Fast Photochemical Oxidation of Proteins (FPOP)

Information about the Mass Spectrometry Center's expertise and available applications in fast photochemical oxidation of proteins (FPOP) is provided below.

Fast photochemical oxidation of proteins (FPOP) is a hydroxyl radical protein footprinting method used for the study of protein structure and interactions. Hydroxyl radicals are generated via photolysis of hydrogen peroxide by an excimer laser at 248 nm. The radicals oxidatively modify solvent accessible sites in proteins. Upon the binding of a ligand or an alteration in the conformation of the protein, solvent accessibility changes, leading to differences in the labeling pattern in a differential experiment (i.e., comparison of modified residues in the ligand-bound state versus the ligand-free state of a protein). Mass spectrometry is used to identify modified residues and quantitate the levels of labeling thereby providing information on the amino acid level. The method modifies proteins on the microsecond timescale so weak interactions with fast off rates can be observed. FPOP is a general method that can study a wide array of proteins independent of size.

Applications of FPOP include:

  • Identification of protein-protein and protein-ligand interaction sites
  • Identifcation of regions of proteins that undergo conformation changes upon ligand binding
  • Epitope mapping

Currently, FPOP can be performed for in vitro studies. Collaborative projects fof in cell studies will be available in the future.

For FPOP related inquires, please contact Lisa Jones at