Changes of fluorescence spectra of thymine in aqueous solution by radiation.

Aqueous solution of thymine (5 X 10(-4) M, buffered at pH 7.0) was irradiated with 60Co gamma-rays under four different atmospheric conditions. In the presence of t-BuOH-N2, there was little increase in the fluorescence intensity as was previously reported in the radiolysis of cytosine. Under O2 there was also no significant increase differing from the case of cytosine. The fluorescence intensity was found to increase appreciably under N2O but it was less under N2 indicating that OH radical is mainly responsible for the formation of the highly fluorescent products. However, the fluorescence yields under these conditions were much lower in thymine radiolysis than cytosine radiolysis.