High-Resolution 1H NMR Spectroscopy of Fish Muscle, Eggs and Small Whole Fish via Hadamard-Encoded Intermolecular Multiple-Quantum Coherence

Abstract

Background and PurposeNuclear magnetic resonance (NMR) spectroscopy has become an important technique for tissue studies. Since tissues are in semisolid-state, their high-resolution (HR) spectra cannot be obtained by conventional NMR spectroscopy. Because of this restriction, extraction and high-resolution magic angle spinning (HR MAS) are widely applied for HR NMR spectra of tissues. However, both of the methods are subject to limitations. In this study, the feasibility of HR 1H NMR spectroscopy based on intermolecular multiple-quantum coherence (iMQC) technique is explored using fish muscle, fish eggs, and a whole fish as examples.Materials and MethodsIntact salmon muscle tissues, intact eggs from shishamo smelt and a whole fish (Siamese algae eater) are studied by using conventional 1D one-pulse sequence, Hadamard-encoded iMQC sequence, and HR MAS.ResultsWhen we use the conventional 1D one-pulse sequence, hardly any useful spectral information can be obtained due to the severe field inhomogeneity. By contrast, HR NMR spectra can be obtained in a short period of time by using the Hadamard-encoded iMQC method without shimming. Most signals from fatty acids and small metabolites can be observed. Compared to HR MAS, the iMQC method is non-invasive, but the resolution and the sensitivity of resulting spectra are not as high as those of HR MAS spectra.ConclusionDue to the immunity to field inhomogeneity, the iMQC technique can be a proper supplement to HR MAS, and it provides an alternative for the investigation in cases with field distortions and with samples unsuitable for spinning. The acquisition time of the proposed method is greatly reduced by introduction of the Hadamard-encoded technique, in comparison with that of conventional iMQC method.

On the use of ultracentrifugal devices for routine sample preparation in biomolecular magic-angle-spinning NMR

“…The g-forces associated with the advocated sample packing approach can exceed 100,000 × g (Table 1), which may indeed lead to irrevocable changes in certain samples (Han et al 2010; Renault et al 2013; Cai et al 2014). Whilst this is not an unreasonable concern, it is important to realize that this may be a moot point when samples are used for MAS ssNMR.…”

Complete Protocol for Slow-Spinning High-Resolution Magic-Angle Spinning NMR Analysis of Fragile Tissues

“…Recent studies have illustrated the deleterious effects of high-frequency MAS on the morphology of human glioblastoma tumors 27 or fish eggs. 28 In this latter case, the globular and plump eggs became shriveled and bleached, because of the rupture of the egg membrane and the dehydration of egg cells. Figure 5 shows photographs of a set of lumpfish eggs before and after 15 min of MAS at either 4 kHz or 400 Hz.…”

Two-Dimensional J-Resolved NMR Analyses of Fish and Its Products via Spatially Encoded Intermolecular Double-Quantum Coherences

“…Metabolites are assigned according to the literature (Cai et al 2014;Gribbestad et al 2005). As displayed in Table 1, 15 peaks in the 2D UfiDQCJRES spectrum and 19 peaks of the 2D MAS spectrum are both classified into nine metabolites, while only seven signal peaks in the conventional 2D JRES spectrum are assigned into four metabolites.…”

“…A detailed comparison of observed metabolite information between 2D UfiDQCJRES and conventional 2D JRES spectra is presented in Table 2. All peaks observed in UfiDQCJRES and conventional JRES spectra are assigned according to the literature (Cai et al 2014;Gribbestad et al 2005). As shown in Table 2, 24 peaks in the 2D UfiDQCJRES spectrum could be assigned to 15 metabolites, including seven peaks assigned to fatty acids.…”

“…Therefore, inadequacies of these two methods may become pronounced for studies in intact biological food samples, such as fish and its products. During these years, intermolecular multiple-quantum coherences (iMQCs), originating from distant intermolecular spin interactions (Ahn et al 1997;Chung et al 2013), have proven to be applicable for high-resolution spectra in inhomogeneous fields (Baishya et al 2008;Cai et al 2014;Chen et al 2004;Vathyam et al 1996). Recently, an iMQC method is proposed for high-resolution two-dimensional J-resolved (2D JRES) applications to biological samples (Huang et al 2014).…”