Fig. 6From: 3D-QSAR study of steroidal and azaheterocyclic human aromatase inhibitors using quantitative profile of protein–ligand interactionsScheme of steroid structure used to define interactions of 19 heteroatoms with the heme–iron. X is hydroxyl (OH) or oxo (= O). R1 and R2 are hydrogens. R3 is hydrogens or ketone. R4 is any functional groupBack to article page