Hydrogen atoms within 4 Å of the phosphorus atom of IMP (A,B), of the NADPH monophosphate P (C,D) and the NADPH diphosphates P atoms (E,F) in the IN (A,C,E) and OUT (B,D,F) complexes (PDB entry 2C6Q). Protons within 4 Å of the phosphorus are shown as a ball, protons within 3 Å are colored light green. This figure was produced with UCSF Chimera 17.