• Preventive Nutrition and Food Science
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• 제1권1호
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• pp.106-110
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• 1996

Bromelain(EC 3.4.22.4), the collective name for the proteolytic enzymes found in tissues of the plant family Bromeliaceae(pineapple), has been used as a tenderizing agent in food processing, and as an antiinflammatory agent in pharmaceuticals. In this paper, we describe the simple purification method of bromelain using Korean pineapple fruit. After removing contaminants at 30% saturation of ammonium sulfate, the supernatant obtained was treated again with ammonium sulfate to 80% saturation. Wit the above salt fractionation, partially purified bromelain could be obtained. To get highly purified bromelain, the previous 30% to 80% ammonium sulfate treated precipitate was dialyzed against 25mM sodium acetate buffer(pH 5.0) followed by passing through a CM- cellulose cation exchange column. Fruit bromelain was eluted as a major peak at 0.5~0.8M NaCI gradient. The present method is simpler with high wield than the traditional purification method-acetone treatment and several consecutive chromatographic processes.

• Tribology and Lubricants
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• 제30권6호
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• pp.323-329
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• 2014

The friction-reducing properties of lubricants containing ionic liquids based on ammonium dithiocarbamate are studied. The ionic liquids are produced through the following two steps: the synthesis of sodium alkyl dithiocarbamates via the substitution reaction of dialkylamine and carbon disulfide and their subsequent conversion into ammonium dithiocarbamate-based ionic liquids through an ion-exchange reaction with a quaternary alkyl ammonium halide salt. The structures of the ionic liquids are characterized by NMR spectroscopy and Fourier transform infrared spectroscopy. The isolated yields of the ionic liquids, which are viscous and pale yellow, are approximately 92%. The Brookfield viscosities and pour points of the ionic liquids are determined. Further, their wear resistances are measured through the four-ball wear test and the Schwingung Reibung Ver-schleiss (oscillation, friction, wear) test. The wear scar diameter of the lubricants containing 1 wt of the quaternary alkyl ammonium dithiocarbamate-based ionic liquids (0.475-0.631 mm) is significantly lower than that of the base oil (0.825 mm), proving that the ammonium dithiocarbamate-based ionic liquids have good friction-reducing characteristics. However, these friction-reducing characteristics fade significantly after long-term storage, owing to the degradation of the ionic liquids.

• Bulletin of the Korean Chemical Society
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• 제15권9호
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• pp.743-748
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• 1994

Photochemical reactions of saccharin with tertiary amines were explored. Saccharin was found to undergo an acid-base reaction with N-trimethylsilylmethyl-N,N-diethyl amine to form N-trimethylsilylmethyl-N,N-diethyl ammonium saccharin salt which is in equilibrium with free saccharin and N-trimethylsilylmethyl-N,N-diethyl amine insolution. Photoreaction of N-trimethylsilylmethyl-N,N-diethyl ammonium saccharin in $CH_3OH\;or\;CH_3CN$ results in the generation of desilylmethylated product, N,N-diethyl ammonium saccharin mainly along with benzamide. Photoreaction of N-methylsaccharin with N-trimethylsilylmethyl-N,N-diethyl amine in $CH_3OH$ leads to the production of o-(N-methylcarbamoyl)-N-ethylbenzenesulfonamid e as the major product along with N-methylbenzamide as the minor product. On the other hand, photoreaction of N,N,N-triethyl ammonium saccharin, generated from saccharin and triethylamine, produces N-methylbenzamide as the exclusive product. These photoreactions are quenched by oxygen indicating that triplets of saccharin and N-methylsaccharin are the reactive excited states. Based on the consideration of the redox potentials of saccharin and N-trimethylsilylmethyl-N,N-diethyl amine, and the nature of photoproducts, pathways involving initial triplet state single electron transfer are proposed for photoreactions of the saccharins with the ${\alpha}$-silylamine.

• 공업화학
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• 제10권1호
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• pp.129-134
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• 1999

4차 암모늄염 촉매 존재하에서 poly(glycidyl methacrylate)[poly(GMA)]에 이산화탄소를 직접 부가시켜 poly[(1,3-dioxolane-2-oxo-4-yl)methyl methacrylate][poly(DOMA)]를 합성하였다. 4차 암모늄염 촉매는 높은 이산화탄소 고정화 효율을 나타내었으며, 양이온의 크기가 클수록, 짝음이온의 친핵성이 강할수록 높은 촉매 활성을 나타내었다. 또한 반응온도가 높을수록 높은 이산화탄소 부가율을 나타내었다. 한편 고압 회분 반응기에서 이산화탄소의 압력변화를 관찰함으로써 실시한 속도론적 고찰 결과 반응속도는 poly(GMA)와 이산화탄소의 농도에 대하여 각각 1차 반응이었고, 이때 반응속도상수 k는 $0.69L/mol{\cdot}h$이었다. DMSO를 용매로 사용한 경우 $80^{\circ}C$에서의 $CO_2$의 Henry 상수 H'는 $6.8{\times}10^{-4}mol/L{\cdot}KPa$로 나타났다.

• 청정기술
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• 제22권1호
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• pp.35-44
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• 2016

본 연구에서는 이론화학 또는 분자모델링이라 불리는 계산화학을 기존에 연구된 촉매반응 실험결과를 해석하는 데 접목시켜 보았다. 온실효과의 주범인 이산화탄소를 에폭사이드와 반응을 통해 고정화하고 카보네이트를 생성하는 반응을 선택하였는데 이 반응은 활성화 에너지(55~59 kcal/mol)가 높아 촉매의 사용이 불가피하다. 많은 기존 연구들 중에 ZIF-90/ionic liquid immobilized ZIF-90 (IL-ZIF-90), polystyrene-supported quaternized ammonium salt, KI/KI-glycine, dimethylethanolamine (DMEA)를 촉매로 사용한 경우에 대해 반응의 각 단계를 계산하여 반응의 경로를 예측하고 단계별로 구한 에너지를 바탕으로 에너지도를 구성함으로써 실험결과를 열역학적으로 해석하였다. ZIF-90/IL-ZIF-90과 KI/KI-glycine의 경우는 실험적으로 후자들이 상대적으로 높은 수율을 얻었는데 계산 결과 활성화에너지가 낮아진 이유가 아니라 전자들의 경우 반응 중간체가 높은 에너지를 가져 반응물로 되돌아가는 역반응에 의해 정반응의 진행이 방해를 받은 것으로 밝혀졌다. DMEA를 촉매로 사용하였을 경우는 활성화 에너지를 ~42 kcal/mol로 낮춰줌으로써 금속이나 할로겐염 없이도 촉매의 활성이 잘 일어남을 증명하였다. 폴리스티렌(polystyrene)으로 지지된 quaternized 암모늄염 촉매의 경우 클러스터 가정을 사용하여 계산을 진행하였으며 암모늄염의 -NH기와 에폭사이드의 O 원자 사이의 상호작용의 가능성을 확인할 수 있는 반응경로를 제시하였다.

• 공업화학
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• 제7권5호
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• pp.1020-1026
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• 1996

천연고분자인 chitin의 탈아세틸화물인 chitosan의 유리아미노기에 알킬 길이가 다른 알데히드를 이용하여 N-alkyl chitosan 유도체를 각각 합성한 다음, 이들을 methyl iodide로 4차화시킴으로서 4차 암모늄기가 도입된 새로운 수용성 chitosan 유도체를 합성하여, 도입된 알킬기의 길이에 따른 항균성을 그람양성균인 S. aureus(ATCC 6538P)와 그람 음성균인 E. coli(ATCC 14339)에 대해서 shake flask법을 이용하여 검토하였다. 그 결과 소수성이 증대될수록 항균력은 증가하였고, 특히 그람음성균인 E. coli에 비해 그람양성균인 S. aureus에 대한 항균력이 더욱 증대됨을 확인할 수 있었다. 이는 cytoplasmic membrane의 구조상의 차이에서 기인한 것으로 생각된다.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2299-2302
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• 2007

A series of quaternary ammonium-based ionic liquids (ILs) containing an alkyl carbonate group on the cation was first prepared and their physical and electrochemical properties including density, viscosity, thermal stability, electrochemical stability, and ionic conductivity were reported. These ILs exhibited wide electrochemical windows of at least 5.0 V and relatively high conductivities. In contrast to dialkyl-substituted ionic liquids, the ILs with an alkyl carbonate group on the cation showed much smaller drop in conductivities when mixed with a lithium salt, due to the interaction of lithium ions with carbonate groups. Upon interaction with a Li salt, the carbonyl stretching frequency of the carbonate group shifted to a lower frequency whereas the peak associated with C-O single bond moved to a higher frequency.

• Corrosion Science and Technology
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• 제6권6호
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• pp.304-307
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• 2007

As to the reflection electrode of LCD (liquid crystal displays), silver-copper-gold alloy (hereafter, it is called as ACA (Ag98%, Cu1%, Au1%)) is an effective material of which weathering resistance can be improved more compared with pure silver. However, there is a problem that gold remains on the substrate as residues when ACA is etched in cerium ammonium nitrate solution or phosphoric acid. Gold can not be etched in these etchants as readily as the other two alloying elements. Gold residue has actually been removed physically by brushing etc. This procedure causes damage to the display elements. Another etchant of iodine/potassium iodide generally known as one of the gold etchants can not give precise etch pattern because of remarkable difference in etching rates among silver, copper and gold. The purpose of this research is to obtain a practical etchant for ACA alloy. The results are as follows. The cyanogen complex salt of gold generates when cyanide is used as the etchant, in which gold dissolves considerably. Oxygen reduction is important as the cathodic reaction in the dissolution of gold. A new etchant of sodium cyanide / potassium ferricyanide whose cathodic reduction is stronger than oxygen, can give precise etch patterns in ACA alloy swiftly at room temperature.

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2633-2636
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• 2011

A new type of ionic liquid based on N-(3-aminepropyl)imidazolium iodide, called IIQAI, which consists of imidazolium and quaternary ammonium salt, and APII-(hydroxyethyl, propyl, hexyl) were synthesized and used as ionic liquid in dye-sensitized solar cells. APII-hexyl is solid, whereas IIQAI, APII-(hydroxyethyl, propyl) are viscous liquids. The synthesized ionic liquid showed relative thermal stability compared to the commercial ionic liquid of DMII. Among them, IIQAI was more stable than the other ionic liquid because of the two salt groups. APII-hydroxyethyl, which contains two hydroxyl groups, showed low viscosity with good flow. New types of ionic liquids were examined by $^1H$-NMR spectroscopy, thermo gravimetric analysis (TGA). IIQAI enabled a solar energy conversion efficiency of 6.3%, which is slightly higher than that of the referenced (DMII, 6.2%).

• 폴리머
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• 제31권3호
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• pp.255-262
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• 2007

고분자 습도센서 막으로 사용하기 위한 두 가지 타입의 공중합체를 라디칼 중합방식에 의하여 제조하였다. 각각 공중합체는 세 가지의 단량체를 포함하여 제조하였는데, 각 단량체들은 습도 저항성, 막 안정성, 유연성, 임피던스 및 전극 부착력을 증대시키는 효과를 가지도록 하였다. 염 형태의 MDBAB는 제조된 습도 막의 임피던스를 감소시키는 효과를 보였으며 아민과 반응하여 가교 구조를 생성하였다. DAEMA, 4-VP, 및 2-EHA를 사용하여 습도막 제조를 위하여 몇 가지 조성물을 제조하였다. 특정 조성 조건에서 성능 및 장기 내구성 측면에서 우수한 결과를 얻을 수 있었다.