Mechanisms for radiation damage in DNA. Progress report, June 1, 1991--May 31, 1992
In this project we have proposed several mechanisms for radiation damage and recently radiation protection to DNA and its constituents, and have detailed a series of experiments utilizing electron spin resonance spectroscopy, HPLC and GC-mass spectroscopy to test the proposed mechanisms. In this years` work we have continued the investigation of the localization of the initial charges on DNA after irradiation through experiment and through the use of ab initio molecular orbital theory. The experimental results and MO calculations are in agreement that cytosine, not thymine, is likely the principal locus for excess charge; whereas guanine is confirmed as the initial site for the cationic charge. The mechanism for the anion localization on cytosine is clarified by MO calculations of DNA base pair and stacked base pair (GC/AT) ion radicals. In addition predictions made from a new model of ion transfer in DNA are tested and confirmed by an ESR investigation of irradiated single stranded DNA. In this years` effort in joint work with Wake Forest University we have also made excellent progress in the study of products produced from the direct effect of radiation on DNA. The release of unaltered bases and DNA base damage products are shown to be a function of hydration layer and evidence for a demarcation between the direct and indirect effect of radiation is presented. DNA base products from irradiations at ambient temperatures are shown to be those that would be predicted from ESR studies at low temperatures. In addition initial studies of radiation effects on DNA-protein complexes and certain sensitive amino acids have been initiated to shed light on the role of histones on DNA radiation damage. 16 refs., 2 figs., 1 tab.
- Research Organization:
- Oakland Univ., Rochester, MI (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-86ER60455
- OSTI ID:
- 10104342
- Report Number(s):
- DOE/ER/60455--5; ON: DE91019079
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400600
AMINES
CHARGE TRANSPORT
CHEMICAL RADIATION EFFECTS
CHROMATIN
DNA
ELECTRON SPIN RESONANCE
GAMMA RADIATION
HISTONES
HOLES
HYDRATION
PROGRESS REPORT
RADIATION CHEMISTRY
RADICALS
RADIOLYSIS
RADIOPROTECTIVE SUBSTANCES
REACTION INTERMEDIATES
STRAND BREAKS
THIOLS