[Study on the interaction between DNR-D3 (daunorubicin derivative)and ctDNA by spectroscopic methods]

The interaction of DNR-D3 (daunorubicin derivative) synthesized in our laboratory with ctDNA was investigated by UV spectrum and fluorescence spectrum under physiological conditions (pH 7.4) for the first time. The red shifts and hypochromicities were observed from the absorption titration experiments. These results suggest that DNR-D3 was intercalated into the DNA base pairs. Through the fluorescence quenching data measured at different temperatures (20 degrees C, 30 degrees C and 37 degrees C), it is known that the quenching mechanism of fluorescence of DNR-D3 by ctDNA is a static quenching type. On the other hand, the binding constant, the number of binding sites and thermodynamic parameters were also obtained. These data also indicate that the binding mode of the interaction between DNR-D3 and ctDNA is intercalation. Additionally, the types of interaction force are mainly hydrogen bonding and electrostatic interaction, and the binding is exothermic enthalpy-entropy cooperative driven process. When the degree of fluorescence quenching of DNR-D3 is 50%, the ratio of the molar concentration of DNR-D3 to ctDNA is 7/25, which indicates that the DNR-D3 anthracycline was intercalated into the DNA base pairs and that DNR-D3 showed a strong anti-cancer activity. DNR-D3 is expected to become one of the drug candidates from our investigations.