• Journal of the Korean Magnetic Resonance Society
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• v.22 no.2
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• pp.34-39
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• 2018

The Nuclear Magnetic Resonance (NMR) technique using Dynamic Nuclear Polarization (DNP) procedures is one of the promising techniques that enable overcoming low sensitivity problems in NMR spectroscopy. We constructed an ODNP-NMR system using a commercial benchtop EPR spectrometer. The $^1H$ NMR peak area of water in aqueous solutions of 4-hydroxy-TEMPO was enhanced more than 95 times in the ODNP-NMR experiments. Our signal enhancement results were about 55% of the previously reported result. This could be due to non-uniform microwave power over a sample and unwanted sample heating by microwave. However, this portable ODNP-NMR spectrometer will be eventually useful for site-specific detection with nano-scale spatial resolutions and molecular dynamics studies with significantly improved signal sensitivity.

• Journal of the Korean Magnetic Resonance Society
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• v.15 no.1
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• pp.14-24
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• 2011

We have performed Liquid Chromatography-Solid Phase Extraction-NMR (LC-SPE-NMR) analysis for liquid crystalline mixture and elucidated the structures of selected components by NMR spectra. Combining the results of one-dimensional 1H experiments as well as homonuclear and heteronuclear two-dimensional experiments, we could analyze the molecular structure of the liquid crystal singles whose structure had not been interpretable by mass spectrometry alone.

• Journal of the Korean Magnetic Resonance Society
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• v.17 no.1
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• pp.19-23
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• 2013

The temperature dependences of the NMR spectrum and the spin-lattice relaxation times in $KH_2PO_4$ were investigated via single-crystal NMR and MAS NMR. The stretched-exponential relaxation that occurred because of the distribution of correlation times was indicative of the degree of the distribution of the double-well potential on the hydrogen bond. The behaviors responsible for the strong temperature dependences of the $^1H$ and $^{31}P$ spin-lattice relaxation times in the rotating frame $T_{1{\rho}}$ in $KH_2PO_4$ are likely related to the reorientational motion of the hydrogen-bond geometry and the $PO_4$ tetrahedral distortion.

• Journal of the Korean Magnetic Resonance Society
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• v.26 no.2
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• pp.21-23
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• 2022

High-pressure (HP) NMR is a powerful method to elucidate various structural features of amyloidogenic proteins. Following the previous mini-review recapitulating the HP-NMR application for amyloid-β peptides of the last issue [J. H. Kim, J. Kor. Mag. Reson. Soc. 26, 17 (2022)], the recent advancements in the HP NMR application for α-synuclein (α-Syn) are briefly summarized and discussed here. Although α-Syn is a well-known intrinsically disordered protein (IDP), several studies have shown that it can also exhibit heterogeneous yet partially folded conformations, which may correlate with its amyloid-forming propensity. HP NMR has been a valuable tool for investigating the dynamic and transient structural features of α-Syn and has provided unique insights to appreciate its aggregation-prone characters.

• BMB Reports
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• v.45 no.7
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• pp.419-424
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• 2012

High-fat diets (HFD) and high-carbohydrate diets (HCD)-induced obesity through different pathways, but the metabolic differences between these diets are not fully understood. Therefore, we applied proton nuclear magnetic resonance ($^1H$ NMR)-based metabolomics to compare the metabolic patterns between C57BL/6 mice fed HCD and those fed HFD. Principal component analysis derived from $^1H$ NMR spectra of urine showed a clear separation between the HCD and HFD groups. Based on the changes in urinary metabolites, the slow rate of weight gain in mice fed the HCD related to activation of the tricarboxylic acid cycle (resulting in increased levels of citrate and succinate in HCD mice), while the HFD affected nicotinamide metabolism (increased levels of 1-methylnicotineamide, nicotinamide-N-oxide in HFD mice), which leads to systemic oxidative stress. In addition, perturbation of gut microflora metabolism was also related to different metabolic patterns of those two diets. These findings demonstrate that $^1H$ NMR-based metabolomics can identify diet-dependent perturbations in biological pathways.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.2
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• pp.88-94
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• 2015

Bub1 is one of the spindle checkpoint proteins and plays a role in recruitment of the related proteins to kinetochore. Here, we studied the structural characteristic of the evolutionarily conserved 160 amino acid region in the N-terminus (hBub1 CD1), using Circular Dichroism (CD) and NMR. Our CD results showed that hBub1 CD1 is a highly helical protein and its structure was affected by pH: as pH was elevated to basic pH, the helical propensity increased. This could be related to the surface charge of the hBub1 CD1. However, the structural change did not largely depend on the salt concentration, though the thermal stability a little increased. The previous NMR analysis revealed that the hBub1 CD1 adopts eight helices, which is consistent with the CD result. Our result would be helpful for evaluating the molecular mechanism of the hBub1 CD1 and protein-protein interactions.

• Journal of Life Science
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• v.9 no.2
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• pp.207-211
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• 1999

Biologically active compounds in Polygonatum sibiricum were extracted using organic solvents as hexane, CHCl$_3$, n-butanol corresponding each component. Compound I was purified from hexane layer and the chemical structure of compound I was characterized using 1H-NMR, 13C-NMR, DEPT135, COSY, HMQC, HMBC spectrum and MS-spectrum. Consequently, the chemical structure of compound I was determined as 9,12-(9E,l2E)-octade cadienoic acid.

• Journal of the Korean Chemical Society
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• v.39 no.5
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• pp.414-420
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• 1995

$\alpha$-Bromo-$\omega$-fluoroalkanes are synthesized in 19∼55% yields from the reactions of dibromoalkanes with AgF and TBABr in acetonitrile at $82^{\circ}C$ for 20 minutes. The reaction is monitored with gas-chromatography. 1^H$ NMR and $19^F$ NMR-Spectrometer are used for identification of $\alpha$-Bromo-$\omega$-fluoroalkanes, difluoroalkane, fluoroalken and bromoalkene.

• Journal of the Korean Magnetic Resonance Society
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• v.5 no.2
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• pp.91-98
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• 2001

The $^1$H and $^{13}$ C NMR spectra of chivosazole F from Sorangium cellulosum were completely assigned by a combination of ID and 2D NMR techniques. The configurations of double bonds were confirmed from the ROESY spectra. The stereochemistry at asymmetric carboncenters was partially assigned on the basis of the results of NOE analysis.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1559-1562
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• 2009

The influence of hot pressing on the pore structures of Nafion membranes was investigated by observing the Nafion before and after hot pressing with $^1H$ nuclear magnetic resonance (NMR) spectroscopy. The freezing point depression and chemical shift data of water in the Nafion indicated the presence of two different pore size ranges in Nafion. Hot pressing mainly reduced the sizes and number of the big pores. The reduction of water uptake and proton conductivity after hot pressing was explained by this variation of pore size and number. We demonstrated the potential application of chemical shift data and NMR cryoporometry experiments to measure the relative pore sizes, on a nano scale, and numbers.