The detection of irradiated food based on modifications to DNA

Most foods are derived from living organisms and consequently contain DNA. DNA is the most important cellular target for radiation induced damage. On irradiating DNA, both single and double strand breakage occur, along with sugar and base alterations. Immunological assays offer the required sensitivity and some preliminary results are presented on the development of an ELISA (Enzyme Linked Immunosorbent Assay) to determine thymidine glycol which is produced by ionising radiation in DNA in both the presence and absence of oxygen. The problem of very low yields of specific products can be overcome by measuring the overall disruption of the DNA double helix, which is a sum of all the individual types of damage. In native DNA, the bases are stacked, disruption of the double helix causes destacking and an increase in UV-absorbance, the so-called hyperchromic effect. At the same time, disruption of the double helix exposes the bases to attack by reactants, such as formaldehyde, present in the solution. The changes in hyperchromicity and rate of reaction with formaldehyde, for calf thymus DNA irradiated in solution and DNA extracted from irradiated wheat have been combined to give a ratio which seems to be a good measure of radiation damage