Acquisition of Pulsed EPR and ENDOR/ESEEM

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This award provides funding to upgrade a continuous wave X-band electron paramagnetic resonance (EPR) spectrometer to a pulsed configuration. The pulsed EPR spectrometer will be able to provide structural information that is only accessible using advanced EPR techniques such as ENDOR (electron-nuclear double resonance) spectroscopy and ESEEM (electron spin echo envelope modulation) spectroscopy. EPR is used to detect molecules and sites in materials that contain unpaired electrons such as those that exist in the biologically important transition metals iron, cobalt, copper, nickel and manganese; in light-induced radicals in photosynthetic systems; in solid catalysts comprised of pyrolytic carbon or metal oxides with or without additional transition metals; and in permanent spin labels and spin traps that can be introduced into organic and biological molecules as probes. When used to its fullest capacity, EPR is an advanced structural tool (similar in principle to NMR spectroscopy) that can be applied to large molecules in frozen or liquid solution (unlike X-ray crystallography, which requires high-quality crystals) or to solid materials such as catalysts and adsorbents, with no size limit (unlike NMR spectroscopy, which, with certain exceptions, can only be performed on macromolecules below a certain mass). Ongoing projects affected by the acquisition of this instrument include: 1) Identification of Protein Factors that Influence the Redox Potentials of Organic Cofactors in Photosynthetic Systems; 2) Detection of Metallated Artificial Oligopeptide-DNA; 3) Study of Protein-Bound Radicals in Biological Systems; 4) Experimental and Theoretical Studies of Thiolate-Heme Enzymes; and 5) Elucidation of Lipoic Acid Biosynthesis and Study of Serine Deaminase. Some of the societal benefits of the research to be conducted with this instrument include: 1) A better understanding of oxygen transfer chemistry in thiolate-ligated heme-proteins, which could result in improved catalysts for industrial applications. The thiolate-ligated heme enzymes to be studied use only electrons, protons, and dioxygen (or peroxide) to oxidize substrates. The only by-product is water. Thus, these enzymes are particularly "green" catalysts, and synthetic systems that could mimic their chemistry would be of obvious value. 2) A better understanding of the biochemistry of ribonucleotide reductase. This enzyme has central importance in human health. 3) Insight into the design and fabrication of a biological/organic hybrid electrochemical half-cell that couples Photosystem I with hydrogenases to generate hydrogen gas using sunlight. This long-term goal would lead to a "green" method of generating hydrogen gas using sunlight alone.Graduate and undergraduate students will be educated and trained in advanced EPR with the new instrumentation. They will be exposed to interdisciplinary research at the border of chemistry and biology. Students will learn advanced spectroscopic techniques as well as molecular biology and computational methods. This award will broaden the access of underrepresented groups to advanced instrumentation. The PIs have ongoing collaborations with faculty at local undergraduate colleges. Research undergraduates at Susquehanna University, for example, carry out biological research at their home institution during the school year and perform EPR spectroscopy at Penn State during the summer.