Dear Forum Members, I am a molecular biologist. One of my projects is focused on the identification of a protein that interacts with a known organic molecule. Namely, I try to chase a transmembrane protein that is known to transport one organic acid. If possible, I would like to get an idea on whether it is possible to induce measurable radioactivity in a protein molecule by subjecting it to a radio-labeled interacting substrate. My idea is to label the transport substrate with a radioisotope, then isolate the whole spectrum of proteins from a given biological membrane, and finally identify the protein that physically interacted with the radiolabeled substrate (namely, transported it) by tracing the induced radiation in that protein. Specifically, my questions are as follows: 1. Would the strength of the induced signal be measurable? 2. If yes, which method would be the most sensitive? 3. Which isotope would be the most efficient in the induction (out of N, C, O, or H)? Finally, do you see any alternative way of inducing a measurable change in a target protein? Thank you in advance! Igor.