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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Magnetic Resonance Society
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Korean Magnetic Resonance Society
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Volume 3, Issue 2 - Dec 1999
Volume 3, Issue 1 - Jun 1999
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Nonlinear effects in solution NMR: A numerical study on dynamics of dipolar demagnetizing field and radiation damping
Sangdoo Ahn ; Lee, Sanghyuk ;
Journal of the Korean Magnetic Resonance Society, volume 3, issue 2, 1999, Pages 71~83
The dynamics of the dipolar demagnetizing field is investigated by numerical simulation. The effects of radiation damping, molecular diffusion, and relaxation processes on the dipolar demagnetizing field are examined in terms of the modulation pattern of the z-magnetization and the signal intensity variation. Simulations for multi-components suggest applications for sensitivity enhancement in favorable conditions.
NMR Quadrupole Coupling Constants and Asymmetry Parameters in
Woo, Ae-Ja ; Park, Young-Sun ;
Journal of the Korean Magnetic Resonance Society, volume 3, issue 2, 1999, Pages 84~89
The 87Rb quadrupole coupling constants (e2qQ/h) and the asymmetry parameters (η) in RbMnCl3 were determined from a nonlinear least-squares fit to the 87Rb NMR powder spectra. The spectra were acquired in the temperature range from 260K to 330K. An important feature in this work is the determination of the quadrupole coupling constants and the asymmetry parameters for two physically nonequivalent Rb sites, Rb(I) and Rb(II), as a function of temperature. In addition, a structural phase transition at room temperature was conformed with the changes in the quadrupole coupling constant and the asymmetry parameter of Rb(II) site.
Quadrupole Interaction Studies of Boron-doped Graphite Electrode for Lithium Secondary Battery
Lee, Youngil ; Han, Duk-Young ; Lee, Donghoon ; Woo, Ae-Ja ; Lee, Sam-Hyeon ; Kim, Kyung-Han ; Lee, Man-Ho ;
Journal of the Korean Magnetic Resonance Society, volume 3, issue 2, 1999, Pages 90~99
Doping of boron atoms in graphite has been well known method to increase the discharge capacity as the negative electrode material for lithium secondary battery. Herein, the boron-doped graphites are prepared by mixing 1, 2.5, 5, and 7 wt. % of boron carbide in carbon during the graphitizing process. The structural states of boron in boron-doped graphites are investigated by solid-state 11B NMR spectroscopy. The resonance lines for substitutional boron atoms are identified as the second order quadrupolar powder pattern with the quardrupole coupling constant, QCC = 3.36(2) MHz. The quantitative analysis of 11B NMR spectra with boron-doped graphite has also been performed via simulation.
The Preliminary Study on the Structure of Cop Protein by CD and NMR
Kim, Yun-Kyong ; Park, Sang-Ho ; Lee, Jee-Hyun ; Kwak, Jin-Hwan ; Lee, Bong-Jin ;
Journal of the Korean Magnetic Resonance Society, volume 3, issue 2, 1999, Pages 100~108
Cop protein is the transcription repressor protein in rolling circle replication plasmid. With antisense RNA, Cop protein controls the copy number of plasmid. Cop family proteins have been found in various plasmids. Among Cop family proteins, Cop studied in this paper consists of 55 amino acids (Mw. 6,400), and was known to have trimer structure. Since no structural facts are elucidated, we have carried out preliminary experiments aimed at the elucidation of its three dimensional structure. The secondary structure of Cop is studied by CD and NMR. To solve the aggregation of Cop at high concentration, we tested various detergents and salts. The addition of detergents and salts could not solve the aggregation problem. However, we found that concentration is important in solving the aggregation problem. We knew that 0.18mM in 50mM potassium phosphate without any other ingredients is maximum concentration not to aggregate. Wa also investigated the pH dependence of Cop protein, and knew that Cop protein is more stable in acid state. At various temperatures, 15N-1H HSQC spectra were measured in order to find the optimal experimental condition. To enhance the peak resolution, 3D NOESY-HSQC spectrum is acquired. Since there are NOE peaks in the NH-NH region, we knew that Cop protein has
-helical content, which was also confirmed by CD.
Adsorbate Interactions of Cu(II) Ion-Exchanged into Mesoporous Aluminosilicate MCM-41 Analyzed by Electron Spin Resonance and Electron Spin Echo Modulation
Kim, Jeong-Yeon ; Yu, Jong-Sung ;
Journal of the Korean Magnetic Resonance Society, volume 3, issue 2, 1999, Pages 109~126
The location of Cu(II) exchanged into measoporous aluminosilicate MCM-41(AlMCM-41) material and its interaction with various adsorbate molecules were investigated by electron spin resonance and electron spin echo modulation spectroscopies. Cu(II) is fully coordinated to adsorbates in a wide open mesopore of AlMCM-41 for the formation of favorable complexes. It was found that in the fresh hydrated material, Cu(II) is octahedrally coordinated to six water molecules as evidenced by an isotropic room temperature ESR signal. This species is located in a cylindrical MCM-41 channel and rotates rapidly at room temperature. Evacuation at room temperature removes some of these water molecules, leaving the Cu(II) coordinated to less water molecules and anchored to oxygens in an MCM-41 channel wall. Dehydration at 450
produces one Cu(II) species located on the internal wall of a channel, which is easily accessible to adsorbates. Adsorption of adsorbate molecules such as water, methanol, ammonia, pyridine, aniline, acetonitrile, benzene, and ethylene on a dehydrated Cu-AlMCM-41 material causes changes in the ESR spectrum of Cu(II), indicating the complex formation with these adsorbates. Cu(II) forms a complex with six molecules of methanol as evidenced by an isotropic room temperature ESR signal and ESEM analysis like upon water adsorption. Cu(II) also forms a square planar complex containing four molecules of N-containing adsorbates such as ammonia, pyridine and aniline based on resolved nitrogen superhyperfine interaction and their ESR parameters. However, Cu(II) forms a complex with six-molecules of acetonitrile based on ESR parameters. Only one molecule of benzene or ethylene is coordinated to Cu(II).
Multiple Quantum Coherence and Magic Angle in Solid NMR Spectroscopy
Shin, Yong-Jin ; Kim, Nam-Su ; Ryang, Kyung-Seung ; Cho, Gyung-Goo ; Jeong, Gwang-Woo ;
Journal of the Korean Magnetic Resonance Society, volume 3, issue 2, 1999, Pages 127~139
In this paper we discussed how multiple quantum coherences evolve in the presence of anisotropic distribution of dipolar couplings. The magnitude of dipolar couplings were varied by changing the tile angle of crystal axis. The stronger was dipolar coupling, the higher was frequency of multiple quantum coherence. That is, the order of multiple quantum coherence varies in proportion to the magnitude of dipolar couplings. The theoretical prediction for the multiple quantum coherence at magic angle 54.7
in solid NMR spectroscopy was verified in this study. The excitation pattern of n-quantum coherence, which can induce the effective size to characterize spin system, is expected in a larger and more complicated spin system for understanding of the relation of dipolar coupling and multiple quantum coherence.
Correlation between Metabolite Peak Area Ratios on the Influence of Poor Shimming by
Baik, Hyun-Man ; Choe, Bo-Young ; Suh, Tae-Suk ; Lee, Hyuong-Koo ;
Journal of the Korean Magnetic Resonance Society, volume 3, issue 2, 1999, Pages 140~148
Using 1H magnetic resonance spectroscopy (MRS), we quantitatively evaluated correlation representing linear relationship between the metabolite peak area ratios associated with poor shimming conditions. The inadequate shimming due to linear shim offsets directly affected overall MR spectral quality as well as peak area for each metabolite. Three major peaks such as N-acetylaspartate (NAA), creatine (Cr,) choline (Cho) were used as a reference for data analysis. Despite considerable variations of metabolite peak area, a significant correlation between the metabolite peak area ratios relative to Cr was established while the correlation between the peak area ratios relative to Cho and NAA was not. The present study suggested that metabolite peak area ratios based on the metabolite of Cr could be an acceptable quantification method even under the poor shimming in clinical MRS examination.