To identify photoaffinity-labelled amino acid residue(s), we devised an effective method utilizing immunoaffinity purification of photolabelled fragments, followed by matrix-assisted laserdesorption ionization-time of flight (MALDI-TOF) MS and nanoelectrospray ionization tandem MS (nano-ESI-MS\MS) analysis. Human serum albumin (HSA) was photolabelled with an azidophenyl derivative of semotiadil,HSA is a major binding protein for semotiadil in serum. After lysyl endopeptidase digestion, photolabelled HSA fragments were adsorbed selectively on to Sepharose beads on which an anti-semotiadil antibody was immobilized, and fractions were eluted quantitatively by 50 % acetonitrile\10 mM HCl. MALDI-TOF MS analysis of the eluted fraction showed that it contained two photolabelled fragments of m\z 2557.54 (major) and 1322.44 (minor), corresponding to Lys-414-Lys-432 and Ala-539-Lys-545, respectively. Further nano-ESI-MS\MS analysis revealed that Lys-414 was the photolabelled amino acid
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.