• 폴리머
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• 제30권1호
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• pp.28-34
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• 2006

메톡시폴리에틸렌글리콜(MPEG)과 카프로락톤(CL)과 L-락타이드(LA)로 구성된 MPEG-PCLA 블록공중합체의 단량체를 다양한 비율로 $Sn(Oct)_2$의 존재 하에서 개환중합을 통해 합성하였다. MPEG-PCLA 블록공중합체의 특성은 $^1H-NMR$, GPC, DSC 그리고 XRD를 이용하여 결정하였다. 동역학적 변화를 측정하기 위하여 $Sn(Oct)_2$의 존재 하에서 MPEG-PCLA 블록공중합체의 중합 시 중합시간, 온도, 첨가하는 촉매의 양을 달리하면서 중합을 실시하였다. 그 결과 $110\;^{\circ}C$의 중합온도와 첨가하는 촉매의 양은 개시제 대비 1.2배의 경우에서 가장 높은 중합률을 보였다. 또한 합성된 블록공중합체의 수용액상에서의 시간에 따른 생분해 거동은 GPC를 이용한 분자량 분포의 비교를 통해 측정하였다. 합성된 블록공중합체의 생분해 거동을 측정한 결과 MPEG-PCLA 블록공중합체의 L-락타이드 함량이 증가할수록 생분해성도 증가하는 것을 확인하였다. 본 연구를 통해 MPEG-PCLA 블록공중합체의 $Sn(Oct)_2$의 존재 하에서 개환중합을 실시함에 있어 다양한 중합조건에 따른 중합속도를 확인하였으며 MPEG-PCLA 블록공중합체는 PCLA 블록의 PCL 대비 PLA의 함량 비율에 따라 생분해 기간을 조절할 수 있는 가능성을 확인하였다.

• 폴리머
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• 제32권2호
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• pp.143-149
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• 2008

생체적합성을 가진 친수성 poly(ethylene glycol)(PEG)블록과 생분해성 고분자인 Poly(D,L-lactide)(PLA) 또는 poly(lactide-co-glycolide)(PLGA)를 소수성 블록으로 하는 양친성 이중 블록공중합체를 합성하여 난용성 당뇨병 치료제인 pioglitazone의 가용화를 위한 고분자 미셀을 제조하였다. PEG 말단으로부터 LA의 개환중합에 의해 합성된 고분자의 화학적 조성과 분자량은 반응액 내 당량비로 조절하였고, 합성된 고분자는 수용액 상에서 $10{\sim}30\;nm$ 크기인 구형의 자기조립 미셀을 형성하였다($CMC=0.001{\sim}0.0076\;mg/mL$). 투석법과 고체분산법을 이용하여 약물을 봉입한 후 AFM, DLS, HPLC 분석을 통하여 미셀의 특성을 비교하였다. 결론적으로 PEG-PLA(또는 PLGA) 공중합체를 이용한 고체분산법을 통해 pioglitazone을 효과적으로 가용화시킬 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2616-2622
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• 2013

A novel zwitterionic monomer 3-[(2-acrylamido)dimethylammonio]propanesulfonate (DMADAS) was designed and synthesized in this study. Then it was polymerized with acrylamide (AM) by free radical polymerization in 0.5 mol/L NaCl solution with ammonium persulfate ($(NH_4)_2S_2O_8$) and sodium sulfate ($NaHSO_3$) as initiator. The structure and composition of DMADAS and acrylamide-3-[(2-acrylamido)-dimethylammonio]propanesulfonate copolymer (P-AM-DMADAS) were characterized by FT-IR spectroscopy, $^1H$ NMR and elemental analyses. Isoelectric point (IEP) of P-AM-DMADAS was tested by nanoparticle size and potential analyzer. Solution properties of copolymer were studied by reduced viscosity. Antipolyelectrolyte behavior was observed and was found to be enhanced with increasing DMADAS content in copolymer. The results showed that the viscosity of P-AM-DMADAS is 5.472 dl/g in pure water. Electrolyte was added, which weakened the mutual attraction between sulfonic acid group and quaternary ammonium group. The conformation became loose, which led to the increase of reduced viscosity. The ability of monovalent and divalent cation influencing the viscosity of zwitterionic copolymer obeyed the following sequence: $Li^+$ < $Na^+$ < $K^+$, $Mg^{2+}$ < $Ca^{2+}$ < $Ba^{2+}$, and that of anion is in the order: $Cl^-$ < $Br^-$ < $I^-$, $CO{_3}^{2-}$ > $SO{_3}^{2-}{\approx}SO{_4}^{2-}$.

• 대한화학회지
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• 제46권3호
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• pp.233-240
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• 2002

본 연구에서는 잠재성 양이온 개시제 (N-benzyl pyrazinium hexafluoroantiminate, BPH)를 이용한 에폭시/폴리우레탄 블랜드계의 혼합조성에 따른 경화거동과 유변학적 특성 그리고 기계적 물성 변화에 대하여 연구하였다. 블랜드계의 반응성은 DSC를 이용하여 반응 온도에 따른 전환률을 구하여 측정하였으며, 유변학적 특성은 레오미터를 이용한 등온 실험을 통하여 측정하였고, 가교 활성화에너지(Ec)는 겔화 시간과 경화 온도를 이용하여 Arrhenius 방정식으로 구하였다. 한편, 경화된 시편의 기계적 물성은 충격강도 실험을 통하여 측정하였다. 실험결과, 블랜드계의 열잠재성 촉매로 사용된 BPH는 어떤 공개시제 없이도 우수한 촉매 특성을 나타내었다. 본 블랜드계의 가교 활성화에너지 및 충격강도는 PU가 30 wt% 첨가되었을 때 최대를 나타내었는데, 이는 EP와 PU간의 수소결합으로 인한 치밀한 가교밀도의 증가 때문이라고 사료된다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권4호
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• pp.344-350
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• 2006

Thermoplasma acidophilum is a thermoacidophilic archaeon that grows optimally at $59^{\circ}C$ and pH 2. Along with another thermoacidophilic archaeon, Sulfolobus solfataricus, it is known to metabolize glucose by the non-phosphorylated Entner-Doudoroff (nED) pathway. In the course of these studies, the specific activities of glyceraldehyde dehydrogenase and glycerate kinase, two enzymes that are involved in the downstream part of the nED pathway, were found to be much higher in T. acidophilum than in S. solfataricus. To characterize glycerate kinase, the enzyme was purified to homogeneity from T. acidophilum cell extracts. The N-terminal sequence of the purified enzyme was in exact agreement with that of Ta0453m in the genome database, with the removal of the initiator methionine. Furthermore, the enzyme was a monomer with a molecular weight of 49kDa and followed Michaelis-Menten kinetics with $K_m$ values of 0.56 and 0.32mM for DL-glycerate and ATP, respectively. The enzyme also exhibited excellent thermal stability at $70^{\circ}C$. Of the seven sugars and four phosphate donors tested, only DL-glycerate and ATP were utilized by glycerate kinase as substrates. In addition, a coupled enzyme assay indicated that 2-phosphoglycerate was produced as a product. When divalent metal ions, such as $Mn^{2+},\;CO^{2+},\;Ni^{2+},\;Zn^{2+},\;Ca^{2+},\;and\;Sr^{2+}$, were substituted for $Mg^{2+}$ the enzyme activities were less than 10% of that obtained in the presence of $Mg^{2+}$. The amino acid sequence of T. acidophilum glycerate kinase showed no similarity with E. coli glycerate kinases, which belong to the first glycerate kinase family. This is the first report on the biochemical characterization of an enzyme which belongs to a member of the second glycerate kinase family.

• Nutrition Research and Practice
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• 제8권2호
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• pp.132-137
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• 2014

BACKGROUND/OBJECTIVES: In this study, the apoptogenic activity and mechanisms of cell death induced by hexane extract of aged black garlic (HEABG) were investigated in human leukemic U937 cells. MATERIALS/METHODS: Cytotoxicity was evaluated by MTT (3-(4, 5-dimethyl-thiazol-2-yl)-2, 5-diphenyl tetrazoliumbromide) assay. Apoptosis was detected using 4,6-diamidino-2-phenyllindile (DAPI) staining, agarose gel electrophoresis and flow cytometry. The protein levels were determined by Western blot analysis. Caspase activity was measured using a colorimetric assay. RESULTS: Exposure to HEABG was found to result in a concentration- and time-dependent growth inhibition by induction of apoptosis, which was associated with an up-regulation of death receptor 4 and Fas legend, and an increase in the ratio of Bax/Bcl-2 protein expression. Apoptosis-inducing concentrations of HEABG induced the activation of caspase-9, an initiator caspase of the mitochodrial mediated intrinsic pathway, and caspase-3, accompanied by proteolytic degradation of poly(ADP-ribose)-polymerase. HEABG also induced apoptosis via a death receptor mediated extrinsic pathway by caspase-8 activation, resulting in the truncation of Bid, and suggesting the existence of cross-talk between the extrinsic and intrinsic pathways. However, pre-treatment of U937 cells with the caspase-3 inhibitor, z-DEVD-fmk, significantly blocked the HEABG-induced apoptosis of these cells, and increased the survival rate of HEABG-treated cells, confirming that HEABG-induced apoptosis is mediated through activation of caspase cascade. CONCLUSIONS: Based on the overall results, we suggest that HEABG reduces leukemic cell growth by inducing caspase-dependent apoptosis through both intrinsic and extrinsic pathways, implying its potential therapeutic value in the treatment of leukemia.

• The Journal of Advanced Prosthodontics
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• 제7권5호
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• pp.386-391
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• 2015

PURPOSE. The purpose of this preliminary study was to investigate the effects of adding 4,4'-bis(N,N-diethylamino) benzophenone (DEABP) as a co-initiator to a binary photoinitiating system (camphorquinone-amine) to analyze on the degree of conversion (DC) of a light-cured resin for dental 3D printing. MATERIALS AND METHODS. Cylindrical specimens (N=60, n=30 per group, ${\phi}5mm{\times}1mm$) were fabricated using bisphenol A glycerolate dimethacrylate (BisGMA) both with and without DEABP. The freshly mixed resins were exposed to light in a custom-made closed chamber with nine light-emitting diode lamps (wavelength: 405 nm; power: $840mW/cm^2$) for polymerization at each incidence of light-irradiation at 10, 30, 60, 180, and 300 seconds, while five specimens at a time were evaluated at each given irradiation point. Fourier-transform infrared (FTIR) spectroscopy was used to measure the DC values of the resins. Two-way analysis of variance and the Duncan post hoc test were used to analyze statistically significant differences between the groups and given times (${\alpha}$=.05). RESULTS. In the DEABP-containing resin, the DC values were significantly higher at all points in time (P<.001), and also the initial polymerization velocity was faster than in the DEABP-free resin. CONCLUSION. The addition of DEABP significantly enhanced the DC values and, thus, could potentially become an efficient photoinitiator when combined with a camphorquinone-amine system and may be utilized as a more advanced photopolymerization system for dental 3D printing.

• Asian Pacific Journal of Cancer Prevention
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• 제16권9호
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• pp.3753-3758
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• 2015

Background: Polymeric nanoparticles are attractive materials that have been widely used in medicine for drug delivery, with therapeutic applications. In our study, polymeric nanoparticles and the anticancer drug, chrysin, were encapsulated into poly (D, L-lactic-co-glycolic acid) poly (ethylene glycol) (PLGA-PEG) nanoparticles for local treatment. Materials and Methods: PLGA: PEG triblock copolymers were synthesized by ring-opening polymerization of D, L-lactide and glycolide as an initiator. The bulk properties of these copolymers were characterized using 1H nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. In addition, the resulting particles were characterized by scanning electron microscopy. Results: The chrysin encapsulation efficiency achieved for polymeric nanoparticles was 70% control of release kinetics. The cytotoxicity of different concentration of pure chrysin and chrysin loaded in PLGA-PEG ($5-640{\mu}M$) on T47-D breast cancer cell line was analyzed by MTT-assay. Conclusions: There is potential for use of these nanoparticles for biomedical applications. Future work should include in vivo investigation of the targeting capability and effectiveness of these nanoparticles in the treatment of breast cancer.

• 공업화학
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• 제4권2호
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• pp.284-290
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• 1993

AN을 친수성 공단량체로 하고, KPS를 개시제로 하여 St/BD의 무유화제 유화중합을 해 본 결과, 전환율 50% 이하에서 Rp의 $[AN]^n$ 및 $[KPS]^n$에 대한 의존성은 각각 n=1.617-1.050 및 n=0.83-0.96을 보였으며, 입자수 밀도 (Np)의 $[AN]^n$ 및 $[KPS]^n$ 의존성은 n=1.533 및 n=0.733이었다. 그리고 pH=5, 총단량체 (g)/물(g)=0.5일 때 전환율이 가장 높았으며, 얻어진 SBR은 상용 SBR에 비해 가류속도가 훨씬 빠르고, tensile strength, 300% modulus, elongation 등 기본 물성에서 열세였다.

• 공업화학
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• 제19권4호
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• pp.370-375
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• 2008

비수계 분산(NAD : non-aqueous dispersion) 중합을 이용하여 친환경적인 아크릴 수지를 합성시 최적의 중합조건에 대해 연구하였다. 중합된 고분자 입자들 간의 응집을 방지하기 위한 안정제의 적정량은 20 wt%로 나타났고 안정된 NAD 상태를 유지하기 위한 혼합 용매의 적정 혼합비는 지방족과 방향족 용매의 비율이 80 : 20인 것으로 나타났다. NAD 수지의 점도는 반응시간뿐만 아니라 개시제의 양 및 교반 속도 등에 의해 영향을 받는 것으로 나타났다. 또한 NAD 수지의 입자 크기 및 분포도, 안정제의 양, 개시제의 농도 등에 의해 영향을 받는 것을 확인하였다. 단량체의 투입시기는 단량체를 초기에 모두 투입하면 용매의 극성이 증가하여 입자의 크기가 커져서 입자의 안정성이 저하되므로 단계별로 지속적으로 투입할 필요가 있는 것으로 관찰되었다.