Electronic Excitation Energy Transfer in DNA. Nature of Triplet Excitations Capturing Centers

Abstract

Spectral properties, energy structure, and electronic processes in DNA, poly(dAdT)₂, d(CCCGGGTTTAAA), d(ATC), d(AT), dGMP, dAMP, dCMP, dTMP were studied. The DNA lowest excited electronic singlet and triplet levels are connected with guanine and adenine bases, correspondingly. The DNA fluorescence is close to a linear combination of the guanine and cytidine emissions and connected, to a greater extent, with the singlet energy transfer to these bases. The origin of the DNA phosphorescence is associated with AT-sequences that are traps of triplet excitations in DNA. The triplet energy transfer to these centers and adenine bases (that are most photostable) leads to the DNA self-protection against a damage induced by electronic excitations of DNA.

Keywords:

• DNA
• energy structure
• energy transfer
• triplet states

Acknowledgments

We are grateful to Prof. Paras N. Prasad, Prof. Dmytro M. Govorun, Dr. Tymish Yu. Ohulchanskyy, Prof. Petro Doroshenko, Dr. Volodymyr P. Vorobyov, and Prof. Volodymyr I. Melnik for their ideas and help.

This work was supported in part by STCU (Project No 3104) and the Ministry of Education and Science of Ukraine (Project No. M/229-2004).