• Polymer(Korea)
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• v.35 no.6
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• pp.505-512
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• 2011

Effects of structural features of 4 dinuclear constrained geometry catalysts having paraxylene derivative bridge (DCGC) on copolymerization of ethylene and 1-hexene were investigated. The bridges of three catalysts have para-xylene backbone with a different substituent at benzene ring. The substituents were hydrogen (Catalyst 1), isopropyl (Catalyst 2), n-hexyl (Catalyst 3) and 1-octyl (Catalyst 4). It was found that Catalyst 1 having hydrogen as a substituent exhibited the greatest activity among the four dinuclear CGCs. On the other hand, Catalyst 2 containing isopropyl as a substituent showed the smallest activity. Very interestingly, Catalyst 2 was able to produce about 6 times higher molecular weight polymer than Catalyst 3 and 4. Catalyst 3 and 4 having a long alkyl chain substituent revealed the biggest comonomer response to generate polyethylene copolymer containing more than 40% 1-hexene contents. These results suggest that the control of the substituent of para-xylene bridge of dinuclear CGC can provide a proper method to adjust the microstructure of polyethylene copolymers.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.504-509
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• 1989

The effect of oxygen-deficiency on the charge distributions and orbital energies for small copper oxide clusters representing the superconducting materials $YBa_2Cu_3O_x (6{\leq}x{\leq}7)$ were investigated by the extended Huckel molecular orbital (EHMO) method with the tight-binding model. Our calculations show +3 oxidation state of Cu(1) in the $CuO_3$ chain and +2 or +1 of Cu(2) in the $CuO_2$ layers for $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 (or +5), while for $YBa_2Cu_3O_6$ +1 oxidation state of Cu(1) and +3 (or +2) of Cu(2) in the $CuO_2$ layers with the nominal charge of $Cu_3$ = +7 (or +5). For $Cu_3O_{12}$ cluster representing $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 the Cu(2) $d_{{x^2}-{y^2}}$ orbitals in the $CuO_2$ layers is a typical Jahn-Teller $d^9$ system with the partial hole and the Cu(1) $d_{{_z2}-{_y2}}$ orbital in the $CuO_3$ chain contains hole occupancy. For $Cu_3O_{10}$ cluster representing $YBa_2Cu_3O_6$ with the nominal charge of Cu = +5 the orbital character of the highest partially occupied MO (HPOMO) and the lowest completely unoccupied MO (LCUMO) of $Cu_3O_{12}$ representing $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 is reversed, and the character of Cu(1) $d{{x^2}-{y^2}}$ orbital of LCUMO of the $Cu_3O_{12} $cluster is vanished. It is suggested that the local crystal field environment of Cu(1) by the oxygens in the Cu(1) chain may play a vital role in conductivity and superconductivity, either alone or through cooperative electronic coupling with the Cu(2) layers in $YBa_2Cu_3O_7.$.

• Food Science and Preservation
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• v.25 no.1
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• pp.155-163
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• 2018

The present study was carried out to investigate the physicochemical properties of hot water extracts of red ginseng powder prepared by two-stage hot air drying method using steamed ginseng and steaming liquid for 2.5 h under high-temperature and high-pressure autoclave condition. The total polyphenols, total flavonoids, total sugar, acid polysaccharides and crude saponin in hot water extracts from red ginseng powder were analyzed and determined, and the flavor components of ginseng were measured using color difference meter and an electronic tongue. The total polyphenol, total flavonoid, total polysaccharide, and acid polysaccharide of the red ginseng hot water extract obtained by autoclaving (ARG) were 9.06 mg GAE/g, 3.38 mg NE/g, 35.22 g/100 g, and 10.90 g/100 g, respectively. The final contents of the total polyphenols, total flavonoids, crude saponin were higher than those determined using other red ginseng methods; the time required for steamed red ginseng production reduced. The total ginsenoside content of ginseng including Rb1 was 10.69 mg/g, which is the lowest ARG. The processing conditions affected the conversion to ginsenosides unique to red ginseng. Red ginseng and steaming liquid obtained from the autoclave are expected to be in need for non-food materials and products as well as foods by improving the flavor components through conversion of red ginseng components into low molecular weight.

• Atmosphere
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• v.31 no.3
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• pp.267-282
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• 2021

Characteristics of carbonaceous components and organic compounds in PM_2.5 over the atmosphere of the Yellow Sea were investigated. PM_2.5 samples were collected onboard the meteorological research vessel, GISANG 1, over the Yellow Sea during the YES-AQ campaign in 2018 and 2019, respectively. The average concentrations of carbonaceous components in this region were 2.59 ± 1.59 ㎍ m^-3 for the OC, 0.24 ± 0.10 ㎍ m^-3 for the EC, 2.14 ± 1.30 ㎍ m^-3 for the WSOC and 1.17 ± 0.94 ㎍ m^-3 for the HULIS-C, respectively. The total concentration of 56 organic compounds (ΣOCs) accounts for 10% of OC. The main group among organic compounds were dicarboxylic acids which account for 57% of ΣOCs, followed by n-alkanoic acids accounting for 34% of ΣOCs. In n-alkanoic acid distribution, hexanoic (C_6:0) and octanoic (C_8:0) acids which are low molecular weight n-alkanoic acids and known as emitted from marine biogenic activities were dominant in this region. Furthermore, non-HULIS-C fraction increased when the air mass originated from the marine region rather than the continental region. When the Asian dust episode was observed, the WISOC concentrations along with the levoglucosan were increased, while the haze episodes caused the increase of WSOC, HULIC-S and DCAs. In this study, we found that the components of carbonaceous and organic aerosols in PM_2.5 over the Yellow Sea were changed with the specific air pollution episodes. It indicates that the physicochemical properties of PM_2.5 can be changed by the air pollution episodes in this region.

• Journal of Life Science
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• v.31 no.7
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• pp.686-697
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• 2021

Propolis is a resinous substance produced by honeybees, which they use to protect their hives. Honeybees produce propolis by mixing exudates from the various trees and plants with saliva and beeswax. It has been used since around 300 B.C. as a folk medicine to cure wounds. Propolis contains many physiologically active components, such as flavonoids, phenolic compounds, and beeswax. Because of its functional components, propolis has a wide spectrum of biological applications. The compounds in propolis and its biological activity can vary according to the location of nectar source and extraction method. Propolis is most commonly known for its anti-microorganism activity against bacteria, viruses, and fungi. Artepillin C and caffeic acid phenethyl ester (CAPE) have been identified as regulatory compounds that reduce inflammation and exert immunosuppressive reactions on T lymphocytes. Through its anti-inflammatory activity, propolis exhibits anti-tumor activity, including the inhibition of cancer cell proliferation, the blocking of tumor signaling cascades, and antiangiogenesis. However, for the more apply of propolis its analysis of nectar source, identifying of propolis compound, the molecular mechanism of propolis and the investigation of compounds synergistic effects are essential. In this study, we described the physiological activity of propolis isolated from honeybees.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.445-454
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• 2019

Layered double hydroxides (LDHs) nanoparticles have emerged as novel nanomaterials for bio-imaging applications due to its unique layered structure, physicochemical properties, and good biocompatibility. Bio-imaging is one of the most important fields for medical applications in clinical diagnostics and therapeutics of various diseases. Enhanced diagnostic techniques are needed to realize new paradigm for next-generation personalized medicine through nanoscale materials. When nanotechnology is introduced into bio-imaging system, nanoparticle probes can endow imaging techniques with enhanced ability to obtain information about biological system at the molecular level. In this review, we summarize structural features of LDH nanoparticles with current issues of bio-imaging system. LDH nanoparticle probes are also discussed through in vitro as well as in vivo studies in various bio-imaging techniques including fluorescence imaging, magnetic resonance imaging (MRI), positron emission tomography (PET), and computed X-ray tomography (CT), which will have the potential in the development of the advanced nanoparticles with high sensitivity and selectivity.

• Journal of Microbiology and Biotechnology
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• v.29 no.7
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• pp.1043-1052
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• 2019

Active lipase-producing bacterium Burkholderia gladioli Bps-1 was rapidly isolated using a modified trypan blue and tetracycline, ampicillin plate. The electro-phoretically pure enzyme was obtained by purification using ethanol precipitation, ion-exchange chromatography, and gel filtration chromatography. The molecular weight was 34.6 kDa and the specific activity was determined to be 443.9 U/mg. The purified lipase showed the highest activity after hydrolysis with $p-NPC_{16}$ at a pH of 8.5 and $50^{\circ}C$, and the $K_m$, $k_{cat}$, and $k_{cat}/K_m$ values were 1.05 mM, $292.95s^{-1}$ and $279s^{-1}mM^{-1}$, respectively. The lipase was highly stable at $7.5{\leq}pH{\leq}10.0$. $K^+$ and $Na^+$ exerted activation effects on the lipase which had favorable tolerance to short-chain alcohols with its residual enzyme activity being 110% after being maintained in 30% ethanol for 1 h. The results demonstrated that the lipase produced by the strain B. gladioli Bps-1 has high enzyme activity and is an alkaline lipase. The lipase has promising chemical properties for a range of applications in the food-processing and detergent industries, and has particularly high potential for use in the manufacture of biodiesel.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.81-87
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• 2019

In this study, synthetic methods and physical properties for a new class of glycidyl azide polymer (GAP) were investigated for energetic thermoplastic elastomers (ETPE). Four kinds of GAP copolymer polyols were synthesized by introducing nucleophiles such as azide, alkoxide and alkyl amine into poly(epichlorohydrin) (PECH). The GAP copolymer synthetic reaction can be evaluated as an environmental benign and efficient synthetic method due to the simultaneous one-step reaction using two kinds of nucleophiles and the complete consumption of sodium azide. The relative stoichiometric substitution ratio analysis and the progress of reaction were checked and monitored by inverse gated decoupled $^{13}C$ NMR and Fourier transform infrared (FT-IR) spectroscopy. The glass transition temperature and molecular weight were measured by differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) analysis. The synthesized poly($GA_{0.8}-butoxide_{0.2}$), poly($GA_{0.7}-n-butylamine_{0.3}$), poly($GA_{0.7}-dipropylamine_{0.3}$) and poly($GA_{0.7}-morpholine_{0.3}$) had a glass transition temperature ranged from -39 to $-26^{\circ}C$.

• Journal of Life Science
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• v.29 no.9
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• pp.964-971
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• 2019

Hepatic lipid accumulation and insulin resistance increases in patients with non-alcoholic fatty liver disease. Piperine is a major compound found in black pepper (Piper nigrum) and long pepper (P. longum). Piperine has been used in fine chemical for its anti-cancer, anti-obesity, anti-diabetic, anti-inflammatory and anti-oxidant properties. However, the signaling-based mechanism of piperine and its role as an inhibitor of lipogenesis and insulin resistance in human hepatocyte cells remains ill-defined. In the present study, we explored the effects of piperine on lipid accumulation and insulin resistance, and explored the potential underlying molecular mechanisms in palmitate-treated HepG2 cells. Piperine treatment resulted in a significant reduction of triglyceride content. Furthermore, piperine treatment decreased palmitate-treated intracellular lipid deposition by inhibiting the lipogenic target genes, sterol-regulatory-element-binding protein 1c (SREBP-1c) and fatty acid synthase (FAS); whereas the expression of carnitine palmitoyl transferase (CPT-1) and phosphorylation of acetyl coenzyme A carboxylase (ACC) gene involved in fatty acid oxidation was increased. Moreover, piperine also inhibited the phosphorylation of insulin receptor substrate (IRS)-1 (Ser307). Piperine treatment modulated palmitate-treated lipid accumulation and insulin resistance in HepG2 cells with concomitant reduction of lipogenic target genes, such as SREBP-1 and FAS, and induction of CPT-1-ACC and phosphorylation of IRS-1 (Tyr632)-Akt pathways. Therefore, piperine represents a promising treatment for the prevention of lipid accumulation and insulin resistance.

• Journal of Life Science
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• v.29 no.10
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• pp.1136-1143
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• 2019

The purpose of this study was to investigate the biological activities of an aqueous extract of Angelica gigas (Ag) fermented by Saccharomyces cerevisiae (Sc). First, the soluble solids of the F/3 group, in which the Ag was fermented by Sc for 3 days, decreased from $1^{\circ}Bx$ to $0.9^{\circ}Bx$. On the other hand, the pH increased with the number of days of fermentation. The result of a TLC experiment confirmed that it gradually decomposed into a low-molecular weight sugar form upon fermentation. The total phenolic compounds and flavonoid contents were higher in the fermented group than in the non-fermented group. K and Ca contents were increased by fermentation in the following order: F/3, NF, and F/0 groups. Decursin and decursinol angelate contents were highest in the F/3 group. The DPPH (${\alpha}$, ${\alpha}{\prime}$-diphenyl-${\beta}$-picrylhydrazyl) radical scavenging activity of the NF, F/0, and F/3 groups were 41.89%, 39.51%, and 60.26%, respectively. The inhibition activities of tyrosinase and lipoxygenase were stronger in the F/3 group than in the NF group. This experiment showed that the fermentation of Ag Nakai can lead to an increase in its antioxidant ability, physiological activity, whitening and anti-inflammatory effects. Thus, this oriental herbal medicine can be developed into a functional material that can be utilized in the development of cosmetic products in future.