Figure 2. Activity cliff network and cluster topologies.

In ( A), the complete activity cliff network is shown. Nodes represent compounds and edges activity cliffs. Nodes of highly and lowly potent cliff partners are colored green and red, respectively, and nodes representing a compound that is a highly and lowly potent partner in different activity cliffs are colored yellow. Small sections of the network containing exemplary activity cliff cluster topologies are magnified. On the right, examples of the three most frequently occurring (main) topologies are displayed, which include so-called star, chain, and rectangle topology. In ( B), main activity cliff cluster topologies and observed extensions as well as hybrid and irregular topologies are schematically illustrated (pink nodes: star; light blue: chain; purple: rectangle topology; gray: no topology assignment). Dual-color nodes indicate compounds belonging to cluster components with hybrid topologies. Squared nodes represent variable compound numbers ( n) for a given topology. For each topology, the number ( #) of instances in the network is reported.