Formation of pyrene dimer radical cation at the internal site of oligodeoxynucleotides

Doubly internally pyrene (Py) modified oligodeoxynucieotides (ODNs) were synthesized, and the formation rates of the Py dimer radical cation (PY2.+) were measured upon one-electron oxidation during pulse radiolysis. The formation Of Py-2(.+) with an optical absorption at 1550 nm (charge resonance band) was observed in the time range of 1 mus to 1 ms after an electron pulse during the pulse radiolysis of a D2O solution of the doubly internally Py modified ODN in the presence of K2S2O8. The formation rate Of Py-2(.+) in DNA reflected the dynamics of the DNA, which allows the interaction between Py.+ and Py, and was affected by the distance between the two Py's and the local environment of each Py. The trapping of the transiently formed DNA conformation by the attractive charge resonance interaction was demonstrated to be useful to obtain structural and dynamic information of the fluctuating DNA in the time range of 1 mus to 1 ms.