Nucleic acids quantitation in polyacrylamide disc gels with a modified double beam spectrophotometer.

Quantitation of RNA and protein bands separated in polyacrylamide disc gel electrophoresis is time consuming and not reliable when performed after staining processes. The best theoretical approach is the use of absorption spectra of the samples. The present paper reports the construction of an efficient and inexpensive adapter to perform direct scanning of 100 mm gels in a Unicam SP-800 double beam spectrophotometer. Conditions for gel casting and electrophoresis were established for RNA. A linear response between 0.25 micrograms and 15 micrograms per individual peak was found with a quantitative limit of detection of 0.25 micrograms. Spectral analysis of each band can be performed allowing identification of samples as nucleotides and detection of contaminants.