Dynamic Nuclear Polarization for Neutron Crystallography

X-ray crystallography has been a widely used technique to study the macromolecular structure of proteins, however x-rays do not diffract well off lighter elements, so determining the precise location of the hydrogens in a molecule isn’t feasible. A solution is to use neutrons instead. Neutrons are much more sensitive to lighter elements and can fill in these hydrogen gaps. The low flux of neutrons leads to a need for large protein crystals, which are technically challenging to grow in a lab. Dynamic Nuclear Polarization (DNP) works to polarize the hydrogen atoms in a protein crystal using high magnetic field (2.5 – 5T), low temperature (≤1K), and microwave irradiation, which greatly increases the coherent scattering cross-section and decreases the S/N ratio. We built a proof-of-concept DNP system at Oak Ridge National Laboratory to study single protein crystals. We tested several T4 lysozyme protein crystals soaked in TEMPO prior to freezing in LN2. This was tested on the IMAGINE beamline, a Laue diffractometer, at the High Flux Isotope Reactor. Preliminary results and a description of the test apparatus will be presented.