Acrylamide gels of the PDE8A1 catalytic domain. Left lane, molecular weight markers; lane 1, E. coli cell before induction; lane 2, total cell after induction; lane 3, supernatant; lane 4, pellet; lane 5, proteins from the Ni-NTA column; lane 6, HTP column; lane 7, Q-Sepharose column after thrombin cleavage of the 10 residue tag; lane 8, finally concentrated PDE8A1 from Sephacryl S300 column; right, the native gel of PDE8A1.