Taming Radicals for Novel Peptide and Protein Fragmentation
Professor Ryan Julian
Department of Chemistry
University of California, Riverside
Friday, November 16, 2012
Abstract: Radical reactions play a very important role in the biochemistry of proteins in both productive and harmful ways. Radicals are critical in cell signaling, catalysis, and energy production. Unchecked radicals lead to oxidative stress, which is likely the reason that radical damage is strongly correlated with numerous diseases. Protein radicals are therefore inherently interesting and are involved in several projects that are ongoing within the Julian lab. These projects aim to reveal both practical and fundamental biochemical information. We use photodissociation to site- specifically generate radicals for a variety of experiments including: 1) directing fragmentation of proteins or peptides in gas phase experiments, 2) elucidation of gas phase protein structure, 3) identification of post-translational modifications including racemization of amino acids, and 4) elucidation of fundamental peptide and protein radical chemistry. To carry out these experiments, we have developed a suite of chemical functionalities that undergo direct, homolytic dissociation upon activation by a UV photon. Typically, this involves cleavage of a carbon-iodine or carbon-sulfur bond with a 266nm photon to generate a radical, followed by examination of the outcome via various mass spectrometry based methods.