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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 & Issues
Volume 4, Issue 2 - Dec 2000
Volume 4, Issue 1 - Feb 2000
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Characterization of Vanadium Oxide Supported on
Solid-State NMR Spectroscopy
Park, Eun-Hee ; Lee, Sung-Won ; Lee, Man-Ho ;
Journal of the Korean Magnetic Resonance Society, volume 4, issue 1, 2000, Pages 1~11
Supported vanadium oxides are being used extensively as catalysts for a variety of reactions, including partial oxidations and ammoxidations. A series of vanadium oxide supported on TiO2-ZrO2 was obtained by impregnating ammonium metavanadate slowly into a mixed precipitateof Ti(OH)4-Zr(OH)4, followed by calcining in air at high temperatures. The prepared catalysts were characterized by 51V solid-state NMR. In the calcined catalysts 51V NMR studies indicated the peaks corresponding to distorted tetrahedral vanadia species at low V2O5 contents and octahedral vanadia species at high vanadia loadings. These results illustrate the suitability of 51V NMR as a unique quantitative spectroscopic tool in the structural analysis of vanadium(V) oxide catalytic materials.
Characterization of Metakaolinite with Multiple Quantum MAS NMR
Han, Oc-Hee ; Stefan Steuernagel ;
Journal of the Korean Magnetic Resonance Society, volume 4, issue 1, 2000, Pages 12~18
Metakaolinite produced by thermal transformation from kaolinite was studied by 27Al multiple quantum magic angel spinning (MQMAS) NMR technique in addition to 1-dimensional 27Al and 29Si MAS NMR. Our results confirm that 4-, 5-, 6- coordinated aluminum sites co-exit with some distribution of isotropic chemical shifts. This is consistent with amorphous character of metakaolinite observed with X-ray diffraction. In addition, characterization with MQMAS is briefly discussed in comparison with other NMR techniques to identify different aluminum sites especially when peaks are severely overlapped in 1-dimensional 27Al MAS NMR spectra.
MR Spectroscopic Study on Levodopa-Treated Parkison's Disease
Choe, Bo-Young ; Baik, Hyun-Man ; Son, Byung-Chul ; Kim, Moon-Chan ; Kim, Euy-Neyung ; Suh, Tae-Suk ; Lee, Hyoung-Koo ; Shinn, Kyung-Sub ;
Journal of the Korean Magnetic Resonance Society, volume 4, issue 1, 2000, Pages 19~28
Authors evaluated alterations of observable metabolite ratios between the cerebral lesion and the contralateral region related to the clinical symptomatic side in levodopa-treated Parkinson's disease (PD) and investigated correlation between age in patients with PD and metabolite ratios of the lesion. Patients with levodopa-treated PD (n = 54) and age-matched normal controls (n = 15) underwent magnetic resonance spectroscopy (MRS) examinations using a stimulated echo acquisition mode (STEAM) pulse sequence that provided 2
2 cm3 volume of interest in the selected regions of substantia nigra (SN) and putamed-globus pallidus (PG). To evaluate dependence of metabolite ratios on age, we divided into two groups (i.e., younger and older age). We quantitatively measured N-acetylaspartate (NAA), creatine (Cr), choline-containing compounds (Cho), inositols (Ins), and the sum of glutamate (Glx) and GABA levels and obtained proton metabolite ratios relative to Cr using a Marquart algorithm. Compared with the contralateral region, a significant neuronal laterality of the NAA/Cr ratio in the lesion of SN related to the clinical symptomatic side was established (P = 0.01), but was not established in the lesion of PG (P = 0.24). Also, Cho/Cr ratio tended toward significance in the lesion of SN (P = 0.07) and was statistically significant in the lesion of PG(P = 0.01). Compared with that in the younger age group, NAA/Cr ratio in the older age was decreased in the lesion of SN (P = 0.02), while NAA/Cr ratio was not statistically significant in the lesion of PG ( P = 0.21). Significant metabolic alterations of NAA/Cr and Cho/Cr ratios might be closely related with functional changes of neuropathological process in SN and PG of levodopa treated PD and could be a valuable finding for evaluation of the PD. A trend of NAA/Cr reduction, being statistically significant in older patients, could be indicative of more pronounced neuronal damage in the SN of the progressive PD.
An NMR Study on Internal Rotation of
Group in 1,1,1-Trichloroethane
Hyung Namgoong ; Kim, Joa-Jin ; Lee, Jo-Woong ;
Journal of the Korean Magnetic Resonance Society, volume 4, issue 1, 2000, Pages 29~40
Coupled carbon-13 relaxation study of 1,1,1-trichloroethane dissolved in DMSO has been performed to gain some crucial insight into the dynamics of methyl group in this compound. For this purpose the relaxation behaviors of several observable magnetization modes for CH3 spin system generated by various perturbing pulse sequences have been carefully investigated and various dipolar spectral densities were estimated by nonlinear numerical fittings of the observed data with the relaxation curves, which were then employed to determine the three principal values for the diffusion tensor for end-over-end molecular rotation as well as internal rotational parameters of methyl group. In this process we could uniquely determine two correlation times
int(2) which give valuable information on internal rotor dynamics and thus obtained data were interpreted on the basis of various proposed models for internal rotation. compound undergoes three-fold jumps at 25
. The fact that the ratio
int(2) is close to 1.0 may be interpreted as indicating that methyl group in this C.
Tertiary Structure of PreSl(21-47) of Hepatitis B Virus Studied by NMR Spectroscopy
Kyeunghee Yu ; Cho, Eun-Wie ; Shin, Song-Yub ; Kim, Kol-Lyong ; Kim, Yangmee ;
Journal of the Korean Magnetic Resonance Society, volume 4, issue 1, 2000, Pages 41~49
To design more efficient peptide antagonist against the HBV, preSl(21-47) which carries the HBV receptor binding site for hepatocytes was synthesized and the solution structure of preSl(21-47) was investigated using CD spectroscopy and NMR spectroscopy in membrane-mimicking environments. According to CD spectra, preSl(21-47) has a random structure in aqueous solution, while conformational change was induced by addition of TFE and SDS micelle. Tertiary structures as determined by NMR spectroscopy shows that preSl(21-47) has a very flexible structure even in SDS micelle.
Particles Incorporated into Silica Gels Studied by EPR Spectroscopy
Ahn, Sang-Won ; Kang, Kee-Hoon ; Hong, Dea-Il ;
Journal of the Korean Magnetic Resonance Society, volume 4, issue 1, 2000, Pages 50~63
Titanium dioxide particles with three different average sizes, prepared by three different methods, were incorporated into silica gel pores by impregnation. The titanium dioxide incorporated into the silica gel pores was photoionized by 240-400 nm irradiation at 77 K by a one-photon process to from trapped hole centers on OH group and trapped electron centers on titanium which were detected by electron paramagnetic resonance at 77 K. During the impregnation the smallest size range of TiO2 particles can be incorporated into silica gels with 2.5-1.5 nm pores. However, the largest size range of TiO2 particles can only be incorporated into silica gels with 6-15 nm pores and not into silica gels with 2.5-4 nm pores. The photoyield and stability of photoinduced hole and electron centers depends on the silica pore sizes of silica gels and surface area as well as on the TiO2 loading. In large pore silica gels and large particle size of TiO2, photoinduced charge separation reaches to a plateau at shorter irradiation times and the trapped hole and electron centers are more stable to decay.
Evaluation of Selective Saturation and Refocousing Pulses in Chemical Shift NMR Imaging
Shin, Yong-Jin ; Park, Young-Sik ;
Journal of the Korean Magnetic Resonance Society, volume 4, issue 1, 2000, Pages 64~73
There are several methods to achieve selective NMR image of differing chemical species with the three most popular methods of Dixon's, CHESS, and SECSI. A major problem common to all chemical shift imaging methods is the uniformity of the static magnetic field and distortions introduced when RF coils are loaded with a conducting specimen. Without magnetic field shimming, these methods cannot be used to acquire selectively image protons in fat and water which are separated by approximately 3.0ppm. Experiments with a phantom, with linewidths of 2.5 to 3.5ppm, were quantitatively evaluated for the three methods and a new chemical shift imaging method. In this study the new chemical shift imaging method (modified CHESS+SECSI technique) which included a selective saturation and refocusing pulse, was developed to determine the ratios of water and fat in different samples.