PARENT SESSION
9:00 AM to 11:00 AM
Sunday, April 21, 2002
Symposium 3
Clustered Radiation Damage in DNA: An Interdisciplinary Approach
Room: Nevada 8-9-10
Chair: Zimbrick, John²²Purdue University, West Lafayette, IN
Speakers: Bowman, Michael ⁴; Green, Nicholas⁵; O'Neill, Peter⁶; Wallace, Susan⁷⁴Pacific Northwest National Laboratory, Richland, WA⁵King's College, London, England⁶MRC Radiation and Genome Stability Unit, Didcot, Oxon, Ox11 ORD, UK⁷University of Vermont, Burlington, VT

(S03-1) Spatial Distribution of Damage in Irradiated Biomaterials.

Bowman, Michael^*,1, Zimbrick, John², ¹ WR Wiley Environmental Molecular Sciences Laboratory, Richland, Washington² School of Health Sciences, West Lafaeyette, Indiana

ABSTRACT-
Ionizing radiation deposits energy non-uniformly in tissues, resulting in a non-uniform distribution of damage. The different types of radiation, e.g., photons and charged particles, produce different physiological effects as a result of these differences in the spatial distribution of damage. Some materials, such as tooth eneamel at ambient temperatures or biological materials at cryogenic temperatures, trap much of the irradiation induced damage as free radicals that can be observed and studied by electron spin resonance (ESR or EPR) spectroscopy. Newly developed pulsed EPR methods now make it possible to quantitatively measure small, distance-dependent interactions between free radicals and reconstruct the distribution of distances between free radicals in these irradiated materials. In tooth enamel, the distribution of trapped free radicals resulting from -rays and 2 MeV protons have been measured by EPR with diameters of 27 and 37 nanometers respectively. These are undoubtedly expanded distributions resulting from diffusion of mobile, radiation-produced precursors prior to trapping as stable free radicals. However, they do reveal the spatial distribution of damage products soon after the ionizing events and they also offer the potential for reconstructing the radiation history of irradiated material. This work was supported by the DOE and NIH and was performed in part at the WR Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by DOE/OBER at Pacific Northwest National Laboratory.

KEYWORDS: EPR, ESR, Tooth Enamel