• 대한화학회지
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• 제30권3호
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• pp.265-272
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• 1986

MeOH-1,1,2,2-tetrachloroethane 혼합용매에서 할로겐화삼차부틸(t-BuCl, t-BuBr, t-BuI)의 가메탄올 분해반응을 속도론적으로 연구하였으며, 이온화에 미치는 용매효과를 고찰하기 위하여 6가지 indicater를 이용한 분광용매화비교법을 적용하였다. 이결과 할로겐화삼차부틸의 가메탄올 분해반응에 미치는 용매화의 작용은 용매의 극상-편극성에 기인되는 상호작용이 주된 것이긴 하지만 halide leaving group의 living ability에 미치는 electrophilic assistance와 t-Butyl 양이온쪽에 대한 nucleophilic assistance도 상당히 작용함을 알 수 있다. 특히 hydrogen bonding에 의한 electrophilic assistance는 basicity가 큰 leaving group일수록 커지며 ($I^-), 탄소 중심일수록 커짐을 밝힐 수 있었다. (t-BuCl

• 한국수소및신에너지학회논문집
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• 제27권4호
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• pp.378-385
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• 2016

In this study, we synthesized a biocatalyst consisting of glucose oxidase (GOx), polyethyleneimine (PEI) and carbon nanotube (CNT) with addition of glutaraldehyde (GA)(GA/[GOx/PEI/CNT])for fabrication of glucose sensor. Main bonding of the GA/[GOx/PEI/CNT] catalyst was formed by crosslinking of functional end groups between GOx/PEI and GA. Catalytic activity of GA/[GOx/PEI/CNT] was quantified by UV-Vis and electrochemical measurements. As a result of that, high immobilization ratio of 199% than other catalyst (with only physical adsorption) and large sensitivity value of $13.4{\mu}A/cm^2/mM$ was gained. With estimation of the biosensor stability, it was found that the GA/[GOx/PEI/CNT] kept about 88% of its initial activity even after three weeks. It shows GA minimized the loss of GOx and improved sensing ability and stability compared with that using other biocatalysts.

• Carbon letters
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• 제4권1호
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• pp.1-9
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• 2003

Recently, the control of pore-characteristics of nano-porous materials has been studied extensively because of their unique applications, which includes size-selective separation, gas adsorption/storage, heterogeneous catalysis, etc. The most widely adopted techniques for controlling pore characteristics include the utilization of pillar effect by metal oxide and of templates such as zeolites. More recently, coordination polymers constructed by transition metal ions and bridging organic ligands have afforded new types of nano-porous materials, porous metal-organic framework(porous MOF), with high degree and uniformity of porosity. The pore characteristics of these porous MOFs can be designed by controlling the coordination number and geometry of selected metal, e.g transition metal and rare-earth metal, and the size, rigidity, and coordination site of ligand. The synthesis of porous MOF by the assembly of metal ions with di-, tri-, and poly-topic N-bound organic linkers such as 4,4'-bipyridine(BPY) or multidentate linkers such as carboxylates, which allow for the formation of more rigid frameworks due to their ability to aggregate metal ions into M-O-C cluster, have been reported. Other porous MOF from co-ligand system or the ligand with both C-O and C-N type linkage can afford to control the shape and size of pores. Furthermore, for the rigidity and thermal stability of porous MOF, ring-type ligand such as porphyrin derivatives and ligands with ability of secondary bonding such as hydrogen and ionic bonding have been studied.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권4호
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• pp.357-363
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• 2006

Monolithic molecularly imprinted columns were designed and prepared by an in-situ thermal-initiated copolymerization technique for rapid separation of tryptophan and N- CBZ-phenylalanine enantiomers. The influence of polymerization conditions and separation conditions on the specific molecular recognition ability for enantiomers and diastereomers was investigated. The specious molecular recognition was found to be dependent on the stereo structures and the arrangement of functional groups of the imprinted molecule and the cavities in the molecularly imprinted polymer (MIP). Moreover, hydrogen bonding interactions and hydrophobic interactions played an important role in the retention and separation. Compared to conventional MIP preparation procedures, the present method is very simple, and its macroporous structure has excellent separation properties.

• 펄프종이기술
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• 제33권2호
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• pp.1-7
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• 2001

Use of high yield pulp and recycled fiber as raw materials and water system closure result in higher fines content and buildup of organic and inorganic contaminants in white water. These are detrimental for the effectiveness of chemical additives including retention aids. Thus it is imperative to employ a retention systems that maintains its efficiency in closed papermaking system for reducing fresh water consumption. The performance of four different microparticle retention systems including cationic polyacrylamide (C-PAM)/bentonite, highly charged cationic starch (HCS)/silica, C-PAM/micropolymer, cationic guar gum (CGG)/silica was evaluated and compared at three different levels of papermaking system closure. Buildup of detrimental substances in a closed white water system increased cationic demand and finally reduced the performance of retention systems. Cationic starch and guar gums maintained their effectiveness in retention in closed white water systems contaminated with anionic trashes because of their structural rigidity and hydrogen bonding ability. Particularly, cationic guar gums, due its stiffness of molecular structure, appeared perform better than catinonic starch.

• Bulletin of the Korean Chemical Society
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• 제14권6호
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• pp.704-708
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• 1993

The intramolecular charge transfer (ICT) phenomena of the photoexcited 2-biphenylcarboxylic acid (2BPCA) and 4-biphenylcarboxylic acid (4BPCA) have been investigated in some surfactant micellar solutions. The ICT emission of 4BPCA and 2BPCA in aqueous solution at sufficiently low pH (1-3) has been observed to be markedly quenched and blue-shifted upon addition of a cationic surfactant, cetyltrimethylammonium chloride (CTAC) in contrast to little change in anionic sodium dodecyl sulfate (SDS) and neutral Brij 35. An anionic emission band has been observed to be enhanced at expense of the ICT emission as a function of the concentration of CTAC. These results with the micellar effects on the fluorescence decay kinetics of 4BPCA suggest that formation of the ICT state of the excited acids is inhibited by CTAC-induced proton transfer as well as the decrease in the polarity and/or hydrogen-bonding ability of the micellar microenvironment entrapping the acids.

• Bulletin of the Korean Chemical Society
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• 제7권6호
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• pp.458-461
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• 1986

The fluorescence intensity of khellin-dimethylfumarate C$_4$-cycloadduct (KDF) is very sensitive to temperature and to the nature of solvents, especially hydrogen-bonding ability. The fluorescence quantum yields of KDF in ethanol and isopentane at 77K are 0.73 and 0.54, respectively, both of which are much larger than the room temperature values. The phosphorescence lifetime is very long and decreases with decreasing the solvent polarity. The phosphorescence and fluorescence quantum yield ratio is very small and decreases with decreasing solvent polarity. The solvent relaxation plays an important role in the excited states of KDF. The internal conversion is a major decay process of the excited singlet state of KDF in all the solvents used at room temperature.

• 대한화학회지
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• 제39권2호
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• pp.94-102
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• 1995

모세관 기체크로마토그래피에 의한 cyclodextrin 정지상들(PH-${\beta}$-CD, DA-${\beta}$-CD, TA-${\gamma}$-CD)을 이용하여 라세미 알코올들과 그 유도체들의 분리를 연구하였다. 실험에 사용한 모든 알코올들은 trifluoro acetic anhydride, acetic anhydride, trichloro acetic anhydride를 써서 유도화하였다. 거울상체들의 분리선택성은 acylation 시약의 형태에 상당히 의존하는 것을 알았다. 알코올과 그 유도체들의 광학분활에 대한 최상의 실험조건은 용질분자들의 극성에 따라 다르다. 그리고 키랄분리에 관해서 온도, 컬럼이 극성, 수소 결합력, 알코올과 CD 정지상의 입체효과 등의 의존에 관한 연구를 행하였다. 키랄 인식 기구는 키랄 정지상의 종류에 의존하지 않고, 라세미 알코올의 유도체화에 의존하는 것으로 나타났다.

• 대한의생명과학회지
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• 제11권4호
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• pp.487-492
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• 2005

The baculovirus/insect cell expression system is of great value in the study of structure-function relationships in mammalian glucose-transport proteins by site-directed mutagenesis and for the large-scale production of these proteins for mechanistic and biochemical studies. Spodoptera frugiperda Clone 21 (Sf2l) cells grow well on TC-100 medium that contains $0.1\%$ D-glucose as the major carbon source, strongly suggesting the presence of endogenous glucose transporters. However, very little is known about the properties of the endogenous sugar transporter(s) in Sf2l cells, although a saturable transport system for hexose uptake has been previously revealed in the Sf cells. In order to further examine the substrate and inhibitor recognition properties of the Sf2l cell transporter, the ability of hexoses to inhibit 2-deoxy-D-glucose (2dGlc) transport was investigated by measuring inhibition constants $(K_i)$. The $K_i's$ for reversible inhibitors were determined from plots of uptake versus inhibitor concentration. Transport was effectively inhibited by D-mannose and D-glucose. Of the hexoses tested, L-glucose had the least effect on 2dGlc transport in the Sf2l cells, indicating that the transport is stereoselective. Unlike the human HepG2 type glucose transport system, D-mannose had a somewhat greater affinity for the Sf2l cell transporter than D-glucose, implying that the hydroxyl group at the C-2 position is not necessary for strong binding. However, epimerization at the C-4 position of D-glucose (D-galactose) resulted in a dramatic decrease in affinity of the hexose for the Sf2l cell transporter. Such a lowering of affinity might be the result of the involvement of the C-4 hydroxyl in hydrogen bonding. It is therefore suggested that Sf2l cells were found to contain an endogenous sugar transport activity that in several aspects resembles the human HepG2 type glucose transporter, although the insect and human transporters do differ in their affinity for cytochalasin B.

• Applied Biological Chemistry
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• 제25권4호
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• pp.224-231
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• 1982

liposome에 결합되어 있는 ${\alpha}-Tocopherol$의 형광을 이용하여 liposome의 상전이온도를 측정할 수 있었다. 이는 ${\alpha}-Tocopherol$의 vitamin E로서의 중요성 이외에 형광성 프로브로서의 새로운 가치의 발견이다. 형광성 프로브로서 그 응용의 확대를 위한 필수적인 기초자료의 수집을 위해, 분자분광학적성질을 조사하였다. 용액중의 ${\alpha}-Tocopherol$은 monomer와 dimer의 두가지 형태로 존재하며, 단파장흡수대$(291{\sim}294nm)$의 monomer는 형광성인데 반하여 dimer는 298nm 부근을 흡수하는 비형광성이고 분자간수소결합에 의하여 형성되었음이 밝혀졌다. liposome에 결합된 ${\alpha}-Tocopherol$은 각종 유기용매 중에서의 ${\alpha}-Tocopherol$과는 판이한 형광성질을 갖고 있었고 chromanolate이온형태의 화학종으로부터 생긴 것으로 해석되었다.