title: Complete protocol for slow-spinning high-resolution magic-angle spinning NMR analysis of fragile tissues.
abstract: High-resolution magic-angle spinning (HR-MAS) nuclear magnetic resonance (NMR) is an essential tool to characterize a variety of semisolid systems, including biological tissues, with virtually no sample preparation. The "non-destructive" nature of NMR is typically compromised, however, by the extreme centrifugal forces experienced under conventional HR-MAS frequencies of several kilohertz. These features limit the usefulness of current HR-MAS approaches for fragile samples. Here, we introduce a full protocol for acquiring high-quality HR-MAS NMR spectra of biological tissues at low spinning rates (down to a few hundred hertz). The protocol first consists of a carefully designed sample preparation, which yields spectra without significant spinning sidebands at low spinning frequency for several types of sample holders, including the standard disposable inserts classically used in HR-MAS NMR-based metabolomics. Suppression of broad spectral features is then achieved using a modified version of the recently introduced PROJECT experiment with added water suppression and rotor synchronization, which deposits limited power in the sample and which can be suitably rotor-synchronized at low spinning rates. The performance of the slow HR-MAS NMR procedure is demonstrated on conventional (liver tissue) and very delicate (fish eggs) samples, for which the slow-spinning conditions are shown to preserve the structural integrity and to minimize intercompartmental leaks of metabolites. Taken together, these results expand the applicability and reliability of HR-MAS NMR spectroscopy. These results have been obtained at 400 and 600 MHz and suggest that high-quality slow HR-MAS spectra can be expected at higher magnetic fields using the described protocol.
authors.affiliation: Institut de Chimie des Substances Naturelles, CNRS UPR 2301 , Avenue de la Terrasse, 91190 Gif sur Yvette, France.
authors.forename: Marion
authors.initials: M
authors.lastname: André
authors.forename: Jean-Nicolas
authors.initials: JN
authors.lastname: Dumez
authors.forename: Lamya
authors.initials: L
authors.lastname: Rezig
authors.forename: Laetitia
authors.initials: L
authors.lastname: Shintu
authors.forename: Martial
authors.initials: M
authors.lastname: Piotto
authors.forename: Stefano
authors.initials: S
authors.lastname: Caldarelli
mesh_terms: D000818:Animals; D002417:Cattle; D005260:Female; D008099:Liver / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*