Molecular Aspects of DNA Damage and its Modification

  • P. O. ’Neill
  • E. M. Fielden
Part of the NATO ASI Series book series (NSSA, volume 124)


The time scale of radiation induced events in a biological system is illustrated in Figure 1. The initial energy deposition events occur on a time scale related to the passage of a particle moving at the velocity of light crossing an atomic diameter, i. e., of the order of 10−16 seconds. Starting from that moment there is a period in which the deposited energy is redistributed among the energy levels of several molecules, bonds are broken and secondary electrons thermalized. From about 10−12 seconds after the initial energy deposition, recognizable and observable chemical events take place. Because the free radicals produced initially often have strongly oxidizing or reducing properties, these initial radical reactions may be very rapid and complete within microseconds. The products of these reactions themselves are usually radicals, but of a less reactive nature, and thus a chain of chemical reactions is initiated which ultimately, within the space of ∿ 1 second, leads to a relatively stable chemical modification of biological molecules. Cells and organisms have various ways in which they deal with such insults, which may be either wholly repaired or may lead to modified biological function; be it cell death or permanent modification of genetic material. Thus, the biological changes induced by radiation, which may be only expressed or observed hours or even years after exposure to radiation, are a consequence of radiation induced chemical events taking place on a much shorter time scale.


Electron Transfer Process Pulse Radiolysis Radical Adduct Thiol Level Thiyl Radical 
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Copyright information

© Springer Science+Business Media New York 1986

Authors and Affiliations

  • P. O. ’Neill
    • 1
  • E. M. Fielden
    • 1
  1. 1.Division of Molecular ProcessesMRC Radiobiology UnitHarwell, Didcot, OxonUK

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