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

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. [ABSTRACT FROM AUTHOR]