Post-separation detection of nucleic acids and proteins by neutron activation

We describe approaches to neutron activation analysis and their application to post-separation autoradiographic detection of biological compounds. Specifically, we have extended the use of a "direct-labeling" method to the post-separation detection of DNA after gel electrophoresis and to the detection of nucleotides separated by TLC. In addition, we describe a more generally applicable "indirect-labeling" method in which separated compounds of interest are selectively bound to ligands containing highly neutron-activatable elements, such as manganese (55Mn), europium (151Eu), or dysprosium (164Dy), and then irradiated with thermal neutrons. This method is illustrated with nucleotides separated by TLC and with proteins separated by polyacrylamide gel electrophoresis. In contrast to the direct-labeling approach, the indirect-labeling method can be adapted to detect any class of substances for which a highly neutron-activatable, selectively binding ligand is available. The theoretically achievable sensitivity of the indirect-labeling method is in the attomole (10(-18) mol) range.