Theoretical study on the bifunctional substitution reactions between gold(III) dithiocarbamate derivative Au(DMDT)Cl2 (DMDTÂ =Â N,N-dimethyldithiocarbamate) and target molecules

In this study, we further research the bifunctional substitution reactions between anticancer drug Au(DMDT)Cl2 and cysteine (Cys), DNA purine bases (G/A), which are based on the results of its monofunctional substitution reactions. Our calculations demonstrate that the activation free energies for guanine is lowest in the aqueous solution, which predicts that the N7 site of guanine is the strongest and superior to active sites of cysteine. On the contrary, the higher activation free energies reveal that the O site of cysteine and N7 site of adenine are unfavorite. The activation energies do not differ significantly no matter S site or N site of cysteine acts as attacking group when three monofunctional adducts are the active agents in the aqueous solution respectively, whereas the differences of corresponding activation energies in gas phase become larger.