INDUCTION OF SINGLE‐STRAND BREAKS (ALKALI‐LABILE BONDS) IN BACTERIAL AND PHAGE DNA BY NEAR UV (365 nm) RADIATION*

Abstract

Irradiation at 365 nm results in the induction of approximately 2.4 X and 1.2 X to-" single-strand breaks (alkali-labile bonds) per 10' daltons per J m-* in extracted phage T4 DNA and in Escherichia coli bacterial DNA, respectively. The rate of break induction in DNA of intact phage is approximately one-fourth that for extracted phage DNA. 2-aminoethylisothiouronium bromide-HBr protects against break induction in both phage systems. No breaks are induced in the DNA of bacteria irradiated under anaerobic conditions over the dose range tested. Possible induction mechanisms are suggested. Consideration is given to the relative importance of pyrimidine dimers and single-strand breaks in the bactericidal action of 365 nm radiation.

Mouse models of UV-induced melanoma: genetics, pathology, and clinical relevance

“…14 UVA is a less potent DNA-damaging agent and can damage DNA indirectly through oxidative damage from reactive oxygen species and through formation of CPDs at TT sites (Figure 1a), which usually do not lead to C>T transitions. 15–17 Human cutaneous melanomas are highly mutated with a predominance of C>T transitions at dipyrimidine sites but fewer CC>TT transitions, which is consistent with UVR mutagenesis. Genomic studies have identified important oncogenes (especially BRAF and NRAS) and tumor suppressors (eg, CDKN2A and NF1) involved in melanoma that have advanced our understanding of different melanoma subtypes and therapeutics.…”

Effects of Near‐ultraviolet Radiation on Microorganisms

“…Tyrrell et a/. [48] show that single-strand breaks in E. coli DNA are formed in uiuo by 366nm radiation at approximately one-half the rate of formation of pyrimidine dimers. Since both types of lesion are capable of repair, it is difficult to know which one (if either) contributes most to near-UV lethality.…”

“…This protection does not extend to the far UV. Furthermore, Tyrrell et al [48] have shown that AET protects against near-UV-induced single-strand breaks in DNA in vitro and in vivo, suggesting that single-strand breakage might be the important lethal lesion. Many earlier findings, notably by Peak and co-workers, have indicated that near-UV lethality is caused in a quite different way from far-UV lethality, as would be expected by the very low absorption of DNA bases in the near UV.…”

Genetic Damage in Escherichia coli K12 AB2480 by Broad-spectrum Near-Ultraviolet Radiation

“…Because of light scatter in solutions of DNA, it has not been possible to measure accurately the true absorption of DNA at wavelengths longer than 320 nm, but progress has been made (4). Other evidence suggests that many of the biological effects observed at wavelengths longer than 320 nm occur through indirect mechanisms such as photodynamic action, which is oxygenenhanced, or triplet sensitization, which is not enhanced by oxygen (5)(6)(7)(8). The answers to these questions are important structure was confirmed by elemental analysis and nuclear magnetic resonance.…”

“…ROBERT B. WEBB MICKEY S. BROWN Division ofBiological and Medical Research, Argonne National Laboratory, Argonne, Illinois 60439 Many hermit crab species carefully select the gastropod shells they inhabit (1-4) and exhibit a complex behavioral sequence before accepting a shell (2,5). Briefly, the selection process begins with the hermit crab grasping a shell with its walking legs and running its opened chelae over the surface.…”