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Photoaffinity labeling is a powerful technique to identify ligand-binding proteins in a crude mixture and localize their binding-site. Benzophenone photophore has several favorable features compared with the classical photoreactive unit, aromatic azides, that is why its application is expanding. Benzophenone can easily be attached to biologically active ligands by using a tritiated heterobifunctional crosslinker reagent: [3H]-BZDC-NHS or a photoreactive amino acid; [3H]-4-benzoyl-L-phenylalanine. Tethered inositol polyphosphates and antimitotic agents were prepared first and reacted with the high specific activity photocrosslinker reagent in microscale. The photoactivatable ligands obtained were used for studying IP3 receptor, alpha-Trinozitol receptor, PLC delta enzime, beta-tubullin and glycoprotein P. Thrombin receptor was investigated by a short peptide antagonist containing the photoactivatable amino acid. The results demonstrate the versatility of photoaffinity labeling and prove that this technique has a potential providing much more information about the receptor and mechanism than simply identifying a single polypeptide: it contributed to solve the 3D structure of the IP3 binding domain and to reveal a unique activation of the PLC delta. The results confirmed the superiority of benzophenone. Using that photophore glycoprotein P, which is responsible for the MDR, and thrombin receptor were labelled at the first time.