The efficiency of multiple-dimensional heteronuclear correlation experiments in membrane protein studies is partially determined by the efficiency of double cross polarization (DCP). DCP is a basic block in the pulse sequences to probe the connections between the ¹⁵N and ¹³C nuclei. In this study, three membrane proteins were studied experimentally to determine how the dynamics properties of the proteins affect the DCP efficiency in solid-state heteronuclear correlation experiments. Under the same experimental conditions, the AQPZ protein showed the highest DCP efficiency (31%), while the EV71 2B protein had the lowest efficiency (14%) and the DAGK protein in between (23%). Longitudinal lattice relaxation time in the rotating frame (T_1ρ) and dipole coupling constant (D_HN) were also measured for these proteins. It was found that the DCP efficiency depended strongly on T_1ρ, but only weakly on D_HN. Based on the experimental data, a model to correlate the T_1ρ of protein to the DCP efficiency was established, with which the DCP efficiency could be predicted by measuring the T_1ρ of membrane proteins.

Human serum albumin (HSA) contains many metabolite binding sites. It has been widely studied for its functions in drug transportation. Nuclear magnetic resonance (NMR) is a frequently used tool to study HSA. However, due to its high molecular weight, the NMR spectra of HSA acquired with the conventional methods are often crowded, making spectral assignment and data interpretation difficult. In this study, a new method, which combined radiation damping water-ligand observed via gradient spectroscopy (RD-WaterLOGSY) with transverse relaxation weighted (T₂W) techniques, was proposed to simplify the NMR spectra of HSA. With the T₂W-RD-WaterLOGSY technique, the effect of pH on HSA was studied, as well as the interactions between HSA and Zn²⁺. The results showed that the relative changes in chemical shift could be used as a probe to analyze the pH changes in HSA solution and the interactions between HSA and Zn²⁺.

Acquisition parameters for chemical exchange saturation transfer (CEST) imaging were optimized on a GE Signa HDe 1.5 T magnetic resonance imaging (MRI) scanner with phantoms and clinical cases. The effects of matrix size, number of averages (NEX) and flip angles on the quality of CEST images were assessed. It was shown that the signal-to-noise ratio (SNR) of the CEST images acquired on the 1.5 T scanner was relatively low, and the stability and uniformity of the B₀ field affected the outcome significantly. Reducing matrix size and increasing NEX improved the SNR of the CEST images. Optimal flip angle for magnetization transfer was found to be 105°. With a NEX of 2, usable Z spectra could be obtained. The Z spectra indicated that, with the saturation pulse frequency centered at -294~-194 Hz, signal differences could be observed for 30% Glu, I₃₂₀, H₂O, and Cr. Maximal signal differences were observed when the saturation pulse applied at -244~-214 Hz. Amide proton transfer (APT) imaging on patients showed that 25 cases of brain tumor had high CEST signals, 12 cases of cerebral infarction had low CEST signals. It was therefore possible to differentiate brain tumor from infarction with CEST imaging. There were also 12 cases which failed due to long acquisition time, patient movements, and temperature changes in the scanner room.

Cardiac magnetic resonance imaging (CMRI) is a non-invasive technique that features multi-contrast and allows imaging at arbitrary orientations. However, the clinical applications of cardiac MRI are limited, mainly due to its long scan time. To speed up cardiac CINE imaging, a multi-fold accelerated cardiac CINE imaging method based on simultaneous multi-slice imaging and reconstruction technique was proposed. By combining the controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) technique and a partial parallel acquisition (PPA) scheme, a four-fold acceleration (i.e., 2-fold along the phase encoding direction and 2-fold along the slice encoding direction) was achieved. The proposed technique was tested and verified on phantoms and human subjects using an improved image reconstruction method SENSE/GRAPPA. Results demonstrated that the proposed method is effective in reducing cardiac CINE scan time, while preserving image quality and accuracy of cardiac function assessment.

In magnetic resonance imaging (MRI), data averaging is often used to improve signal-to-noise ratio (SNR) of the images. However, image blurring can be induced by averaging if movements occur during scanning. Inspired by the patch-matching method used in the non-local means algorithm, a new method to find out local offsets of structures in multiple images was proposed by comparing the neighborhood similarities of the image patches. The local offsets could then be corrected before weighted averaging of the images. The performance of the proposed method was verified with both phantom and patient images. The results demonstrated that the proposed algorithm could improve SNR while preserving the image edges and details correctly.

We synthesized TPP-Lys(Acp-DOTA-Gd)-COOH (Gd-DOTA-TPP) as a novel T₂-weighted MRI contrast agent, and used it to label human mesenchymal stem cells (hMSCs) via electroporation. hMSCs labeled with Gd-DOTA-TPP presented a rather dark T₂-weighted image at a cellular Gd content of about 9×10⁹ Gd/cell. The labeled cells were syringe-injected into a mouse brain with defined cell numbers followed by T₂-weighted MRI on an 11.7 T system, which yield an in vivo imaging sensitivity of about 10³ cells.

Shikimate metabolic pathway exists in plants, microorganisms and parasites as an important route for biosynthesis of aromatic amino acids, antibiotics, plant hormones and secondary metabolites with essential physiological activities. Although the NMR data and assignments of relevant metabolites are available in the literature, these data were not easily adaptable to modern metabonomics studies, in which water and acetonitrile were frequently used as solvents. In addition, the NMR data for some of the metabolites, such as 5-hydroxyindoleacetic acid and indolelactic acid, were either incomplete or incompletely assigned, especially for the quaternary carbons. With ¹H NMR and ¹H-¹³C HMBC two-dimensional NMR, we completely assigned the ¹H and ¹³C NMR signals of 26 metabolites associated with the shikimate pathway, including 2 non-aromatic carboxylic acids, 2 plant hormones, 3 essential aromatic amino acids, and 19 plant secondary metabolites. A databank was constructed for the ¹H and ¹³C NMR spectra of these metabolites in D₂O and acetonitrile, providing a systematic and useful data collection for phytochemistry and metabonomics studies.

A ¹H nuclear magnetic resonance (¹H NMR) method for quantitative analysis of the content of styrene-butadienestyrene (SBS) blocks in polymer-modified asphalt was proposed. ¹H NMR spectra were acquired from multiple samples of modified asphalt with known SBS content. The integral of SBS peaks was calculated and normalized to yield SBS content. The results obtained with ¹H NMR were compared to those obtained with Fourier transform infrared spectroscopy (FTIR). A good linearity for the calibration curve (R²=0.999 9) was obtained, indicative of excellent reproducibility and accuracy. The measurement errors were found to be larger with FTIR than with ¹H NMR.

2,3:4,5-bis-O-(1-methyl ethylidene)-β-D-fructopyranose is also called diacetonefructose, which is an important intermediate for drug synthesis, and contains chiral carbon atoms. In this study, one-dimensional (i.e., ¹H NMR, ¹³C NMR and DEPT135) and two-dimensional (i.e., ¹H-¹³C HMBC, ¹H-¹³C HSQC, ¹H-¹H COSY and NOESY) NMR methods were used to elucidate the structure of this compound. The ¹H and ¹³C NMR chemical shifts of the compound were assigned. Theoretical calculation was used to confirm the correctness of the stereochemistry configuration deduced from the NMR data.

A multi-channel parallel radiofrequency (RF) transmitter was developed for high-field magnetic resonance imaging (MRI) scanners. With a single field programmable gate array (FPGA) and a multi-channel digital analog converter (DAC), the transmitter can generate multi-channel RF pulses in parallel. The frequency, phase and amplitude of the RF pulses can be adjusted quickly and independently. The FPGA reads the parameters of the RF pulses previously stored in a dual-port random access memory (RAM), and uses them to carry out modulation and direct digital frequency synthesis (DDS) for each RF pulses, resulting in multi-channel digital RF signals. The digital signals were then converted into analog RF signals with a high-performance DAC. The use of intellectual property core provided by Xilinx greatly reduced development time, difficulty and cost in achieving the main functions of the transmitter, such as DDS and modulation. The developed multi-channel RF transmitter has the merits of high integration, small size, low cost and good universality, providing an efficient component for high field MRI systems.

Spectrometer is a key control unit in magnetic resonance imaging (MRI) systems. Pulse programmer of the spectrometer outputs multi-channel instructions to control each hardware component separately, and to coordinate work, collect data, and reconstruct image. Relative time delay among the hardware components may disable the system, or affect the quality of the images acquired. This work designed a pulse programmer whose output channels all boasted adjustable time delay capability. The maximal time delay for each channel was 819 μs, and the step time delay was 50 ns. As such, accurate compensation to relative time delay could be achieved. By adding independent delay circuits on every output channel of the pulse programmer, adjustable time delay capability was achieved. The pulse programmer proposed has the advantages of simple structure and high flexibility.

A multi-functional spectrometer, capable of dynamic nuclear polarization (DNP) and electron paramagnetic resonance (EPR) experiments, is put forward on the basis of a home-built DNP-magnetic resonance imaging (MRI) spectrometer. A key component of the multi-functional spectrometer, microwave bridge, was designed and implemented. The microwave bridge was used to integrate the microwave transmitter of the DNP spectrometer and to enable the EPR capability. A transmitter system with high spectrum purity and dynamic range as well as a detector with low noise figure were also implemented by structure designing, circuit simulation and system evaluation. DNP and continuous wave EPR experiments were conducted to verify the reliability of the microwave bridge.

In vivo electron paramagnetic resonance (EPR) tooth dosimetry can be used to estimate the absorbed radiation dose quickly and noninvasively. In this study, a magnet modulation driving device was developed for in vivo EPR tooth dosimetry. The device included a driving amplifier, a couple of coil sets generating modulation magnet field, a modulation frequency setting unit and a display unit. The driving amplifier used a switching circuit based on multi N-MOSFET H-bridge, instead of the traditional linearly analogue circuit. The amplifier had the characters of higher power capacity, high efficiency, simple structure and high flexibility for frequency setting. Experimental results showed that (1) the device could generate modulation magnet field, 0~0.9 mT in amplitude and 10~100 kHz in frequency, in the center of the two magnet poles separated more than 9 cm apart; (2) line broadening process feature of 1,1-diphenyl-2-picrylhydrazyl (DPPH) was observed with increasing modulation amplitude and radiation induced free radical signals in intact tooth. The preliminary results demonstrated that the device developed for in vivo EPR tooth dosimetry had high-efficiency and practicability.

Ancient architectures such as the Great Wall are symbols and pride of the Chinese nation, and precious treasures of the world. Portable NMR detection devices have been proposed to examine the building materials of such ancient architectures non-invasively, and to provide information regarding the science, technology and engineering behind these architectures. In this study, the magnets for such portable NMR detection devices were designed and built, which were all based on a semi-Halbach magnet structure. On top of the basic design, different modules were added to achieve different functionality, including the magnet for mobile measurement, the magnet for high depth measurement, and the "homogeneous" field mode. The measured magnetic field (B₀) distributions for these magnets agreed well with the simulated results, with only slight differences. Experiments on bricks were performed to verify the performance of these magnets.

Low noise pre-amplifier is an important component in the radiofrequency (RF) receiving subsystem of magnetic resonance systems. The performance of pre-amplifier determines the quality of the final images directly. Currently, low noise pre-amplifiers on the market mostly are designed for high-field magnetic resonance systems. Few such low noise pre-amplifiers were designed specifically for low-field magnetic resonance systems. Moreover, commercially-available low noise pre-amplifiers are relatively expensive, and most of the designs use a complicated two-stage amplification structure. For these reasons, a low noise pre-amplifier with only one-stage amplification structure was developed in this study for 0.5 T low-field magnetic resonance systems using the advanced design system (ADS) software. The circuit design and layout effects were presented. Experimental measurement showed that the noise figure of on-resonance frequency 21 MHz was about 0.5 dB, and a gain of 30 dB was achieved.