Upgrade of Bruker Time-domain EPR Spectrometer

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This SIG (Shared Instrumentation Grant) project requests NIH funds for a major upgrade of an existing and fully functional Bruker Biospin time domain E580 electron paramagnetic resonance (EPR) spectrometer configured to operate at X- (9.5 GHz) and Q-band (34 GHz) resonance frequencies and acquired back in 2009. The proposed upgrade will significantly expand capabilities of the existing instrument for obtaining atomic-level details on the structural organization of catalytic metal centers in enzymes, free radical intermediates of biochemical and photosynthetic processes, and structural organization oligonucleotides, water soluble proteins, and membrane protein complexes. The specific components of the proposed upgrades include adding (1) pulse-shaping and frequency chirping capabilities enabled by AWG (arbitrary waveform generator) technology, (2) 300 W Q-band (34 GHz) amplifier to achieve a further - up to 5.5-fold - increase in the excitation bandwidth, and (3) cryogen-free variable temperature (5 K to 300 K) accessory to carry out these EPR experiments at optimal temperatures and eliminate dependence on a non-renewable liquid Helium which short supply is creating a major bottleneck in the research. The upgraded instrument will allow for carrying out time-domain EPR experiments at lower protein concentrations, increase the distance range and improve accuracy of longer-range distance constrains, and expand studies of protein systems and, particularly, membrane protein complexes, we have currently major difficulties with because of the equipment limitations. These capabilities will benefit a group if six Major and four Minor users from North Carolina State University and other collaborating groups in North and South Carolina and the USA.