• Journal of the Korean Magnetic Resonance Society
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• v.14 no.2
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• pp.88-104
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• 2010

Human melanocortin-4 receptor (hMC4R) has a critical role in part of energy homeostasis, and their heterozygous mutations related in genetic cause of severe human obesity. In order to study the structure and function of these membrane proteins, it is important to prepare the samples. However, the preparation of transmembrane peptide is seriously difficult and time-consuming. Overexpression and purification of membrane proteins was reported to be difficult due to their innate insoluble and toxic properties. Among the many difficulties, the most important is the difficulty in obtaining sufficient quantities of purified protein. Recently, we succeed to produce large amounts of the second transmembrane domain from the wild-type hMC4R (wt-TM2) and D90N mutant hMC4R (m-TM2) and proposed the structural difference of them in membrane-like environments. In this paper, we demonstrate the optimization procedures to express and purify wt-TM2 or m-TM2 peptides, and solution NMR studies in different detergents to get high-resolution spectra were also described.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1175-1182
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• 2007

A series of new organic semiconductors hexyl end-capped thiophene-anthracene oligomers containing the anthracene moiety in the center of the oligomers are synthesized. The target oligomers have been obtained by Stille coupling reactions as key step reactions. The synthesized thiophene-anthracene oligomers were characterized by 1H-NMR, 13C-NMR and high-resolution mass spectroscopy, respectively. All of the oligomers are soluble in chlorinated solvents. Their optical, thermal and electrochemical properties were measured. The hexyl end-capped oligomers and their unsubstituted oligomers exhibit the same absorption behavior in dilute toluene solution. Hexyl end-capped bis-terthienylanthracene oligomer is observed to show liquid crystalline mesophase at 166 oC in heating process. The thermal analyses as well as the electrochemical measurement data indicate that the designed materials show better thermal and oxidation stability than the corresponding oligothiophenes without anthracene core. Fluorescence lifetimes and fluorescence quantum yields of the thiophene-anthracene oligomers are measured to be 10-14 ps and 3.4-9.9 × 10?3 which are much shorter and lower than those of oligothiophenes respectively.

• Applied Biological Chemistry
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• v.38 no.6
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• pp.516-521
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• 1995

In order to find a potent anti-methicillin resistant Staphylococcus aureus (MRSA) antibiotic, actinomycetes isolated from the samples collected in Korean marine silt were screened. From the culture broth of the isolated Streptamyces strain AM045, a substance showing excellent biological activity against MRSA was found, isolated and named AM3. The compound showed strong activities against MRSA, S. epidermidis, E. faecium and E. faecalis, which were better than those of vancomycin and teicoplanin. Unfortunately, AM3 was identified as Actinomycin V. However, this paper reports the three dimensional study of AM3 based on high resolution nmr and Computer Aided Molecular Modeling(CAMM), and the fact that the structure of the pentapeptide lactone ring with oxo-proline in chloroform solution does not have 'C conformation' any more.

• Journal of the Korean Magnetic Resonance Society
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• v.16 no.2
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• pp.147-161
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• 2012

Human melanocortin-4 receptor (hMC4R) among MC-Rs, expressed in the brain, is in charge of the control on energy homeostasis and food intake. The structure and function of human MC4R have been studied to understand their essential function and roles. To investigate the structure and function, it is necessary to prepare sufficient amounts of proteins. However, their expression and purification is demanding and time-consuming due to their innate insoluble and toxic properties. The heterozygous mutations of hMC4R, exchange of Asp 90 to Asn located in second transmembrane, cause severe obesity in human. To obtain purified hMC4R wt-TM2 for structural studies, it was first over-expressed and purified by fast protein liquid chromatography (FPLC) and then solution NMR studies were performed to get high-resolution spectra. In here, we established optimized purification scheme to get more purified target peptide.

• Fisheries and Aquatic Sciences
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• v.15 no.1
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• pp.15-19
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• 2012

A new cyclic peptide (six-membered amino acid), gamakamide-E (L-Leu-L-Met (SO)-L-Me-Phe-L-Leu-D-Lys-L-Phe), was isolated as a strongly bitter tasting compound from cultured oysters, Crassostrea gigas. The molecular formula of $C_{43}H_{61}N_7O_8S$ was deduced from high resolution fast atom bombardment mass spectrometry (HR FAB-MS) ($[M+H]^+$ m/z 836.4356 ${\Delta}$= -2.4 mmu). Its unique structure including a hydantoin structure was firstly elucidated by nuclear magnetic resonance (NMR) analysis. Stereochemistries of constituent amino acids were determined by chiral high performanced liquid chromatography analysis of natural and synthesized peptides.

• Natural Product Sciences
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• v.27 no.1
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• pp.45-48
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• 2021

One new compound, macasiamenene V (1), and two known stilbenes (2-3) were isolated from Macaranga inermis Pax & K.Hoffm leaves. The structure of 1 was fully assigned based on the information on high-resolution MS and (1D, 2D) NMR spectra. The cytotoxic of compounds 1-3 was evaluated against 4T1 and HeLa cells. Compounds 2-3 showed high activity against HeLa cells with an IC50 value of 1.09 and 0.88 ㎍/mL, respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.2021-2026
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• 2011

AgNPs (silver nanoparticles) has been widely used for the commercial products, which have antimicrobial agent, medical devices, food industry and cosmetics. Despite, AgNPs have been reported as toxic to the mammalian cell, lung, liver, brain and other organs and many researchers have investigated the toxicity of AgNPs. In this study, we investigated toxicity of the AgNPs to the liver cell using metabolomics based on HRMAS NMR (High Resolution Magic Angle Spinning Nuclear Magnetic Resonance) technics, which could apply to the intact tissues or cells, to avoid the sample destruction. Target profiling and multivariative statistical analysis were performed to analyze the 1D $^1H$ spectrum. The results show that the concentrations of many metabolites were affected by the AgNPs in the liver cell. The concentrations of glutathione (GSH), lactate, taurine, and glycine were decreased and most of amino acids, choline analogues, and pyruvate were increased by the AgNPs. Moreover, the levels of the metabolites were recovered upto similar level of metabolites in the normal cell by the pre-treatment of NAC, external antioxidant. The results suggest that the depletion of the GSH by the AgNPs might induce the conversion of lactate and taurine to the pyruvate.

• Progress in Medical Physics
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• v.5 no.1
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• pp.55-66
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• 1994

After proving home-made imaging pulse sequences including tailored RF pulse by phantom, susceptibility-contrast-enhanced MR venograms of cat brain were obtained using tailored RF gradient-echo(TRGE) method. Sagittal MR imaging of the cat brain obtained by TRGE technique shows several veins, for example, dorsal sagittal sinus, straight sinus, vein of corpus callosum and internal cerebral vein, etc., compared with cats anatomical figure. Tailored RF waveform was generated by PASCAL language in ASPECT 3000 computer(Switzland, Bruker). Rectangular-shaped slice profile with bi-linear ramp function as phase distribution in the slice, at which maximum value was 2$\pi$, was fourier transformed to make tailored RF pulse. Experimental MR imaging parameters were TR/TE=205/10 msec, slice thickness TH=7mm, maxtrix size=256$\times$256, in-plane resolution=0.62$\times$0.31mm$^2$, and field of view(FOV)=8cm for both conventional gradient-echo(GE) imaging and TRGE imaging techniques.

• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.271-282
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• 2012

We explore the effect of removal of organic ligand on the atomic configurations around oxygen in hydroxyl groups in amorphous silica gel (synthesized through hydrolysis of $SiCl_4$ in diethyl-ether) using high resolution $^{17}O$ solid state NMR spectroscopy. $^1H$ and $^{29}Si$ MAS NMR spectra for amorphous silica gel showed diverse hydrogen environments including water, hydroxyl groups (e.g., hydrogen bonded silanol, isolated silanol), and organic ligands (e.g., alkyl chain) that may interact with surface hydroxyls in the amorphous silica gel, for instance, forming silica-organic ligand complex (e.g., Si-$O{\cdots}R$). These physically and chemically adsorbed organic ligands were partly removed by ultrasonic cleaning under ethanol and distilled water for 1 hour. Whereas $^{17}O$ MAS NMR spectra with short pulse length ($0.175{\mu}s$) at 9.4 T and 14.1 T for as-synthesized amorphous silica gel showed the unresolved peak for Si-O-Si and Si-OH structures, the $^{17}O$ MAS NMR spectra with long pulse length ($2{\mu}s$) showed the additional peak at ~0 ppm. The peak at ~0 ppm may be due to Si-OH structure with very fast relaxation rate as coupled to liquid water molecules or organic ligands on the surface of amorphous silica gel. The observation of the peak at ~0 ppm in $^{17}O$ MAS NMR spectra for amorphous silica gel became more significant as the organic ligands were removed. These results indicate that the organic ligands on the surface of amorphous silica gel interact with oxygen atoms in Si-OH and provide the information about atomic structure of silanol and siloxane in amorphous silica gel. The current results could enhance the understanding of dehydration mechanism of diverse silicates, which is known as atomic scale origins of intermediate depth (approximately, 70~300 km) earthquakes in subduction zone.

• Journal of the Mineralogical Society of Korea
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• v.29 no.3
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• pp.155-165
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• 2016

Understanding the effect of boron content on atomic structures of boron-bearing multicomponent silicate melts is essential to reveal the atomistic origins of diverse geochemical processes involving silica-rich magmas, such as explosive volcanic eruption. The detailed atomic environments around B and Al in boron-bearing complex aluminosilicate glasses yield atomistic insights into reactivity of nuclear waste glasses in contact with aqueous solutions. We report experimental results on the effect of boron content on the atomic structures of sodium borate glasses and boron-bearing multicomponent silicate melts [malinkoite ($NaBSiO_4$)-nepheline ($NaAlSiO_4$) pseudo-binary glasses] using the high-resolution solid-state NMR ($^{11}B$ and $^{27}Al$). The $^{11}B$ MAS NMR spectra of sodium borate glasses show that three-coodrinated boron ($^{[3]}B$) increases with increasing $B_2O_3$ content. While the spectra imply that the fraction of non-ring species decreases with decreasing boron content, peak position of the species is expected to vary with Na content. Therefore, the quantitative estimation of the fractions of the ring/non-ring species remains to be explored. The $^{11}B$ MAS NMR spectra of the glasses in the malinkoite-nepheline join show that four-coordinated boron ($^{[4]}B$) increases as $X_{Ma}$ [$=NaBSiO_4/(NaBSiO_4+NaAlSiO_4)$] increases while $^{[3]}B$ decreases. $^{27}Al$ MAS NMR spectra of the multicomponent glasses confirm that four-coordinated aluminum ($^{[4]}Al$) is dominant. It is also observed that a drastic decrease in the peak widths (full-width at half-maximum, FWHM) of $^{[4]}Al$ with an addition of boron ($X_{Ma}=0.25$) in nepheline glasses. This indicates a decrease in structural and topological disorder around $^{[4]}Al$ in the glasses with increasing boron content. The quantitative atomic environments around boron of both binary and multicomponent glasses were estimated from the simulation results of $^{11}B$ MAS NMR spectra, revealing complex-nonlinear variation of boron topology with varying composition. The current results can be potentially used to account for the structural origins of the change in macroscopic properties of boron-bearing oxide melts with varying boron content.