Amyloid fibrils are fibriform aggregates of amyloid proteins, which are implicated in many protein deposition diseases. Knowing the structures of amyloid fibrils will shed light on the molecular mechanism of fibrillation, facilitating the prevention and therapy of related diseases. Solid-state NMR is the most prospective technique for elucidating the structures of amyloid fibrils, since they are insoluble and non-crystalline such that they are difficult to be studied by liquid-state NMR and X-ray diffraction approaches. In this paper, recent progresses on using solid-state NMR methods to elucidate structural information of proteins, especially amyloid fibrils, are reviewed.

Fusion between viral and cellular membranes is an essential process for enveloped viruses to enter into cells. This process is usually mediated by fusion proteins on the surfaces of viral membranes. When pH changes from 7.0 to 5.0, the fusion proteins transform and expose their fusion peptide to anchor the cellular membrane and induce the subsequent fusion process. Ha133 (HaF) is the fusion protein of baculoviruse Helicoverpa armigera Single  Nucleocapsid Nucleopolyhedrovirus (HearNPV). Its fusion peptide is composed of 20 residues, and located at the N-terminus of the F₁ subunit. In this study, NMR methods were used to determine the solution structure of the fusion peptide in a membrane-mimicking environment at pH 7.0. It was found that the structure of the fusion peptide is composed of a 3₁₀ -helix from V⁷ to S⁹, a turn at V¹⁰, a regular α-helix from D¹¹ to G¹⁶ and two flexible coils at the N- and C-terminus. Comparing this structure to the available structure of this fusion peptide at pH 5.0, it is noted that, with decreasing pH, the conformation of the fusion peptide alters to be more stable and to have a more complete amphiphilic surface. These results should allow us to further investigate the mechanism of membrane fusion.

Non-Local Means (NLM) is an excellent filter for noise removal and has been applied successfully to MR images. However, just like every other denoising filters, it inevitably blurs fine structures in images to certain extent. In this paper, we propose to combine high frequency components (HFC) extracted from the original image with the NLM-denoised image to recover the lost details. High frequency components, which contain rich edge information, are extracted with a multiresolution method based on Laplacian Pyramid. Then the HFCs are combined with the image denoised by NLM using a continuous edge map produced by an edge detector which is based on SUSAN operator and modified to be more robust to noises. The experiment showed that the proposed scheme achieved good suppression of noise in smooth regions while preserves or even enhances image details. Furthermore, images were enhanced subtly without artifacts that are typical in enhanced images.

Compressed sensing (CS) is a new technique for reconstructing image from undersampled k-space data. In dynamic imaging, data sparsity can be introduced by applying Fourier transformation along the temporal dimension or calculating difference images with respect to a reference frame. In this work, a selective dualdirection sequential CS method was proposed to achieve greater data sparsity in dynamic MR imaging, by calculating difference images  between adjacent frames. Both time sequential or inversed time sequential reconstruction were used for better reconstruction results, while the total computation time remained the same. Experimental results demonstrated that the proposed algorithm showed improved quality relative to the traditional compressed sensing algorithm, differencing algorithm and keyhole imaging technology.

Lipid metabolic dysfunction is a well-accepted risk factor of diabetic complications. Cardiovascular complications of diabetes are the leading cause of diabetic death. In this work, the dynamic changes in plasma levels of unsaturated fatty acids (UFAs) were measured, using diffusion-edited ¹H NMR spectroscopy, in a rat model of streptozotocin (STZ)-induced type 1 diabetes. The results showed that STZ treatment induced elevated UFAs and monounsaturated fatty acids levels in the plasma, and the dynamic changes of fatty acid ratios correlated well with the progression of diabetes. It was proposed that plasma levels of UFAs might be more sensitive indicators for development of type 1 diabetes than clinical lipid screening indices, such as triglyceride (TG) and high-density lipoprotein (HDL) levels. 

Magnetic resonance elastography can be used to measure the elastic stress of the liver and the extent of hepatic fibrosis quantitatively. This paper describes the principles and practical implementation of magnetic resonance elastography, including tissue biomechanical model analysis, development of the shear wave developing stimulator, design of elastic imaging sequence and fitting algorithms for elastography. Magnetic resonance elastography measurements on ex vivo pork liver and human volunteers were demonstrated experimentally.

Preliminary tests were carried out to evaluate the performance of the magnet system in an EPR spectrometer dedicated for in vivo tooth dosimetry. To reduce spectrum distortion, a method was proposed to rectify the nonlinearity of the scanning field via correcting of the driving current. The results of preliminary tests also demonstrated the feasibility of using horizontal magnet field for in vivo EPR.

Eight 2-aryloxymethyl-1H-benzimidazole acetic acid hydrazides (4) have been synthesized by hydrazinolysis of the corresponding esters 3. Among them, the compounds 4c, 4d, 4f and 4g are new. The structures of the target compounds 4 were characterized by elemental analysis, IR and ¹H NMR. ¹H and ¹³C NMR signals assignments and spatial structure of representative compound 4e are confirmed by its two-dimensional (¹H-¹H COSY, HSQC, HMBC and NOESY) NMR spectra. The tautomerism of compound 4e were studied by the variable-temperature experiment and solvent experiment (DMSO-d₆ and CDCl₃). The experimental results indicate that the target compounds 4 in DMSO at room temperature exist in the tautomeric keto and imine enol forms, and the dominant keto form isomer consists 88.2%~92.6%, while the imine enol form is the only structure in CDCl₃ at room temperature.

Two compounds were isolated from the 75% EtOH extract of Boschniakia rossica Fedtsch et Flerov. The compounds were characterized as  β-D-glucopyranose 1-(3,7-dimethyl-2-trans-6-octadienoate) (1) and 6,7-dihydrofoliamenthoic acid diglucoside (2) by ¹H and ¹³C NMR and 2D NMR techniques (i.e., ¹H-¹H COSY, HSQC, HMBC, and NOESY).  Compound 1 was found to be a new compound, while compound 2 was obtained from Orabanchaceae family for the first time.

¹H and ¹³C NMR signals of N-substituted indole derivatives were assigned using 1D and 2D NMR techniques. The effects of C-N bond rotation barrier on the ¹H and ¹³C NMR signals in compound m was studied using variable-temperature NMR. Rotation rate and free energy were calculated under coalesce temperature. The rotation barrier dependence on the solvent effects of m was also studied. It was found that the rotation barrier about C-N in m was higher in polar solvent.

The interaction between β-cyclodextrin (β-CD) with 3S-tetrahydro-isoquinoline-3-carboxylic acid (THIQA) was studied by high-resolution liquid-state NMR spectroscopy. The spectra of β-CD and the β-CD/THIQA inclusion complex were compared. The results of 2D ROESY experiments further revealed the interactions between H5/H6 of β-CD and THIQA.

2,6-Bis(trimethyltin)-4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b´]dithiophene, the monomer of a polymer solar cells material, was synthesized from 4,8-dihydrobenzo[1,2-b:4,5b´]dithiophen-4,8-dione. The structure of the compound was determined by multinuclear NMR spectroscopy, including ¹H, ¹³C, ¹¹⁹Sn, ¹¹⁷Sn NMR, DEPT, selective 1D TOCSY and 2D NMR techniques including ¹H-¹H COSY, gHSQC and gHMBC. The ¹H, ¹³C, ¹¹⁹Sn, ¹¹⁷Sn NMR chemical shifts were assigned and the spectral features of the compound were discussed.

The applications of magnetic resonance molecular imaging are often hindered  by low sensitivity. Magnetic resonance signal of hyperpolarized ¹²⁹Xe can be enhanced 4~5 orders of magnitude by spin-exchange optical pumping. Ultrasensitive ¹²⁹Xe magnetic resonance molecular imaging shows a huge advantage in sensitivity comparing with the conventional MRI. In this paper, the improvement of the sensitivity of MRI and its applications to scientific research are introduced; the basic structures and principle of Xe-based biosensors are interpreted; the updated methodology and technology of molecular imaging are reviewed, and the advance of magnetic resonance molecular imaging with hyperpolarized ¹²⁹Xe is commented.

Two-dimensional (2D) NMR parameter maps are widely used in NMR-based well logging and conventional NMR experiments to distinguish different components in mixtures. In recent years, much research efforts were dedicated to develop inversion algorithms that could convert raw experimental data into 2D NMR maps. This paper reviews the recent progresses in this area of research. The methodological complexity of 2D inversion, relative to 1D inversion, was discussed. There are two major approaches for 2D inversion: regularization using penalty terms and regularizing in subspace. The advantages and disadvantages of the approaches were analyzed. It is concluded that all the existing 2D inversion algorithms have limitations such that  further development are needed.