Photochemistry and photobiology of DNA containing 5-iodouracil and 5-iodocytosine. [Escherichia coli, Bacillus subtilis]

The quantum yields for the photolysis of iodinated derivatives of cytosine (leading to the loss of iodine) has been measured for 313 nm radiation and found to decrease from 0.024 for IodCMP down to 0.007 for both Poly(C) and DNA containing 5-IodCyt. In DNA, approximately 1 clean chain break and 1 alkali-labile bond were formed for every 10 iodines lost. Incorporation of iodinated cytosine or uracil into the DNA of Escherichia coli or Bacillus subtilis was shown to have a large effect on the biological survival following 313 nm radiation