BROMINE ANALYSIS IN 5-BROMOURACIL-LABELED DNA BY X-RAY FLUORESCENCE

The degree of replacement of thymine by 5-bromouracil in the deoxyribonucleic acid (DNA) of the thymine-deficient bacterium Escherichia coli B 15 T(-) has been determined by a nondispersive x-ray fluorescence method. A measure of the fraction by weight of bromine in the purified DNA is required for determining the degree of thymine replacement. This fraction is experimentally determined on 35-microg samples of DNA by x-ray spectroanalysis.