The general toxicology studies. DEREK had specificities of 78 to 82% when used as single. To believe that a positive computational prediction based. The Toxicity Estimation Software Tool (TEST) was developed to allow users to easily estimate the toxicity of chemicals using Quantitative Structure Activity.

Fahren Lernen Max Keygen Software. Abstract The performance of two computer programs, DEREK and TOPKAT, was examined with regard to predicting the outcome of the Ames bacterial mutagenicity assay. The results of over 400 Ames tests conducted at Glaxo Wellcome (now GlaxoSmithKline) during the last 15 years on a wide variety of chemical classes were compared with the mutagenicity predictions of both computer programs. DEREK was considered concordant with the Ames assay if (i) the Ames assay was negative (not mutagenic) and no structural alerts for mutagenicity were identified or (ii) the Ames assay was positive (mutagenic) and at least one structural alert was identified. Conversely, the DEREK output was considered discordant if (i) the Ames assay was negative and any structural alert was identified or (ii) the Ames assay was positive and no structural alert was identified. The overall concordance of the DEREK program with the Ames results was 65% and the overall discordance was 35%, based on over 400 compounds.

About 23% of the test molecules were outside the permissible limits of the optimum prediction space of TOPKAT. Another 4% of the compounds were either not processable or had indeterminate mutagenicity predictions; these molecules were excluded from the TOPKAT analysis. If the TOPKAT probability was (i) ≥0.7 the molecule was predicted to be mutagenic, (ii) ≤0.3 the compound was predicted to be non-mutagenic and (iii) between 0.3 and 0.7 the prediction was considered indeterminate. From over 300 acceptable predictions, the overall TOPKAT concordance was 73% and the overall discordance was 27%. While the overall concordance of the TOPKAT program was higher than DEREK, TOPKAT fared more poorly than DEREK in the critical Ames-positive category, where 60% of the compounds were incorrectly predicted by TOPKAT as negative but were mutagenic in the Ames test.

For DEREK, 54% of the Ames-positive molecules had no structural alerts and were predicted to be non-mutagenic. Alternative methods of analyzing the output of the programs to increase the accuracy with Ames-positive compounds are discussed. Introduction Several computer packages have been developed to study structure–activity relationships (SAR) in toxicology (for reviews see;;, ). These programs are designed to predict toxicological outcomes such as skin sensitization, LD 50 and aquatic toxicity; in particular, the predictions of end points of mutagenicity and carcinogenicity have received considerable attention (;;,; ). In general, the approaches followed by these toxicity prediction packages fall into two categories: (i) rule-based expert systems that rely on a set of chemical structure alerts and (ii) correlative structure–activity relationship methods based on statistical analysis. We present our experience with DEREK, a rule-based system, and TOPKAT, a correlative SAR system, for the prediction of bacterial mutagenicity. DEREK ( deductive estimate of risk from existing knowledge) uses a set of rules derived from the collective expertise of toxicologists from academia, industry and government.

The premise of the system was clearly stated by its originators (): if chemical structure feature is present then specific toxic action is a possibility DEREK is a system which indicates whether a specific toxic response may occur; it does not provide a quantitative estimate of the prediction. DEREK has several rule bases, consisting of descriptions of molecular substructures (structural alerts) that have been associated with toxic end points (e.g. Mutagenicity, carcinogenicity or skin irritation). Download Harta Romania Pentru Gps Garmin.

Since substructures can exist in a variety of molecular contexts, the rules are not chemical-specific, but rather serve as broad generalizations with regard to the chemical structure (e.g. Alkylating agent, acid or halogen-containing molecule). The development of the rules is a continuous process that is monitored by the DEREK Users Group.