Dynamic aspects of proteins are increasingly recognized as being important for describing their biological functions such as protein-protein and protein-drug interactions. Consequently, considerable efforts have been made to characterize protein dynamic motions. Among these methods, nuclear magnetic resonance (NMR), in particular, is capable of providing valuable information on the nature of internal motions of proteins in solution. In this review, the NMR-based approaches for studying protein side chain dynamics are reviewed, with emphasis on those methods for probing fast time scale internal motions.

The kinetics of cross-polarization (CP) between ¹H and ¹³C nuclei in the crystalline regions of elongated polyethylene fiber was studied. It was found that, with a moderate magic angle spinning (MAS) rate, the CP build-up curves of both orthorhombic and monoclinic crystals of PE can be described by I-I*-S- model. For the fiber sample aligning with the MAS axis in the rotor, the CP build-up curves of both orthorhombic and monoclinic crystals exhibit oscillation, while those of the disoriented samples exhibit monotonic increase. These results demonstrated that, to a certain extent, both orthorhombic and monocline crystals are oriented along the direction of elongation. The degree of orientation of the monoclinic crystal is higher than that of the orthorhombic crystal. Measurement of the kinetics of cross-polarization can be employed as a new technique to determine the degree of orientation of polymer chain.

In this paper, we report quantitative determination of interphase thickness and domain size in poly (styrene)-block-poly (butadiene) and poly (styrene)-block-poly (butadine)-block-poly (styrene) copolymers (PS-PB and PS-PB-PS) by novel solid-state NMR methods developed recently in our group. It was found that the block copolymers having equal polystyrene (PS) weight fractions (32.5%) and different block structures have the same interphase thickness (d_itp). These experimental results were in agreement with theoretical prediction of the interphase thickness in polymer blends made by Helfand using SCFT theory.

High-resolution ¹³C NMR spectra of atactic polyacrylonitrile (PAN) and isotactic-rich PAN were obtained under optimized solution concentration and experimental temperature. Assignments of nitrile carbon atoms with heptads were obtained and shown to be different from previously reported. The methenyl carbon atoms with pentads and heptads were assigned, respectively. It was shown that the atactic PAN obeys Bernoullian statistics. First-order and second-order Markov statistics were applied to calculate the content of the n-ads in isotactic-rich PAN. The number-average lengths of the isotactic and syndiotactic sequences calculated by “block” statistics confirmed the assignments of the heptads by ¹³C NMR spectroscopy.

Analysis of mixture is important in pharmaceutical studies, in which NMR can be a very useful method. In present study, the relative concentrations of aescin A, B, C and D in the mixture of sodium aescinate were determined with HPLC. ¹H and ¹³C NMR characteristics of these compounds were analyzed using band-selective 2D constant-time HMBC and other 2D NMR methods. The high resolution provided by the band-selective constant-time 2D experiment made correct assignments of almost overlapped resonant peaks from compounds with similar structures possible. The results of this study suggest that selective 2D NMR techniques can be used to facilitate the analysis of mixture.

The hom-and heteronuclear correlation spectroscopy techniques were used to make unambiguous assignments of ¹H and ¹³C chemical shifts of chlorpromazine hydrochloride (CPZ· HCl), a well-known psychotropic agent. By comparing of the completely assigned spectra of CPZ· HCl in different solvents (acetone-d₆, chloroform-d and deuterium oxide), it was concluded that the aggregation state of CPZ· HCl differs drastically in different solutions. The data from NMR spectroscopy studies were combined with the results obtained by theoretical calculations to derive the side chain conformations of CPZ· HCl. It was shown that the side chains are in folded forms in acetone and chloroform solutions whereas they inclined to adopt an extended style in aqueous solution.

In this paper, the geometric configurations of eight derivatives of N(4′-mehylpyrimidine)-N-substitute-2-nitro-benzenesulfonylurea were optimized by theoretical calculations. The structures of these compounds were optimized by the HF method at the level of 6-31G(d) and their ¹H NMR spectra were predicted by the B3LYP method at the level of 6-31G(d). It was shown that the results of theoretical calculation were consistent with the experimental results.

In this study, NMR techniques, including ¹H NMR, ¹³C NMR, DEPT, ¹⁹F NMR, HSQC, and HMBC, were used in combination to assign the ¹H and ¹³C chemical shifts of lansoprazole in room temperature. On the basis of the assignments and the results of variable-temperature experiments, a hypothesis was put forward to explain the existence of several low broad lines in the ¹H and ¹³C NMR spectra of the compound. It was proposed that there exist two inter-converting tautomers at room temperature. The inter-conversion rate increased and the broad lines became narrower as the temperature increased, and vice versa. The low broad lines in the ¹H spectra of the compound disappeared at -70 ℃, indicating the existence of only one tautomer and the termination of the inter-conversion process. The ¹H spectra of lansoprazole obtained at -70 ℃ were assigned, which were shown to be consistent with the results obtained at in room temperature.

A multiple linear regression model for calculating ¹³C chemical shifts in acridone alkaloids from the structural indices namely the atomic electronegative interaction (AEIV) vector and the atomic hybridation state index (AHSI) was established. ¹³C chemical shifts of 792 equivalent carbon atoms in 42 acridone alkaloids were calculated based on their AEIV and AHSI indices. The correlation coefficients and standard deviation of modeling estimation and leave-one-out cross-validation are 0.957, 0.956 and 12.247,12.331, respectively. An external prediction set was applied to validate the prediction capabilities of the model. The results show that both AEIV and AHSI are excellent topological indices with satisfactory estimation stability and favorable predictive ability.

Wavelet transformation has been widely used for image denoising. Different schemes of noise thresholding have been suggested. A good wavelet thresholding scheme should reflect the correct mapping of the wavelet coefficients of the noised images to that of clean images. In this study, we proposed a new method of image denoising, which utilizes neural networks to search the mapping relations in the wavelet domain. The method was applied to denoise MRI images and proven to be satisfactory in performance and insensitive to noisedistribution.


This paper presents an FPGA-based design scheme of NMR digital orthogonal transmitter. Utilizing embedded blocks such as RAM and the resources of logic gate of the FPGA and based on ARM7 and other communication systems, the realized transmitter is shown to be able to provide accurate high speed pulsed output with FM, PM or AM. Synchronously controlling two pieces of DDS using the FPGA, the transmitter is able to provide orthogonal RF output. In addition, both of the signals in orthogonal output can be regulated independently. This flexible design can be conveniently extended to the design of multi-channel transmitter.

Based on the semi-self-constant-field (semi-SCF) d-orbital model and the complete energy matrix diagonalization procedure (CDP), the optical spectra and g factor of CaF₂:Co²⁺ were explained from the local structure of the impurities. The local structure was shown to have collapse effects, but remain an eight-coordinate cubic symmetry. In addition, the dependence of the g factor on the crystal splitting parameter D_q was discussed by the perturbation method (PTM) and CDP. The third order perturbation formula proposed by Macfarlane was shown to be a good approximation, but its validity became worse with decreasing D_q. At last, the applicability of the g formulae constructed on the basis of CDP and spin Hamiltonian theory, together with the difficulties in the case of orbital degeneration, were discussed.

The fruit hull of mangosteen, Garcinia mangostana, has been used for many years as a medicine for treatment of skin infection, wounds and diarrhea. In the present study, ¹D ¹H NMR, ¹³C NMR, DEPT and 2D HMBC, HSQC, ¹H-¹H COSY, ROESY methods were used to identify the structure of 1, 3, 6-trihydroxy-7-methoxy-2, 8-bis-(3-methyl-2-butenyl)-9-xanthenone α-mangostin extracted from the fruit hull of mangosteen. The 1H and ¹³C chemical shifts of α-mangostin were assigned.

Irradiation effects on chlorinated polyethylene (CPE) were studied by 1D and 2D NMR spectroscopy, measurements of proton spin-spin relaxation time (T₂) and spin-lattice relaxation time (T₁) and FT-IR. The results indicated that degradation reactions took place after CPE was irradiated by ⁶⁰Co γ-rays. It was shown that HCl emitted during irradiation. The higher the absorbed doses was, the more HCl emitted. The quantity of some sequential structures (e.g., CH₂CHClCHClCH₂CHCl, CH₂CH₂CHClCH₂CH₂, CHClCH₂CHClCH₂CH₂, and CHClCH₂CHClCH₂CHCl) of CPE were found reduced after irradiation, but there were no evidence indicating that new sequential structures were formed. The values of T₁ and T₂ also provided very important information about the segmental motion of the molecules.

Both NMR T₂ spectra and mercury intrusion capillary pressure reflect pore structure of a rock, to a certain extent. Comparison and theoretical analyses of NMR T₂ spectra and mercury intrusion pore-throat frequency distribution curve indicate significant correlation between these two sets of data, thus it is possible to calculate pore radius distribution from NMR T₂ spectra. In this paper, several methods (e.g., interpolation arithmetics, methods based on least square principle and other mathematical methods) for converting NMR T₂ spectra into pore radius distribution were evaluated and compared, using mercury intrusion pore-throat distribution data as a reference. Mercury intrusion saturation was considered to be an important factor that can influence the result of conversion. The practical applicability of the methods was tested using sandstone samples. The results suggested that it is necessary to emphasize the main sections of NMR T₂ spectra and mercury intrusion pore-throat distribution, and consider the influence of inadequate mercury intrusion saturation in the conversion process. The conversion result was shown to be more reliable when both the factors were taken into consideration.

A triterpene saponin was extracted from the barks of Pseudorix kaempferi for the first time,and determined to be dammar-24(25)-ene-3β, 6α, 12β, 20 (S)-tetraol-20-O-β-D-pyranoglucoside on the basis of NMR analysis. The chemical shifts of this compound were completely assigned using 2D NMR spectroscopy.

Soil organic matters (SOM) are important components in soil, and they would affect the physicochemical, chemical and biological properties of the soil directly or indirectly. Many researchers and various advanced techniques have been involved in the investigation of SOM. As a powerful technique for organic analysis, NMR has played an important role in this field. In this paper, the analytical methods commonly used in agrology research were reviewed, and the NMR methods were discussed in detail.