Peptide mixture, simple labeled

In discussing photoaffinity labeling experiments with radioactive reagents, I shall focus mainly on the labeling of protein receptors with small photola-bile ligands. The same principles may be applied to related experiments. The general approach to identifying a receptor in a mixture of proteins is first described. The mixture may be extremely complex, e.g. whole cells or a membrane preparation, or relatively simple, e.g. a purified multisubunit protein. Second, experiments to locate a label within a protein are described. This may be at the level of a low resolution peptide map or in favorable cases the identification of a labeled amino acid residue. 

---