Search

Dynamic nuclear polarization (DNP) is used to improve the inherently poor sensitivity of nuclear magnetic resonance spectroscopy by transferring spin polarization from electrons to nuclei. However, DNP radicals within the sample can have detrimental effects on nuclear spins close to the polarizing agent. Chirped microwave pulses and electron decoupling (eDEC) attenuate these effects in model systems, but this approach is yet to be applied to intact cells or cellular lysates. Herein, we demonstrate for the first time exceptionally fast 1H T1DNPtimes of just 200 and 300 ms at 90 and 6 K, respectively, using a newly synthesized methylated trityl radical within intact human cells. We further demonstrate that eDEC can also be applied to intact human cells and human and bacterial cell lysates. We investigate eDEC efficiency at different temperatures, with different solvents, and with two trityl radical derivatives. At 90 K, eDEC yields a 13C signal intensity increase of 8% in intact human cells and 10% in human and bacterial cell lysates. At 6 K, eDEC provides larger intensity increases of 15 and 39% in intact human cells and cell lysates, respectively. Combining the manipulation of electron spins with frequency-chirped pulses and sample temperatures approaching absolute zero is a promising avenue for executing rapid, high-sensitivity magic-angle spinning DNP in complex cellular environments.

•Spinning frequency > 68 kHz of 2 mm spherical rotors using helium spinning gas.•Magic angle adjustment at spinning frequency of 59.3 kHz using KMnO4.•Nonregulated spinning stability of ±0.5% during data acquisition.•Improvements on stator and RF coil results in three-fold increase in NMR sensitivity.•Customized narrow-bore transmission line probe for 2 mm spheres.

•A new stator for spinning spherical MAS rotors is designed and 3D-printed for use in an NMR probe.•The new stator enables fine and stable control of the spinning angle of a sphere rotor with no mechanical adjustment required.•The angle adjustment sensitivity is measured by observing the off-magic angle lineshape of a deuterated solid and comparing to simulated spectra.