The review is a random walk through aspects of ESR studies, mainly of DNA systems, after exposure to ionising radiation at low temperatures. Under these conditions I suggest that "direct" damage is a major significance, and ESR evidence for the concept of the initial formation of electron-gain and electron-loss centres localised within the DNA bases, and deeply trapped by proton-gain and loss, will be discussed. It is stressed that "negative" evidence, showing that various phosphate and sugar centred radicals are not detected, is of major importance since the ESR "fingerprints" for base-radicals are relatively ill defined.
The use of additives that selectively scavenge "holes" and electrons is outlined together with the use of strand-break studies as a rough measure of overall damage. There is a brief diversion on the use of polyammonium cations (polyamines) to enhance the efficiency of "drug" delivery to DNA. How far electrons move within the base-stacks is discussed, and the use of intercalators outlined.
The links between UV damage and that induced by ionising radiation is considered, and the situation that arises at the threshold of ionisation is stressed. A sideways look at the way DNA copes with UV generated thymine dimmers is also touched on.