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The following graph display a part of the transformations related to Aquatic toxicity. Arrows point the direction of increasing toxicity. For example, it can be seen that the presence of Bromine is potentially more toxic than the presence of Chlorine.
References
The article with description of a use of MMPs to analyze models has been published in Prediction-driven matched molecular pairs to interpret QSARs and aid the molecular optimization process. Sushko Y, Novotarskyi S, Körner R, Vogt J, Abdelaziz A, Tetko IV. J Cheminform. 2014 Dec 11;6(1):48. doi: 10.1186/s13321-014-0048-0.