Elastic response and length change of single DNA molecules induced by a combination of cisplatin and transplatin.

Magnetic tweezers were employed to investigate the interactions between DNA and cisplatin (transplatin). Cisplatin shortened DNA and reduced its persistence length more significantly than transplatin due to the formation of many more diadducts than those formed by transplatin. Interestingly, the presence of transplatin could enhance the ability of cisplatin in shortening DNA. An optimal concentration ratio of transplatin to cisplatin existed at which cisplatin showed the highest ability in shortening DNA. Moreover, abrupt length changes were also observed when DNA was treated with a mixture of cisplatin and transplatin at high concentrations. A model was proposed to qualitatively explain well these results.