High-resolution Magic-angle Spinning (HR-MAS) NMR Spectroscopy

Abstract

Since the beginning of high-resolution magic-angle spinning (HR-MAS) NMR spectroscopy in 1990s, we have witnessed tremendous instrumentation and methodological advancements in the HR-MAS NMR technique for semisolids. With HR-MAS, it is now possible to acquire reliable high-quality spectra in a routine and high-throughput fashion, and it has become a well-integrated metabolic screening tool for ex vivo biospecimens such as tissue biopsies, cells and organisms for NMR-based metabolomics research. This chapter provides the basic principles of HR-MAS and describes a few recent noteworthy developments that could strengthen the role of HR-MAS as a frontline NMR technique for metabolomics.

High-Resolution Magic Angle Spinning (HR-MAS) NMR-Based Fingerprints Determination in the Medicinal Plant Berberis laurina

“…In such, NMR spectroscopy is widely used in multidisciplinary “omics”, such as metabolomics, metabolic profiling, fingerprinting, and phenotyping [ 11 , 12 , 13 , 14 ], as well as in identification and structural determination of organic compounds in various samples such as food [ 4 ], ice [ 8 ], serum [ 10 ], environmental [ 15 ], material science [ 16 ], and water [ 17 ]. In addition, high-resolution magic angle spinning (HR-MAS) is a multipurpose NMR tool allowing the acquisition of NMR data directly from semi-solid (i.e., gel-like) materials (e.g., plant tissues) in their natural, unaltered states, without laborious sample preparation steps, and then preventing changes in the chemical composition during these process [ 18 , 19 ]. Moreover, the HR-MAS NMR technique uses specialized HR-MAS probes that allow to collect high-resolution spectra from heterogeneous samples with remarkably similar spectral resolutions as those observed for homogeneous samples in a liquid state (i.e., solution state).…”

“…Due to restricted and low molecular tumbling conditions, botanical samples contain several anisotropic trends such as dipolar (through bonds and space) interactions, magnetic susceptibility, and chemical shift anisotropy [ 18 , 20 ]. These trends directly affect T2 relaxation, which produces a nonuniform shift (line-broadening), also causing low signal-to-noise and resolution in NMR spectra [ 18 , 21 , 22 , 23 ]. Dipolar coupling is proportional to the “3cos 2 θ−1” term in the second-order Legendre polynomial equation: “P 2 (cos 2 θ) = 1\2(3cos 2 θ−1)”.…”

“…Dipolar coupling is proportional to the “3cos 2 θ−1” term in the second-order Legendre polynomial equation: “P 2 (cos 2 θ) = 1\2(3cos 2 θ−1)”. Therefore, the line-broadening effects coming from dipolar interactions can be minimized by spinning the sample at high spinning rates at the so-called magic angle ( θ MAS = 54.74°) [ 18 , 22 ]. Additionally, in order to improve spectral resolution [ 18 ], the HR-MAS technique is to be applied to the swollen sample in a suitable NMR solvent that provides some molecular motions [ 19 , 22 ].…”

“…Therefore, the line-broadening effects coming from dipolar interactions can be minimized by spinning the sample at high spinning rates at the so-called magic angle ( θ MAS = 54.74°) [ 18 , 22 ]. Additionally, in order to improve spectral resolution [ 18 ], the HR-MAS technique is to be applied to the swollen sample in a suitable NMR solvent that provides some molecular motions [ 19 , 22 ]. In addition to the liquid state, HR-MAS NMR has been used in metabolic analyses in human, plant, and food stuff quality managements, genotype, phenotype, and organism cataloging, with interindividual comparisons, environmental toxicity, and pollution [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ].…”

HR-MAS NMR Applications in Plant Metabolomics

“…The major advantage of HR-MAS NMR over liquid-state NMR is that there is no extraction step necessary which can lead to the loss of signals from non-soluble metabolites. It is a non-destructive method, which makes it possible to use the samples for other experiments such as transcriptomics analysis [ 79 , 80 ]. The pre-processing steps of the one-dimensional HR-MAS NMR spectra need to be done carefully.…”