Rapid identification and efficient structural elucidation of metabolites are vitally important in metabonomics, phytochemistry and drug discoveries from the natural sources. In this work, the potentials of the hyphenated HPLC-DAD-SPE-CryoNMR-MS techniques were demonstrated in characterization and structural elucidation using the complex extracts of rosemary (Rosmarinus of ficinalis L.) as an example. 6 metabolites, including 1 phenolic diterpene (carnosol), 2 phenolic acids (rosmarinic acid and caffeic acid), 2 flavonoids (6-methoxyluteolin-7-glucoside and homoplantaginin) and 1 coumaric acid (cis-4-glucosyloxycinnamic acid), were successfully identified from two rosemary extracts with chloroform-methanol (v/v, 3/1) and 50% aqueous methanol on the basis of HPLC, UV, NMR and MS data. Such structural determination benefited from the capability of acquiring the high-quality homo- and heteronuclear 2D NMR spectra with the analytical HPLC separation. The results have not only provided whole set spectroscopic data for these metabolites, but also proved the hyphenated HPLC-DAD-SPE-CryoNMR-MS method to be an important structural elucidation platform for the components in natural products and probably other complex mixtures, even when multiple components in the same chromatographic peak are present with concentration differences in an order of magnitude.

In this contribution, the temperature-induced phase changes of the silk gland of Bombyx mori silkworm were studied using high-resolution ¹³C solid-state NMR spectroscopy. The silk gland samples were obtained from alive silkworms which were stored under either normal temperature or 6 ℃ for 2 weeks. The results showed that storing the alive silkworms at 6 ℃ could induce a phase transition in the fibroin gland in the middle and anterior parts of the middle division of the lumen, from an isotropic phase to an anisotropic liquid crystalline phase. Such phase transition was not observed in the silkworms stored under normal temperature. Previous studies have demonstrated, both experimentally and theoretically, lowering temperature can induce an action equivalent to a shearing stress in many elastic polymers (including proteins), and shearing stress may play an important role in the spinning of the silkworm. The results of this study suggest that lowering temperature or applying strong shearing may be used as ways to control the process to fabricate silklike fibers of high performance.

An NMRbased metabonomic approach was applied to characterize the dynamic changes of regional metabolic profiles in the brain of chick embryo during development from incubation day 12 to postnatal day 1. The NMR spectra of intact brain tissues from the cerebrum, cerebellum and optic lobes of chick embryo were acquired using high-resolution magic-angle-spinning (HR-MAS) ¹H NMR spectroscopy, and statistically classified using principle component analysis (PCA). The levels of 25 metabolites were measured quantitatively. The results indicated that the metabolic profiles were different among each other in three brain regions during development. The main contributors to the classification were the concentrations of GABA, NAA, taurine and myo-inositol.

Rh/SBA-15 and ligand (triphenyl phosphine PPh₃) modified heterogeneous PPh₃-Rh/SBA-15 catalysts for the reaction of propene hydroformylation were prepared. The reaction process of propene hydroformylation on the Rh/SBA-15 and PPh₃-Rh/SBA-15 catalysts was studied by in situ high-pressure（HP）MAS NMR techniques under the batch-like conditions. ¹³C MAS NMR spectra indicated that, with increasing temperature, propene and syngas could be converted into butyraldehyde on Rh/SBA-15 catalyst while the PPh₃ modified heterogeneous PPh₃-Rh/SBA-15 catalyst exhibited higher n/i ratio of butyraldehyde at 1.0 MPa.

A high performance gradient waveform generator based on the peripheral component interconnect (PCI) bus, digital signal processing (DSP) and 24-bit digital-to-analog converter (DAC) technologies were designed and made for uses in magnetic resonance imaging. The main feature of the design is that the gradient waveform generator contains up-to 5 pre-emphasis units with different time constants and corresponding amplitudes. The details about the design of the gradient waveform generator and the experimental result obtained using this device were given in the paper.

The metabolic profiles in normal human liver tissues(n=9), benign hepatic tumor tissues (n=7) and hepatocellular carcinoma (HCC, n=9) tissues were measured by high-resolution magic angle spinning ¹H nuclear magnetic resonance (HR-MAS ¹H NMR) spectroscopy. Semi-quantitative analyses showed that the HCC tissues contained significantly higher levels of glycine, taurine, choline, glutamate, alanine, valine and lactate, as compared to the normal and benign liver tissues. The results of this study suggest that the metabolic profiles in the HCC tissues were significantly different from normal liver tissues and benign hepatic tumor tissues, and such differences may be used as references for the diagnosis of HCC.

An empirical model for calculating ¹³C chemical shifts of aliphatic alcohols was proposed, in which the parameters describing the chemical environment of the focused carbon atoms are in were used as the independent variables. The parameters included electronegativity, atomic polarizability and those representing the steric effects. The experimentally-measured ¹³C NMR chemical shifts of 747 carbon atoms in 120 model compounds (91 alcohols and 29 diols) were used as the training set to derive the weights for the independent variables. The correlation coefficient R of the model was found to be 0.998. Leave-one-out cross-validation demonstrated good predictive ability and stability of the model. The model proposed was used to calculate the ¹³C chemical shifts of 69 different carbon atoms in 5 compounds that were not included in the training set, and the results proven to be satisfactory. The proposed model may be useful for calculating ¹³C NMR chemical shifts in alcohols with complex structures.

Variable-temperature probe system is a key component in the desktop nuclear magnetic resonance analytic instrument. Semiconductor frigorific flake has been widely used as the frigorific element in various applications because of the advantages it possesses including small volume, low power loss and being easy to control. In this work, semiconductor frigorific modules were used as key components to develop a variabletemperature probe system, with which the sample temperature could be varied from -20 ℃ to 60 ℃. The performance of the probe system was tested on an NMI20-Analyst desktop nuclear magnetic resonance analytic instrument with 3.5% CuSO₄ solution as the sample. It was shown that, compared to the conventional variable-temperature probe system, the probe system developed has a relatively simple structure and high performance to cost ratio. The potential improvements for the variable-temperature probe system were also discussed.

The irradiation effects on the aggregate state and microstructure of Xinjiang long-staple cotton fiber were studied by solid state ¹³C CP/MAS NMR, ¹H relaxation time measurements and ESR spectroscopy. The results showed that the microstucture of the long-staple cotton fiber were not altered after 5 Gy γ irradiation, while the crystallization state of the cotton fiber changed significantly under 75 Gy γ irradiation. It was also shown that γ irradiation induced production of different types of free radicals whose concentrations increased with the irradiation dose. The results of ¹H NMR relaxation time measurements suggested that γ irradiation could cause changes of molecular motions in the Xinjiang long-staple cotton fiber.

A flavonoid glycoside, 2″-O-α-L-arabinoisorientoside, was isolated from Capsella bursa-pastoris(L.) Medic. The 95% ethanol extract of the whole plant was processed by column chromatography (macroporous adsorption resin, polyamide and Sephadex LH-20) and semi-preparative liquid chromatography to yield the pure compound. Physicochemical properties and NMR data of the compound were used to determine its structure. The NMR chemical shifts of the compound were completely assigned.

In this study, phosphoramide mustard was coupled to 2-phenyl-4-quinolone by a facile phosphorylation reaction to yield a novel quinoline-4-phosphoramidate derivative. Complete assignment of the ¹H and ¹³C NMR chemical shifts of the compound was obtained using 2D NMR techniques, including DEPT, ¹H-¹H COSY, ¹³C-¹H HSQC and ¹³C-¹H HMBC. Mass spectrum of the compound was also recorded to study its fragmentation behaviors.

A phloroglucinol derivative (agrimophol) was isolated from the petroleum ether extract of the root sprouts of Agrimonia pilosa Ledeb., and shown to have with significant anthelmintic activity. The ¹H and ¹³C chemical shifts of the compound were assigned and its structure was elucidated.

NMR (¹H NMR, ¹³C NMR, ¹H-¹H COSY, HSQC and HMBC) and mass spectra of a fluorine derivative of tetrahydroberberine were reported and interpreted. The NMR signals were assigned and the substituted positions for the fluorine atom was identified. The structure of the compound was determined with the spectral data. The probably fragmentation pathways of the compound were also discussed.

Teniposide is a semisynthetic podophyllotoxin obtainable from the extracts of the roots and the rhizomes of May apple or mandrake plant Podophyllum peltatum. As an anticancer agent, Teniposide has become a major chemotherapy drug for the treatment of intracranial malignant tumor. In this study, the ¹³C and ¹H chemical shifts of the compound were assigned using 1D NMR and 2D NMR techniques including COSY, TOCOSY, NOESY, gHSQC and gHMBC. Its structure was determined from the NMR data.

Solid dispersions of dicarboxylic acid norcantharidin in chitosan were prepared using the spray drying method. The UV, IR, ¹H NMR and MS spectra of cantharidin, norcantharidin, sodium demethylcantharidate and solid dispersions of dicarboxylic acid norcantharidin in chitosan were obtained to characterize the raw materials and the products. The results showed that UV, IR, ¹H NMR and MS spectroscopy can be used to elucidate the structures of cantharidin and its derivatives, and may play important roles in the production of solid dispersions of dicarboxylic acid norcantharidin in chitosan using the spray drying method.

Metal ions interact with protein using a great variety of mechanisms to regulate protein functions. Some metal ions bind tightly and specifically to proteins and markedly regulate protein function, while others interact loosely and nonspecifically with proteins and only act as cofactors for protein functioning. In this review, we describe nuclear magnetic resonance (NMR) techniques which are widely used to investigate inter-molecular interactions between proteins and diamagnetic/paramagnetic metal ions. Special emphasis is put on the NMR techniques the can be used to elucidate the structure and function of metalloproteins, including chemical shift mapping, paramagnetic NMR and backbone dynamics detection. Examples are given to illustrate how the NMR techniques can be used to map inter-molecular interaction between proteins (calmodulin, zinc fingers and prion proteins) and metal ions.