• Bulletin of the Korean Chemical Society
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• 제18권1호
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• pp.18-23
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• 1997

Data from structure/activity studies in vir gene induction system have led to evaluate the working hypothesis of interaction between phenolic inducers and phenol binding proteins. The primary specificity in the association of a phenolic inducer with its receptor in our system is hypothesized to be the hydrogen bonding interactions through the ortho methoxy substituents as well as the proton transfer between the inducer and the binding protein. In this paper the proposed working model for phenol-mediating signal transduction was evaluated in several ways. The importance of the general acid-base catalysis was first addressed by the presence of an acidic residue and a basic residue in the phenol binding protein. Series of compounds were tested for vir gene expression activity to confirm the generation of a strong nucleophile by an acidic residue and an involvement of a basic residue as a proton acceptor. An attempt was made to correlate the pKa values of the phenolic compounds with vir gene induction activities as inducers to further support the proposed proton transfer mechanism. Finally, it was also observed that the regioselectively attached methoxy group on phenol compounds is required as the proper hydrogen bond acceptor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.991-994
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• 2003

Electronic Paper용 무기소재로 $TiO_2$ 나노입자를 적용하기 위해서는 분산시 침전문제, 입자의 전기영동 속도향상을 위한 충분한 $\xi-potential$확보, 분산제 첨가시 안정적 결합을 위한 acidic site의 확보등의 문제가 해결되어야 한다. 이를 위해 저온균일침전법으로 $TiO_2$ 나노입자를 제조하였고, 폴리머 체인을 통하여 encapsulation하여 최적의 분산과 전기영동조건 확보를 위한 공정조건에 대해 연구하였다. 실험결과 다양한 분산매에 계면활성제를 1.0wt% 첨가시 유전율상수가 2.5인 분산매에서 가장 좋은 $\xi-potential$을 얻을 수 있었으며 이를 바탕으로 acidic site에 따른 폴리머 체인의 흡착실험 결과 pH $1{\sim}2$의 조건에서 제조된 $TiO_2$ 나노입자의 경우가 체인과의 흡착정도가 가장 좋아 분산특성을 향상시킬 수 있었다.

• 한국토양비료학회지
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• 제39권4호
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• pp.195-203
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• 2006

길항미생물 MP-1은 여러 종의 곰팡이와 효모 및 음식물을 부패시키는 세균 (그람양성 및 음성) 에 대하여 항균활성을 보였다. MP-1의 16S rRNA gene 염기서열은 기존에 밝혀진 Brukholderia sp.의 염기서열과 99-100% 유사하였다. 배양액으로부터의 항균물질은 에틸아세테이트 (EtOAc)를 사용하여 분리하였으며 EtOAc에 용해된 산성 분획은 silica gel, Sephadex LH-20, ODS 컬럼크로마토 그래피 및 HPLC를 사용하여서 정제를 실시 하였다. 최종적으로 Gas chromatographic-mass 스펙트럼을 통한 분석을 통하여 4 종의 항균 활성을 나타내는 물질은 phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid 및 4-hydroxyphenylacetate methyl ester로 확인 되었다. 각각의 항균 활성물질들의 미생물에 대한 최소저해농도(MIC)는 $250{\sim}2500ug\;ml^{-1}$ 인 것으로 나타났다. 또한 6 mm paper disc 에서의 1mg (건물중) 산성 분획의 항균활성은 같은 비율로 혼합한 표준혼합용액 보다 더 효과적인 것으로 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제41권4호
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• pp.287-292
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• 2013

진한 산 가수분해 반응 중 2차 가수분해 조건에서 포도당과 자일로스의 반응을 수소 핵자기 공명 분광분석을 통하여 정량적으로 분석하였다. 정량분석은 아노머성 수소, 퓨란과 개미산의 특징적인 피크를 이용하여 실시하였다. 진한 산 가수분해의 2차 가수분해 조건에서 포도당의 일부가 5-hydroxymethylfufural (5-HMF) 중간 구조를 거쳐 levulinic acid와 개미산으로 분해되었음을 확인하였다. 자일로스는 furfural 중간 구조를 거쳐 개미산으로 분해가 되었으며, 포도당은 자일로스보다 2차 가수분해 조건에서 산에 의한 퓨란계 화합물의 전이가 느리게 전환되어 단당의 안정성이 높았다. 퓨란계 화합물로 전환된 이후, 산에 민감한 5-HMF는 쉽게 formic acid와 levulinic acid로 전환되었지만, furfural은 formic acid로의 분해 반응이 더디게 진행되어 furfural의 농도가 5-HMF보다 상대적으로 높게 나타났다.

• Journal of Animal Science and Technology
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• 제59권9호
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• pp.20.1-20.9
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• 2017

Background: Ribonuclease (RNase) is one of the few toxic proteins that are present constantly in snake venoms of all types. However, to date this RNase is still poorly studied in comparison not only with other toxic proteins of snake venom, but also with the enzymes of RNase group. The objective of this paper was to investigate some properties of RNase from venom of Vietnam cobra Naja atra. Methods: Kinetic methods and gel filtration chromatography were used to investigate RNase from venom of Vietnam cobra. Results: RNase from venom of Vietnam cobra Naja atra has some characteristic properties. This RNase is a thermostable enzyme and has high conformational stability. This is the only acidic enzyme of the RNase A superfamily exhibiting a high catalytic activity in the pH range of 1-4, with $pH_{opt}=2.58{\pm}0.35$. Its activity is considerably reduced with increasing ionic strength of reaction mixture. Venom proteins are separated by gel filtration into four peaks with ribonucleolytic activity, which is abnormally distributed among the isoforms: only a small part of the RNase activity is present in fractions of proteins with molecular weights of 12-15 kDa and more than 30 kDa, but most of the enzyme activity is detected in fractions of polypeptides, having molecular weights of less than 9 kDa, that is unexpected. Conclusions: RNase from the venom of Vietnam cobra is a unique member of RNase A superfamily according to its acidic optimum pH ($pH_{opt}=2.58{\pm}0.35$) and extremely low molecular weights of its major isoforms (approximately 8.95 kDa for RNase III and 5.93 kDa for RNase IV).

• 터널과지하공간
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• 제26권3호
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• pp.154-165
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• 2016

본 연구에서는 산성수 및 하중의 화학 역학적 영향이 암석 물성에 미치는 영향을 파악하기 위한 실내 실험을 실시하였다. 실험에서는 암석시료에 pH 및 하중조건을 부여한 후, 유효 공극률을 포함한 다양한 암석 물성 변화를 측정하였다. 실험결과, 일정한 하중조건에서 암석을 침수시킨 산성수의 pH가 낮을수록 물성 변화가 증가하는 것으로 나타났다. 이는 산성수의 pH가 낮을수록 암석과 산성수 사이의 화학반응 속도가 증가했기 때문으로 예측된다. 또한 일정한 pH의 산성수에 침수된 암석에서 가해진 하중이 증가함에 따라 암석물성 변화가 감소하는 것으로 나타났다. 이는 균열개시응력 이하의 하중에서 발생된 압축으로 암석과 산성수 사이의 화학반응 영역이 감소했기 때문으로 여겨진다.

• 한국인쇄학회지
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• 제15권2호
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• pp.25-40
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• 1997

This research was carried out to investigated the effect of base paper and latex binder on printability and obtical properties of coated paper. Especially, it examined the effect of th pH of vase paper surface and functional groups of latices on the interactions between coating color components and on the structure of coated layer. It was found that the behavior of coating color containing amphoeric latex depends on the pH in the boundary region between coating color and base paper. Thus, the coating color formulated with amphoteric latex formed bulky coating layer by inducing stronger interaction between paper surface and coating components than the coating color with anionic latex. The coated paper with amphoteric latex showed better optical properties (i.e.gloss and optical) and printability (i.e. ink receptivity, wet ink receptivity, and ink set off) than the conventional anionic latex in the acidic and alkaline paper. However, dry pick strength of the coated paper was less decreased. This result indicated that amphoteric latex could also be applied practically to the alkaline paper.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.2
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• pp.331-336
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• 2006

The aim of this work was to inhibit the heat-and moisture-induced yellowing of ECF/TCF bleached hard wood kraft pulp (HBKP) retaining hexenuronic acid (HexA). We have already reported that one of the derivatives of HexA, 5-formyl-2-furancarboxylic acid (FFA), causes yellowing of HBKP in acidic paper, and that FFA might polymerize or react with pulp components to form new chromophoric groups (1). In this study, it was shown that the carboxylic base of FFA interacts with that of glucuronic acid or galacturonic acid, resulting in strong yellowing. Therefore, it seems that preventing the reaction of carboxylic bases could be effective in suppressing this yellowing. We have discovered that polycarboxylic acids (for example, citric acid, tartaric acid, etc.) are useful as a yellowing inhibitor.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.96-102
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• 2002

This paper was studied on the wear-corrosion behavior of ductile cast iron in the acidic environment. In the dry atmosphere and variety of pH solution, wear-corrosion characteristics and friction coefficient of GCD 60 with various sliding speed and distance were investigated. And electrochemical polarization test of GCD 60 was examined in the environment of various pH value. The main results are as following : In the dry atmosphere, boundary friction appears below nearly 5 $kg_{f}$ of contact load, and it is considered that solid friction occurs over nearly 5 $kg_{f}$ of contact load. As pH value becomes low, wear-corrosion loss in the aqueous solution increases. As the corrosion environment is acidified, corrosion potential of GCD 60 becomes noble, polarization resistance becomes low, and corrosion current density increases.

• Journal of Microbiology and Biotechnology
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• 제19권7호
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• pp.698-708
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• 2009

High rate sulfate reduction under acidic conditions opens possibilities for new process flow sheets that allow the selective recovery of metals from mining and metallurgical waste and process water. However, knowledge about high-rate sulfate reduction under acidic conditions is limited. This paper investigates sulfate reduction in a membrane bioreactor at a controlled pH of 5. Sulfate and formate were dosed using a pH-auxostat system while formate was converted into hydrogen, which was used for sulfate reduction. Sulfide was removed from the gas phase to prevent sulfide inhibition. This study shows a high-rate sulfate-reducing bioreactor system for the frrst time at pH 5, with a volumetric activity of 188 mmol $SO_4^{2-}$/I/d and a specific activity of 81 mmol $SO_4^{2-}$volatile suspended solids/d. The microbial community at the end of the reactor run consisted of a diverse mixed population including sulfate-reducing bacteria.