Phosphodiesterases (PDEs) catalyze the hydrolysis of second messengers cAMP and cGMP in regulating many important cellular signals and have been recognized as important drug targets. Experimentally, a range of specificity/selectivity toward cAMP and cGMP is well-known for the individual PDE families. The study reported here reveals that PDEs might also exhibit selectivity toward conformations of the endogenous substrates cAMP and cGMP. Molecular dynamics simulations and free energy study have been applied to study the binding of the cAMP torsional conformers about the glycosyl bond in PDE10A2. The computational results elucidated that PDE10A2 is energetically more favorable in complex with the syn cAMP conformer (as reported in the crystal structure) and the binding of anti cAMP to PDE10A2 would lead to either a nonreactive configuration or significant perturbation on the catalytic pocket of the enzyme. This experimentally inaccessible information provides important molecular insights for the development of effective PDE10 ligands.

Using Streptomyces erythreus isolated from pharmaceutical residues as a biosorbent, the characteristics and mechanism of its absorbing Pb2+ was studied. The results showed that absorptive ability of bacterial mycelia modified by sodium hydroxide was improved greatly. The reaction mechanism of modified bacterial mycelia uptake Pb2+ was analyzed by back scattered electron microscope(BSEM) and infrared spectroscopy (IR). The results of experiments indicated that some chemical groups such as -COO-、C-H and O-H among cell walls of bacterial mycelia might play the key functions adsorbing Pb2+. It was presumed that the process of modified bacterial mycelia lead uptake might be a chemical and physical process collaboratively which occurred on the cell surface of bacterial mycelia chiefly based on exchangeable reaction.