• Current Research on Agriculture and Life Sciences
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• v.33 no.2
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• pp.57-63
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• 2015

In this study, the antioxidant activity of water and ethanol extracts from Hibiscus esculentus, Cirsium japonicum, Zizania latifolia and Kalopanax pictus for functional food source were examined. The optimal conditions for phenolic compounds extraction from medicinal plants were at 50% ethanol with Hibiscus esculentus and Cirsium japonicum var. ussuriense, at 40% ethanol with Kalopanax pictus and at 60% ethanol with Zizania latifolia. The total phenolic contents from the extracts of medical plants were determined to be 2.72~34.15 mg/g in the water extracts and 2.83~34.23 mg/g in the ethanol extracts. The electron-donating abilities (EDA) of the water and ethanol extracts were both above 74% at the low concentration of $50{\mu}g/mL$. The ABTS radical-cation decolorization was above 88% at $100{\mu}g/mL$ concentration in all the extracts of various medicinal plants. The antioxidant protection factor (PF) in the water and ethanol extracts of the Cirsium japonicum var. ussuriense extracts was $1.73{\pm}0.02PF$ and $1.76{\pm}0.01PF$ at $50{\mu}g/mL$ concentration respectively, and was higher than those of the other medicinal-plant extracts. The TBARs inhibition rates of all the medicinal-plant extracts, were above 80% at the $50{\mu}g/mL$ concentration except Hibiscus esculentus. These results confirmed that the various oriental medicinal plants (Hibiscus esculentus, Cirsium japonicum var. ussuriense, Kalopanax pictus and Zizania latifolia) that were included in this study are useful anti-oxidant and functional-food resources.

• Journal of Plant Biotechnology
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• v.33 no.1
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• pp.1-9
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• 2006

Peroxiredoxins (Prxs) are ubiquitously distributed and play important functions in diverse cellular signaling systems. The proteins are largely classified into three groups, such as typical 2-Cys Prx, atypical 2-Cys Prx, and 1-Cys Prx, that are distinguished by their catalytic mechanisms and number of Cys residues. From the three classes of Prxs, the typical 2-Cys Prx containing the two-conserved Cys residues at its N-terminus and C-terminus catalyzes $H_2O_2$ with the use of thioredoxin (Trx) as an electron donor. During the catalytic cycle, the N-terminal Cys residue undergoes a peroxide-dependent oxidation to sulfenic acid, which can be further oxidized to sulfinic acid at the presence of high concentrations of $H_2O_2$ and a Trx system containing Trx, Trx reductase, and NADPH. The sulfinic acid form of 2-Cys Prx is reduced by the action of sulfiredoxin which requires ATP as an energy source. Under the strong oxidative or heat shock stress conditions, 2-Cys Prx in eukaryotes rapidly switches its protein structure from low-molecular-weight species to high-molecular-weight protein structures. In accordance with its structural changes, the protein concomitantly triggers functional switching from a peroxidase to a molecular chaperone, which can protect its substrate denaturation from external stress. In addition to its N-terminal active site, the C-terminal domain including 'YF-motif' of 2-Cys Prx plays a critical role in the structural changes. Therefore, the C-terminal truncated 2-Cys Prxs are not able to regulate their protein structures and highly resistant to $H_2O_2$-dependent hyperoxidation, suggesting that the reaction is guided by the peroxidatic Cys residue. Based on the results, it may be concluded that the peroxidatic Cys of 2-Cys Prx acts as an '$H_2O_2$-sensor' in the cells. The oxidative stress-dependent regulation of 2-Cys Prx provides a means of defense systems in cells to adapt stress conditions by activating intracellular defense signaling pathways. Particularly, 2-Cys Prxs in plants are localized in chloroplasts with a dynamic protein structure. The protein undergoes conformational changes again oxidative stress. Depending on a redox-potential of the chloroplasts, the plant 2-Cys Prx forms super-molecular weight protein structures, which attach to the thylakoid membranes in a reversible manner.

• Microbiology and Biotechnology Letters
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• v.39 no.4
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• pp.382-386
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• 2011

Microbial fuel cells (MFC), devices that use bacteria as a catalyst to generate electricity, can utilize a variety of organic wastes as electron donors. The current generated may differ depending on the organic matter concentrations used, when other conditions, such as oxidant supply, proton transfer, internal resistance and so on, are not limiting factors. In these studies, a single-cathode type MFC (SCMFC) and dual-cathode type MFC (DCMFC) were used to ascertain the current's improvement through an increase in the contact area between the anode and the cathode compartments, because the cathode reaction is one of the most serious limiting factors in an MFC. Also an MFC was conducted to explore whether an improvement in electricity generation resulted from oxidizing the carbon sources and nitrates. About 250 mg $L^{-1}$ sodium acetate was fed to an anode compartment with a flow rate of 0.326 mL $min^{-1}$ by continuous mode. The current generated from the DCMFC was higher than the value produced from MFC with a single cathode. COD removal of dual-cathode MFC was also higher than that of single-cathode MFC. The nitrate didn't affect current generation at 2 mM, but when 4 and 8 mM nitrate was supplied, the current in the single-cathode and dual-cathode MFC was decreased by 98% from $5.97{\pm}0.13$ to $0.23{\pm}0.03$ mA and $8.40{\pm}0.23$ to $0.20{\pm}0.01$ mA, respectively. These results demonstrate that increasing of contact area of the anode and cathode can raise current generation by an improvement in the cathode reaction.

• Journal of Applied Biological Chemistry
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• v.54 no.4
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• pp.238-243
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• 2011

Amelanchier asiatica fruits have been used as a traditional medical food. This research was investigated to assess angiotensin converting enzyme, xanthine oxidase (XOase) and elastase inhibitory activity and antioxidant activities. The content of total phenolic compounds in A. asiatica fruits extracts was 17.6mg/mL. In extracts, the electron donating ability by 1,1-diphenyl-2-picrylhydrazyl free radical scavenging test of A. asiatica fruits extracts was 90.18% at $200{\mu}g/mL$. The 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid radical decolorization of A. asiatica fruits extracts was 98.81% at $200{\mu}g/mL$. The inhibition rate of the antioxidant protection factor was 1.03, and thiobarbituric acid reactive substance was 73.27% at $200{\mu}g/mL$. The XOase inhibition activity of A. asiatica fruits extracts of showed to be 13.19% at $200{\mu}g/mL$. The angiotensin converting enzyme activity was significantly inhibited by A. asiatica fruits extracts as 82.52% inhibitory rate at $200{\mu}g/mL$. Elastase inhibitory activity in the A. asiatica fruits extracts (41.48% at $200{\mu}g/mL$) was higher than vitamin C (12.8% at $200{\mu}g/mL$). These results suggests that A. asiatica fruits extracts have the greatest property as a functional food and functional cosmetic source.

• The Korean Journal of Pharmacology
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• v.30 no.3
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• pp.321-330
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• 1994

The protective effect of 'ischemic preconditioning (PC)' on ischemia-reperfusion injury of heart has been reported in various animal species, but without known mechanisms in detail. In an attempt to investigate the cardioprotective mechanism of PC, we examined the effects of PC on the myocardial oxidative injuries and the oxygen free radical production in the ischemia-reperfusion model of isolated Langendorff preparations of rat hearts. PC was performed with three episodes of 5 min ischemia and 5 min reperfusion before the induction of prolonged ischemia (30 min)-reperfusion(20 min). PC prevented the depression of cardiac function (left ventricular pressure x heart rate) observed in the ischemic-reperfused heart, and reduced the release of lactate dehydrogenase during the reperfusion period. On electron microscopic pictures, myocardial ultrastructures were relatively well preserved in PC hearts as compared with non-PC ischemic-reperfused hearts. In PC hearts, lipid peroxidation of myocardial tissue as estimated from malondialdehyde production was markedly reduced. PC did not affect the activity of xanthine oxidase which is a major source of oxygen radicals in the ischemic rat hearts, but the myocardial content of hypoxanthine (a substrate for xanthine oxidase) was much lower in PC hearts. It is suggested from these results that PC brings about significant myocardial protection in ischemic-reperfused heart and this effect may be related to the suppression of oxygen free radical reactions.

• Journal of the Korean Wood Science and Technology
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• v.38 no.3
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• pp.262-273
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• 2010

In the enzymatic hydrolysis of rice straw and wood meals using extra-cellular enzymes from Fomitopsis palustris, key factors which enhanced the sugar conversion yield were investigated in this work, such as enzyme production and enzyme reaction conditions, surfactant effects, and the surface structure of substrates. F. palustris cultured with softwood mixture produced 12.0 U/$m{\ell}$ for endo-${\beta}$-1,4-gulcanase (EG), 116.68 U/$m{\ell}$ for ${\beta}$-glucosidase (BGL), 18.82 U/$m{\ell}$ for cellobiohydrolase (CBH), and 13.33 U/$m{\ell}$ for ${\beta}$-xylosidase (BXL). These levels of BGL, CBH, and BXL activities were two to four folds more than enzyme activities of F. palustris cultured with rice straw. The optimum reaction conditions of cellulase-RS which produced by F. palustris with rice straw and cellulase-SW which produced by F. palustris with softwood mixture were pH 5.0 at $45^{\circ}C$ and pH 5.0 at $50^{\circ}C$, respectively. The sugar conversion yield of cellulase-SW had the highest value of $40.6{\pm}0.6%$ within 72 h when rice straw was used as substrate. By adding 0.1% Tween 20 (w/w-substrate), the sugar conversion yield of rice straw was increased to 44%, which was about four fifths sugar conversion yield of commercial enzyme, Celluclast 1.5L (Novozyme A/S). A low crystallinity and an intensive fibril surface observed by the scanning electron microscope may explain the high sugar conversion yield of rice straw.

• The Korean Journal of Food And Nutrition
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• v.25 no.3
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• pp.564-569
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• 2012

Selenium was initially considered toxic to humans, but it was then discovered that selenium is essential for normal life processes. Selenium plays important roles in antioxidants. It is expected that chitosan microcapsules containing nano-selenium will be able to be used as a key material in bio-medical and cosmetic applications. The high concentration of chitosan derivatives guarantees increased antioxidative activity. Both inorganic and organic forms of selenium can be nutritional sources. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals. The objective of this experiment was to study the antioxidative activity of chitosan nano-selenium. Our experiments were divided into five groups, in the presence of various concentrations(0.1%, 0.3%, 0.5%, 0.7%, and 0.9%) of chitosan. We performed an assessment of the antioxidant properties and cytotoxicity of respective concentrations of chitosan nano-selenium. The antioxidant activity was examined by the free radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl(DPPH) assay. The cytotoxicity effect was measured by means of 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay. As a result, the electron donating abilities of 0.1%, 0.3%, 0.5%, 0.7%, and 0.9% of chitosan nano-selenium exhibited effective andioxidant scavenging activity at 12.5 ${\mu}g/m{\ell}$ against DPPH radicals. 0.3% chitosan nano-selenium did not show cytotoxicity on human keratinocytes. In general, the cytotoxicity of 0.1% and 0.9% chitosan nano-selenium showed the lowest effects. Though low cytotoxicity of 0.5% and 0.7% chitosan nano-selenium exhibited 29.67% and 38.4% against human keratinocytes on adding 100 ${\mu}g/m{\ell}$ and 50 ${\mu}g/m{\ell}$, respectively, cell vitality was recovered with 200 ${\mu}g/m{\ell}$. These findings support the notion that chitosan nano-selenium may be useful as a new active ingredient source for bioactive compounds.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.189-198
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• 2000

The stochiometric mixture of evaporating materials for the $CuGaSe_2$single crystal thin films were prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuGaSe_2$, it was found tetragonal structure whose lattice constant $a_0}$ and $c_0$ were 5.615 $\AA$ and 11.025 $\AA$, respectively. To obtains the single crystal thin films, $CuGaSe_2$mixed crystal was deposited on throughly etched GaAs(100) by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $610^{\circ}C$ and $450^{\circ}C$ respectively, and the growth rate of the single crystal thin films was about 0.5$\mu\textrm{m}$/h. The crystalline structure of single crystal thin films was investigated by the double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by pizoelectric scattering in the temperature range 30 K to 150 K and by polar optical scattering in the temperature range 150 K to 293 K. The optical energy gaps were found to be 1.68 eV for CuGaSe$_2$sing1e crystal thin films at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation then the constants in the Varshni equation are given by $\alpha$ = $9.615{\times}10^{-4}$eV/K, and $\beta$ = 335 K. From the photocurrent spectra by illumination of polarized light of the $CuGaSe_2$single crystal thin films. We have found that values of spin orbit coupling $\Delta$So and crystal field splitting $\Delta$Cr was 0.0900 eV and 0.2498 eV, respectively. From the PL spectra at 20 K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0626 eV and the dissipation energy of the acceptor-bound exciton and donor-bound exciton to be 0.0352 eV, 0.0932 eV, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.8
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• pp.554-563
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• 2013

The purpose of this study is to evaluate the possibility of nutrient release at up and downstream of Kangchun weir, upstream of Yuju and Ipo weir in Namhan River. For this survey, we measured basic characteristics of the sediments (water content, ignition loss, TOC, TP, SRP, TN, phosphorus fractionation) and conducted nutrients release experiments under both aerobic and anaerobic condition. The overlying water from the sediment-water column was analyzed for nutrients (i.e. TP, $PO_4$-P, TN, $NO_3$-N, $NH_3$-N) everyday for 18days. Result of soil texture experiment showed that sediments are Sand. SRP concentration before the release experiment was different with the value after the release experiment. According to this result, we can find that there were more activated release processes in anaerobic condition. $PO_4$-P increased from 1 to 8 days and remained at the maximum value (7~8 days) afterward. The rapidly increase of $PO_4$-P was observed from 1 to 2~3 days whereas the TP continuously increase from 1 to 18 days. The $PO_4$-P release rate calculated by up to 7~8 days data highly correlated with initial SRP concentration with $R^2$=0.8502. $NO_3$-N release rate appears constantly decreasing trend as -5.7~-3.08 $mg/m^2{\cdot}day$, otherwise the $NH_3$-N release rate, by-product of a organic matter decomposition using nitrate as electron acceptor, was 0.57~2.41 $mg/m^2{\cdot}day$. Substantial portion in TN can be induced by organic nitrogen which originated from the tributary passing through non-point pollutant source. Compared with other similar researches, phosphorus and nitrogen release rates obtained in this study can be considered as relatively low values. Since this study targeted the sediments accumulated by one time of flooding season, there are limitation to generalize theses results. Therefore, it is necessary to consistently monitor and investigate the accumulation of nutrients in the sediment for understanding the effect of weir construction on the overlying water quality.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.3-4
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• 2000

Many researchers are interested in the synthesis and characterization of carbon nitride and diamond-like carbon (DLq because they show excellent mechanical properties such as low friction and high wear resistance and excellent electrical properties such as controllable electical resistivity and good field electron emission. We have deposited amorphous carbon nitride (a-C:N) thin films and DLC thin films by shielded arc ion plating (SAIP) and evaluated the structural and tribological properties. The application of appropriate negative bias on substrates is effective to increase the film hardness and wear resistance. This paper reports on the deposition and tribological OLC films in relation to the substrate bias voltage (Vs). films are compared with those of the OLC films. A high purity sintered graphite target was mounted on a cathode as a carbon source. Nitrogen or argon was introduced into a deposition chamber through each mass flow controller. After the initiation of an arc plasma at 60 A and 1 Pa, the target surface was heated and evaporated by the plasma. Carbon atoms and clusters evaporated from the target were ionized partially and reacted with activated nitrogen species, and a carbon nitride film was deposited onto a Si (100) substrate when we used nitrogen as a reactant gas. The surface of the growing film also reacted with activated nitrogen species. Carbon macropartic1es (0.1 -100 maicro-m) evaporated from the target at the same time were not ionized and did not react fully with nitrogen species. These macroparticles interfered with the formation of the carbon nitride film. Therefore we set a shielding plate made of stainless steel between the target and the substrate to trap the macropartic1es. This shielding method is very effective to prepare smooth a-CN films. We, therefore, call this method "shielded arc ion plating (SAIP)". For the deposition of DLC films we used argon instead of nitrogen. Films of about 150 nm in thickness were deposited onto Si substrates. Their structures, chemical compositions and chemical bonding states were analyzed by using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and infrared spectroscopy. Hardness of the films was measured with a nanointender interfaced with an atomic force microscope (AFM). A Berkovich-type diamond tip whose radius was less than 100 nm was used for the measurement. A force-displacement curve of each film was measured at a peak load force of 250 maicro-N. Load, hold and unload times for each indentation were 2.5, 0 and 2.5 s, respectively. Hardness of each film was determined from five force-displacement curves. Wear resistance of the films was analyzed as follows. First, each film surface was scanned with the diamond tip at a constant load force of 20 maicro-N. The tip scanning was repeated 30 times in a 1 urn-square region with 512 lines at a scanning rate of 2 um/ s. After this tip-scanning, the film surface was observed in the AFM mode at a constant force of 5 maicro-N with the same Berkovich-type tip. The hardness of a-CN films was less dependent on Vs. The hardness of the film deposited at Vs=O V in a nitrogen plasma was about 10 GPa and almost similar to that of Si. It slightly increased to 12 - 15 GPa when a bias voltage of -100 - -500 V was applied to the substrate with showing its maximum at Vs=-300 V. The film deposited at Vs=O V was least wear resistant which was consistent with its lowest hardness. The biased films became more wear resistant. Particularly the film deposited at Vs=-300 V showed remarkable wear resistance. Its wear depth was too shallow to be measured with AFM. On the other hand, the DLC film, deposited at Vs=-l00 V in an argon plasma, whose hardness was 35 GPa was obviously worn under the same wear test conditions. The a-C:N films show higher wear resistance than DLC films and are useful for wear resistant coatings on various mechanical and electronic parts.nic parts.