Dynamic nuclear polarization-enhanced solid-state NMR spectroscopy of GNNQQNY nanocrystals and amyloid fibrils.

Dynamic nuclear polarization (DNP) utilizes the inherently larger polarization of electrons to enhance the sensitivity of conventional solid-state NMR experiments at low temperature. Recent advances in instrumentation development and sample preparation have transformed this field and have opened up new opportunities for its application to biological systems. Here, we present DNP-enhanced (13)C-(13)C and (15)N-(13)C correlation experiments on GNNQQNY nanocrystals and amyloid fibrils acquired at 9.4 T and 100 K and demonstrate that DNP can be used to obtain assignments and site-specific structural information very efficiently. We investigate the influence of temperature on the resolution, molecular conformation, structural integrity and dynamics in these two systems. In addition, we assess the low-temperature performance of two commonly used solid-state NMR experiments, proton-driven spin diffusion (PDSD) and transferred echo double resonance (TEDOR), and discuss their potential as tools for measurement of structurally relevant distances at low temperature in combination with DNP.