• Tribology and Lubricants
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• 제20권2호
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• pp.97-101
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• 2004

This paper reports the studies on the wear-corrosion behavior of Al-Mg alloy in various pH environments. In various pH of sea water, corrosion and wear-corrosion loss of Al-Mg alloy were investigated. Also, the polarization test of Al-Mg alloy using potentiostat/galvanostat was carried out. And the rubbed surface of Al-Mg alloy using scanning electron micrographs after wear-corrosion test was examined in various pH values of sea water. The main results are as following : The polarization resistance of Al-Mg alloy in pH 4 solution is higer than that in pH 6.7 solution, and the corrosion current density in pH 4 is controlled than in pH 6.7 solution. The wear-corrosion loss of Al-Mg alloy with lowering pH becomes sensitive. As the oxide product of Al-Mg alloy appears granular structure and exholiation phenomenon, wear-corrosion loss of Al-Mg alloy increases.

• Journal of the Korean Chemical Society
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• 제58권1호
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• pp.92-99
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• 2014

The pH sensitive hydrogels composed of N-isopropylacrylamide (NIPA) and acryloyl phenylalanine (APA) were prepared by redox polymerization using N,N'-methylenebisacrylamide (MBA) as a crosslinker. Anti-inflammatory and analgesic agent, Keterolac Tromethamine (KT), was loaded successfully into poly(NIPA-co-APA) copolymeric hydrogels by swelling equilibrium method. To understand the nature of drug in the polymeric matrix, the newly synthesized drug loaded poly(NIPA-co-APA) copolymeric hydrogels were characterized by using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The scanning electron microscopy (SEM) technique result indicates the spherical smooth surface of the hydrogels. The drug (KT) releasing nature of the poly(NIPA-co-APA) hydrogels was studied in pH 1.2 and 7.4. Effects of drug loading, crosslinking agent, pH and the ionic strength of the external medium on swelling of hydrogels were also investigated.

• Journal of Pharmaceutical Investigation
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• 제40권spc호
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• pp.45-61
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• 2010

Polymeric based nanomedicines have been developed for diagnosing, treating, and preventing diseases in human body. The nanosized drug delivery systems having various structures such as micelles, nanogels, drug-conjugates, and polyplex were investigated for a great goal in pharmaceutics: increasing therapeutic efficacy for diseases and decreasing drug toxicity for normal tissues. The functional polymers used for constituting these drug delivery systems should have several favorable properties such as stimuli-responsibility and biodegrdability for controlled drug release, and solublization capacity for programmed drug encapsulation. This review discusses recent developments and trends of functional polymers (e.g., pH-sensitive polymers, biodegradable polymers, and cationic polymers) used for nanosized drug carriers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.762-765
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• 2003

에틸렌글리콜(ethyleneglycol)을 이용한 폴리비닐에테르(polyvinyl ether)와 같은 고분자물질을 활용하여 Co$^{30}$ 방사선원으로부터 ${\gamma}$선을 조사시켜, 고분자 물질의 성질을 변화시킴으로써 화학, 전기전자, 환경 및 기타 여러 가지 응용분야에 적용하여 이용할 수 있는 기술을 개발하였다. 이를 바탕으로 관련재료의 단량체(monomer)로부터 중합체(polymer)를 합성하여 water swelling을 시키는 과정에서 각종 (금속) 이온을 흡입-제거하는 방법의 환경복원기술, 흡입 금속이온을 표면에 밀집시켜 금속막을 형성하는 응용기술, 생체조직의 대용물질로 활용하는 의용공학 및 열감지특성(thermal sensitive property) 또는 pH 감지특성(pH sensitive property)을 이용하여 의용기술에 적용하는 polymer 응용기술 등의 폭넓은 활용을 위하여 그 일환으로 전도성 고분자 제조기술로의 활용가능성을 연구하였다.

• Journal of Biomedical Engineering Research
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• 제28권3호
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• pp.344-347
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• 2007

A interpenetrating polymer network (IPN) hydrogel, composed of chitosan (CS) and poly(diallydimethylammonium chloride) (PDADMAC) was prepared, which exhibited electrical sensitive behavior. The swelling behavior of the CS/PDADMAC SIPN hydrogel was studied by immersion of the gel into various pH buffer solutions, and their stimuli response in electric fields also investigated. In order to clarify the relationship between the equilibrium swelling ratio and bending behavior of the SIPN hydrogels, the state of water in the SIPN hydrogel was also investigated using differential scanning calorimetry (DSC).

• Korean Journal of Microbiology
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• 제10권2호
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• pp.69-72
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• 1972

The studies of neutral protease which was obtained by passing through Sephadex A-50 had been reported not long ago. Since that time the author also conducted the research to be investigated the physical properties of acid protease absorbed by Sephadex A-50. The results are summarized as follows : 1) Cultivating Aspergillus oryza SHW-131 on a wheat bran medium, the acid protease including neutral protease is very sensitive for temperature. 3) Activity of acid protease is very sensitive for temeprature. 3) This enzyme was proved, what is called, to be a sort of weak acid protease. It's optimum pH was lied in about 4.5. 4) A range of pH for stability is far more narrow than any other protease. 5) The acid protease is dropped by EDTA solution in its activity.

• BMB Reports
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• 제40권1호
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• pp.53-57
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• 2007

The enzymatic properties of NADH:quinone oxidoreductase were examined in Triton X-100 extracts of Bacillus cereus membranes by using the artificial electron acceptors ubiquinone-1 and menadione. Membranes were prepared from B. cereus KCTC 3674 grown aerobically on a complex medium and oxidized with NADH exclusively, whereas deamino-NADH was determined to be poorly oxidized. The NADH oxidase activity was lost completely by solubilization of the membranes with Triton X-100. However, by using the artificial electron acceptors ubiquinone-1 and menadione, NADH oxidation could be observed. The activities of NADH:ubiquinone-1 and NADH:menadione oxidoreductase were enhanced approximately 8-fold and 4-fold, respectively, from the Triton X-100 extracted membranes. The maximum activity of FAD-dependent NADH:ubiquinone-1 oxidoreductase was obtained at about pH 6.0 in the presence of 0.1M NaCl, while the maximum activity of FAD-dependent NADH:menadione oxidoreductase was obtained at about pH 8.0 in the presence of 0.1M NaCl. The activities of the NADH:ubiquinone-1 and NADH:menadione oxidoreductase were very resistant to such respiratory chain inhibitors as rotenone, capsaicin, and $AgNO_3$, whereas these activities were sensitive to 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO). Based on these results, we suggest that the aerobic respiratory chain-linked NADH oxidase system of B. cereus KCTC 3674 possesses an HQNO-sensitive NADH:quinone oxidoreductase that lacks an energy coupling site containing FAD as a cofactor.

• Macromolecular Research
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• 제17권10호
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• pp.734-738
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• 2009

Biodegradable, pH-sensitive, glycol chitosan (GC) hydrogels were prepared using divinyl adipate (DVA) as a crosslinker and acetic acid as a catalyst. DVA has highly reactive double vinyl ester groups and GC contains a high density of hydroxyl groups, with two in every glucosamine unit. The transesterification reaction between vinyl esters and hydroxyl groups produced crosslinked GC hydrogels. The initial crosslinking reaction was monitored by measuring the viscosity of the reaction mixture. When DVA was added to the GC solution and heated to $50^{\circ}C$, the viscosity of the GC solution gradually increased, implying a crosslinking reaction and hydrogel formation. A new peak from the ester group was observed in the FTIR spectra of the GC hydrogels, confirming the crosslinking reaction. The synthesized GC hydrogel showed pH-dependent water absorbency, mainly due to the presence of amine groups ($-NH_2$) at the C-2 position of the glucosamine unit of GC. The water absorbency greatly increased at acidic pH and slightly decreased at alkaline pH. The GC hydrogel gradually degraded in $37^{\circ}C$ water due to hydrolysis of the ester bonds, which were intermolecular crosslinking sites. A red dye, 5-carboxyltetramethyl-rhodamine (CTMR), was entrapped in the GC hydrogels as a model compound. CTMR was released from GC hydrogels in two steps: an initial burst release mainly due to desorption and diffusion, and a second sustained release possibly due to gradual degradation.

• Journal of Microbiology and Biotechnology
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• 제6권6호
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• pp.391-396
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• 1996

The Gram-negative marine bacterium Marinomonas vaga, which requires 0.5 M NaCl concentration for optimal growth, is slightly halophilic. The growth of M vaga was highly resistant to the proton conductor, carbonyl cyanide m-chlorophenylhydrazone (CCCP) under alkaline pH conditions (pH 8.5) but very sensitive to CCCP under acidic pH conditions (pH 6.5). These results suggest that the respiratory chain-linked NADH oxidase system of M. vaga may lead to generation of a $Na^{+}$ electrochemical gradient. In order to examine the existence of $Na^{+}$-stimulated NADH oxidase in M. vaga, membrane fractions were prepared by the osmotic lysis method. The membrane-bound NADH oxidase oxidized both NADH and deamino-NADH as substrates and required $Na^{+}$ for maximum activity. The maximum activity of NADH oxidase was obtained at about pH 8.5 in the presence of 0.2 M NaCl. The site of $Na^{+}$-dependent activation in the NADH oxidase system was at the NADH:quinone oxidoreductase segment. The NADH oxidase and NADH:quinone oxidoreductase were very sensitive to the respiratory chain inhibitor, 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO) in the presence of 0.2 M NaCl but highly resistant to another respiratory inhibitor, rotenone. Based on these findings, we conclude that M. vaga possesses the $Na^{+}$-dependent NADH:quinone oxidoreductase that may function as an electrogenic $Na^{+}$ pump.

• The Korean Journal of Physiology and Pharmacology
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• 제23권5호
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• pp.381-392
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• 2019

Sperm function and male fertility are closely related to pH dependent $K^+$ current (KSper) in human sperm, which is most likely composed of Slo3 and its auxiliary subunit leucine-rich repeat-containing protein 52 (LRRC52). Onion peel extract (OPE) and its major active ingredient quercetin are widely used as fertility enhancers; however, the effect of OPE and quercetin on Slo3 has not been elucidated. The purpose of this study is to investigate the effect of quercetin on human Slo3 channels. Human Slo3 and LRRC52 were co-transfected into HEK293 cells and pharmacological properties were studied with the whole cell patch clamp technique. We successfully expressed and measured pH sensitive and calcium insensitive Slo3 currents in HEK293 cells. We found that OPE and its key ingredient quercetin inhibit Slo3 currents. Inhibition by quercetin is dose dependent and this degree of inhibition decreases with elevating internal alkalization and internal free calcium concentrations. Functional moieties in the quercetin polyphenolic ring govern the degree of inhibition of Slo3 by quercetin, and the composition of such functional moieties are sensitive to the pH of the medium. These results suggest that quercetin inhibits Slo3 in a pH and calcium dependent manner. Therefore, we surmise that quercetin induced depolarization in spermatozoa may enhance the voltage gated proton channel (Hv1), and activate non-selective cation channels of sperm (CatSper) dependent calcium influx to trigger sperm capacitation and acrosome reaction.