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.