• Bulletin of the Korean Chemical Society
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• 제5권4호
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• pp.140-145
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• 1984

A theory is given for determining the molecular weights of block copolymers from the experimental elution volume in GPC. Interaction effect between a sample of block copolymer and a column packing material as well as the size effect are separately considered for the first time applying the partial exclusion mechanism proposed by Dawkins. The molecular weight determination shows 6${\%}$ standard-deviation from the molecular weights measured by an osmometric method for eight block copolymers, which is much more improved result than other methods, e.g., the universal plot method (13 ${\%}$) and the Runyon's method (12 ${\%}$). The reason which explains the better result is that our theory takes into account the interaction effect correctly.

• Bulletin of the Korean Chemical Society
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• 제20권11호
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• pp.1323-1328
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• 1999

Interdiffusion between two partially miscible polymers of similar chemical structures with different molecular weights is characterized theoretically by using the reptation model for the interdiffusion. This model provides more reliable results than the early Rouse model for same molecular weights, compared with the experiments. Furthermore, by introducing the molecular weight ratio R into the reptation model, we can see the dynamic effect of molecular weight on the diffusion behaviors of the asymmetric system. Near the critical point the diffusion behaviors of asymmetric binary polymer mixtures are well characterized by the interfacial width W(t), the mass transport M(t) for the different values of the Flory Χ parameter and different molecular weight ratios ofpolymers of the diffusion couple. These two quantities and composition profiles by this model give betteragreement with experiments.

• Archives of Pharmacal Research
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• 제12권2호
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• pp.88-93
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• 1989

In order to obtain some informations about the effect of molecular weight on the release rate of drug from drug carrier, two types of poly-L-glutamic acid (PLGA)-cytarabine (ara-C) conjugates, PLGA-ara-C:I and PLGA-ara-C:II, were synthesized using two types of PLGA having different average molecular weight, 43,000 and 77,800, respectively. The PLGA-ara-C conjugates were synthesized by mixed anhydride method and found to be covalently linked. Both types of conjugates charged negatively at biological pH. The pH-dependent release rate of ara-C was observed in both cases, and the release rate was accelerated in basic, acidic conditions (the k values were 0.015 $day^{-1}$ at pH 7.0, 0.024 $day^{-1}$ at pH 5.0, and 0.059 $day^{-1}$ at pH 9.0 in the case of PLGA-ara-C:I) and in the presence of pretense. The time required for the release of 16.5% of ara-C from PLGA-ara-C:I were 8 hr and 144 hr in the presence and absence of protease, respectively. Although both types of conjugates showed similar drug substitution ratio, they showed different release rates. Between the two types of conjugates, PLGA-ara-C:II showed the faster release rate (0.030 vs 0.042 $day^{-1}$ in pH 7.4 phosphate buffer solution at $37^{\circ}C$) and the smaller activation energy for the release of drug (12.5 vs 7.7 Kcal/mol) than PLGA-ara-C:I. The characteristic effect of molecular weight on the release rates of PLGA-ara-C conjugates suggests that the drug release rate might be effectively controlled over a prolonged period of time by the combined use of the different types of PLGA-ara-C conjugates having different molecular weights.

• Journal of Nutrition and Health
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• 제30권7호
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• pp.751-769
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• 1997

This study was performed to investigate the effect of chitosan and NOCC from different sources and of different molecular weights on cadmium toxicity. Sprague-Dawley rats were blocked into 26 groups according to body weight, and were raised for 4 weeks. Cadmium chloride was given at the level of 0 or 400 ppm in diet. Various forms of chitosan and NOCC were given at the level of 0 or 4%(w/w) of diet. Cd toxicity was alleviated by various chitosan and NOCC supplements. However, the alleviating effects were different with fiber source(crab and shrimp), type(chitosan and NOCC), and molecular weight (low, medium, and high). Molecular weight had no significant effect. Compared with shrimp-source-fiber-fed groups, crab-source-fiber-fed groups showed lower Cd concentrations in blood and kidney, lower kidney metallothionein concentration, and lower liver and kidney MT-Cd contents. Compared with NOCC -fed groups, chitosan-fed groups showed lower intestine and liver Cd concentrations, lower liver and kidney MT concentrations and MT-Cd content, and higher fecal Cd excretion. Among cadmium-exposed group, low molecular weight shrimp chitosan group showed low Cd concentrations of liver and kidney, high fecal Cd excretions, and the lowest intestine and liver MT concentrations and liver MT-Cd content. In summary, a crab source fiber was more effective than shrimp source fiber, chitosan was more effective than NOCC, and the most effective one in alleviating Cd toxicity was low molecular weight shrimp chitosan.

• Elastomers and Composites
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• 제48권4호
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• pp.294-299
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• 2013

수용성 단량체인 메타크릴산 (MAA)을 단량체로 potassium persulfate (KPS)를 개시제로 이용하여 $70^{\circ}C$에서 $90^{\circ}C$ 사이의 선택된 온도에서 용액중합을 진행하였다. 물에 대한 메타크릴산의 농도가 감소하거나 개시제의 농도가 증가하면 분자량은 감소하였다. 중합반응온도는 폴리메타크릴산 (PMAA)의 분자량에 크게 영향을 미치지 않았다. Weissenberg 효과는 대부분의 반응온도에서 나타났으며, $90^{\circ}C$에서는 약하게 관찰되었다. 대부분의 중합반응에서 분산성지수는 1.5 이하로 관찰되었다. 교반속도가 증가하면서 분자량은 점진적으로 증가하다, 교반속도가 800 rpm에 이르면서 수평균 및 중량평균분자량이 동일하게 791,000 g/mol의 분자량을 갖는 단분산성의 PMAA가 구하여졌다. 유리전이온도는 $162^{\circ}C$로 측정되었다.

• 한국수산과학회지
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• 제54권4호
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• pp.543-551
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• 2021

Changes in gluten surface hydrophobicity, which play an important role in the functional characteristics of protein, were measured according to various protein concentrations, pH levels, electrolytes concentrations, and alginate molecular weights using 8-anilino-1-naphthalene sulfonic acid (ANS) as a fluorescent probe. Gluten surface hydrophobicity decreased as gluten concentration increased, reaching a maximum pH of 7.0. The effects of alginate molecular weights and alginate concentration on the surface hydrophobicity, emulsifying activity index (EAI), and emulsion stability index (ESI) of gluten-sodium alginate dispersion (GAD) were measured. Gluten surface hydrophobicity rapidly increased the asl NaCl concentration of gluten solution up to 300 mM and showed no significant increase above 300 mM. However, gluten surface hydrophobicity notably decreased until the concentration of CaCl₂ and MgCl₂ reached 30 mM, indicating no significant variations above 30 mM. GAD surface hydrophobicity increased as the concentration and molecular weight of sodium alginate increased, however, gluten concentration increased as the GAD surface hydrophobicity decreased. The EAI and ESI of GAD increased as both molecular weight and concentration of sodium alginate increased.

• Journal of Nutrition and Health
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• 제30권7호
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• pp.770-780
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• 1997

This study was performed to investigate the effect of chitosan and NOCC from different sources and of different molecular weights on lipid metabolism. Sprague-Dawley rats were blocked into 26 groups according to body weight, and were raised for 4 weeks. Cadmium chloride was given at the level of 0 or 400 ppm in diet. Various chitosan and NOCC sources were given at the level of 0%(w/w) of diet. Total serum cholesterol and serum triglyceride concentrations were little affected by chitosan and NOCC supplements. However, HDL-cholesterol concentration and HDL : total cholesterol ratio were increased , and liver lipid, cholesterol , and triglyceride concentration were decreased by chitosan and NOCC supplements. The cholesterol and lipid lowering activity depends on fiber sources(crab and shrimp); type (chitosan and NOCC); and molecular weight(low , medium , and high). Among cadmium-free groups, chitosan-fed groups showed greater activity than NOCC -fed groups in lowering cholesterol and lipid levels, and greater fecal excretion of lipids and bile acids. Crab chitosans were more effective in cholesterol and lipid lowering activity than shrimp chitosans. The group fed high molecular weight crab chitosan showed the highest fecal excretion of lipids and bile acids. This indicated that high molecular weight crab chitosan was most effective in interfering with cholesterol and lipid absorption.

• 한국식품저장유통학회지
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• 제24권5호
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• pp.688-696
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• 2017

본 연구는 불등풀가사리로부터 분리된 조다당류와 산가수분해된 다당류의 분자량에 따른 이화학적 품질특성과 항산화 활성 및 피부 주름 개선 효과를 확인하였다. 산가수분해 분자량별 다당류의 수율은 100 kDa 이상에서 29.6%로 가장 높았으며, 10 kDa 이하에서 10.4%로 가장 낮았다. 이화학적 특성으로 총당, uronic acid, sulfate 함량은 100 kDa 이상에서 각각 85.82%, 32.85 g/100g 및 39.04%로 조다당에 비해 증가하였다. 색도은 분자량이 증가함에 따라 L 값, a 값 및 b 값이 감소하였으며, 점도는 분자량이 높을수록 증가하였다. ORAC 활성은 100 kDa 이상에서 $180.07{\mu}M$을 나타내어 조다당 $34.70{\mu}M$에 비해 항산화활성이 우수하였다. L132 세포 사멸에 대한 보호효과는 $H_2O_2$ 처리 구간대비 분자량 100 kDa 이상($0.5-5{\mu}g/mL$)에서 87.34-103.85%로 세포 활성이 증가하여 세포 보호효과를 나타내었다. MMP-1 활성은 세포에 UVB를 조사한 후 분자량 100 kDa 이상 $0.05-0.5{\mu}g/mL$ 농도에서 69.67-100.87%의 저해 활성을 나타내었다. 또한, pro-collagen 생합성 역시 UVB를 조사한 후 분자량 100 kDa 이상 $0.05-0.5{\mu}g/mL$ 농도에서 64.91-77.80%의 합성능을 나타내어 농도 의존적으로 증가하는 것을 확인하였다. 따라서, 불등풀가사리 유래 산가수분해된 다당류의 분자량에 따른 주름 개선 효과를 통해 피부 항노화 기능성 소재로 다양하게 활용 가능할 것으로 사료된다.

• 분석과학
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• 제15권3호
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• pp.229-235
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• 2002

폴리스티렌 시료의 표면을 플라즈마 이온주입(PSII) 기술로 처리하여 친수성을 향상시켰다. 친수성이 향상된 표면은 시간이 지남에 따라 원래 성질인 소수성으로 되돌아가려는 특성 (aging effect)이 있는데 본 연구에서는 각각 분자량이 다른 폴리스티렌 필름을 이용하여 분자량에 따른 에이징 효과를 살펴보았다. 무게평균 분자량이 각각 $M_w$ = 760, 2430, 31600, 115700, 280000, 903600 인 폴리스티렌을 가스종류와 펄스전압 등의 PSII 실험 변수에 따라 표면 친수성 변화를 측정하였고 PSII 처리 후 보관온도를 달리하여 분자량에 따른 에이징 정도를 관찰하였다. 분자량이 큰 폴리스티렌이 시간에 따른 에이징 현상이 적게 일어났으며 펄스전압과 보관온도가 높은 조건에서도 사슬이 긴 폴리스티렌이 에이징이 덜 되었다. 물 접촉각을 측정하여 표면 친수성을 나타내었으며 처리 후 표면 구조 변화를 관찰하기 위하여 SEM과 AFM을 이용하였고, TOF-SIMS와 XPS를 통하여 표면에 생성된 작용기들을 확인하였다.

• 한국식품영양과학회지
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• 제30권2호
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• pp.277-282
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• 2001

The effects of chitosans with two different molecular weights (150 and 37 kDa) on the clarification of persimmon vinegar were investigated. The coagulated solids increased with increasing chitosan concentrations. Chitosan treatment had no effect on pH and acidity. Turbidity, browning, contents of tannin and soluble solids decreased with increasing chitosan concentrations. An increase in chitosan concentration resulted in an increase in color L* value and a decrease in a* and b* values. Reduction in turbidity and tannin contents somewhat differed depending on the molecular weights of chitosan. In sensory evaluation, chitosan treatment did not affect color and flavor over all concentrations tested. However, astringent taste was noticeably strong by treatment with 500mg/L chitosan, resulting in low overall acceptability. Therefore, the most effective clarification of persimmon vinegar was achieved by treatment with 400mg/L chitosan, irrespective of molecular weight.