Chinese Journal of Magnetic Resonance

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Synthesis and NMR Characterization of a New Coumarin-7, 8-cyclophosphoramide Derivative Collect

CHEN Xiao-lan；ZHOU Ya-dong；YUAN Jin-wei；LIU Xiang-qian；
ZHANG Shou-ren；QU Ling-bo；ZHAO Yu-fen

Chinese Journal of Magnetic Resonance, 2009, 26(3): 301-307.

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The Mannich reaction was used to aminomethylate 7-hydroxycoumarin selectively at the 8-C position. The product, 8-(N-alkylaminomethyl) coumarin, was then coupled with bis-β-chloroethyl dichlorophosphamide to form a novel coumarin-7, 8-cyclophosphoramide derivative via the cyclized reaction. The intermediate and the product were analyzed by NMR spectroscopy. The results confirmed the reaction pathway. The structure of the final product was elucidated by DEPT and 2D NMR techniques including ¹H-¹H COSY, HSQC and HMBC. All ¹H and ¹³C NMR chemical shifts of the title compound were assigned.

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Determination of Clarithromycin Content by NMR Collect

SHA Yi; LI Wen; SHEN Hui-en

Chinese Journal of Magnetic Resonance, 2009, 26(3): 308-315.

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An NMR-based method for determining clarithromycin content in the capsules of the drug was developed. The linear range of the method was found to be 1.03~24.72 mg/mL. The regression equation derived was y=0.025 1X-0.026 (r=0.999 2). The average recovery rate was shown to be 98.7% (n=9), and the error was less than 0.2%. The results of this study showed that the NMR-based method for analyzing clarithromycin content has high sensitivity and good repeatability, and is easy to use.

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An NMR Study on Parisaponin I and Parisvietnaside A Isolated from Paris polyphylla Smith var. yunnanensis Collect

LIU Yi-xun；KANG Li-ping；ZHAO Yu；CHEN He-bing；ZOU Peng；
XIONG Cheng-qi；ZHAO Yang；TAN Da-wei；MA Bai-ping

Chinese Journal of Magnetic Resonance, 2009, 26(3): 316-326.

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Two steroidal saponins were isolated from the rhizome of Paris polyphyllaSmith var. yunnanensis. Their structures were elucidated as (25R)-26-O-β-D-glucopyranosyl-3β, 22α, 26-trihydroxy-furost-5-ene-3-O-α-L-rhamnopyranosyl-(1→2)-[α-L-arabinofuranosyl-(1→4)]-β-D-glucopyranoside (1, parisaponin I) and (25R)-3β, 5α, 6β-trihydroxy-7(8)-ene-spirostanol-3-O-β- D-glucopyranosyl-(1→3)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (2, parisvietnaside A) by MS, 1D and 2D NMR spectroscopy. The ¹H and ¹³C chemical shifts of the compounds were assigned, and the incorrect assignments in previous literatures were corrected. Compound 2 was isolated from the plant for the first time.

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A Theoretical Study on Nuclear Spin-Spin Coupling Constants of C-X (X=H, C) Bonds Collect

HUANG Rong-yi; YE Shi-yong

Chinese Journal of Magnetic Resonance, 2009, 26(3): 327-334.

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A theoretical model for calculating the nuclear spinspin coupling constants of the directly-boned C-H and C-C bonds was formulated using the s-character of the hybrid orbitals and the atomic net charges as the variables. The model was applied to calculate ¹J_CX (X=C, H) of a number of hydrocarbons based on the maximum overlap symmetry molecular orbital (MOSMO) method under PM3 approximation and the maximum bond order hybrid orbital (MBOHO) procedure. The calculated values were found to be in good agreement with the experimental data, supporting the notion that the Fermi contact term are a dominant factor in determining the carbonhydrogen and carboncarbon spinspin coupling constants over one bond. The method developed provided a platform to interpret and calculate ¹J_CH and ¹J_CC based on simple valence bond theory.

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Software Testing for the Console System of an NMR Spectrometer Collect

FANG Hui-ru；CHEN Yi-qun；JIANG Ting-ting；LIU Chao-yang

Chinese Journal of Magnetic Resonance, 2009, 26(3): 335-342.

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Software testing has been widely used as a way to improve the quality of software. In this paper, a method for software testing in the development of a nuclear magnetic resonance (NMR) spectrometer was developed. Beginning with the introduction of the concepts for testing, the difficulties and solutions during the testing were analyzed according to the software structure of the console system of the spectrometer and the characteristics of the NMR experiments. The realization of software testing, which played a constructive role in improving the reliability and stability of the NMR spectrometer, was introduced in detail.

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The Design of a Data Exchange Method for Integrated Nuclear Magnetic Resonance Spectrometer Collect

ZHOU Juan; ZHOU Min-xiong; LEI Du; SHANG Yun; JIANG Yu

Chinese Journal of Magnetic Resonance, 2009, 26(3): 343-350.

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A data exchange method for integrated nuclear magnetic resonance spectrometer and a design concept of ARM-based embedded operation system software were proposed in this paper, aiming at solving the problems found in the previous designs. The test results of each module in the spectrometer were provided and discussed.

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An ARM- and CPLD-Based Preamplifier Control System for NMR Spectrometers Collect

WANG Wen-juan; HU Peng; MAO Wen-ping; LIU Chao-yang

Chinese Journal of Magnetic Resonance, 2009, 26(3): 351-358.

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This paper presented an ARM- and CPLD-based design scheme for the NMR spectrometer preamplifier control system. ARM was used as the center control CPU, and CPLD as the perform unit to control the working conditions of the high-band and broadband preamplifiers, mixer and lock preamplifier. The system developed has the following main functions: 1) to convert the input TTL gate signal levels into +5V/15V signal, which is then used to control the switching between the receiver mode and the transmitter mode of the high-band and broadband preamplifiers; 2) to give users a reference signal for tuning; 3) to relay the switch channels to lock transmitter and broadband receiver in deuterium gradient shimming experiments; and 4) to display the data sent from the console PC or ADC on LED in real-time.

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The Design of a Digital Receiver System for MRI Scanners Collect

LI Rui；XIAO Liang；WANG Wei-min

Chinese Journal of Magnetic Resonance, 2009, 26(3): 359-368.

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The receiver system is an integrating part in the magnetic resonance imaging (MRI) scanner, and the performance of which affects the image quality directly. In this paper, the design of a digital receiver system was presented, which took into account the intrinsic properties of the MRI signals including weak amplitude, high frequency and narrow bandwidth. The role and the design of each part of the receiver system, such as controlled amplifier, high speed A/D, digital demodulator and decimating filter, were discussed in detail. A special sample rate distribution and filter design method were developed for the multi-stage decimating filter. The receiver system designed was used on diagnostic MRI systems, and showed good performance in terms of signal noise ratio.

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Analyses on the Signal- to- Noise Ratio of the Atomic Discrimination Signal in Rubidium Atomic Frequency Standard Collect

QI Feng; ZHAO Feng; WANF Fang; KANG Song-bai; MEI Gang-hua

Chinese Journal of Magnetic Resonance, 2009, 26(3): 369-374.

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Frequency stability is the most important parameter of a rubidium atomic frequency standard, which depends mainly on the signal-to-noise ratio (SNR) of the rubidium atomic discrimination signal (RADS). In this paper, we analyzed the effects of several factors on the SNR of the RADS, including the configuration of the microwave cavity, the spectrum purity of the rubidium spectrum lamp and the isotope filtering scheme. It was shown that the SNR of the RADS could be improved by using a microwave cavity with proper microwave field mode and high microwave filling factor, a rubidium spectrum lamp with high spectrum purity and a separated isotope filtering scheme in the physics package design. The performance of the rubidium atomic frequency standard could be improved by taking all these factors into consideration.

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Design of a Digital Temperature Control Circuit for Rubidium Atomic Frequency Standard Collect

HE Chang-ming；ZHANG Xian-yi；YAN Shi-dong；MEI Gang-hua；ZHONG Da

Chinese Journal of Magnetic Resonance, 2009, 26(3): 375-384.

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A digital temperature control system based on single chip processor, ADC and PID control algorithm was developed for a miniaturized digital rubidium atomic frequency standard (MRAFS) with low power consumption. The basic theory underlying the PID control algorithm and the strategies for tuning the operational parameters were discussed. The experimental results showed that the digital system developed had low power consumption and smaller volume relative to the traditional analog temperature control system, and similar accuracy of temperature control. The digital temperature control system developed could meet the operational requirement of MRAFS.

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An Information Database on Detecting Hidden Explosives with NQR-Based Methods Collect

YANG Zhen-lei; XU Geng-guang; WANG Zhen-hua; LIU Ke-zhong

Chinese Journal of Magnetic Resonance, 2009, 26(3): 385-392.

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Many parameters need to be taken into account when using nuclear quadrupole resonance (NQR) to detect explosive, since the frequency and SNR of the NQR signals of the explosives are affected by the type of atomic nucleus of interest, the choice of excitation pulse and other parameters describing the test conditions. In the past, the NQR data of explosives could not be recorded and managed effectively due to the lack of a unified explosive parameter information database. In this study, a hidden explosive information database was designed and constructed after comprehensive analyzing the relationship between the testing parameters and the NQR frequencies of the explosives. The database can be used to collect and record parametric information of the explosives effectively, and will provide a useful platform for future NQR studies on explosives.

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¹H and ¹³C NMR Chemical Shift Assignment for Tenatoprazole Collect

LIN Zhen-guang; LIN Ji-mao; HU Zhan-kun; CAO Zhen-yan

Chinese Journal of Magnetic Resonance, 2009, 26(3): 393-399.

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Tenatoprazole is a novel proton pump inhibitor currently undergoing phase III clinical trail. In this study, the ¹H and ¹³C chemical shifts of this compound were assigned using 2D NMR techniques, including DEPT, HMQC, HMBC, COSY, NOESY and TOCSY. The asymmetric structure of the compound was elucidated by NOESY. All quaternary carbons of the compound were also assigned by HMBC.

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NMR Characterization of 7-oxo-aporphine Alkaloids Collect

LI Ning; ZHANG Peng; LIANG Dong; XIAO Wan; LI Xian

Chinese Journal of Magnetic Resonance, 2009, 26(3): 400-407.

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Aporphine alkaloids found in plants have good antihypertensive and antibacterial activities. In this study, three 7-oxo-aporphine alkaloids were isolated from Liriodendron Chinese and characterized by ¹H and ¹³C NMR and 2D NMR techniques (including ¹H-¹H COSY, HSQC, HMBC and NOESY). The chemical shifts of the three compounds were assigned. Assignment mistakes found in the literature were corrected.

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Theoretical Investigation of the EPR Spectra and Local Structure of Cu^2+Doped PTO Crystal Collect

GONG Jin-tao; WANG Li-juan

Chinese Journal of Magnetic Resonance, 2009, 26(3): 408-412.

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The crystalfield theory was used to simulate the electron paramagnetic resonance (EPR) spectra of Cu²⁺-doped PbTiO₃ (PTO) crystal and to study the local lattice structure of the crystal. The simulations used the superposition model, the third-order perturbation formula of g factor and the hyperfine structure constants A for the 3d⁹ electronic configuration in the distorted tetragonal crystal-field. The quantitative relationship between the local lattice structure of the Cu²⁺-doped PTO crystal and the corresponding EPR spectrum was established. The results obtained by theoretical simulations were found in good agreement with the experimental results.

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Intermolecular Interactions Studied by Microwave Spectroscopy Collect

GOU Qian; XIA Zhi-ning; TANG Shou-yuan

Chinese Journal of Magnetic Resonance, 2009, 26(3): 413-423.

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Microwave spectroscopy, which works at microwave frequencies, developed rapidly in recent years as an analytical tool for studying molecular geometrical structures and intermolecular interactions with high resolution and sensitivity. This review introduces the principles underlying this technique, as well as its applications in studying the weakly bounded complexes, namely van der Waals complexes, hydrogen bond complexes and halogen bond complexes. The pulsed-nozzel Fourier transform microwave spectrometer was also briefly introduced.

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NMR Application in Selective Separation for Natural Products and Their Structural Investigation Collect

GENG Zhu-feng；OUYANG-Jie；DENG Zhi-wei；SHEN Sheng-min；DU Shu-shan

Chinese Journal of Magnetic Resonance, 2009, 26(3): 424-436.

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NMR has played an important role in Natural Product Chemistry. In this work, NMR technique was used as a valid monitor in the separation process of natural products, in addition to its application in the structural elucidation of natural compounds. In the selective separation of diterpenoid-like compounds from the natural plants, ¹H NMR was performed in time after each step of the separation. Combining with the knowledge about the spectral characteristics of the target compounds, the information obtained from ¹H NMR spectra was well used to handle the separation work.