A compound was isolated from Evodia rutaecarpa and identified to be Limonin. The NMR signals of the compound were assigned by 2D NMR. The results show that the assignment of some proton signals made in the previous studies was erroneous. Correction was made for the incorrect assignment.

The stereochemical structures of two new compounds, 5-(3-chlorophenyl)-2-furfur-aldehyde-N-4-methylphenyloxyacetylhydrazone and 5-(3-chlorophenyl)-2-furfuraldehyde-N-4-nitrophenyloxyacetylhydrazone, were determined by DPFGSE-NOE experiments performed in DMSO-d₆ at 25 ℃ and variable-temperature ¹H NMR. The ¹H chemical shifts of the compounds were completely assigned at 25 ℃ and 90 ℃.

A triterpene saponin was extracted from the seeds of Acanthopanax Senticosus, and determined to be hederagenin 3-O-β-D-glucuronopyranpside on the basis of MS and NMR measurements. The ¹H and 1³C NMR chemical shift of this compound was assigned using 2D NMR spectroscopy.
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It is known that free radicals in cigarette smoke do harm to the human health. The most common way to detect the reactive free radicals is electron spin resonance (ESR) spectroscopy in conjunction with the spin trapping method. In this paper with a highly efficient and novel spin trap DEPMPO,  the alkyl radicals and hydroxyl radical were obtained in the aqueous medium,  among of which no adducts of alkoxyl radicals were discovered. In view of the fact that more oxygen molecule dissolved in organic solvents as well as the priority of the ability of DEPMPO in capturing reactive free radicals and its character of ESR spectrum to those of PBN and DMPO,  we considered that the trapped alkoxyl radicals in the previous paper may derive from the secondary radical products by oxidation of alkyl radicals.

A spectral-spatial 2D ESR imaging system was installed on a Bruker ER 200 D ESR spectrometer. It consists of a pair of field gradient coils, power supplies and a computer system used for image reconstruction. Spectral-spatial 2D ESR imaging was performed on several free radical samples using the filtered back-projection method. The spatial distribution of the spin densities of the free radicals and the corresponding spectral parameters were acquired simultaneously from the 2D images. The relationship between the imaging parameters and the accuracy of the images was discussed.

The chemical structures of three serratane type triterpenoids isolated from the moss Homalia trichomanoides (Hedw.) B. S. G. were elucidated as 3α-methoxyserrat-14-en-21β-ol (1), 3β-methoxy-serrat-14-en-21β-ol (2) and 3β-methoxyserrat-14-en-21-one (3). Their ¹H and ¹³C chemical shifts were assigned using 1D and 2D NMR spectroscopy (including ¹H-¹H COSY, HMQC and HMBC). Stereochemistry of C-3 for the three compounds and that of C-21 for compounds 1 and 2 were determined by coupling patterns in the ¹H NMR spectra.

Three lignans were isolated from the fruits of Schisandra chinensis bail, and identified as mesodihydroguaiaretic acid(Ⅰ), Gomisin J(Ⅱ) and Gomisin D(Ⅲ) using 1D and 2D NMR techniques. Complete assignment of NMR signals was obtained for compounds Ⅱand Ⅲ. The stereo configuration of Gomisin D was simulated by three molecular simulation methods using the SYBYL software, and the most stable configuration of Gomisin D was calculated.

The derivatives of (9S)-12-methyleneerythromycin A,  compound (5) and (6),  were obtained by elimination reaction between thionyl chloride and corresponding 2′-O,  4″-O-dibenzoyl-(9S)-9-O, 11-O-isopropylerythromycin A. The structure of (6) was established using ¹³C NMRDEPT spectroscopy.

²⁷Al MAS and 3Q MAS NMR spectroscopy was applied to study the aluminum coordination in dealuminated zeolite mordenite and amorphous silica alumina. A signal ascribed to distorted tetrahedral coordinate Al (DTA) was detected. By comparison with amorphous silica alumina, it was found that the presence of distorted tetrahedral coordinate species is a typical feature in crystalline zeolites after activation and dealumination. From these experimental results we suggest that the DTA species, which are absent in amorphous silicaalumina, locate at the interface between the crystalline framework lattice and the extra-framework species formed by dealumination.

Oil saturation is an important physical parameter of petroleum used in petroleum exploration and development. At present,  the conventional method can only give the grade of oil saturation in the logging measurement of rock cuttings and can't determine oil saturation quantitatively. In this paper,  we present a method by which oil saturation in rock cuttings can be determined fast and quantitatively using nuclear magnetic resonance on the well site. Relaxation additives were applied in determining oil saturation in cuttings under laboratory settings,  and optimized. The precision of oil saturation measurement in cuttings by nuclear magnetic resonance was also demonstrated.

This paper provides a equation,  δ_cal(¹⁷O)=δ_0n+C×Σ Δ,  for calculating carbonyl ¹⁷O chemical shifts of substituted benzamides,  substituted N-methyl benzamides and substituted N, N-dimethyl benzamides. Eleven substituent parameters were obtained by least square linear regression analysis. The equation is checked regressively by 33 carbonyl \{\}\+\{17\}O chemical shifts of these compounds,  and the results show that the confidence limit is 99.5% and the calculating errors (Δδ) of more than 90% of the compounds are less than 1.0 (relative errors less than 0.1%).

The two isomers of isophrone diisocyanate (IPDI) were characterized by  \{\}\+1H and  \{\}\+\{13\}C NMR spectroscopy. The stability of the compounds at different temperatures was studied by  \{\}\+\{13\}C NMR. The results show that the chemical shift and the peak area of the two isomers didn't change at 40～80 ℃  so that it may be concluded that the two isomers were stable in this temperature range.

In recent years residual dipolar couplings have been employed to obtain the long-range conformational constraints such as the relative orientations between the chemical bonds in biomolecules for calculation or refinement of three-dimensional structures of proteins and protein complexes in solution. This review describes the measurement of residual dipolar couplings using multi-dimensional NMR techniques and their applications in determination of protein structures: refining protein structures, evaluating protein structures, determining the relative orientation between protein domains, obtaining information about ligand conformation and orientation, etc.

Pattern recognition (PR) is the technology of making a decision on a concrete object which category it belongs to. PR can be used to solve many problems in understanding complex systems. One of its applications is the comprehension and analysis of biomedical magnetic resonance spectroscopy data. Previous studies using high-resolution liquid NMR spectroscopy have shown that the levels of metabolites in biological samples change with the time after pathological or other perturbation. PR can be used not only to identify the differences of the pathological from the normal, but also to find which bio-fingerprints result in such differences, thus supplying valuable information for diagnosis. In this review, various statistical PR methods used in biomedical magnetic resonance spectroscopy are discussed, and the latest progresses in this field are introduced.

Magnesium ion (Mg²⁺) plays important roles in many biochemical reactions occurring in cells,  and determination of intracellular free Mg²⁺ concentration is essential for understanding the functioning of intact cells. Nuclear magnetic resonance (NMR),  a spectroscopic technique that measures magnetic nuclei and their interactions with the environment,  has gained considerable success and popularity in studying metal ions in vivo. ³¹P and ¹⁹F NMR can be used to measure intracellular concentration of free Mg²⁺,  and these techniques has the advantage of noninvasiveness so that free Mg²⁺ in the intracellular environment can be observed in essentially unperturbed living systems. In this review,  the theories and applications of ³¹P  and ¹⁹F NMR for determining intracellular concentration of free Mg²⁺ are discussed:.