Field-domain rapid-scan EPR at 240GHz for studies of protein functional dynamics at room temperature.

We present field-domain rapid-scan (RS) electron paramagnetic resonance (EPR) at 8.6T and 240GHz. To enable this technique, we upgraded a home-built EPR spectrometer with an FPGA-enabled digitizer and real-time processing software.

Order-of-magnitude SNR improvement for high-field EPR spectrometers via 3D printed quasi-optical sample holders.

Here, we present a rapidly prototyped, cost-efficient, and 3D printed quasi-optical sample holder for improving the signal-to-noise ratio (SNR) in modern, resonator-free, and high-field electron paramagnetic resonance (HFEPR) spectrometers. Such spectrometers typically operate in induction mode: The detected EPR ("cross-polar") signal is polarized orthogonal to the incident ("co-polar") radiation. The sample holder makes use of an adjustable sample positioner that allows for optimizing the sample position to maximize the 240-gigahertz magnetic field and a rooftop mirror that allows for small rotations of the microwave polarization to maximize the cross-polar signal and minimize the co-polar background.

Triggered Functional Dynamics of AsLOV2 by Time-Resolved Electron Paramagnetic Resonance at High Magnetic Fields.

We present time-resolved Gd-Gd electron paramagnetic resonance (TiGGER) at 240 GHz for tracking inter-residue distances during a protein's mechanical cycle in the solution state. TiGGER makes use of Gd-sTPATCN spin labels, whose favorable qualities include a spin-7/2 EPR-active center, short linker, narrow intrinsic linewidth, and virtually no anisotropy at high fields (8.6 T) when compared to nitroxide spin labels.

Reflection terahertz time-domain spectroscopy for imaging and identifying concealed interfaces in insulated systems.

Polarization-resolved reflection spectroscopy enabled by a custom ultrahigh molecular weight polymer dove prism is used to identify spectral characteristics that manifest in the time domain at terahertz frequencies, which shows promise in combination with terahertz time-domain reference-free reflection imaging at a concealed interface. The method is used to produce 100×100 pixel images of an interface concealed by an ultrahigh molecular weight polymer using TE and TM polarized terahertz fields. The construction of material-specific image filters is guided by a theoretical reflection model by identifying reflection pulse characteristics unique to an interface.