• Journal of the Korean Magnetic Resonance Society
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• v.15 no.2
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• pp.128-136
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• 2011

A new sesterterpenoid, phorbaketal derivative, was isolated from the marine sponge Phorbas species. Its planar structures was completely determined from a combination of extensive 1D and 2D NMR experiments and MS data, and also the stereochemistry on the chiral centers were established by the ROESY experiment and the comparison with the $^1H$ and $^{13}C$ chemical shifts of the known phorbaketal compounds. This compound 1 moderately showed cytotoxicity effect against hepatoma cancer HepG2 cell.

• Journal of the Korean Magnetic Resonance Society
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• v.15 no.2
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• pp.157-174
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• 2011

Although the use of apodization functions in connection with postprocessing of a 2D NMR spectrum proves improved spectral quality, there is usually a trade-off between resolution enhancement and noise suppression due to a classical "uncertainty principle." In this study, therefore, a mathematical deconvolution technique called "Maximum Likelihood Deconvolution (MLD)" was adopted to achieve the spectral resolution and sensitivity enhancement simultaneously. The MLD technique greatly facilitates visualization and restoration of the genuine spectral information from complex 2D NMR spectra that would be problematic with the conventional apodization/FT processing. In particular, application of the MLD to the 2D-NOE spectrum would be very useful to derive the important proton connectivities, which are essential to achieve elucidating the 3D molecular structure.

• Journal of the Korean Magnetics Society
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• v.2 no.2
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• pp.132-139
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• 1992

We have designed a magnetic field gradient useful for cylindrical imaging in NMR-CT. The direc¬tion of the designed field is parallel to the axis and the gradient in the radial direction of cylindrical coordinate is monotonically increasing. The ratio of the gradient in the radial and axial direction is greater than 10 near the center of coordinate. This ratio depends on solenoid length, the number of reverse current turns at center, and the amount of the reverse current. We built a gradient coil based on the numerical simulation and tested the field generated by NMR-CT. The resulting image matches with the theoretical expectation within 10% error. Since the data acquisition time of 1-D imaging is significantly shorter than 2-D imaging, it becomes possible to image much more dynamic objects by the use of this gradient field.

• Journal of the Korean Magnetic Resonance Society
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• v.24 no.4
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• pp.136-142
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• 2020

Apolipoprotein B-100 (apo B-100), the main protein component that makes up LDL (Low density lipoprotein), consists of 4,536 amino acids and serves to combine with the LDL receptor. The oxidized LDL peptides by malondialdehyde (MDA) or acetylation in vivo were act as immunoglobulin (Ig) antigens and peptide groups were classified into 7 peptide groups with subsequent 20 amino acids (P1-P302). The biomimetic peptide P99 (KGTYG LSCQR DPNTG RLNGE) out of B-group peptides carrying the highest value of IgM antigens were selected for structural studies that may provide antigen specificity. Circular Dichroism (CD) spectra were measured for peptide secondary structure in the range of 190-260 nm. Experimental results show that P99 has pseudo α-helice and random coil structure. Homonuclear (COSY, TOCSY, NOESY) 2D-NMR experiments were carried out for NMR signal assignments and structure determination for P99. On the basis of these completely assigned NMR spectra and proton distance information, distance geometry (DG) and molecular dynamic (MD) were carried out to determine the structures of P99. The proposed structure was selected by comparisons between experimental NOE spectra and back-calculated 2D NOE results from determined structure showing acceptable agreement. The total Root-Mean-Square-Deviation (RMSD) value of P99 obtained upon superposition of all atoms were in the set range. The solution state P99 has mixed structure of pseudo α-helix and β-turn(Gln[9] to Thr[13]). These NMR results are well consistent with secondary structure from experimental results of circular dichroism. Structural studies based on NMR may contribute to the prevent oxidation studies of atherosclerosis and observed conformational characteristics of apo B-100 in LDL using monoclonal antibodies.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.275-280
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• 1999

Cellulose has three hydroxyl groups with different reactivity. By substitution reaction, trimethylsiloxyl-, vinyldimethylsiloxyl-, allyldimethylsiloxyl-, phenyldimethylsiloxyl-, 3,3,3-trifluoropropyldimethylsiloxyl- and tris(trimethylsiloxy)siloxylcellulose were synthesized IR, NMR, and elemental analysis were used for confirming their structures, degree of substitution (D.S.) and the reactivity of siloxylation agent, respectively. The D.S. values were 2.5, 2.2, 2.1, 2.2, 2.6, 0.7 for the corresponding siloxylcellulose.

• Polymer(Korea)
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• v.39 no.2
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• pp.287-292
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• 2015

Characterization of a series of bio-based terpolymers containing various amounts of ethylene glycol, 1,4-cyclohexylene dimethanol, and isosorbide units were studied by $^1H$ NMR and $^{13}C$ NMR. The NMR results revealed that they had all random microstructures and that their sequence distribution was affected by the content of isosorbide. From DSC data for the terpolymer series investigated, it was observed that the glass transition temperature increased mainly as the content of isosorbide increased. The glass transition temperatures of terpolymers were estimated from the composition by extended Fox equation.

• BMB Reports
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• v.31 no.1
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• pp.89-94
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• 1998

The structures of the self-complementary decamer duplexes, $d(ACGTATACGT)_2$ (TATA-duplex) and $d(ACGTTAACGT)_2$, (TTAA-duplex) has been obtained in solution by proton NMR spectroscopy and restrained molecular dynamics. The duplexes are essentially B-type, with distortions apparent at the TATA and TTAA steps. Theses distortions and their effects on dynamics have been investigated by the measurement of imino proton exchange time of the base-pairs. The unusual opening kinetics of central A T base-pairs could be correlated to the abnormal structural properties of the corresponding sequences.

• BMB Reports
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• v.30 no.6
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• pp.421-425
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• 1997

The 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT) has been used as intercalating DNA binding drugs in the photo-chemotherapy of skin diseases. The conformation and stability of DNA octamer duplex, $d(GGGTACCC)_2$, cross-linked with AMT has been studied by NMR spectroscopy. All the proton resonances of the psoralen cross-linked octamer were assigned and meting temperature studies were carried out based on the assignment of the proton resonances. The aromatic proton chemical shift data suggest that the conformation of the helix cross-linked with psoralen is destabilized more to furanside of the psoralen. possibly due to the protrusion of the aminomethyl side chain of the psoralen.

• Journal of the Korean Magnetic Resonance Society
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• v.14 no.1
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• pp.1-8
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• 2010

Four 5,8-epidioxy sterols were isolated from the marine sponge Plakortis simplex. Their structures were completely determined by an extensive NMR analysis and comparison with NMR data of similar compounds for absolute stereochemistry of the side chain. The compounds were assigned as 5,8-epidioxy- (24S)-ethylcholesta-6,22(E),25-trien-3-ol(1), 5,8-epidioxy-(24S)-methylcholesta- 6,22(E)-dien-3-ol(2), 5,8-epidioxycholesta-6,22(E)-dien-3-ol(3) and 5,8- epidioxycholesta-6-en-3-ol (4).

• Journal of the Korean Magnetic Resonance Society
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• v.11 no.2
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• pp.122-128
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• 2007

Three sterol sulfates were isolated from AMPK activity-guided fraction of a marine sponge Acanthodoryx fibrosa. Their structures were determined by an extensive NMR analysis, MS data, and two compounds were confirmed as unusual phosphorylated sterol sulfates by comparing with NMR data of the known compounds. Compound 3 was given to be a new dephosphated sterol sulfate derivative. Compound 1 moderately showed AMPK activation effect on L6 myoblast cell through Western blot analysis.