An intermediate of higher carbon sugar-derived amino alcohol (1αS, 2αR, 3αS, 4S, 7E, 9αR, 10αR)-1, 2∶9, 10-di-O-isopropylidene-3-nitromethyl-5, 6-dideoxy-dec-7-enos-4-ulose-1, 4∶7, 10-difuranose-4, 8-pyranose) (compound 1) was synthesized from D-xylose using hetero-Diels-Alder addition followed by Henry reaction. Compound 2 (1αS, 2αR, 3αS, 4S, 7αS, 8βR, 9αR, 10αR)-1, 2∶9, 10-di-O-isopropylidene-3-aminomethyl-5, 6-dideoxy-dec-4-ulose-1, 4∶7, 10-difuranose-4, 8-pyranose) was synthesized stereoselectively by catalytic hydrogenation of compound 1. Complete assignment of ¹H and ¹³C chemical shifts of compounds 1 and 2 was obtained by 2D NMR techniques, including ¹H-¹H COSY, HMQC and HMBC. ESI-MS/MS spectra of compound 1 were also measured to study its fragmentation behaviors. The structure of compound 2 was determined.

15mer DNA  d(GGTTGGTGTGGTTGG) is a  thrombin-binding DNA aptamer (TBA), with inhibits clotting, of a high affinity with thrombin. In the presence of K⁺, TBA forms a right-handed-helix chair-like conformation with two stacked G-quartets and a regular phosphodiester backbone. The two G-quartets are linked by two TT loops at one end and a TGT loop at the other. The Hydrogen exchange rates of the imino protons of TBA in the presence of K⁺ were measured in this study. The results show that the G2, G11 and G15 iminos outside both the TGT loop and the two TT loops exchange faster, and in comparison the G6, G5 and G14 iminos have lower exchange rates because of the protection from the TGT loop and the TT loops. We also found that the stability of the TGT loop is similar to the two TT loops, and that the bases T4, T13 and T9 play more important roles in keeping the hydrogen bond stable in the K⁺: TBA complex than in the Sr²⁺: TBA complex. Evidence was obtained for the unfolding mechanism for the thrombin-binding aptamer. The data show that the hydrogen bonds between G2 and G14, G11 and G5, G15 and G1 outside the loops break first, and when the temperature increases further, the TGT loop and the two TT loops also become random coils.

The chemical fingerprints of 35 tea samples collected or purchased from Fujian、Yunnan、Guangdong、Jiangxi provinces were analyzed by ¹H NMR. Upon initial signal assignment, about 20 chemical constituents in tea were identified, including amino acids, theanine, catechins (EGC, EC, EGCG, ECG and unknown catechins), sucrose, unknown sugars, fatty acids, caffeine, quinic acid and so on. The NMR data were then analyzed by the principal component analysis (PCA) technique. The results show that different kinds of tea and Tieguanyin tea from different producing areas can be differentiated based on their chemical composition. Furthermore, the chemical constituents that can be used as the fingerprints for differentiating different types of tea were found. Compared to the green tea and the oolong tea, the red tea and the black tea were found to contain higher levels of certain amino acids and some unknown substances, and lower levels of catechins. Xiping Tieguanyin, as compared to Xianghua and Gande Tieguanyin, was found to have higher levels of certain amino acids, caffeine, EGCG, ECG and some unknown substances, and lower levels of EC, EGC. Hierarchical cluster analysis (HCA) of the data shows similar results as those obtained by PCA.

¹³C NMR spectra of Flos lonicera extracts were obtained by PFT-NMR. The ¹³C chemical shifts were assigned and compared with those of the chlorogenic acid, the effective component of Flos lonicera. The results suggest that the ¹³C NMR spectra of the Flos lonicera extracts show good reproducibility, and the spectral characteristics of the extracts obtained from different Flos lonicera sample are, in general, similar to those of chlorogenic acid. Therefore,  the ¹³C NMR fingerprints of Flos lonicera extract can be used as a criterion to check the authenticity of Flos lonicera and Flos lonicera products. Comparison of the ¹³C NMR fingerprints between the high grade Flos lonicera and those of lower quality was performed, and the results show that it is feasible to use the differences in the ¹³C NMR fingerprints to measure the quality of Flos lonicera with sufficient reliability.

⁶⁰Co γ irradiation induced polymerization of acrylinitrile (AN) was studied by ¹H and ¹³C NMR spectroscopy. The results show that the signal intensities of AN monomer peaks decrease after irradiation, and this is accompanied by the appearance of a polymer peak, whose signal intensity increases with the irradiation dose. The sequence distribution of polyacrylonitrile was assigned using ¹³C NMR data. The results of variable temperature experiments indicate that there exist hydrogen bonds, as well as proton exchange, between residual water and the -OH group on the polymer. Relaxation time measurements show that the motion of polymer segments is not influenced significantly by the increase of irradiation dose.

The structure of 4-(3-methoxyl-4-hydroxyphenyl)-phthalazin-1-one(OO-DPHZ) was  determined by NMR spectroscopy and MS spectrometry. The ¹H and ¹³C chemical shifts of the compound were assigned using two dimensional NMR spectroscopy, including gCOSY, gHSQC and gHMBC.

To understand the properties of restricted diffusion of multiple-quantum coherences (MQCs) between two parallel plates, the restricted diffusion theory of single-quantum coherences (SQCs) was extended to MQCs. The method of finite difference was employed to simulate the NMR signal attenuation due to the restricted diffusion in combination with the product operator matrix and Bloch equations. The results show that, like SQCs, the MQC signal attenuation due to restricted diffusion gives diffraction-like pattern. However, the pulsed-field-gradient intensity required for MQCs to produce same diffraction-like pattern is only 1/|n| of that for SQCs. The small distance between two arbitrary planes can be deduced when the relationship of signal attenuation due to diffusion with different inter-plane distance is obtained. The simulation method used herein can be further extended to study more complicated systems.

A PCI based complete digital frequency source for use in the nuclear magnetic resonance spectrometer is described. This frequency source is capable of generating a frequency- and phase-continuous tunable signal with output frequencies ranging from dc to 135 MHz. The frequency source is designed in such a way that it can be inserted into one PCI slot of a personal computer. There are two pieces of on board SRAM(128 k) for storing the pre-defined waveform. The RF output waveform is controlled by an external trigger signal. The present design is suitable for use in low field NMR or MRI spectrometer because of its simplicity, high performance and low cost.

Here we propose a second decimation algorithm for widening the range of sweep width in the AD9874 based digital receiver to meet the sweep width requirement set by the clinic imaging pulse sequences. The algorithm is implemented using a two-step approach. First, the best over-sampling number is found adaptively and adjusted automatically to the sweep width of the digital receiver. Secondly, digital filtering and decimation processing are employed. The performance of the proposed second decimation algorithm was tested on a 0.3 T imaging system using a single pulse experiment and an imaging experiment.

This paper provides an equation: δ_cal（¹⁵N）=-380.2+ΣΔα+ΣΔβ+ΣΔγ+ΣΔδ+ΣC  for calculation of ¹⁵N chemical shifts of substituted aliphatic amines. Eleven substituent parameters were obtained by linear least square regression analysis. The calculated results were checked regressively by 133 ¹⁵N NMR chemical shifts of 133 substituted aliphatic amines. The confidence limit was 99.5 % and the calculating errors for about 94.7 % of the compounds were less than δ 5 (with relative errors of 0.5 %).

A multiple linear regression model for calculating ¹³C chemical shifts in saturated ketones from the structural indices namely the atomic electronegative interaction (AEIV) vector and the atomic hybridation state index (HSI) was established using the ¹³C chemical shifts of 153 carbon atoms in 55 saturated alphatic ketones as the training set. The estimation correlation coefficient (R) and the standard deviation (SD) of molecular modeling (MM) were R_MM=0.997 and SD_MM=7.155, respectively. Leave-one-out (LOO) cross-validation (CV) was used to measure the prediction capability of the model, resulting in a correlation coefficient (R_CV) of 0.993 and a standard deviation (SD_CV) of 10.195.  Furthermore, the validity of this method was tested using the ¹³C chemical shifts of three sets of saturated ketones selected randomly as the test sets, resulting in correlation coefficients of 0.996, 0.996 and 0.999, respectively. The results show that the model based on AEIV and HSI can be used to predict ¹³C chemical shifts in saturated ketones satisfactorily and with sufficient stability. 

Potassium sodium dehydroandrographolide succinate (PSDS) is a new antibacterial and antiviral agent derived from andrographolide, a compound found in the extract of medicinal herb Andrographis paniculata (Burm. f.) Nees. In this study, the ¹³C and ¹H chemical shifts of the compound were assigned using 1D NMR and 2D NMR techniques including gCOSY, gHSQC, gHSQC-TOCOSY and gHMBC. Its structure was determined from the NMR data.

The structure of cefpirome sulfate, a new compound belonging to the fourth generation super broad-spectrum cephalosporins antibiotics, was studied using 1D  and 2D  NMR techniques. Complete assignments of the ¹H, ¹³C  and ¹⁵N NMR chemical shifts were obtained. The structural parameters obtained from the NOESY experiment were found to be useful for determining its stereo-structure.

A model was proposed for calculating ³¹P chemical shifts of the phosphorus atoms in phosphine and its derivatives from the ionicity indices (INI) and the stereoscopic effect parameters (α, β, γ)of the compounds: δ_P=-163.695 3-1.003 1INI+34.632 7α+13.892 9β-3.331 7γ. Correlation coefficients of the proposed model and leave-one-out cross-validation were 0.976 5 and 0.973 9, respectively. This model not only provides a new method to calculate ³¹P chemical shifts of phosphines, but also establishes the relationship between the ³¹P chemical shifts of phosphines and their molecular structures. In addition, it can be used to predict the ³¹P chemical shifts of phosphine derivatives.

The calculation methods for permeability of porous rock from its NMR T₂ relaxation distribution are introduced. There are three available models (i.e., SDR, Coates-cutoff and Coates-sbvi model). The Coates-cutoff model and Coates-sbvi model are very sensitive to the precision of irreducible fluid model, and thus the permeability results calculated by these two models are strongly affected by the precision of moveable/irreducible fluid volume calculation. On the other hand, the SDR model is not affected by irreducible fluid model, but it is sensitive to the property of the fluid in the core’s pores. Because there is only one variable coefficient in these models, the calculation errors are large when the permeability is very low. We found that the SDR-REV model, developed recently with three variable coefficients, is much suitable for calculating permeability of the core samples with lower permeability.