The method, protocol describes a technique of the quantitation of DNA using Hoechst 33258, a fluorescent dye that binds to double-stranded DNA.  Fluorometry is simple and more sensitive than spectrophotometry, and allows the detection of nanogram quantities of DNA.  The assay can only be used to measure the concentration of DNAs whose sizes exceed ~1 kb, as Hoechst 33258 binds poorly to smaller DNA fragments.

Protocol: Fluorometric Quantitation of DNA Using Hoechst 33258 Protocol