Abnormal aggregation of α-synuclein, an intrinsically disordered protein in Lewy bodies, is considered a hallmark of Parkinson's disease (PD). The mechanisms underlying abnormal α-synuclein aggregation, however, are yet to be understood. Protein disulfide isomerase (PDI) is an important molecular chaperone in the endoplasmic reticulum, which can prevent disordered protein forming aggregation. PDI is shown to be overexpressed in the brain of PD patients, but with reduced activity due to S-nitrosylation of the cysteine residues in the active site. In vitro experiments have demonstrated that PDI can inhibit the aggregation of α-synuclein with unknown mechanisms. Hence, it may be of importance to study the inhibition mechanisms of PDI on α-synuclein aggregation. In this study, the interaction between α-synuclein and PDI was studied by NMR spectroscopy. It was found that the binding sites between the two are located on the N-terminal of α-synuclein. A variant PDI (PDI C-S) was prepared, in which all six cysteines were mutated to serines. It was found that the binding sites between PDI C-S and α-synuclein are located on the C-terminus of α-synuclein. The results of thioflavin T (ThT) fluorescence experiment showed that the inhibition activity of PDI C-S on α-synuclein aggregation was lower than the wild type, suggesting that wild type PDI may inhibit α-synuclein aggregation through binding to its N-terminal.

Complete and correct chemical shift assignments of NMR resonances are critical to obtain a reliable and high-quality three-dimensional protein structure with liquid NMR spectroscopy. For experts in the field, the use of auto-assignment software programs can facilitate and expedite the process of protein resonance assignments. However, correct understanding and application of the auto-assignment results can be challenging for those who are new to the field and without sufficient knowledge of NMR resonance characteristics of the atoms in a protein. Incomplete or wrong chemical shift assignments will lead to deviations or even mistakes in the calculation of protein structure. In attempt to provide a better understanding of protein NMR resonances and chemical shift assignments for those are new to this field, we reviewed protein NMR resonance characteristics, such as isotope effect and conformational stereoisomer, in this paper. Examples were given to facilitate understanding.

Methane hydrates (CH₄·nH₂O) mainly composed of methane and water are ice-like crystalline clathrate compounds. They form a large natural gas reservoir due to their abundance. Solid-state NMR and laser Raman spectroscopy are two techniques which can be used for microscopic analysis for methane hydrates. In this paper, a low temperature solid-state ¹³C NMR technology was used to study the structures of synthesized methane hydrates. It was shown that ¹H high power decoupling (¹H HPDEC) had a better performance than ¹³C cross polarization (¹³C CP) for quantitative analysis for methane hydrates. The NMR results indicated that the methane hydrates synthesized by mixing methane gas with ice powder had a type-I structure, with large and small cage occupancies of 0.988 and 0.824, respectively, and a hydrate number of 6.07. Methane hydrates synthesized by mixing the methane gas with the continental slope of the South China Sea site SH2 sediments and ice powder also had a type-I structure, with large and small cage occupancies of 0.987 and 0.887, respectively, and a hydrate number of 5.98. The result showed that addition of site SH2 sediments could reduce hydrate number of methane hydrates, and make small cage occupancy and hydrate saturation higher, which were verified by laser Raman spectroscopy.

In situ variable-temperature ¹H, ¹⁹F and ³¹P NMR spectroscopy was employed to study the thermal decomposition mechanisms of ionic liquid. At a temperature as low as 80℃, ionic liquid[C₄mim] [PF₅], composed of 1-butyl-3-methylimidazolium cation (C₄mim⁺) and hexafluorophosphate anion (PF₅^-), had a slow, but detectable decomposition. For dehydrated[C₄mim] [PF₅], the ionic liquid started to decompose at temperature higher than 80℃. Small amount of PF₅ and HF formed first. The proton in HF came from the proton at 2-position of 1-butyl-3-methylimidazolium cation ring. After losing the proton, a carbene structure was formed, which then formed complex with PF₅. Free PF₅ and PF₅/carbene complex reached equilibrium at a ratio of 7:3.

We proposed a novel method for correcting intensity inhomogeneity in magnetic resonance images based on the coherent local intensity clustering (CLIC) model. The method used edge information to help identify tissue boundaries. A large Gaussian kernel was used to keep the bias field smooth. Split Bregman iteration was used to accelerate convergence. Phantom and in vivo images were used to evaluate the performance of the proposed method.

This paper describes a new nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) graphical pulse sequence design software utilizing Eclipse graphical modeling framework (GMF) technology. The software has a what-you-see-is-what-you-get trait for users. Pulse sequences drawing can simply be achieved by dragging and dropping the elements, and the results look almost the same as those shown on the textbooks and literatures. An experiment parameter management module is also provided to make previews of NMR experiment design and execution available. Due to the excellent model-view-controller pattern and strong ability of code generation of the GMF, the software has significantly improved expansion capacity, and the software development cycle was shortened greatly.

1,2-O-(1-methylethylidene)-3-C-methylnitro-α-D-allofuranose (2) was obtained through selective deprotection of 1,2;5,6-Di-O-isproplidene-3-C-methylnitro-α-D-allofuranose (1) under an acidic condition. C-3 nitrostyrenes (3) was synthetized through Moffatt dehydration from compound 1 under an acidic condition. A hydrolysis product 1,2-O-(1-methylethylidene)-3-C-methylnitro-α-D-glocufuranose (2') which had a reversed C-3 configuration was obtained by an unexpected oxa Michael addition. Compounds 2 and 2' were C-3 diasteroisomers. Compound 2' was characterized with NMR spectroscopy techniques, including ¹H NMR, ¹³C NMR, DEPT-135, ¹H-¹H COSY, gHSQC and gHMBC. ¹H and ¹³C chemical shifts of compound 2' were also fully assigned. The molecular structure of compound 2' was determined.

Infrared, ultraviolet, NMR (i.e., ¹H NMR, ¹³C NMR, DEPT-135, COSY, HSQC and HMBC), and mass spectroscopic data of cabazitaxel were collected and interpreted. Differential thermal analysis, X-ray power diffraction and elementary analysis were also used to characterize the compound. All ¹H and ¹³C NMR signals were assigned. Possible fragmentation pathways were discussed based on the information provided by the mass spectra. The infrared spectrum was used to analyze the types of vibration of the functional groups in the compound. The structure of the compound was determined.

Long-term stability is a key specification for rubidium atomic frequency standards (RAFS), which is influenced by magnetic frequency shift caused by C-field stability. Taking advantage of the linear relationship between the transition frequency of ⁸⁷Rb ground state and external magnetic field, we measured the C-field intensity inside the physical package of RAFS, as well as the magnetic shielding factor of the magnetic shield case. Experimental results indicated that C-field fluctuation inside the physical package could be attenuated by using the magnetic shield case. The axial magnetic shield factor was measured to be about 3 828, which could shield geomagnetic field efficiently and keep the magnetic frequency shift in a proper range.

Compared to the conventional reservoirs, karstic carbonate reservoir has more complex structure, larger difference in the size of fracture cavity, and the property that the fracture functioning mainly as a way for communication. It is difficult to study flow characteristics and distribution in karstic carbonate reservoir with the conventional methods. In this paper, we had built an on-line NMR instrument to test the stress sensitivity of 15 Tahe Oilfield tight matrix limestone cores. The T₂ spectrum was measured at each stage. On the basis of the T₂ spectra measured, the pore size, porosity and permeability changes of the limestone rocks were determined. It was shown that the on-line NMR measurement technology can be employed in the laboratory tests to provide microscopic information on the changes of core permeability.

The molecular structure of fluid influences its physical and chemical properties significantly. Current laboratory analysis methods, such as spectroscopy and spectral method, have the following disadvantages:low measuring efficiency, requirement of chemical reagents, and poor reproducibility. Low-field NMR fluid component analysis is a mature technology. In this study, we developed a set of low-field and on-line NMR fluid detection system and a rapid two-dimensional NMR relaxation measurement pulse sequence, which can be used for rapid, non-destructive, clean, efficient fluid component detection. The performance of the system and the pulse sequence was evaluated experimentally.

Silicone rubber composite insulators are widely used in the power system because of advantages such as excellent hydrophobicity, high mechanical strength and light weight. Currently the methods for accuracy and effective analysis of the aging status of the composite insulators are still lacking. Although previous studies have investigated the degradation of composite insulator shied, none of them focused on composite insulator rod sheath. To measure the aging status of rod sheath, a nuclear magnetic resonance (NMR) sensor was designed, which could be applied to arc-shaped samples. The magnet structure was optimized to have a main magnetic field distribution matching up with the curvature of the rod sheath. A flexional helical radio frequency transmission coil was designed and optimized. The sensor was applied to three kinds of rod sheath with different ages. A CPMG pulse sequence was used to acquire T₂ relaxation curves of the samples, which were then subjected to an inverse Laplace transformation to obtain T₂ spectrum. The result showed that the T₂ of the rod sheath decreased with increasing operation time. It is concluded that the parameter T^{2, long mean} calculated from the T₂ spectrum can be used for measuring the aging status of rod sheath.

Microwave-induced optical nuclear polarization (MIONP) can enhance nuclear spin polarization by several orders of magnitude. In MIONP, non-equilibrium electronic polarization was first enhanced through photo-excited triplet states, which is then transferred to nuclei by microwave irradiation. The potential applications of MIONP include probing structure and dynamics of proteins, studies of photochemical and photophysical processes, quantum computing and low-field NMR/MRI. In this review, we introduce the principles of MIONP and its application in nuclear polarization enhancement. The experimental setups, recent progresses, novel applications and future possibilities of MIONP are discussed.

Food quality and safety evaluation is essential for public health. NMR and MRI techniques have been applied for food quality and safety evaluation, attracting more and more attention. Both NMR and MRI are well-known to be non-destructive and non-invasive, and they are capable of detecting multiple components in the food simultaneously in real time, and providing both chemical and structural information. In order to promote their further applications in food science, the applications of NMR/MRI techniques in food quality and safety evaluation are summarized here.