Electron attachment to oligonucleotide dimers in water: Microsolvation-assisted base-stacking forms

The study of DNA subunit anions is an important recent chapter in the development of biophysical chemistry. The dinucleoside phosphate dTpdA and dApdT systems are among the largest to be studied by reliable theoretical methods. Exploring electron attachment to these subunits of DNA single strands enables one to approach reliable predictions of the electron affinities of DNA single strands. DNA single strands are found to have a strong tendency to host low-energy electrons and to form electronically stable radical anions. The effect of base stacking and water-microsolvation in stabilizing the radical anions of the DNA components is crucial. Aqueous solution dramatically increases the electron-capturing ability of the water-microsolvated oligonucleotides, by up to 1 eV. The stable structures of the stacked bases suggest that the H-bonding network through the microsolvating water molecules linking to the neighboring bases might also be an important factor in the stabilization of the stacked bases.