Degradation mechanism of four brominated nucleobases (BrX), potential DNA radiosensitizers, is studied in explicit water solution, using ab initio molecular dynamics. Several fs long dynamics is needed to localize an electron on the nucleobase. Produced by electron attachment BrX anion radical degrades through the bromide anion abstraction, barrier-free (purines) or with low barrier (pyrimidines), to a reactive nucleobase radical. Such differences in dissociative behavior of purines and pyrimidines suggest that brominated purine anions should dissociate more effectively than their pyrimidine counterparts. (C) 2014 Elsevier B.V. All rights reserved.