Electro-Optic Measurement of γ-Ray Induced Damage in DNA

  • C. T. O’Konski
  • R. S. Farinato


The effects on aqueous superhelical PM2 and linear calf thymus DNA’s due to γ-radiation from a 60Co source have been studied by pulsed electric birefringence relaxation techniques. In a nitrogen atmosphere the average field-free relaxation time, T, for calf thymus DNA first increased, then decreased as a function of dose in the range 0–13 kRad. A much more rapid decrease in T as a function of dose was determined in the presence of ambient oxygen. Significant differences were easily measurable at the lowest dose tried (~ 0.3 kRad). Solutions of superhelical PM2 DNA in the presence of ambient oxygen showed an asymptotic increase in T by a factor of about 2. This was predicted for supercoil relaxation from a previous electro-optic study of PM2 DNA with ethidium bromide. Significant changes in T were easily discernable at the lowest doses measured (~ 0.3 kRad), with a 50% effect at 0.5 kRad.


Strand Break Double Strand Break Ambient Oxygen Electric Field Pulse Contour Length 
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Copyright information

© Plenum Press, New York 1979

Authors and Affiliations

  • C. T. O’Konski
    • 1
  • R. S. Farinato
    • 1
  1. 1.Department of ChemistryUniversity of CaliforniaBerkeleyUSA

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