THE DISTRIBUTION OF ELECTRON TRAPPING IN DNA - ONE-ELECTRON-REDUCED OLIGODEOXYNUCLEOTIDES OF ADENINE AND THYMINE

A series of single- and double-stranded oligodeoxynucleotides of adeni ne and thymine, 8 to 12 nucleotides in length, were one-electron-reduc ed at 10 K in a >8 M LiCl/H2O glass. The Q-band electron paramagnetic resonance (EPR) spectra of these radicals show that thymine is the dom inant trapping site for mobile electrons in these oligomers. The spect ra of the reduced oligomers in the series pd(A(n)T(10-n)). pd(A(10-n)T (n)) with n = 5-->10 showed a trend which is interpreted as either an increase in the probability of trapping at an adenine base in tracks o f adenine >7 base pairs in length, or the presence of different proton ated states of the one-electron-reduced bases due to the adoption of a different conformational state for longer tracks of adenine, or a com bination of these two possibilities. Analysis of the trends in the EPR spectra of the radicals as a function of sequence using multicomponen t analysis is presented. (C) 1995 by Radiation Research Society