Dynamic Nuclear Polarization (DNP) for Solid-state NMR of Biological Samples

Kent R. Thurber

Laboratory of Chemical Physics, NIDDK, NIH

Dynamic Nuclear Polarization (DNP) can increase Nuclear Magnetic
Resonance (NMR) signals by 100-fold or more by transferring spin
polarization from electron spins to nuclear spins.We have constructed a
NMR probe that allows cooling the sample to 25 K, while also spinning
the sample at the magic angle (MAS) at 7 kHz.To create DNP, electron
spins in the sample are saturated with 264 GHz microwaves from an
Extended Interaction Oscillator (EIO).The cross effect DNP mechanism
with magic-angle spinning (MAS) of the sample can be understood using
the Landau-Zener formula.Using DNP allows us to acquire 2D NMR spectra
of relatively dilute proteins frozen in water/glycerol solution, in
hours, rather than weeks.I will discuss current work on preparing
samples for DNP by rapid mixing and freezing, with the aim of trapping
intermediate states in biological samples (such as partially folded
proteins).