A Film Detection Method for Tritium‐Labelled Proteins and Nucleic Acids in Polyacrylamide Gels

A simple method is described for detecting 3 H in polyacrylamide gels by scintillation autography (fluorography) using X‐ray film. The gel is dehydrated in dimethyl sulphoxide, soaked in a solution of 2,5‐diphenyloxazole (PPO) in dimethylsulphoxide, dried and exposed to RP Royal “X‐Omat” film at ‐70 °C. Optimal conditions for each step are described. β‐particles from 3 H interact with the 2,5‐diphenyloxazole emitting light which causes local blackening of an X‐ray film. The image produced resembles that obtained by conventional autoradiography of isotopes with higher emission energies such as 14 C. 3000 dis. 3 H/min in a band in a gel can be detected in a 24‐h exposure. Similarly 500 dis./min can be detected in one week. When applied to the detection of 35 S and 14 C in polyacrylamide gels, this method is ten times more sensitive than conventional autoradiography. 130 dis. 35 S or 14 C/min in a band in a gel can be detected in 24 h.