Dynamic Nuclear Polarization With Electron Decoupling in Intact Human Cells and Cell Lysates

Dynamic nuclear polarization (DNP) is used to improve the inherently poor sensitivity of nuclear magnetic resonance (NMR) 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 has yet to be applied to intact cells or cellular lysates. Here, we demonstrate for the first time exceptionally fast 1H T1DNP times of just 200 ms and 300 ms at 90 K 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 1...