Refined magic-angle coil spinning resonator for nanoliter NMR spectroscopy: enhanced spectral resolution

The magic-angle coil spinning (MACS) resonator allows a simple approach for nanoliter nuclear magnetic resonance (NMR) detections with enhanced sensitivity and high-resolution under sample magic-angle spinning (MAS). Currently, the spectral resolution acquired with MACS is not efficient for detailed characterization of semisolids like biopsies, where subhertz resolution is necessary. Here, we describe the two sources of line broadening from MACS, sample temperature gradient and anisotropic magnetic susceptibility, and present a refined high-resolution magic-angle coil spinning (HR-MACS) resonator that improves the spectral resolution. We demonstrate with the high quality HR-MACS NMR spectra of micronematodes and tissue biopsy, and illustrate its potential for NMR-based metabolomics of nanoliter tissue samples.