数可以很好地用于表达多氯联苯分子理化性质和生物活性与其分子结构间的定量关系．     

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     

Simplex representation of molecular structure as universal QSAR/QSPR tool

Structural Chemistry - We review the development and application of the Simplex approach for the solution of various QSAR/QSPR problems. The general concept of the simplex method and its...     

一种新的分子拓扑指数及其在QSPR/QSAR研究中的应用

通过引入量子数、键参数,认为分子的性质与其中各原子的电负性、价电子数、成键电子数、价层主量子数及各化学键的键长有关,提出了一种新的分子拓扑指数mAY.采用该拓扑指数对饱和烷烃、烷基苯、烷氧氯硅烷、卤代苯、含氮杂环化合物、碱金属卤化物及卤化锡的性质/活性进行了相关关系的研究.结果表明,mAY与有机物和无机物的性质/活性间具有良好的相关性.