Fluorimetric microassay of DNA using a modified thiobarbituric acid assay

A method for the rapid, specific measurement of minute amounts of DNA is presented. The method is sensitive to about 20 ng of DNA, which is equivalent to approximately 3000 mammalian cells. The method employs enzymatic liberation of desoxyribose with DNase and phosphodiesterase. The liberated desoxyribose is reacted with thiobarbituric acid to yield a fluorescing compound with an excitation maximum at 532 nm and an emission maximum at 549 nm, measured with a fluorimeter. The entire procedure is accomplished within a few hours. The result is linear up to about 1 μg DNA or 3 × 10⁵ lymphocytes.