Degradation of DNA in dried tissues by atmospheric oxygen

Recently, DNA of extinct creatures have been brought into analyses. The difficulty in this field of research is DNA degradation. Oxidative damage is considered to be one of the causes of the DNA degradation. We studied how DNA in dried tissue was affected by atmospheric oxygen using freeze-dried rat liver as a model. In tissues exposed to oxygen, DNA degradation occurred within several months and the amount of 8-hydroxy-2'-deoxyguanosine in DNA rapidly increased. The DNA degradation was inhibited by lipid extraction prior to the exposure to atmospheric oxygen. Purified lambda phage DNA was not affected by oxygen. Cellular DNA and RNA were degraded slowly in nitrogen air. These results suggest that both atmospheric and endogenous oxygens play a role in DNA degradation in dried tissues.