Evaluating the Sulfate Radical Anion as a New Reagent for In-Cell Fast Photochemical Oxidation of Proteins.

Fast photochemical oxidation of proteins (FPOP) has demonstrated the ability to inform on the higher order structure of proteins. Recent technological advances have extended FPOP to live cells (IC-FPOP) using multiple cell lines and in vivo (IV-FPOP) using C. elegans. These innovations allow proteins to be studied in their native cellular environment. Hydroxyl radicals are generated via the photoloysis of hydrogen peroxide. Hydrogen peroxide is a signaling molecule that can induce changes to some proteins in the cell limiting the proteins that can be studied by IC-FPOP. Here, we evaluate the sulfate radical anion as a footprinting label in IC-FPOP with sodium persulfate as the precursor. Our findings show a 1.5-fold increase in the number of modified proteins compared to IC-FPOP using hydroxyl radicals at the same precursor concentration demonstrating the amenability of this radical with IC-FPOP.