Radioactive reference proteins for the study of labelled proteins by gel electrophoresis: a ready preparation of radiolabelled calibration kits

The use of unlabelled reference proteins as molecular weight markers in the study of radioactive proteins by polyacrylamide gel electrophoresis is rather inconvenient since protein standards should be stained whereas the studied proteins are usually detected by radioautography. A rapid, in vitro method for introducing a radioactive label into reference proteins is described: amino groups are acylated by a highly radioactive, commercially available reagent: N-succinimidyl-[2,3-3H] propionate. Both standard and studied proteins can then be visualized on a single radioautograph; this allows direct comparison of mobilities, thus improving both convenience and accuracy of M/sub r/ determinations, and avoids some major drawbacks of staining, such as the loss of sensitivity of fluorography due to dye-induced quenching. Additionally, in vitro labelling may be used for the detection of proteins in trace amounts, as an alternative method versus silver staining procedures