RESUMO
Cryogenic magic angle spinning (MAS) is a standard technique utilized for dynamic nuclear polarization (DNP) in solid-state nuclear magnetic resonance (NMR). Here we describe the optimization and implementation of a stator for cryogenic MAS with 9.5â¯mm diameter spherical rotors, allowing for DNP experiments on large sample volumes. Designs of the stator and rotor for cryogenic MAS build on recent advancements of MAS spheres and take a step further to incorporate sample insert and eject and a temperature-independent spinning stability of ±1â¯Hz. At a field of 7â¯T and spinning at 2.0â¯kHz with a sample temperature of 105-107â¯K, DNP enhancements of 256 and 200 were observed for 124 and 223⯵L sample volumes, respectively, each consisting of 4â¯M 13C, 15N-labeled urea and 20â¯mM AMUPol in a glycerol-water glassy matrix.