摘要:

This paper summarises the results obtained from recent research at the University of Sheffield into the identification of topological pharmacophores and toxicophores. The published CASE and LOGANA methods were implemented, and several limitations revealed. The CASE method was improved by the use of atom pairs as descriptors. The LOGANA method was improved by the use of hyperstructures to reduce the number of variables available for combination. The paper outlines improvements to the method for hyperstructure generation, and the advantages of hyperstructures for data analysis, compression and visualisation. In the resultant scheme of operation, large datasets can be clustered on the basis of very general fragments, and then hyperstructures of the clusters input to LOGANA to highlight activating and inactivating substructures.

ISSN:1062-936X    

DOI:10.1080/10629369508050152

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Molecular similarity methods were used in selecting K nearest neighbors and in estimating mutagenicity of 95 aromatic amines and boiling points of a large set of over 2,900 compounds. Similarity is analyzed in terms of the concept of tolerance space. Specifically, the role of non-transitivity of the tolerance relation in estimating properties using similarity methods is examined.

ISSN:1062-936X    

DOI:10.1080/10629369508050153

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The objective of the work was to assess the utility of an objective measure of “similarity” between chemicals for assisting in the choice of appropriate chemicals for training sets used to construct QSARs for aquatic toxicity. Measures of molecular similarity were assessed using regression analysis and hierarchical cluster analysis. A group of 18 alcohols, all non-polar narcotics, were selected for the assessment and derivation of the basic QSAR. A good correlation was shown to exist for the selected chemicals between log P and toxicity. However, this correlation was significantly reduced when two chemicals which exhibit toxicity by a different mode of action were introduced into the training set. Measurement of molecular similarity was investigated as an objective means of identifying the two outlier chemicals. Similarity indices were calculated and autocorrelograms plotted for the selected alcohols and outlier chemicals using commercially available software. Statistical analysis of the similarity data was carried out to determine if the outlier chemicals could be identified. One of the two outlier chemicals proved to be clearly “dissimilar” to all of the alcohols but, the other outlier chemical proved to be “similar” to several alcohols.

ISSN:1062-936X    

DOI:10.1080/10629369508050154

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Information on the aqueous solubilities of organic substances are important for understanding hydrophobic interactions in water and for assessing the distribution and toxicity of contaminants in aquatic environments. Environmental contaminants are frequently encountered as mixtures, and the behaviour of a compound in a mixture may not correspond to that predicted from the pure compounds data. In this study, solutions often binary aromatic mixtures were examined, each at several molar ratios. The five individual aromatics were benzene, 2-chlorotoluene, 2-sec-butylphenol, aniline, and 2-nitroanisole. The water solubilities of those individual compounds range from about 400 to about 40,000 mg/l. For all these binary systems, the experimental results indicate that there are significant cosolute interactions on aqueous contaminant concentrations which appear dependent on the structures of the cosolutes. The UNIFAC model and an empirical QSAR (not given) model are used for the prediction and the correlation of the data, respectively. Both methods give reasonably good results.

ISSN:1062-936X    

DOI:10.1080/10629369508050155

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A log P model was derived from a stepwise regression analysis based on a training set of 800 organic molecules presenting highly diverse structures. Chemicals were described by means of the autocorrelation method using the structural fragmental values of Rekker. Our approach was shown to be simpler and more efficient than the classical method of Rekker which generally requires the use of correction factors for calculating log P values.

ISSN:1062-936X    

DOI:10.1080/10629369508050156

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Knowing the values of pKaand partition coefficients between 1-octanol and water (Pow) of ionizable herbicides helps us to understand the movement of these compounds in plants and soil. However, shake-flask and high-pressure liquid chromatography (HPLC) techniques. though valuable for measurement of log Powof herbicide molecules that do not ionize in aqueous solution, are difficult to use for ionizable molecules; this is especially so for molecules that form ion pairs having appreciable log Powvalues, those with multiple ionizations and for bases with high pKavalues. Our aim in this study was to validate the use of the pH-metric technique (based on potentiometric titration) for measurements of pKaand log Powof ionizable standard substances and herbicides. The values obtained show good correlation with results from other techniques, including shake-flask and HPLC. The OECD Guideline for Testing of Chemicals 117, adopted 30th March 1989, describes the use of HPLC for the measurement of log Pow. It is hoped that these studies and further testing of this technique will permit it to be included in these OECD guidelines.

ISSN:1062-936X    

DOI:10.1080/10629369508050157

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A thermodynamic model (SOFA) was used to derive molar (subcooled) liquid volume, heat of vaporization and Scatchard-Hildebrand solubility parameters of polychlorinated biphenyls. Differences in molar volume and heat of vaporization betweencis-transisomers and between enantiomers were accounted for by specific fragment contributions and by an increase or decrease of molar volume and heat of vaporization when mixedcis-transisomers or D-L enantiomers, respectively, occur. The SOFA model was extended by the inclusion of an orientational disorder entropy term. An accurate set of gas chromato-graphic relative retention times (N = 210) and semi-empirical data on heats of vaporization (N = 7) and molar volumes (N = 11) was used for the derivation.

ISSN:1062-936X    

DOI:10.1080/10629369508050158

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:1062-936X    

DOI:10.1080/10629369508050151

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor