This set is composed of one Sybyl atom type descriptor (discriminating 24 different combinations of element types and hybridization states; Table ) and 14 electronic and topological descriptors (Table ). The descriptor set is similar to the one used in FAME 3. However, in FAME 3 the descriptors are calculated with CDK instead of CDPKit, and CDK's stabilizationPlusCharge descriptor is used instead of CDPKit's inductive effect descriptor. In addition to this set of 15 atomic descriptors, the FAME fingerprint, which is a circular, atom-based binary fingerprint, was reimplemented in CDPKit and used in one instance of data set splitting (see the Section "Active Learning").