• 한국막학회:학술대회논문집
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• 한국막학회 1995년도 춘계 총회 및 학술발표회
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• pp.50-51
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• 1995

The swelling behavior of hyddrogels has been interested in many applications of drug carriers. These gels show reversible swelling changes in response to pH, electric currcnt, and temperature. Among others, the temperature-responsive behavior of poly(N-isopropylacrylanxide) (p(NIPAAm)) was studied, because a lower critical solution temperature(LCST) is in the vicinity of 32$\circ$C, and remarkable temperature-response can be obtained. We propose a novel composite membrane, which is appropriate for transporting drug ingredients above the transition temperature. Our object was to design a high permeation system above the shrinking temperature of p(NIPAAm). The membrane was composed of a matrix polymer and thermosensitive p(NIPAAm) hydrogel. The flux pattern of 4-acctamidophen through membrane in response of temperature was opposite to that of p(NIPAAm) membrane.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.434.2-434.2
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• 2014

We observe enhanced pH response of solution-gated field-effect transistors (SG-FET) having 1D-2D hybrid channel of vertical grown ZnO nanorods grown on CVD graphene (Gr). In recent years, SG-FET based on Gr has received a lot of attention for biochemical sensing applications, because Gr has outstanding properties such as high sensitivity, low detection limit, label-free electrical detection, and so on. However, low-defect CVD Gr has hardly pH responsive due to lack of hydroxyl group on Gr surface. On the other hand, ZnO, consists of stable wurtzite structure, has attracted much interest due to its unique properties and wide range of applications in optoelectronics, biosensors, medical sciences, etc. Especially, ZnO were easily grown as vertical nanorods by hydrothermal method and ZnO nanostructures have higher sensitivity to environments than planar structures due to plentiful hydroxyl group on their surface. We prepared for ZnO nanorods vertically grown on CVD Gr (ZnO nanorods/Gr hybrid channel) and to fabricate SG-FET subsequently. We have analyzed hybrid channel FETs showing transfer characteristics similar to that of pristine Gr FETs and charge neutrality point (CNP) shifts along proton concentration in solution, which can determine pH level of solution. Hybrid channel SG-FET sensors led to increase in pH sensitivity up to 500%, compared to pristine Gr SG-FET sensors. We confirmed plentiful hydroxyl groups on ZnO nanorod surface interact with protons in solution, which causes shifts of CNP. The morphology and electrical characteristics of hybrid channel SG-FET were characterized by FE-SEM and semiconductor parameter analyzer, respectively. Sensitivity and sensing mechanism of ZnO nanorods/Gr hybrid channel FET will be discussed in detail.

• Genes and Genomics
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• 제40권11호
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• pp.1199-1211
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• 2018

Soil acidification is one of major problems limiting crop growth and especially becoming increasingly serious in China owing to excessive use of nitrogen fertilizer. Only the STOP1 of Arabidopsis was identified clearly sensitive to proton rhizotoxicity and the molecular mechanism for proton toxicity tolerance of plants is still poorly understood. The main objective of this study was to investigate the transcriptomic change in plants under the low pH stress. The low pH as a single factor was employed to induce the response of the wheat seedling roots. Wheat cDNA microarray was used to identify differentially expressed genes (DEGs). A total of 1057 DEGs were identified, of which 761 genes were up-regulated and 296 were down-regulated. The greater percentage of up-regulated genes involved in developmental processes, immune system processes, multi-organism processes, positive regulation of biological processes and metabolic processes of the biological processes. The more proportion of down-regulation genes belong to the molecular function category including transporter activity, antioxidant activity and molecular transducer activity and to the extracellular region of the cellular components category. Moreover, most genes among 41 genes involved in ion binding, 17 WAKY transcription factor genes and 17 genes related to transport activity were up-regulated. KEGG analysis showed that the jasmonate signal transduction and flavonoid biosynthesis might play important roles in response to the low pH stress in wheat seedling roots. Based on the data, it is can be deduced that WRKY transcription factors might play a critical role in the transcriptional regulation, and the alkalifying of the rhizosphere might be the earliest response process to low pH stress in wheat seedling roots. These results provide a basis to reveal the molecular mechanism of proton toxicity tolerance in plants.

• 미생물학회지
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• 제53권4호
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• pp.297-303
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• 2017

루신-대응 조절 단백질(Lrp)은 18.8 kDa의 분자량을 갖는 글로벌 조절 단백질로서 대장균과 같은 장내세균과에서 많은 대사작용 오페론의 기능적 활성도를 조절한다. 단백질의 4차 구조를 규명하기 위한 목적으로 Lrp단백질 코드하는 유전자가 삽입된 재조합 플라스미드 pQE vector를 발현시킨 6 ${\times}$ His-tag Lrp 야생형과 $^3H$로 표지된 Lrp를 분리 정제한 후 cross linker들인 glutaraldehyde, 1,2,3,4-diepoxy-butane (DEB), ethylene glycol bis (succinimidyl succinate) (EGS)으로 cross link 실험을 수행하여 Lrp가 $0.3{\mu}M$ 이하의 낮은 농도에서나 $5{\mu}M$의 높은 농도에서 이량체, 사량체, 육량체, 팔량체로 존재할 수 있음을 확인하였다.

• 한국안전학회지
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• 제6권4호
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• pp.13-20
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• 1991

Ion-selective electrode responsive to the thiocynate ion prepared by using the quaternary ammonium salts as a active material and PVC as a membrane matrix. The effect of chemical structure and composition of active material, and the membrane thickness on the linear response. the detection limit, and Nernstian slope of the electrode studied. Under the above optimum conditions of membrane, the effect of pH and the selectivity coefficients to various interfering anions were compared and investigated. It was concluded that the functions of thiocynate ion-selective electrode(ISE) were closely related to the chemical structure of the quaternary ammonium salts. The linear response, and the detection limit of the electrode potential increased with the increase of the carbon chain length of the alkyl group in the quaternary ammonium salts in the ascending order of Aliquat 336T, TOAT, TDAT, and TDDAT. The optimum membrane thickness was 0.3mm. The electrode characteristics was better with the decrease of the concentration of active material, and the best concentration was 3 weight percent. The membrane potential was independent of the pH variation in the region from pH 2 to 12. The order of the selectivity coefficients is as follows：Cl $O_4$$^{[-10]}$ ＞ $I^{[-10]}$ ＞N $O_3$$^{[-10]}$ ＞B $r^{[-10]}$ ＞ $F^{[-10]}$ ＞C $l^{[-10]}$ ＞O $A_{c}$ $^{[-10]}$ 〓S $O_4$$^{2-}$.

• 대한화학회지
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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.

• Macromolecular Research
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• 제13권1호
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• pp.45-53
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• 2005

In this study, a series of highly swelling hydrogels based on sodium alginate (NaAlg) and polymethacryl­amide (PMAM) was prepared through free radical polymerization. The graft copolymerization reaction was performed in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N'-methylenebis­acrylamide (MBA) as a crosslinker. The crosslinked graft copolymer, alginate-graft-polymethacrylamide (Alg-g­PMAM), was then partially hydrolyzed by NaOH solution to yield a hydrogel, hydrolyzed alginate-graft-poly­methacrylamide (H-Alg-g-PMAM). During alkaline hydrolysis, the carboxamide groups of Alg-g-PMAM were converted into hydrophilic carboxylate anions. Either the Alg-g-PMAM or the H-Alg-g-PMAM was characterized by FTIR spectroscopy. The effects of the grafting variables (i.e., concentration of MBA, MAM, and APS) and the alkaline hydrolysis conditions (i.e., NaOH concentration, hydrolysis time, and temperature) were optimized systematically to achieve a hydrogel having the maximum swelling capacity. Measurements of the absorbency in various aqueous salt solutions indicated that the swelling capacity decreased upon increasing the ionic strength of the swelling medium. This behavior could be attributed to a charge screening effect for monovalent cations, as well as ionic cross-linking for multivalent cations. Because of the high swelling capacity in salt solutions, however, the hydrogels might be considered as anti-salt superabsorbents. The swelling behavior of the superabsorbing hydrogels was also measured in solutions having values of pH ranging from 1 to 13. Furthermore, the pH reversibility and on/off switching behavior, measured at pH 2.0 and 8.0, suggested that the synthesized hydrogels were excellent candidates for the controlled delivery of bioactive agents. Finally, we performed preliminary investigations of the swelling kinetics of the synthesized hydrogels at various particle sizes.

• 대한화학회지
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• 제42권1호
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• pp.84-91
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• 1998

고분자 전해질 복합체 형성이 poly(N-isopropyl acrylamide)(PNIPAAm) 공중합체의 저임계 용해온도 (lower critical solution temperature, LCST)에 미치는 영향을 조사하기 위하여 N-isopropyl acrylamide (NIPAAm)와 acrylic acid (AAc)를 선택하여 온도 감응성과 pH 감응성을 동시에 지니는 pH/온도감응성 고분자를 합성하였다.합성된 고분자들을 FT-IR과 적정실험을 통해 확인하였다. 고분자전해질로서 poly(allylamine) (PAA)과 poly(L-lysine)(PLL)을 사용하여 pH 2로부터 12에 이르는 넓은 범위의 pH 영역에서 고분자전해질 복합체 형성이 pH/온도감응성 고분자의 LCST에 미치는 영향을 조사하였다. 수용액상에서 poly(NIPAAm-co-AAc)중 PNIPAAm의 LCST는 cloud-point 측정 방법으로 결정하였다. 또한 역적정 실험을 통해 공중합체 중의 AAc 함량을 결정하고 AAc의 이온화 정도가 LCST에 미치는 영향을 조사하였다. 수용액상에서 poly(NIPAAm-co-AAc) 중 PNIPAAm의 LCST는 pH, 고분자전해질의 존재 유무, AAc의 함량, 그리고 고분자 사슬에 존재하는 전하밀도 등에 큰 영향을 받았다. 고분자전해질 복합체는 PAAc의 pKa와 PAA또는 PLL의 pKb 사이인 중성영역에서 형성됐으며 PNIPAAm의 LCST에 미치는 PLL의 영향은 PAA에 비해 크게 나타났다.

• Toxicological Research
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• 제16권2호
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• pp.95-100
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• 2000

In previous study, both constitutive expression and 3-methylcholanthrene (3MC)-mediated elevation of CYP1A2 mRNA were demonstrated in human hepatoma HepG2 cells by reverse transcription-polymerase chain reaction (RT-PCR), suggesting that HepG2 cells would be appropriate for the study of human CYP1A2 regulation(Chung and Bresnick, 1994). Further studies were conducted to determine the basis of this induction phenomenon that is observed in HepG2 cells. Since CYP1A1 gene, another polycyclic hydrocarbon(PH)-inducible gene, is regulated by PHs through their interactions via receptors with cis-elements, the 5'-flanking region of human CYP 1A2 gene was analyzed to search such responsive elements. The promoter activity of various lengths of CYP1A2 gene sequence (-3203/+58bp) was measured in transiently-transfected HepG2 cells by fusion constructs containing the CAT, hGH or luciferase genes as a reporter. This region of the CYP1A2 gene, although containing a XRE, was only weakly responsive (less than 2 fold induction) to 10 nM of TCDD or 1 $\mu$M 3 MC treatment. This small enhancement of promoter activity is inconsistent with the previous observation, i.e., 12 to 14 fold-enhanced CYP1A2 mRNA from 1 $\mu$M 3 MC treated HepG2 cells, suggesting that additional mechanisms would exist for PH-mediated induction of CYP1A2 in these cells.

• BMB Reports
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• 제37권2호
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• pp.139-143
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• 2004

The antioxidant responsive element (ARE) is a cis-acting regulatory element of genes encoding phase II detoxification enzymes and antioxidant proteins, such as NAD(P)H: quinone oxidoreductase 1, glutathione S-transferases, and glutamate-cysteine ligase. Interestingly, it has been reported that Nrf2 (NF-E2-related factor 2) regulates a wide array of ARE-driven genes in various cell types. Nrf2 is a basic leucine zipper transcription factor, which was originally identified as a binding protein of locus control region of ss-globin gene. The DNA binding sequence of Nrf2 and ARE sequence are very similar, and many studies demonstrated that Nrf2 binds to the ARE sites leading to up-regulation of downstream genes. The function of Nrf2 and its downstream target genes suggests that the Nrf2-ARE pathway is important in the cellular antioxidant defense system. In support of this, many studies showed a critical role of Nrf2 in cellular protection and anti-carcinogenicity, implying that the Nrf2-ARE pathway may serve as a therapeutic target for neurodegenerative diseases and cancers, in which oxidative stress is closely implicated.