Formation of pyrene dimer radical cation in DNA reflecting DNA dynamics in the time range of 1 μs to 1 ms

Doubly pyrene (Py)-conjugated oligodeoxynucleotides (ODNs) were synthesized and used for measurement of the formation rates of Py dinner radical cation (Py-2(.+)) upon one-electron oxidation during the pulse radiolyses. Formation of Py radical cation (Py.+) in the time scale of less than 5 us was monitored at 470 nm after an electron pulse during pulse radiolysis of D2O solution of doubly Py-conjugated ODN in the presence of K2S2O8, Concomitant with the decay of Py.+, formation of Py-2(.+) with an absorption peak at 1500 nm (charge resonance band) was observed in the time range of similar to100 mus. The formation rate of PY2.+ in DNA reflected the dynamics of DNA which allows the interaction between Py.+ and Py, since transiently formed DNA structure is trapped by the attractive charge resonance (CR) interaction to give Py-2(.+). The formation rate of Py-2(.+) with a characteristic CR absorption band in the near-infrared (near-IR) region was demonstrated to be useful to obtain the structural and dynamical information of transiently formed DNA in the time range of 1 mus to 1 ms.