Measured by gel electrophoresis scanning,it was shown that the double strand breaks (DSBs) of pBR322 irradiated by γ rays were constituted by two parts,αDSB and βDSB,and the relationship between α,β and scavenging capacity σwas obtained.Results showed that β/α non linearly decreased with increasing σ.Moreover,the yield of the OH free radicals reacting with DNA was analyzed.
Though the radiation-resistant bacteria Deinococcus radiodurans (D. radiodurans) have a high resistance to the lethal and mutagenic effects of many DNA-damaging agents, the mechanisms involved in the response of these bacteria to oxidative stress are poorly understood. In this report, the superoxide dismutase (SOD) and catalase (CAT) activities produced in bacteria (D.radiodurans AS1.633) and their change caused by 20 keV N+ beam exposure were examined. Results showed that the activities of the enzymes were increased in the case of N+ beam exposure from 8×1014 ions/cm2 to 6×1015 ions/cm2. In addition, the treatment of H2O2 and [CHCl3+CH3CH2OH] and the measurement of absorption spectrum showed that the increase of whole SOD activity resulted from inducible activities of Mn-SOD in (a sub^type) D.radiodurans AS1.633. These results suggested that these bacteria possess inducible defense mechanisms against the deleterious effects of oxidization.
