Figure 1.

Principle of CATS descriptor calculation. The molecular structure (Step 1) is reduced to the molecular graph, and feature types are assigned (Step 2; L, lipophilic; R, aromatic; A, hydrogen-bond acceptor; D, hydrogen-bond donor). Then, atom pairs for all feature pairs are counted (Step 3), and the final descriptor values are scaled (Step 4). Here, the raw values were divided by the respective λ value (sum of atom type pair occurrences). Note that not all vertices in the molecular graph are considered ‘pharmacophoric’. These possess no feature types.