A METHOD FOR MEASURING MICROQUANTITIES OF DNA

Quantitative analysis of DNA content represents a critical step when o nly very small amounts of nucleic acids are available. The DNA content of a small RNA-free sample can be measured in a simple and precise wa y using a two-dimensional approach. DNA samples are spotted on the sur face of an agarose gel containing ethidium bromide (EtBr) and the ultr aviolet-induced low-light fluorescence emitted by EtBr molecules inter calated into the DNA is evaluated. The high sensitivity and reproducib ility of this quantitative method has been obtained using an advanced analysis system capable of distinguishing low-light fluorescent patter ns, as in the case of DNA stained with EtBr, from the background. Use of an internal standard is necessary because the intensity of the sign al is due to the aperture of camera diaphragm and to gel conditions. U sing this two-dimensional analysis system it is possible to obtain rap id and precise quantitation of as little as 2 ng of DNA.