Assay for nanogram quantities of DNA in cellular homogenates.

Abstract The DNA concentration of a crude cellular homogenate can be measured accurately in the nanogram range using the fluorescence enhancement of 4′,6-diamidino-2-phenylindole (DAPI) or bisbenzimidazole (Hoechst H 33258) complexed with DNA. A simple assay has been devised including an internal standard, which allows reliable measurement and compensates for any quenching due to cellular components or buffer. The fluorescence enhancement is highly specific for DNA; no other cell component produces significant fluorescence. The response is linear over a broad dynamic range making the measurement of unknown DNA concentrations convenient.