  We employ a large scale molecular simulation based on bond-order ReaxFF to
simulate the chemical reaction and study the damage to a large fragment of
DNA-molecule in the solution by ionizing radiation. We illustrate that the
randomly distributed clusters of diatomic OH-radicals that are primary products
of megavoltage ionizing radiation in water-based systems are the main source of
hydrogen-abstraction as well as formation of carbonyl- and hydroxyl-groups in
the sugar-moiety that create holes in the sugar-rings. These holes grow up
slowly between DNA-bases and DNA-backbone and the damage collectively propagate
to DNA single and double strand break.
