Structural diversity, assessment

Maintenance of soft-bottom benthic invertebrate communities capable of supporting local fish populations. COPC concentrations in sediment will not result in toxicity to the soft-bottom benthic community. Assess the effect of COPCs in sediment on the survival of two amphipod species (Eohaustorius estuarius and Rhepoxynius abronius). Assess the effect of COPCs in sediment on survival and growth of the polychaete, Neanthes arenaceodentata. Assess in situ changes in benthic community structure (diversity and abundance). 

Walter et al. (2002) assessed the effect of a mixture of 11 aquatic priority pollutants on algal reproduction. The chemicals were selected for structural diversity by using chemometric methods. In this study, statistical estimates of effect concentrations down to effect levels of 1% were derived by regression analysis of concentration-response data. Based on these estimates of low effects, IA yielded quite accurate predictions of mixture toxicity. 

An alternative methodology based on the ringcontent of a database, using precalculated structure-based hash codes has been proposed (110). The comparison of the hashcode tables can be used to compare two databases and the number of distinct ring-system combinations can be used as an indicator of database diversity. A method for diversity assessment called the saturation diversity approach, based on picking as many mutually dissimilar compounds as possible from a database was also proposed. The methods were used to compare a number of public databases and gave similar results. 

In summary, a large variety of methods have been deployed to predict ER binding of possible endocrine-disrupting chemicals. Consistently measured data for a large inventory of structurally diverse compounds are available [102,103] that will make extensive validation of the methods in future applications possible and also mandatory before helping regulatory bodies in the risk-assessment process. This validation should also include the prediction of affinities for compound classes that are not part of the training process. 

Fergus, S. Bender, A. Spring, D. R., Assessment of structural diversity in combinatorial synthesis, Curr Opin Chem Biol 2005, 9, 304-309... 

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