• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1719-1721
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• 2012

We have investigated the $H_2$ adsorption structures and binding energies of the metal (M)-doped (M = Li, Na, K, Mg, and Al) silicon complexes, $M-Si_{19}H_{11}$ and $M-Si_{24}H_{12}$, using density functional calculations. Alkali metals are preferred as doping elements because the Mg-Si and Al-$H_2$ interactions are weak. The maximum numbers of $H_2$ molecules that can be adsorbed are four and five for M=Li and K, respectively. We propose that the K-decorated silicon material might be an effective hydrogen storage material with high hydrogen capacity and high reversibility.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.993-996
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• 2012

We investigated fluorescence and fluorescence excitation of diphenylsilane (DPS) in a solution and molecular beams in combination with the aid of the DFT method. When the molecule was photoexcited at 250 nm in a cyclohexane solution, normal and excimer fluorescences were observed in the ranges of 260-320 and 330-450 nm, respectively. The fluorescence excitation spectrum indicates that the channel leading to the intramolecular excimer formation is not efficient in comparison with the normal fluorescence. Vibrationally resolved fluorescence excitation spectra were measured for the DPS molecules cooled in pulsed supersonic expansion of He in the range 262.2-271.7 nm, in which we can see several electronic excitation spectra exhibiting the electronic band origins. We found that the simulated absorption spectrum based on the time-dependent densityfunctional theory calculations accords well with the absorption spectrum.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.521-526
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• 2007

Density functional calculations have been performed for the reactions of perfluoroalkylsilane and alkylsilane with silica surfaces. The (100) and (111) surfaces of ${\beta}-cristobalite$ are used as two possible models of the hydroxylated amorphous silica surface. This is the crystalline phase of silica with density and refractive index closest to those of amorphous silica. Moreover, two ${\beta}-cristobalite$ surfaces have the two types of silanol groups, namely the single silanols and the geminal silanols. We investigate the possible adsorption structure and formation energy of perfluoroalkylsilane and alkylsilane molecules with two type of silanol groups. The results will be compared with cluster and slab model.

• Molecules and Cells
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• v.41 no.1
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• pp.18-26
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• 2018

Mitochondrial quality control systems are essential for the maintenance of functional mitochondria. At the organelle level, they include mitochondrial biogenesis, fusion and fission, to compensate for mitochondrial function, and mitophagy, for degrading damaged mitochondria. Specifically, in mitophagy, the target mitochondria are recognized by the autophagosomes and delivered to the lysosome for degradation. In this review, we describe the mechanisms of mitophagy and the factors that play an important role in this process. In particular, we focus on the roles of mitophagy adapters and receptors in the recognition of damaged mitochondria by autophagosomes. In addition, we also address a functional association of mitophagy with mitochondrial dynamics through the interaction of mitophagy adaptor and receptor proteins with mitochondrial fusion and fission proteins.

• Molecules and Cells
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• v.41 no.1
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• pp.45-49
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• 2018

Autophagy is a lysosome-dependent degradation process that is essential for maintaining cellular homeostasis. In recent years, more studies have focused on the late stages of autophagy. Our group discovered and studied the terminal step of autophagy, namely autophagic lysosome reformation (ALR). ALR is the process that regenerates functional lysosomes from autolysosomes, thus maintaining lysosome homeostasis. ALR involves clathrin-mediated membrane budding from autolysosomes, elongation of membrane tubules along microtubules with the pulling force provided by the motor protein KIF5B, proto-lysosome scission by dynamin 2, and finally maturation of proto-lysosomes to functional lysosomes. In this review, we will summarize progress in unveiling the molecular mechanisms underlying ALR and its potential pathophysiological roles.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.154-160
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• 2008

We investigated molecular polarity by using theoretical means and comparing empirical solvent polarity. Our approach employed electrostatic potentials at the molecular surface calculated by density functional methods. A number of molecular descriptors related to molecular polarities were computed from molecular surface electrostatic potentials. Among computed molecular descriptors, the most positive electrostatic potential provided the best correlation with the empirical solvent polarities. A regression equation was developed in order to predict molecular polarities of molecules whose experimental solvent polarities were unknown. The new regression equations were utilized in estimating solvent polarities of cubane derivatives which are considered important precusors of high-energy density meterials.

• Journal of Microbiology and Biotechnology
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• v.18 no.1
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• pp.107-109
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• 2008

Medicinal fungi, Phellinus linteus and Inonotus xeranticus, produce a cluster of yellow pigment in their fermentation broth that acts as an important element of biological activity. The pigment is composed of diverse polyphenols with a styrylpyrone moiety, mainly hispidin and its dimers, 3,14'-bihispidinyl, hypholomine B, and 1,1-distyrylpyrylethan. Although dimeric hispidins were proposed to be biosynthesized from two molecules of monomer via oxidative coupling by ligninolytic enzymes, laccase and peroxidase, the details of this process remain unknown. In this preliminary study, we attempted to achieve enzymatic synthesis of the hispidin dimer from hispidin by using commercially available horseradish peroxidase (HRP). Consequently, a hispidin dimer, 3,14'-bihispidinyl, was synthesized, whereas the other dimers, hypholomine B and 1,1-distyrylpyrylethan, were not produced. This result suggested that the oxidative coupling at the C-3 and C-14' positions of hispidins was dominant in the process of dimerization by HRP, and indicated that additional catalysts or substrates would be needed to synthesize other hispidin dimers present in the fungal metabolite.

• Journal of the Korean Society of Visualization
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• v.4 no.2
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• pp.6-10
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• 2006

The functional spherical microcapsules were produced through the innovative conjunction of the well-defined amphiphilic block copolymer and the stable droplet phase flow in the micro chemical plant. The microcapsules were formed to have hollow inner cavity and outer surface wall with nano-pores. To examine the potential of encapsulating foreign biochemical molecules, Congo-red dye was loaded into the microcapsule. The release performance in the specific surroundings such as temperature, pH and time was evaluated quantitatively.

• Carbon letters
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• v.4 no.4
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• pp.180-184
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• 2003

The role of KOH in the one-stage KOH-activation of rice straws was studied using FTIR, XPS, TGA, and DTG techniques. It was found that at the impregnation, KOH extracts to some extent the lignin component from rice straw and reacts with hydroxyl groups. On heat-treatment, the impregnated KOH facilitates intermolecular condensation reaction on one hand but retards the thermal degradation of cellulose molecules on the other hand. The oxygen-containing surface functional groups newly created by oxidation of KOH may facilitate the bulk, not controlled, consumption of carbon atoms so that the effective porosities may not be able to be developed by the one-stage activation process.

• Molecules and Cells
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• v.40 no.3
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• pp.169-177
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• 2017

Tissue-specific transcription is critical for normal development, and abnormalities causing undesirable gene expression may lead to diseases such as cancer. Such highly organized transcription is controlled by enhancers with specific DNA sequences recognized by transcription factors. Enhancers are associated with chromatin modifications that are distinct epigenetic features in a tissue-specific manner. Recently, super-enhancers comprising enhancer clusters co-occupied by lineage-specific factors have been identified in diverse cell types such as adipocytes, hair follicle stem cells, and mammary epithelial cells. In addition, noncoding RNAs, named eRNAs, are synthesized at super-enhancer regions before their target genes are transcribed. Many functional studies revealed that super-enhancers and eRNAs are essential for the regulation of tissue-specific gene expression. In this review, we summarize recent findings concerning enhancer function in tissue-specific gene regulation and cancer development.