Xiaohong Cui

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

Background and Purpose Nuclear 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 Methods Intact 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. Results When 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. Conclusion Due 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.

Brown adipose tissue mapping in rats with combined intermolecular double-quantum coherence and Dixon water-fat MRI

Brown adipose tissue (BAT) is a promising therapeutic target in obesity studies. Recently, MRI has been proposed for the mapping of BAT. However, because of the limitation of spatial resolution, similar to the existing positron emission tomography and computed tomography techniques for BAT detection, it fails to distinguish BAT cells when they are mixed with other cells. In this work, a new MRI method is proposed, combining intermolecular double‐quantum coherence and the chemical shift‐encoded Dixon method. Its contrast depends on the water to fat ratio at the cellular scale, which is smaller than the imaging voxel size. The feasibility of this MRI method was shown with computer simulations and phantoms, and preliminary imaging of BAT of rats at 7 T. Both computer simulations and experimental results are consistent with theoretical predictions. The method provides a novel contrast mechanism and can map BAT distribution exclusively. In particular, a mixture of BAT cells and white adipose tissue cells was detected in an older rat, which was undetectable by other noninvasive methods. This method may be applicable to a wide range of uses in BAT‐related studies, including the formation and variation of BAT. Copyright

High-resolution NMR spectroscopy in inhomogeneous fields via Hadamard-encoded intermolecular double-quantum coherences.

A new pulse sequence based on intermolecular double‐quantum coherences was proposed to obtain one‐dimensional high‐resolution liquid NMR spectra in inhomogeneous magnetic fields via Hadamard encoding. In contrast with the conventional intermolecular multiple‐quantum coherences method with a two‐dimensional acquisition to obtain one one‐dimensional high‐resolution spectrum, the new method can provide relatively high‐resolution spectra directly through one‐dimensional acquisition, and can greatly improve the signal‐to‐noise ratio of the spectrum within a relatively short acquisition time. Theoretical derivation was performed and analytical expressions of the resulting signals are given. Solution samples in purposely de‐shimmed magnetic fields and pig brain tissue samples were tested. The experimental results demonstrate that this sequence can retain useful structural information, even when the field inhomogeneity is sufficiently severe to erase almost all spectral information with conventional one‐dimensional single‐quantum coherence techniques, and good solvent suppression can be achieved. This method may provide a promising technique for applications in in vivo and in vitro NMR. Copyright

In vivo spatially localized high resolution 1H MRS via intermolecular single-quantum coherence of rat brain at 7 T

To compare the conventional localized point‐resolved spectroscopy (PRESS) with localized 2D intermolecular single‐quantum coherence (iSQC) magnetic resonance spectroscopy (MRS) and obtain in vivo MRS spectrum of rat brain using the latter technique.

High Resolution 31 P NMR Spectroscopy Generates a Quantitative Evolution Profile of Phosphorous Translocation in Germinating Sesame Seed

Phosphorus metabolism and circulation are essential bio-physicochemical processes during development of a plant and have been extensively studied and known to be affected by temperature, humidity, lighting, hormones etc. However, a quantitative description of how various phosphorous species evolve over time has not been reported. In this work, a combined 31P liquid and solid state NMR spectroscopic methodology is employed, supported by a new extraction scheme and data analysis method, to carry out a quantitative investigation of phosphorous circulation in germinating sesame seeds in dark and under illumination with and without adding a growth hormone. The spectra show that only slight changes occur for phosphorous metabolism at the initial stage but a rapid change takes place between 48–96 hours after germination is started. The metabolism is found to be temperature dependent and affected by illumination and hormone. However, neither illumination nor hormone affects the final residual concentration of phytin. Moreover, phytin does not flow out of cotyledon and the phosphorous flowing to other parts of the plant is always in the inorganic form. The overall evolution profile of phytate consumption is found to be a Gaussian decaying function. These findings can be explained with a dynamic model on phytin conversion.

Author Correction: High Resolution 31 P NMR Spectroscopy Generates a Quantitative Evolution Profile of Phosphorous Translocation in Germinating Sesame Seed

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Cover Feature: Macromolecular Crowding May Significantly Affect the Performance of an MRI Contrast Agent: A 1H NMR Spectroscopy, Microimaging, and Fast-Field-Cycling NMR Relaxometry Study (ChemistryOpen 4/2018)

The Cover Feature shows that macromolecular crowders PEG or BSA in an aqueous solution of a paramagnetic magnetic resonance imaging (MRI) contrast agent generally bring additional proton spin relaxation to the water molecules close to the paramagnetic ion and lead to contrast change in the MRI images. This highlights the importance of considering the effect of macromolecular crowding on the performance of MRI contrast agents and image analysis, as well as diagnosis in clinical and functional MRI. More information can be found in the Full Paper on page 288 in Issue 4, 2018 by R.‐H. Cheng et al. (DOI: https://doi.org/10.1002/open.201700192).

Resolution enhancement in MR spectroscopy of red bone marrow fat via intermolecular double-quantum coherences.

High-resolution (1)H magnetic resonance spectroscopy (MRS) is generally inaccessible in red bone marrow (RBM) tissues using conventional MRS techniques. This is because signal from these tissues suffers from severe inhomogeneity in the main static B0 field originated from the intrinsic honeycomb structures in trabecular bone. One way to reduce effects of B0 field inhomogeneity is by using the intermolecular double quantum coherence (iDQC) technique, which has been shown in other systems to obtain signals insensitive to B0 field inhomogeneity. In the present study, we employed an iDQC approach to enhance the spectral resolution of RBM. The feasibility and performance of this method for achieving high resolution MRS was verified by experiments on phantoms and pig vertebral bone samples. Unsaturated fatty acid peaks which overlap in the conventional MRS were well resolved and identified in the iDQC spectrum. Quantitative comparison of fractions of three types of fatty acids was performed between iDQC spectra on the in situ RMB and conventional MRS on the extracted fat from the same RBM. Observations of unsaturated fatty acids with iDQC MRS may provide valuable information and may hold potential in diagnosis of diseases such as obesity, diabetes, and leukemia.