Radiation Effects at the Macromolecular Level

X-ray-induced Luminescence and Optical Absorption in DNA Films

“…An evaluation of the distribution of trap-depths giving thermoluminescence is shown in the table . If we assume that the observed thermoluminescence results from trapped electron-cation recombination, as suggested by Augenstine et al (1960) and by Singh and Charlesby (1966) for DNA, these trap-depths represent the traps of electrons .…”

“…It has been suggested that the energy traps yielding thermoluminescence in biochemicals consist of excitons (Lehmann and Wallace 1964), or charged species (Augenstine, Carter, Nelson and Yockey 1960) . The latter idea was the basis of the model of thermoluminescence in DNA proposed by Singh and Charlesby (1966), who suggested that the light emission arises from electron-cation recombination proceeding via an excited triplet state of the luminescent centre.…”

The Effects of Ionizing Radiation on Enzymes

“…151). Thus radiation could destroy enzymic activity either by chemically altering the crucial amino acid side chains or by disrupting the conformation essential for proper functioning (24). Mechanisms which have been proposed to account for these alternatives are discussed below and are classified as six models.…”

“…quantum of UV (cf. 24,174,239). The smaller energies imply that weak secondary and tertiary bonds are involved, and the importance of the disruption of cystine groups and hydrogen bonds in UV inactivation has recently been demonstrated (21,26,27).…”

“…DNase did not show such a large increase, and Setlow has speculated that this may indicate a fundamental difference between the energy requirements for inactivation of high-and low-cystine containing proteins (239) (e.g., see model 5 ) . It is of particular interest that Setlow et al found a correlation between the relative yield of ejected electrons and the inactivation cross section in the vacuum-UV region (239,243)) thus suggesting that perhaps not only the amount of energy absorbed but also the possible production of a free radical may be important in determining the extent and/or nature of the damage prodnced (see model 2 and also 24,135).…”