Determination of the Constants of the Alper Formula for Single-strand Breaks from Kinetic Measurements on DNA in Aqueous Solution and Comparison with Data from Cells

Summary

On the basis of rate constants measured in aqueous solution for (i) DNA single-strand break (ssb) formation induced by OH radicals, (ii) prevention of ssb formation by reaction of DNA radicals with glutathione, and (iii) addition of O₂ to DNA radicals, oxygen enhancement ratios (OER) and K values of the Alper equation have been calculated. The values obtained were compared with OER and K values determined for ssb formation in λ DNA irradiated in Escherichia coli as a function of the oxygen concentration. Without adjustment of any parameter the two sets of data are similar when the corrected Alper formula is used. The results support the oxygen fixation-thiol repair model of Howard-Flanders and Alper, and indicate that under selected conditions DNA in aqueous solution may serve as a model system for DNA in cells.