Upgrade of Bruker Time-domain EPR Spectrometer

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.