Electron-Attachment-Induced DNA Damage: Instantaneous Strand Breaks

Low energy electron-attachment-induced damage in DNA, where dissociation channels may involve multiple bonds including complex bond rearrangements and significant nuclear motions, is analyzed here. Quantum mechanics/molecular mechanics (QM/MM) calculations reveal how rearrangements of electron density after vertical electron attachment modulate the position and dynamics of the atomic nuclei in DNA. The nuclear motions involve the elongation of the P–O (P–O3′ and P–O5′) and C–C (C3′–C4′ and C4′–C5′) bonds for which the acquired kinetic energy becomes high enough so that the neighboring C3′–O3′ or C5′–O5′ phosphodiester bond may break almost immediately. Such dynamic behavior should happen on a very short time scale, within 15–30 fs, which is of the same order of magnitude as the time scale predicted for the excess electron to localize around the nucleobases. This result indicates that the C–O phosphodiester bonds can break before electron transfer from the backbone to the base.