Photographic quantitation of DNA in gel electrophoresis.

Abstract A photographic procedure to quantitate the DNA in bands, obtained by gel electrophoresis after staining with ethidium bromide, is described. The relationship between the film darkening and the intensity of the light hitting the film was determined. The densities, measured in densitometric tracings of the negatives, were converted into fluorescence intensities. The fluorescence was found to be linearly proportional to the amount of DNA. Deviations due to gel overloading, to nonuniform electrophoretic migration and uv illumination, and to photodecomposition of ethidium bromide were investigated.