• Applied Biological Chemistry
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• v.47 no.2
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• pp.270-273
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• 2004

Two prenylated flavonoids were isolated from a chloroform extract of the root bark of Cudrania tricuspidata. Both compounds (1, 2) showed antibacterial activity against Gram positive bacteria, Staphylococcus aureus, Bacillus subtilis and Bacillus cereus. Their structures were determined as euchrestaflavanone B (1) and euchrestaflavanone C (2) on the basis of $^1H\;NMR,\;^{13}C\;NMR$ and long-range coupling NMR techniques.

• Journal of the Korean Magnetic Resonance Society
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• v.21 no.2
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• pp.67-71
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• 2017

At high temperature, the roles of $NH_4$ and $H_2O$ in $(NH_4)_2Fe(SO_4)_2{\cdot}6H_2O$ and $(NH_4)_2Zn(SO_4)_2{\cdot}6H_2O$ single crystals were investigated using a pulse NMR spectrometer. Temperature was shown to have a significant influence, causing changes in the deformation of $NH_4$ and $H_2O$. From the $^1H$ NMR and $^{14}N$ NMR spectrum, the forms of environment surrounding $^{14}N$ in $NH_4$ groups is more important than the loss of $H_2O$ groups. NMR studies indicate that $NH_4{^+}$ ions in Tutton salts play an important role in the changes of the crystal structure at high temperatures.

• Journal of the Korean Magnetic Resonance Society
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• v.13 no.2
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• pp.108-116
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• 2009

The HP0902, a homodimeric 22.1 kDa protein, has been suggested as a putative secretory protein from Helicobacter pylori, although the protein possesses no signal peptide for secretion. Since it may be associated with the virulence of the bacterium, NMR study has been initiated in terms of structural genomics. In our previous effort to assign the backbone NMR resonances, using 800MHz NMR machine at pH 7.8, the resonances from eight of the 99 residues could not be assined due to missing of the signals. In this work, to enhance the extent of assignments, a 900 MHz machine was employed and the sample pH was reduced down to 6.5. Finally, almost all signals, except for those from G9 and S24, could be clearly assigned. The determined secondary structure using the assined chemical shifts indicated that the HP0902 consists of 11 ${\beta}$-strands with no helices. In our database search result, HP0902 was predicted to interact with VacA (Vacuolating cytotoxin A), which is a representative virulence factor secreted from Helicobacter pylori. Thus, molecular interaction between HP0902 and VacA would be worthy of investigation, on the basis of the present results of NMR assignments.

• Bulletin of the Korean Chemical Society
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• v.7 no.2
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• pp.89-96
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• 1986

The NMR chemical shift arising from 4d electron angular momentum and 4d electron spin dipolar-nuclear spin angular momentum interaction for a $4d^1$ system in a strong crystal field of octahedral symmetry, when the threefold axis is chosen as the quantization axis, has been investigated. A general expression using a nonmultipole expansion method is derived for the NMR chemical shift. From this expression all the multipolar terms are determined. We find that the nonmultipolar results for the NMR chemical shift ${\Delta}B$, is exactly in agreement with the multipolar results when $R {\ge} 0.20$ nm. It is also found that the 1/$R^7$ term contributes to the NMR chemical shift almost the same as the 1/$R^5$ in magnitude. The temperature dependence analysis of ${\Delta}B$/B(ppm) at various values of R shows that the 1/$T^2$ term has the dominant contribution to the NMR chemical shift but the contributions of other two terms are certainly significant for a $4d^1$ system in a strong crystal field of octahedral symmetry when the threefold axis is chosen to be the axis of quantization.

• Bulletin of the Korean Chemical Society
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• v.15 no.8
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• pp.673-679
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• 1994

$^1H$ NMR spectra of imidazole, 2-and 4(5)-methylimidazole, histamine, L-histidine, L-histidine methyl ester, N${\alpha}$-acetyl-L-histidine, and L-carnosine coordinated to the paramagnetic undecatungstocobalto(II)silicate ($SiW_{11}Co$) and undecatungstonickelo(II)silicate ($SiW_{11}Ni$) anions are reported. For these complexes the ligand exchange is slow on the NMR time scale and the pure resonance lines of the free ligand and the complexes have been observed separately at room temperature. Two different complexes are formed, depending upon which nitrogen atom of the imidazole ring is coordinated to the cobalt or nickel ion of $SiW_{11}M$. Thus the NMR spectrum of a $D_2O$ solution containing a ligand and $SiW_{11}M$ consists of three sets of lines originating from the free ligand and two complexes. All NMR lines of the $SiW_{11}Co$ complexes have been assigned unequivocally using the saturation transfer technique. The temperature dependence of some spectra are also reported. The NMR spectra of some complexes show that the internal rotation of the substituent on the imidazole ring is hampered by the heteropolyanion moiety even at room temperature.

• Journal of the Korean Magnetic Resonance Society
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• v.28 no.1
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• pp.1-5
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• 2024

IscU, the iron-sulfur (Fe-S) cluster scaffold protein, is an essential protein for biogenesis of Fe-S clusters. Previous studies showed that IscU manifests a metamorphic structural feature; at least two structural states, namely the structured state (S-state) and the disordered state (D-state), interconverting in a physiological condition, was observed. Moreover, subsequent studies demonstrated that the metamorphic flexibility of IscU is important for its Fe-S cluster assembly activity as well as for an efficient interaction with various partner proteins. Although solution nuclear magnetic resonance (NMR) spectroscopy has been a useful tool to investigate this protein, the detailed molecular mechanism that sustains the structural heterogeneity of IscU is still unclear. To tackle this issue, we applied a high-pressure NMR (HP-NMR) technique to the IscU variant, IscU(I8K), which shows an increased population of the S-state. We found that the equilibrium between the S- and D-state was significantly perturbed by pressure application, and the specific regions of IscU exhibited more sensitivity to pressure than the other regions. Our results provide novel insights to appreciate the dynamic behaviors of IscU and the related versatile functionality.

• Applied Biological Chemistry
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• v.48 no.3
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• pp.267-272
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• 2005

trans-Cinnamaldehyde, a major component of Cinnamomum cassia, was quantitatively analyzed using the $^1H-NMR$ spectrometry. Applicability of this method was confirmed through observing the variation of chemical shift in the $^1H-NMR$ spectrum of t-cinnamaldehyde and the integration value according to various sample concentrations or running temperatures. When the $^1H-NMR$ spectrometry was run for t-cinnamaldehyde (7.1429 mg/ml) at 19, 25, 30, 40 and $50^{\circ}C$, the chemical shifts of the doublet methine signal due to an aldehyde group were observed at 9.7202, 9.7184, 9.7169, 9.7142 and 9.7124 ppm, respectively, to imply that the running temperature had no significant variation in the chemical shift of the signal. The integration values of the signal were $1.37\;(19^{\circ}C),\;1.37\;(25^{\circ}C),\;1.37\;(30^{\circ}C),\;1.37(40^{\circ}C)$ and $1.37(50^{\circ}C)$, respectively, to also indicate running temperature gave no effect on the integration value. When the sample solutions with various concentrations such as 0.4464, 0.8929, 1.7857, 3.5714, 7.1429 and 14.286 mg/ml were respectively measured for the $^1H-NMR$ at $25^{\circ}C$, the chemical shifts of the aldehyde group were observed at 9.7206, 9.7201, 9.7196, 9.7192, 9.7185 and 9.7174 ppm. Even though the signal was slightly shifted to the high field in proportion to the increase of sample concentration, the alteration was not significant enough to applicate this method. The calibration curve for integration values of the doublet methine signal due to the aldehyde group vs the sample concentration was linear and showed very high regression rate ($r^2=1.0000$). Meantime, the $^1H-NMR$ spectra (7.1429 mg/ml $CDCl_3,\;25^{\circ}C$) of t-cinnamaldehyde and t-2-methoxycinnamaldehyde, another constituent of Cinnamomum cassia, showed the chemical shifts of the aldehyde group as ${\delta}_H$ 9.7174 (9.7078, 9.7270) for the former compound and ${\delta}_H$ 9.6936 (9.6839, 9.7032) for the latter one. The difference of the chemical shift between two compounds was big enough to be distinguished using the NMR spectrometer with 0.45 Hz of resolution. The contents of cinnamaldehyde in Cinnamomum cassia, which were respectively extracted with n-hexane, $CHCl_3$, and EtOAc, were determiend as 94.2 \;mg/g (0.94%), 137.6 mg/g (1.38%) and 140.1 mg/g(1.40%) t-cinnamaldehyde in each extract, respectively, by using the above method.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.1
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• pp.31-40
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• 2021

The hydrogen in nominally anhydrous mineral is known to be associated with lattice defects, but it also can exist in the form of water and hydroxyl groups on the large surface of the nanoscale particles. In this study, we investigate the effectiveness of 1H solid-state nuclear magnetic resonance (NMR) spectroscopy as a robust experimental method to quantify the hydrogen atomic environments of amorphous silica nanoparticles with varying relative humidity. Amorphous silica nanoparticles were packed into NMR rotors in a temperature-humidity controlled glove box, then stored in different atmospheric conditions with 25% and 70% relative humidity for 2~10 days until 1H NMR experiments, and a slight difference was observed in 1H NMR spectra. These results indicate that amount of hydrous species in the sample packed in the NMR rotor is rarely changed by the external atmosphere. The amount of hydrogen atom, especially the amount of physisorbed water may vary in the range of ~10% due to the temporal and spatial inhomogeneity of relative humidity in the glove box. The quantitative analysis of 1H NMR spectra shows that the amount of hydrogen atom in amorphous silica nanoparticles linearly increases as the relative humidity increases. These results imply that the sample sealing capability of the NMR rotor is sufficient to preserve the hydrous environments of samples, and is suitable for the quantitative measurement of water content of ultrafine nominally anhydrous minerals depending on the atmospheric relative humidity. We expect that 1H solid-state NMR method is suitable to investigate systematically the effect of surface area and crystallinity on the water content of diverse nano-sized nominally anhydrous minerals with varying relative humidity.

• Journal of the Korean Electrochemical Society
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• v.12 no.4
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• pp.329-334
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• 2009

This study is to develop a fuel cell system applicable to an in situ NMR (Nuclear magnetic resonance) diagnosis. The in situ NMR can be used in real time monitoring of various reactions occurring in the fuel cell, such as oxidation of fuel, reduction of oxygen, transport phenomena, and component degradation. The fuel cell for this purpose is, however, to be operated in a specifically designed tubular shape toroid cavity detector (TCD), which constrains the fuel cell to have a tubular shape. This may cause difficulties in effective mass transport of reactants/products and uniform distribution of assembly pressure. Therefore, a new flow field designed in a particular way is necessary to enhance the mass transport in the tubular fuel cell. In this study, a tubular-shaped close-type flow field made of non-magnetic material is developed. With this flow field, oxygen is effectively delivered to the cathode surface and the produced water is readily removed from the membrane-electrode assembly to prevent flooding. The resulting DMFC (direct methanol fuel cell) outperforms the open-type flow field and exhibits $36\;mW/cm^2$ even at room temperature.

• Journal of Ginseng Research
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• v.32 no.4
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• pp.291-299
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• 2008

The fresh ginseng roots were extracted in aqueous methanol (MeOH), and the obtained extracts were partitioned using ethyl acetate (EtOA), n-butanol (n-BuOH), and water, successively. The repeated silica gel column chromatography for n-BuOH fraction afforded a purified ginsenoside $Rg_1$. The physico-chemical, spectroscopic and chromatographic data of ginsenoside $Rg_1$, such as crystallization characteristics, melting point, specific rotation, infrared spectrometry (IR) data, fast atom bombardment/mass spectrometry (FAB/MS) data, nuclear magnetic resonance (NMR) data, retention factor (Rf) in thin layer chromatography (TLC) experiment, and retention time (r.t.) in HPLC analysis, were measured and compared with those reported in literatures. Especially, the previous literatures reported different data for ginsenoside $Rg_1$ in the $^{1}H-$ and $^{13}C$-NMR experiments. This paper gives the exactly assigned NMR data through 2D-NMR experiments, such as $^{1}H-^{1}H$ correlation spectroscopy (COSY), hetero nuclear single quantum correlation (HSQC), and hetero nuclear multiple bond connectivity (HMBC).