Amide proton transfer (APT) imaging is a novel molecular MRI technique that generates image contrast based on endogenous cellular proteins in tissue. Theoretically, the APT-MRI signal depends primarily on the mobile amide proton concentration and amide proton exchange rates (which are related to tissue pH). The APT technique has been used for non-invasive pH imaging in stroke (where pH drops) and protein content imaging in tumor (where many proteins are overexpressed). It has been demonstrated recently in animal models that the APT-MRI signal is also a unique imaging biomarker to distinguish between radiation necrosis and active tumor. In this paper, we will briefly introduce the basic principles of APT imaging and review its applications in stroke and brain tumor studies in animal models and patients.

NMR spectra acquired at low field often show severe signal overlap. Under such circumstance, two-dimensional (2D) diffusion-transverse relaxation (D-T₂) correlation data are useful to differentiate signals from different components in the sample. The currently available inversion algorithms for D-T₂ correlation data are time- and memory-consuming. To overcome this problem, we developed an improved 2D D-T₂ inversion algorithm, which is more effective and consumes less memory and time than the traditional inversion algorithms. In brief, the logarithm values of discrete diffusion coefficient and transverse relaxation time were first obtained and used to construct two core matrices according to the signal collection conditions. Singular value decomposition was then carried out for the two matrices, followed by application of a cutoff value to remove negligible values. The inverse matrices of the thresholded core matrices were calculated and used to derive the initial inversion result. Finally, the initial inversion results were iterated with non-negative constraints to derived the final inversion results.

Micro-CT images revealing pore space are widely used in simulation studies of porous media. Compared to three-dimensional (3D) CT images, two-dimensional (2D) thin section images are more readily available. In this paper, a multiple-point statistics (MPS) method was implemented to construct 3D pore space using a stack of 2D thin section images of a rock, assuming the medium is isotropic. A random walk model describing Brownian movement of particles in the rock was then used to simulate the NMR responses. The simulation results obtained with the reconstructed 3D pore space image were found to be similar to those obtained with the true 3D micro-CT image. It is concluded that 3D image reconstructed from 2D thin section images shows similar pore space structure as than revealed by micro-CT images, and thus can be used for pore-scale simulation in porous media.

GABA (γ-aminobutyric acid) is a major inhibitory neurotransmitter in the central nervous system of human brain, and plays a predominant role in the regulation of neuronal activity. Detection of GABA by in vivo magnetic resonance spectroscopy is hindered by its inherent low concentration and overlapping with resonances from other metabolites. GABA cannot be directly detected with the PRESS (point resolved echo spectroscopy) or STEAM (stimulated echo acquisition mode) pulse sequences on the clinical MRI scanners. This paper reported the implementation of a single-voxel spectroscopy J-difference editing sequence (MEGA-PRESS) for detection of GABA. The results from phantom studies and human brain indicated that it is feasible to use MEGAPRESS for detection of GABA on 3 T clinical MRI scanners.

An EPR data acquisition and control system for in vivo tooth dosimetry was developed. Based on the graphical programming language, LabVIEW and using the ART USB2812 data acquisition card as the controller card, the system can perform the basic functions of EPR: controlling the power of the scanning field, displaying the microwave mode signal, adjusting the microwave power, and acquiring EPR signals. The data processing program developed has basic spectrum processing functions: data query, spectral baseline correction and integration.

The feasibility of inducing Ramsey interference by pulsed microwave in hydrogen maser was studied. The key parameters were theoretically determined, and a pulsed microwave signal generator was designed. The Ramsey interference of hydrogen atoms was induced successfully on the physical package of a traditional passive hydrogen maser. Line width of the hydrogen atomic transition was reduced from 3.0 Hz to 1.2 Hz. It is expected that the frequency stability of passive hydrogen maser could be improved by using the design.

A quantitative NMR method for analyzing sulfonamides reference materials based on determination of Sulfameter content was developed. The liner range of the method was found to be 1.00~20.00 mg/mL. The regression equation derived was y=0.112 8x+0.016 2, R=0.999 0, and the relative deviation was less than 0.7%. The results of this study showed that quantitative NMR analysis provides a simple, convenient, accurate and stable method for period verification of sulfonamides reference materials.

The ¹³C  and ¹H NMR chemical shifts of a ring A-seco aryltetralin lignan, 3′,4′-O, O-demethylene-4-O-demethylpodophyllotoxin, were assigned based on 1D and 2D NMR data, including ¹H-¹H COSY, DEPT, HMBC, and HSQC. Stereochemistry was established based on ¹H coupling constants (J- values), NOESY results and circular dichroism (CD) results. The ¹³C  NMR signals of the compound was completely assigned for the first time.

A triterpene saponins compound (compound 1) was isolated from the roots of Dipsacus asperoides C.Y.Cheng et T.M.Ai. and its structure was established as 3-O-[β-D-xylopyranosyl(1-4)-β-D-glucopyranosyl(1-4)][α-L-rhamnopyranosyl (1-3)]β-D-glucopyranosyl(1-3)-α-L-rhamnopyranosyl(1-2)-α-arabinopyranosyl-hederagenin-28-O-β-D-glucopyranoside-(1-6)-β-D-glucopyranoside ester. This paper describes the application of HSQC-TOCSY and other techniques in the NMR assignment and structure elucidation of this compound.

The spectral data of Emtricitabine were reported, including UV, IR, NMR (¹H NMR, ¹H-¹H COSY, ¹³C NMR, DEPT, HMQC and HMBC) and MS data. The NMR signals were assigned. The infrared spectrum was analyzed to derive the types of vibrations of the functional groups in this compound. The molecular structure of emtricitabine was determined.

Meropenem is a second-generation carbapenems antibiotics with an exceptionally broad spectrum of activity, which is currently used in the treatment of a variety of infections. In this paper, the ¹H and ¹³C NMR chemical shifts of the compound in CDCl₃ and CD₃OD (solvents) were assigned. The assignment errors for C-6 and C-7 in the literature were corrected. The C-N bond rotational barrier of protected Meropenem was investigated.

Calcipotriol is a drug for treating psoriasis. In this paper, ¹H and ¹³C NMR, distortionless enhancement by polarization transfer spectrum (DEPT), ¹H-¹H correlated spectroscopy (¹H-¹H COSY), heteronuclear multiple bond correlation (HMBC) and heteronuclear single quantum correlation (HSQC) spectra of calcipotriol are reported. The ¹H  and ¹³C NMR chemical shifts were assigned.

The structure of aristololactam IV isolated from Saruma henryi Oliv. was elucidated via NMR. The ¹³C NMR data and complete assigment of the ¹H and ¹³C chemical shifts of the compound by 2D NMR (HSQC，HMBC) was firstly obtained，and the assignments of H-2 and H-5 of the compound were also corrected.

The proposal and development of two-dimensional nuclear magnetic resonance (2D NMR) provide a broad space for the research and application of NMR. In many cases, however, high-resolution 2D spectra are virtually impossible to obtain because of the inherent heterogeneity of the samples under investigation, as well as the poor homogeneity of the magnetic fields. It is also time-consuming to obtain a conventional 2D NMR spectrum. The ultrafast spatial encoding technique enables acquisition of a 2D or multi-dimensional NMR spectrum within a single-scan, with greatly shortened acquisition time. Schemes based on phase compensation, coherence transfer and intermolecular multiple-quantum coherence in combination with spatial encoding technique have been proposed to ultrafast obtain high-resolution NMR spectra in inhomogeneous fields. In this review, ultrafast high-resolution NMR techniques were introduced and the perspective of these techniques was discussed.

This paper reviews domestic and international research progresses in studying the structures and NMR spectral features of triterpenoid saponins and flavonoids in Labiatae Clinopodium. So far, 42 saponins and 23 flavonoids have been isolated and identified. Base on the NMR data of alkene carbon and carbonyl carbon, the basic structures of triterpenoid saponins can be speculated. According to the chemical shifts of oxygenated carbon and the adjacent carbon, the hydroxyl substitution position can be determined. The type of sugar and connection location can be identified by the carbon spectral date of triterpenoid saponions. Meanwhile, the characteristic spectral features of flavonoids are summarized. NMR spectral characterization of triterpenoid saponins and flavonoids of the Clinopodium will facilitate further identification of new compounds from Clinopodium Linn.