First DNP results from a liquid water-TEMPOL sample at 400 MHz and 260 GHz

Abstract

Using a newly designed liquid-state dynamic nuclear polarization (DNP) spectrometer operating at a magnetic field of 9.2 T, a DNP enhancement of -4.0(1) was achieved for protons in a liquid water-TEMPOL sample. The DNP mechanism was observed to be the Overhauser effect, where the polarization was transfered via electron-proton dipolar relaxation. At full microwave power, the sample was heated by 17 K above room temperature, causing a significant increase in the DNP enhancement. These first results from the Frankfurt liquid-state DNP spectrometer represent a significant step towards the application of DNP to large biomolecules in the liquid state. © 2008 Springer-Verlag.