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. Author manuscript; available in PMC: 2007 Dec 1.
Published in final edited form as: Free Radic Biol Med. 2007 Mar 12;42(11):1632–1650. doi: 10.1016/j.freeradbiomed.2007.02.030

Figure 2. Sequence of Events Following Radiation Energy Absorption.

Figure 2

Following exposure to ionizing radiation, energy is absorbed by tissues very quickly. Secondary radicals are formed within 10−6 sec and it is these molecules that are intercepted by radioprotectors such as nitroxides and endogenous thiols. Between 10−6 to 10−3 sec the BIM radical is formed and is either repaired by thiols or nitroxides or fixed by oxygen. In this way, oxygen increases the biological effectiveness of radiation. BIM oxidation may either be repaired enzymatically or, in the case of DNA, strand breaks may occur. DNA or other BIM damage may prevent or alter cell division causing cell death or lack of proliferation. Alternately, mutated DNA may proliferate resulting in long term genetic effects including cancer. Other late effects such as fibrosis and vascular damage result from the permanent damage to other BIMs over the course of months to years.