When Gram-positive bacterium Bacillus subtilis responds to heat-shock, protein arginine kinase McsB phosphorylates Arg62 (R) in the clpC operon binding region of transcription factor CtsR, leading to dissociation of CtsR and clpC operon and initiation of stress-genes transcription for the ensuing expression of heat-shock proteins. This work investigated the clpC operon binding region (KRGGGG) of CtsR with NMR spectra (i.e., ¹H NMR, ¹H-¹H COSY, ¹H-¹H TOCSY, ¹H-¹⁵N HSQC and ¹H-¹³C HSQC). The ¹H, ¹³C and ¹⁵N chemical shifts of the protein segment were assigned. The interaction between CtsR and clpC operon and the regulatory mechanism of arginine phosphorylation were analyzed.

The intrinsically disordered alpha-synuclein (α-synuclein) directly affects mitochondrial dynamics, morphology and function, and is closely related to Parkinson's disease. Studying the interactions between α-synuclein and mimic mitochondrial membranes/intact mitochondria is an effective way to understand how α-synuclein affects mitochondria. It has been reported that α-synuclein interacts with the mimic inner membrane of mitochondria (IMM), but not with the outer membrane of mitochondria (OMM), and the N-terminal plays an important role in binding with the mitochondria. However, little is known about the positions of interaction. Here, the interactions between α-synuclein and intact mitochondria isolated from rat liver were investigated by nuclear magnetic resonance (NMR). It was found that, different from the previous report, α-synuclein interacted with the OMM and the first 60 residues of N-terminus were crucial for the binding. It was postulated that the interaction between α-synuclein and OMM might depend not only on the lipid composition of the membrane, but also on other factors which were not reflected in the mimic membrane, such as the curvature of membrane and/or other components of the OMM. Our study also indicated that NMR is an effective method for studying the interaction of proteins with intact mitochondria.

Ubiquitin (Ub) is a signaling protein in eukaryotic cells, and it functions in the processes of protein degradation and DNA repairing. The published data indicated that the phosphorylation of Ub on Ser65 leads to two stable solution conformations, which can be regulated by pH. In the present project, it was found that the conformational ratio could also be modulated by temperature. Based on this feature, pUb was chemically labeled with a ¹⁹F probe for determination of conformational ratio under various temperatures using ¹⁹F NMR. We showed that the conformation ratio of pUb was linearly proportional to temperature gradient. Consequently, the temperature of a biological sample can be calculated with a given conformational ratio of pUb, and ¹⁹F-labeled pUb can function as a thermosensor. This thermosensor could be used to monitor temperature of in vitro experiments, and it is also able to be taken to explore regulation of pUb function by temperature. Furthermore, the ¹⁹F-labeled pUb thermosensor could be developed to detect intracellular temperature in-cell NMR assays.

Segmentation of tooth and alveolar bone from the cone beam computed tomography (CBCT) images provides the basic data for the three-dimensional reconstruction and visualization of bone structure. In this paper, according to the characteristics of tooth and alveolar bone, an improved potential well function was combined with the level set model for segmentation of tooth and alveolar bone, overcoming the defects of 'stop evolution' or 'too fast evolution' that might occur with the use of conventional potential well functions. Since it is difficult to effectively filter out the noises in CBCT image with the single variance Gaussian filter, a multiple small variance Gaussian filter stack was used to preprocess the image. As the contours of the same tooth in adjacent images of the image sequence showed only little changes, the segmentation result of the current layer was taken as the initial contour of the curve evolution for the next layer to reduce the times of iteration and increase the speed of segmentation. In addition, the algorithm is also used to segment a single tooth in magnetic resonance image of oral cavity successfully.

The reaction of heterogeneous benzene hydrogenation reaction in a real solid-liquid-gas environment was studied by operando nuclear magnetic resonance (NMR) spectroscopy. During the reaction process, the products need not be separated before the test. Different catalysts (Pd nanoparticles and Pd with different crystal morphology) were performed to investigate the effects of pressure, reaction time and catalyst surface properties on benzene hydrogenation reaction. It was found that the pressure and the reaction time can affect the productivity of hydrogenation reaction, and the products of benzene hydrogenation reaction are determined by the exposed crystal surface of Pd catalysts. This operando NMR method provides a good opportunity to study the mechanism of solid-liquid-gas heterogeneous hydrogenation reaction.

The porosity acquired from nuclear magnetic resonance (NMR) logging is lower than the true value in heavy oil-bearing reservoirs due to the viscosity of heavy oil, which is a great challenge in heavy oil-bearing characterization and NMR logging. To improve the porosity prediction accuracy, the effect of heavy oil should be first corrected. In this study, 10 typical core samples, which were drilled from the Hanjiang Formation of eastern South China Sea Basin, were chosen for the laboratory NMR experimental measurements under four conditions. These four conditions were initial condition, heavy oil saturated condition, residual oil condition and water saturated condition. The effects of heavy-oil volume on NMR porosity were analyzed, and a method to estimate true NMR porosity based on formation resistivity classification was established. The method was applied in our target well A14, and the true formation porosity was predicted from field NMR logging. The result showed that, the average relative error between NMR porosity and convention core derived porosity was improved from 11.19% to 4.84% by oil viscosity correct using this method. Thus the proposed method is able to effectively correct the effect of oil viscosity on NMR porosity.

The pore structure of shale gas reservoir is complex and heterogeneous, leading to great challenges in reservoir characterization and effectiveness evaluation. In order to establish a quantitative evaluation method for pore structure of the shale gas reservoir, 20 cores of the second member of Doushantuo Formation in Yichang area, western Hubei were selected as the experimental sample. An echo interval of 0.069 ms was used to carry out nuclear magnetic resonance (NMR) experiments under 100% salt water saturation. The obtained T₂ spectra were analyzed with the multifractal characteristics method, and the parameters sensitive to the pore structure of the shale reservoirs were extracted. A method and a standard to classify shale reservoir types were developed, based on the minimum and maximum generalized fractal dimension difference (D_min-D_max) and spectral width (Δα). This method is of great significance for improving the prediction accuracy of shale gas reservoirs and guiding development and selection.

The preparation and detection of the nuclear singlet state are valuable and prospective for many applications related with compound molecular analysis. In this work, a proton spin coupled system containing two H nuclei in tripeptide (Ala-Gly-Gly, AGG) was selected as research object, and singlets were prepared with three sets of different pulse sequences based on different principles. The lifetime of those singlets were measured, and the singlet preparation efficiencies of different sequences were compared. The results indicated that for the same spin coupling system of the same molecule, there is no significant difference in the lifetime of the singlet state prepared by different pulse sequences, while their preparation efficiencies could be relatively different.

Three product mixtures of anthracene catalytic hydrogenation under different catalytic conditions were analyzed by nuclear magnetic resonance (NMR) spectroscopy. Dihydroanthracene, tetrahydroanthracene, symmetric octahydroanthracene, and asymmetric octahydroanthracene were successfully detected with diffusion-ordered spectroscopy (DOSY) and one-dimension selective gradient total correlation spectroscopy (selTOCSY) techniques. The ¹H and ¹³C NMR signals of dihydroanthracene, tetrahydroanthracene and symmetric octahydroanthracene were assigned by ¹H NMR, ¹³C NMR, DEPT135, ¹H-¹H COSY, ¹H-¹³C HSQC. The conversion of anthracene and selectivity of the products were calculated by quantitative ¹H NMR (QNMR). The results demonstrated that NMR is a versatile and powerful tool to guide and optimize catalytic reaction conditions for increasing the selectivity of symmetrical octahydroanthracene. The present research provides a systematic NMR analysis scheme for polycyclic aromatic hydrocarbons catalytic hydrogenation.

To meet the requirement of ultra-thin rubidium frequency standard, we developed a non-standard rectangular cavity based on the slotted-tube microwave cavity with 12 mm thickness and a field orientation factor of about 0.9. The data set of ⁸⁷Rb double-resonance signals of the cavity-cell assembly was measured. The results showed that the intrinsic linewidth is about 452 Hz. With the optimized experimental parameters, the cavity-cell assembly has a potential short-term stability of 5.2×10^-13τ^-1/2 limited by the shot noise.

Pure α- and β- isomers of 3, 22-dihydroxyhopane were obtained by the reduction of hydroxyl protected hydroxyhopanone with L-selectride. The absolute configuration of 3β, 22-hydroxyhopane was confirmed by single crystal X-ray diffraction, and the unambiguous ¹H and ¹³C NMR data of two isomers were fully assigned for the first time. The preparation method is suitable for the separation of other unseparated α, β-isomers.

The structure of delafloxacin meglumine was analyzed by infrared absorption (IR), ultraviolet absorption (UV), nuclear magnetic resonance (¹H NMR, ¹³C NMR, DEPT, ¹H-¹H COSY, ¹H-¹³C HSQC and ¹H-¹³C HMBC) spectroscopy, mass spectrometry and elemental analysis. The characteristic absorption peaks in the IR spectra were discussed. The ¹H and ¹³C NMR signals of delafloxacin meglumine were assigned, and the two-dimensional signals were used to elucidate its structure. The crystal structure of delafloxacin meglumine was studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD).

Nuclear magnetic resonance (NMR) is an important characterization method for the depolymerization of lignocellulosic biomass and its structure evolution analysis. The accurate NMR analysis facilitates the selective transformation of different biomass components. In this review, the principles of NMR are presented. Four types of NMR experimental methods, including ¹H NMR, ¹³C NMR, ³¹P NMR and 2D HSQC, and their applications in the structure elucidation, qualitative and quantitative analysis of products, reaction path and catalytic depolymerization mechanism of lignocellulose are mainly introduced. Finally, the main problems and perspectives of NMR method in valorization of lignocellulosic biomass are discussed.