MRI: Acquisition of a Variable Field (X-, Q-band) Pulsed EPR Spectrometer for Research and Training

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With this award from the Major Research Instrumentation Program (MRI) and support from the Chemistry Research Instrumentation Program (CRIF), Professors Jonas Peters, Theodor Agapie and colleagues from the California Institute of Technology aquire an X-, Q-band pulsed electron paramagnetic resonance (EPR) spectrometer and related accessories including electron nuclear double resonance (ENDOR). This instrument allows research in a variety of fields such as those that provide insight on how biologically relevant species with unpaired electrons behave. In general, an EPR spectrometer yields detailed information on the geometric and electronic structure of molecular and solid state materials. It may also be used to obtain information about the lifetimes of free radicals, short-lived, highly reactive species involved in valuable chemical transformations as well as the initiation of pathological tumor growth. In a standard ENDOR experiment, a sample is placed in a magnetic field and irradiated sequentially with a microwave followed by radio frequency. The changes are then detected by monitoring variations in the polarization of the saturated electron paramagnetic resonance transition. These studies impact a number of areas, from the synthesis of inorganic and organic molecules to the development of new solid state materials to compounds of magnetic and biological interest. Employing examples inspired from ongoing research, this instrument is an integral part of research and teaching at the undergraduate and graduate levels at Caltech. Additionally, the investigators have identified a significant number of interested users from the area outside of this institution and also identified a lot of enthusiasm for a hands-on workshop on EPR/pulsed-EPR that is expected to grow the regional user base.The award is aimed at enhancing research and education at all levels, especially in areas such as: (a) the iron-molybdenum co-factor (FeMoco) and nitrogen fixation; (b) models of iron-mediated nitrogen fixation; (c) oxygen-evolving complex in photosynthesis; (d) nickel-catalyzed cross-coupling; (e)photoredox catalysis; (f) spin-active metal-dihydrogen and metal-hydride species; (g) metallonitrenes in catalysis; (h) using C1 and C2 precursors for carbon-carbon couplings; and (i) site directed spin labeling (SDSL) for the study of biogenesis of membrane and secretory proteins.