DNA in glasses at 77 K: high energy ionizing radiation versus UV electron ejection.

Most in the field of ionizing radiation damage to DNA in frozen aqueous solutions agree that two major types of radical ions are formed, i.e. G+/A+ and T-/C-. The main evidence stems from EPR and strand break studies. Fluid solutions exposed to laser light are known to give G+ and esolv- with low yields of single strand breaks. We have explored this contrast by photoionizing DNA solutions at 77 K, in the expectation that this would prevent the formation of esolv- and hence that the results might be similar to those for high energy radiation. They are not: the results show only the formation of G+ (or) (A+), the fate of the ejected electrons is unclear except for sodium perchlorate glasses when they react to give O-.