Secondary pharmacophore filter for CDK2. A) The ATP binding site with specificity-conferring interactions: the position of an atom accepting a hydrogen bond from Lys 89 (red-dotted sphere) and a hydrophobic interaction (yellow sphere). This figure was generated using PyMOL . B) Bar chart showing the percentage of hits (known actives) compared to decoys that are left in the test database after this pharmacophore filter is applied. The absolute number in each group of compounds is marked at the top of the bars.