• 펄프종이기술
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• 제33권3호
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• pp.24-28
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• 2001

The utilization of wastepaper as a papermaking raw material is everlastingly required for the environmental protection of earth. However the recycling of wastepaper for this purpose cause another problem such as the increasing of the load of wastewater treatment, lower strength properties of paper, and poor printability, etc. The interest in the development of the environmentally friendly deinking technology is increased continuously. Thus, our research team have tried to apply the ozone to the deinking of white ledger and ONP, and obtained the positive results which can be considered as an alternative method for the conventional deinking method. The purpose of this study is to investigate the mechanism of ozone deinking. Styrene acrylate and polystyrene were treated with ozone and measured the change of molecular weight with the GPC. The molecular weight distribution obtained with GPC showed only slight increase by the ozone treatment, and gel formation by the polymerization was observed. Therefore the removal of ink particles with ozone treatment seems to be facilitated by the increase of the brittleness and decrease of adhesive property.

• Bulletin of the Korean Chemical Society
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• 제9권4호
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• pp.248-251
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• 1988

Mechanism of electrochemical polymerization of pyrrole (Py) on a Pt electrode in acidic aqueous solutions was studied by means of potentiostatic measurements, cyclic voltammetry and chronopotentiometry. Pyrrole molecule appeared to be initially oxidized via two-electron transfer step to produce oxidized pyrrole ion ($Py^+$), which was coupled with a non-oxidized pyrrole to yield a dimerized species, Py-Py. The Py-Py thus formed was further oxidized again via two-electron transfer step, which was followed by coupling with non-oxidized monomer and by concomitant expulsion of a $H^+$. Then the latter chain extension process was repeated. The chain extension and polypyrrole oxidation reactions occurred competitively.

• 접착 및 계면
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• 제2권4호
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• pp.10-23
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• 2001

생성을 목적으로 하는 그라프트 중합체를 유화제로 하여 유화 그라프트중합을 실시하는 경우는 대체로 그라프트 효율 및 % 골격(backbone) 중합체의 전환율 값은 높으나, 메칠메타아크릴레이트(MMA) 전환율 및 % 그라프트율값 들이 낮다. 이와 같은 결점을 보완하기 위하여 중합계에 비 수용성 용매 및 수용성 용매를 사용하여서 이들 용매의 각각의 효과 및 두종의 용매를 조합한 복합효과 그리고 용매 공존하에서의 교반속도의 영향을 고찰하는 한편, 고분자 유화제의 조성에 따른 MMA의 유화용량, 평균 입경 및 그라프트된 알긴산의 입자 표면 밀도 등을 조사하여 그 중합 메카니즘을 고찰하였다. 그 결과, 고분자 유화제의 그라프트된 폴리메칠메타아클레이트(PMMA) 함량이 클수록 중합체 콜로이드의 MMA 유화용량 및 평균입경은 커지는 반면, 입자 표면의 그라프트된 알긴산의 밀도는 감소하였다. 비 수용성 용매를 MMA에 혼합시켜 중합시키는 경우는 그라프트 효율 및 골격 중합체의 전환율 값들의 저하없이 MMA 전환율 및 % 그라프트 값을 향상 시킬 수 있었으며, 그 효과는 PMMA에 대하여 침전제가 되는 용매가 양용매인 용매에 비하여 컸다. 수용성 용매는 그라프트 효율, 골격 중합체의 전환율을 다소 저하시키는 상태에서 MMA 전환율 및 % 그라프트 값을 보다 크게 향상시켰으며, 그 효과는 PMMA에 침전제인 메탄올에서 보다 현저하였다. 용매 첨가에서 교반속도의 변화에 용매 무첨가시의 MMA 전환율값은 2배 이상, % 그라프트값은 거의 3배로, SA 전환율과 그라프트 효율값은 95% 이상 향상시킬 수 있었다.

• Archives of Pharmacal Research
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• 제26권10호
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• pp.826-831
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• 2003

ADP-ribose pyrophosphatase (ADPRase) hydrolyzes ADP-ribose (ADPR) into AMP and ribose-5'-phosphate. It is classified into two groups, $Mg^{2+}$-dependent and $Mg^{2+}$-independent ADPRase, depending on its $Mg^{2+}$requirement. Here, we purified $Mg^{2+}$-dependent ADPRase from rabbit liver and examined what factors affect $Mg^{2+}$ requirement. The purified enzyme showed a single band with the molecular weight of 34 kDa on SDS-PAGE both in the presence and absence of 2-mercaptoethanol. The molecular weight of the native enzyme calculated by gel filtration was 68 kDa, indicating that ADPRase is a dimer made up of two identical subunits. $Mg^{2+}$-dependent ADPRase with the highest ADPR affinity had a $K_m$ of 160$\pm$10 $\mu$M and a pH optimum of around pH 9.5. Treatment of the purified ADPRase with heated cytosol fractions at 37$^{\circ}C$ for 3 h caused some changes in the chemical properties of the enzyme, including an increase in molecular weight, a decrease in solubility, and a loss of $Mg^{2+}$-dependency. The molecular weight of the cytosol-treated ADPRase measured by gel filtration was over 420 kDa, suggesting, for the first time, that ADPRase could be polymerized by undefined cytoplasmic factors, and that polymerization is accompanied by changes in the solubility and metal ion dependency of the enzyme.

• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.98-107
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• 2015

PURPOSE. The aim of this study was to appraise the some mechanical properties of polymethyl methacrylate based denture base resin polymerized by copolymerization mechanism, and to investigate the cytotoxic effect of these copolymer resins. MATERIALS AND METHODS. 2-hydroxyethyl methacrylate (HEMA) and isobutyl methacrylate (IBMA) were added to monomers of conventional heat polymerized and injection-molded poly methyl methacrylate (PMMA) resin contents of 2%, 3%, and 5% by volume and polymerization was carried out. Three-point bending test was performed to detect flexural strength and the elasticity modulus of the resins. To determine the statistical differences between the study groups, the Kruskall-Wallis test was performed. Then pairwise comparisons were performed between significant groups by Mann-Whitney U test. Agar-overlay test was performed to determine cytotoxic effect of copolymer resins. Chemical analysis was determined by FTIR spectrum. RESULTS. Synthesis of the copolymer was approved by FTIR spectroscopy. Within the conventional heat-polymerized group maximum transverse strength had been seen in the HEMA 2% concentration; however, when the concentration ratio increased, the strength decreased. In the injection-molded group, maximum transverse strength had been seen in the IBMA 2% concentration; also as the concentration ratio increased, the strength decreased. Only IBMA showed no cytotoxic effect at low concentrations when both two polymerization methods applied while HEMA showed cytotoxic effect in the injection-molded resins. CONCLUSION. Within the limitations of this study, it may be concluded that IBMA and HEMA may be used in low concentration and at high temperature to obtain non-cytotoxic and durable copolymer structure.

• Reproductive and Developmental Biology
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• 제37권4호
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• pp.169-174
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• 2013

Sperm capacitation refers to polymerization of filamentous (F)-actin from globular (G)-actin. While the role of actin-related protein 2/3 (Arp2/3) complex in actin polymerization is well appreciated, the underlying mechanism(s) and its relationship with capacitation are poorly understood. Therefore, to evaluate the potential role of Arp2/3 complex on capacitation, bovine spermatozoa were incubated with multiple doses (1, 10 and $100{\mu}M$) of CK-636, an inhibitor of Arp2/3 complex with heparin. The cellular localization of the Arp2/3 complex in spermatozoa was identified by immunohistochemistry, whereas western blot was also applied to detect the protein tyrosine phosphorylation of sperm proteins. Additionally, sperm motility and kinematic parameters were evaluated using a computer-assisted sperm analysis system. CK-636 resulted in significant changes in the ratio of Arp2/3 complex localization between acrosome and equatorial region of the spermatozoa. Short-term exposure of spermatozoa to $100{\mu}M$ of CK-636 significantly decreased sperm motility, however a non-detectable effect on protein tyrosine phosphorylation was observed during capacitation. On the basis of these results, we propose that Arp2/3 complex is associated with morphological changes during capacitation and compromised sperm motility.

• Archives of Pharmacal Research
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• 제27권4호
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• pp.436-441
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• 2004

SJ compounds (SJ8002 and related compounds) are a group of novel anticancer agents (Cho, Chung, Lee, Kwon, Kang, Joo, and Oh. PCT/KR02/00392). To explore the anticancer mechanism of these compounds, we examined the effect of SJ8002 on microtubules of six human cell lines. At a high concentration ($2\;{\mu}g/mL$), SJ8002 effectively disrupted microtubules of the six cell lines within 1 h. At lower concentrations ($0.05\~1.0\;{\mu}g/mL$), the antimicrotubule activity of SJ8002 varied defending on cell lines. The inhibition of in vitro polymerization of pure tubulin by SJ8002 suggested that SJ8002 acts on free tubulin, inhibits the polymerization of tubulin dimer into microtubules, and hence induces the depolymerization of microtubules.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.156-157
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• 2006

Quasi-living polymerization conditions for the copolymerization of ethylene and functionalized norbornenes can be achieved by using an initiator system comprising $[N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-propanamidato-{\kappa}^2N,O]Ni({\Box}^1-CH_2Ph)(PMe_3)\;and\;Ni(COD)_2$. It is possible with this polymerization system to obtain block-copolymer and tapered structures. The latter form microdomains similar to those of standard block co-polymers. The mechanism of the reaction will also be discussed.

• Macromolecular Research
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• 제16권2호
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• pp.169-177
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• 2008

This paper reports a facile synthesis of new water-soluble poly(ethylene oxide) (PEO)-based amphiphilic block copolymers showing pH sensitive phase transition behaviors. The copolymers were prepared by atom transfer radical polymerization (ATRP) of methacrylamide type of monomers carrying a sulfonamide group using a PEO-based macroinitiator and a Cu(I)Br/$Me_6TREN$ catalytic system in aqueous media. The resulting polymers were characterized by a combination of $^1H$-NMR, size exclusion chromatography, and UV/Visible spectrophotometeric analysis. The micellization of the block copolymers as a drug-loading mechanism in aqueous media using fluorescein salt was examined as a function of pH. The stable micelle formation and its loading efficacy suggest that the block copolymers can be used as precursors for drug-nanocontainers.

• Membrane and Water Treatment
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• 제8권4호
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• pp.323-336
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• 2017

The main challenge in many applications of acetic acid is acid dehydration and its recovery from wastewater streams. Therefore, the performance of polyamide thin film composite is evaluated to separate acetic acid from water. To reach this goal, the formation of polyamide layer on polysulfone support membrane was investigated via interfacial polymerization (IP) of meta-phenylenediamine (MPD) in water with trimesoyl chloride (TMC) in hexane. Also, the effect of synthesis conditions, such as concentration of monomers and curing temperature on separation of acetic acid from water were investigated by reverse osmosis process. Moreover, the separation mechanism was discussed. The solute permeation was carried out under applied pressure of 5 bar at $25^{\circ}C$. Surface properties of TFC membrane were characterized by ATR-FTIR, SEM and AFM. The performance test indicated that 3.5 wt% of MPD, 0.35 wt% of TMC and curing temperature of $75^{\circ}C$ are the optimum conditions. Moreover, the permeate flux was $4.3{\frac{L}{m^2\;h}}$ and acetic acid rejection was about 43% at these conditions.