The interactions between unpaired electrons and nuclear spins in proteins, usually represented in paramagnetic relaxation enhancement (PRE), pseudocontact shift (PCS) and residual dipolar couplings (RDC), provide rich sources of structural restraints. These paramagnetic effects are valuable in structure determination of protein and protein-ligand complex as well as in elucidation of protein dynamics. Because most proteins do not have paramagnetic centers, generation of paramagnetic restraints usually relies on site-specific labeling of proteins with paramagnetic ions. In this paper, efforts towards paramagnetic labeling of proteins, especially with lanthanide ions, are summarized, and PCS, as a powerful NMR spectroscopic tool for structural biology, is discussed.

The macroscopic properties of soft matters are largely determined by their composition and the molecular mobility of each component. In this work, we used low field solid-state NMR to study the composition and dynamics of nanocomposite hydrogels with different clay contents. It was found that the content of rigid phase increased, while and the content of soft phase decreased with increasing clay content. A turning point of 12% W_clay/W_water was found, above which the content of rigid phase tended to be a constant. The dipolar coupling constants were measured with double-quantum (DQ) experiments, and the results showed that the confinement of polymer chains and the crosslink density increased with the clay content.

This paper introduces the design and implementation of a preamplifier system for water-cooled ultra-high field NMR spectrometers. The system consists of a controller, a high-band low noise amplifier, a high-band mixer, a broadband low noise amplifier and a broadband mixer. The system was shown to be capable of flexible and fast switching between the transmitter mode and receiver mode, and have low noise figure and large receiving range.

Acquisition of brain magnetic resonance imaging (MRI) data usually starts with a localizer for properly positioning the field of view based on a prior knowledge of brain anatomy and setting corresponding localization parameters for subsequent scans. We propose an automatic localization method that references directly to the brain atlas. The procedure first quickly acquires a 3D localization image at a median spatial resolution, and then calculates its registration parameter to the atlas and uses these parameters to position the subsequent scans, which therefore ensures the scanning configurations for different subjects are consistent with the atlas. The proposed method benefits inter-subject comparisons and referencing, in that it can help investigators locating abnormal structure, tumors or other regions-of-interest more quickly and easily, and therefore using the data in voxel based analysis more efficiently. We also propose an iterative method for automatic localizing individual subject in multiple independent follow-up scans. By iterating “scan, registration, automatic localization” steps several passes, it progressively minimizes the error of the image registration algorithm. Experiments showed that our atlas-based automatic localization method achieved high consistency of spatial location both in imaging data acquired from different subjects and in multiple separate scans from a single subject, and the localization error between multiple scans of a single subject was less than 1.0 mm and 1.0 degree.

Compared with conventional reservoir, shale reservoir is characterized by nanoscale pores, non-Darcy flow and self-generating/self-preserving properties. However, it is difficult to probe components in nanoscale pores with T₂ relaxation time less than 0.1 ms, and to evaluate fluid types and content in shale reservoir with conventional NMR technology. In this study, high resolution 2D NMR technology was adopted to evaluate eleven shale samples collected from three wells in Shahejie formation of Jiyang Depression. By comparing with the data from formation testing and rock pyrolysis, it was confirmed that the T₂spectrum measured with 2D NMR could reflect the properties of nanoscale pores, and D-T₂ spectrum could be used to evaluate fluid types and content. The work suggested that high resolution 2D NMR technology is useful in unconventional resource exploration of shale.

Bupleuuri Radix(Chaihu in Chinese)is a widely utilized traditional Chinese medicine for soothing liver and regulating vital energy. According to Chinese pharmacopoeias,only the roots of Bupleurum chinense are considered to be Bei Chaihu. In practice, However, roots of other Bupleurum plants, such as Bupleurum bicaule, are also sold or used as Bei Chaihu. In order to find to analytical tool to differentiate the roots of Bupleurum chinense and Bupleurum bicaule, we used ¹H NMR to analyze the composition of secondary metabolites of the two species. It was found that the metabolic fingerprint of the Bupleurum chinense is different from that of the Bupleurum bicaule, and thus ¹H NMR can be used to differentiate the two.

Unknown silicon surfactant (NPS-A) was characterized by FT-IR and NMR spectra (including ¹H NMR, ¹³C NMR, DEPT135, COSY, HSQC and HMBC). The results indicated that the sample is a polyether modified silicon surfactant. It is a mixture of three ingredients dissolved in DMSO: (1) M-D₂₀-(D′R)₆-M [M:trimethylsiloxane group; D: dimethylsiloxane group; D′: substituted dimethylsiloxane group and R=CH₂CH₂CH₂-O- (EO)₈-H] with a mean molar weight of 4 046.0, (2) AllyloxyPolyEthyleneGlycol (APEG) with a mean molar weight of 410.0 and (3) polyethylene glycol (PEG) with a mean molar weight 370.0. Furthermore, trace amount of compounds derived from allyl group were identified.

Clostridium thermocellum is a thermophilic anaerobic gram-positive bacteria that can efficiently utilize lignocelluloses. It is one of the most important candidate microorganisms for cellulosic ethanol production with consolidated bioprocessing. Metabolome reflects the interaction between cell and its environmental factors, and is an important component of system biology. In this work, ¹H NMR and 2D NMR techniques were used to analysis the central metabolites of C. thermocellum. Some biologically significant metabolites were identified in the intracellular compartment of C. thermocellum, including such as cellodextrin, phosphoenolpyruvate and d-erythrose-4- phosphate. Preliminary multivariate statistical analysis of the wild type strain and ethanol tolerant strain showed various metabolic differences in several metabolic pathways including actively conversion of cellubiose to cellodextrin, enhancement of non-oxidative pentose phosphate pathway and suppression of Embden-Meyerhof-Parnas pathway.

We present an NMR method for determining stereochemical structure of azabicyclo-type compounds, with 2-pheny-2-cycloamyl-2-hydroxyacetic-N-methly-3 azabiclo [3, 3, 1] nonane-9-carboxylate as the example. We showed that the carbon NMR spectra of azabicyclo-type compounds can be assigned effectively using the combination of multiple-frequency selective excitation double pulsed field gradient spin echo 1D NOESY and selective long-range DEPT, providing valuable information for conformation and stereo structure determination. The method presented is of significant value for studying the stereochemical characteristics and structures of azabicyclo-type compounds.

Compound 2-methyl-6-(2-methylphenyl)-2-heptene (1) was isolated from the flowers of Senecio oldhamianus. Its structure was determined by 2D NMR spectroscopy (i.e., ¹H-¹H COSY, DEPT, HMBC and HSQC). The NMR signals of the compounds were completely assigned.

Ultraviolet spectrum, infrared spectrum, mass spectra and nuclear magnetic resonance spectra of atorvastatin lactone were collected and interpreted. All the NMR signals were assigned. Based on the mass spectral data, the possible fragmentation pathways were discussed. The infrared spectrum was used to analyze the types of vibration of the functional groups in this compound. The structure of the compound was determined.

A new nitro sugar compound 1, 2-O-isopropylidene-3-C-nitromethyl-4- methenyl-α-D-xylofuranose (2) and a known nitro sugar compound 1,2-O-isopropylidene- 3-C-nitromethyl-5-(p-methylbenzenesulfonyl)-α-D-xylofuranose (1) were synthesized from 3-oxoxylose and nitromethane by Henry reaction. The compound 2 was characterized using NMR spectroscopy techniques, including one-dimensional ¹H and ¹³C NMR, ¹H-¹H COSY, HSQC and HMBC. The NMR signals were assigned. The molecular structure of compound 2 was determined.

a, a-Bis(2-hydroxyethyl)phenylacetonitrile (2a) was efficiently synthesized from phenylacetonitrile, lithium diisopropylamide and ethylene oxide by one-pot method. Through the analysis with ¹H NMR, ¹³C NMR, DEPT, HSQC, HMBC spectra, it has proved that there is a tautomerism caused by intramolecular cyclization. This phenomena can be used to explain the low yield of piperidine derivatives synthesized from compounds 2avia mesylation and cyclization.

Functional magnetic resonance imaging (fMRI) is the mainstay of neuroimaging approach in neuroscience after a rapid development during the past twenty years. The optogenetic fMRI (ofMRI) is a novel technology that combines optogenetics and fMRI, which has the potential to be used to analyze the functional roles and properties of specific neurons and/or specific neurocircuits in the whole brain. It opens a new vista for exploring human brain networks both functionally and structurally.