• Title/Summary/Keyword: molecular weight distribution

Search Result 431, Processing Time 0.024 seconds

Contrasting Correlation in the Inhibition Response of ADP-induced Platelet Aggregation and the Anti-coagulant Activities of Algal fucoidans Derived from Eisenia bicyclis and Undaria pinnatifida sporophylls (Mekabu)

  • Jeong, Eui-Sook;Yoon, Yeon-Hee;Kim, Jong-Ki
    • Fisheries and Aquatic Sciences
    • /
    • v.12 no.3
    • /
    • pp.194-202
    • /
    • 2009
  • Sulfated fucans are known to have both anti-thrombotic and anti-coagulant activities. In this study, the variation in platelet aggregation and anti-coagulant activities was investigated in vitro with regard to administered dose, molecular weight distribution, sulfate content, and sugar composition in two algal fucoidans from Eisenia bicyclis and Undaria pinnatifida sporophylls (Mekabu). The anti-coagulant activity largely correlated with sulfate content and with molecular weight distribution in a dose-dependent manner. However, both fucoidans demonstrated inhibitory responses to ADP-induced platelet aggregation in dose- and structure-dependent manners that contrasted with the anti-coagulant activity. Neither molecular weight distribution nor sulfate content greatly affected platelet-aggregation inhibition (PA-inhibition) by the fucoidan fractions, whereas anti-coagulant activity was sensitive to these structural factors. Interestingly, an E. bicyclis fucoidan fraction exhibited almost complete PA-inhibition at a treatment dose of 500 mg/mL while retaining weak anti-coagulant activity. In conclusion, these observations suggest that fucoidan may be a useful anti-thrombotic or anti-platelet agent in various arterial thrombotic disorders, including post-vascular intervention with controlled bleeding complications, due to its anti-coagulant modulating activity.

Molecular Weight Distribution of Liquid Phase AN and Solid Phase Polymer in Precipitation Polymerization of AN By Changing Solution Composition and Temperature

  • Liu, Weiwei;Zhang, Shuangkun;Wang, Jing;Ryu, Seung Kon;Jin, Ri-Guang
    • Carbon letters
    • /
    • v.13 no.3
    • /
    • pp.133-138
    • /
    • 2012
  • According to kinetic mechanisms, liquid phase polymerization and solid phase polymerization are different in acrylonitrile (AN) polymerization, and so the relationship between the contribution ratio and molecular weight distribution (MWD) was obtained through theoretic analysis. The precipitation homopolymerization of AN was carried out in a mixture solution of dimethyl sulfoxide (DMSO) and water at $50{\sim}65^{\circ}C$ using ${\alpha}$,${\alpha}^{\prime}$-azobisisobutyronitrile as an initiator. The contribution ratio decreased and approached 0; the MWD also decreased and approached 2 with the increase of the $H_2O$/DMSO ratio from 10/90 to 90/10. The experimental data were found to coincide well with the theoretical equation derived from the mechanisms.

Structure and Property Modification of Bimodal Molecular Weight Distribution Polyethylene by Electron Beam Irradiation

  • Lee, Sang-Man;Jeon, Hye-Jin;Choi, Sun-Woong;Song, Hyun-Hoon;Nho, Young-Chang;Cho, Kyu-Cheol
    • Macromolecular Research
    • /
    • v.14 no.6
    • /
    • pp.640-645
    • /
    • 2006
  • Polyethylene of bimodal molecular weight distribution was irradiated with an electron beam. The thermal and mechanical properties were examined by DSC, small and wide angle X-ray scattering and static tensile test according to the crystal morphology of the irradiated samples. The crystal morphology change upon irradiation, as revealed by wide angle X-ray scattering, correlated well with the changes in melting enthalpy, whereas the lamellar thickness and the amorphous gap thickness remained virtually unchanged at irradiation doses up to 500 kGy. Crosslinks in the crystal domains became evident at an energy level of 250 kGy, resulting in reduced crystallinity and crystal size of the (110) and (200) planes. The samples became stiff and brittle with increased irradiation dose, which seem to be more relevant to the amount of cross links than the crystal morphology changes.

SPACE CHARGE IN LDPE OF DIFFERENT MOLECULAR CHARACTERISTICS (재료특성에 따른 LDPE의 전하형성)

  • Han, Jae-H.;Koo, Jung-H.;Lee, Kyung-Wan;Suh, Kwang-S.
    • Proceedings of the KIEE Conference
    • /
    • 1994.07b
    • /
    • pp.1262-1264
    • /
    • 1994
  • Effects of molecular characteristics such as melt index and shapes of molecular weight distribution on the charge formation in LDPE have been investigated. Both homocharge and heterocharge were observed in LDPE depending on the value of melt index. It was found that the LDPE having intermediate melt indices shows heterocharge while the LDPE having small and high melt indecies shows homocharge. The shapes of molecular weight distributions were also found to affect the space charge in LDPE. These were explained by the role of short chains having low molecular weight in LDPE.

  • PDF

Formation of Chitin Oligosaccharides during Fermentation of Toha-jeot(Salt-fermented Toha Shrimp) (토하젓의 숙성과정중 Chitin Oligosaccharides 생성)

  • 박원기;박영희;김희경;박복희
    • Journal of the Korean Society of Food Science and Nutrition
    • /
    • v.25 no.5
    • /
    • pp.791-795
    • /
    • 1996
  • Toha-jeot(salt-fermented Toha shrimp) is a traditional fermented food in Korea. Toha-jeot is fermented for 90 days at $4\pm1^{\circ}C$ with 20%(w/w) salt per live Toha shrimp. We expect that the high polymer chitin of Toha shell will be hydrolyzed by chitinase during the fermentation of Toha-jeot and that the low molecular weight of chitin oligosaccharides will be produced. We experimented 7 samples which were taken at the interval of 15 days during the total 90 days of fermentation. We also measured molecular weight of Toha-chitin, viscosity and molecular weight distribution of chitin during fermentation of Toha-jeot, The decrease of viscosity and average molecular weight of chitin were observed as fermentation proceeds. Chitin oligosaccharide with $10^3molecular$ weight was low until 60 days fer-mentation. However, chitin oligosaccharide with $10^3molecular$ weight was high after 75 days fer-mentation. And chitin oligosaccharide with $10^2molecular$ weight were observed after fermenting Toha for 75 days and 90 days, but chitin oligosaccharide with 10'molecular weight did not appear up to 60 days of fermentation.ation.

  • PDF

Graft Polymerization of Acrylic Acid onto nylon 6

  • Park, Jae ho;Lee, Chong-Kwang
    • Nuclear Engineering and Technology
    • /
    • v.8 no.3
    • /
    • pp.159-168
    • /
    • 1976
  • Acrylic acid has been grafted onto nylon fabric with ceric salts and ${\gamma}$-rays from Co-60 as initiators. The distribution of molecular weight of the grafted polyacrylic acid has been determined and it was found that the ratio of weight-average and number-average molecular weight was higher in room temp. than in low temp. (-184$^{\circ}C$). The weight-average molecular weight of the polyacrylic acid was calculated from viscosity measurements in sodium hydroxide solution. The factors affecting graft polymerization of acrylic acid onto nylon were examined. A possible mechanism that the oxidation of nylon probably takes place at the methylene group attached to nitrogen to give a free-radical was discussed.

  • PDF

Trends in Polymer Separations: Better and More Information on Polymer Distributions

  • Schoenmakers, Peter
    • Proceedings of the Polymer Society of Korea Conference
    • /
    • 2006.10a
    • /
    • pp.113-113
    • /
    • 2006
  • Polymer separations are used to obtain information on molecular distributions (molecular-weight distribution, chemical-composition distribution, functionality-type distribution, etc.). The existing methods, such as size-exclusion chromatography are reliable, but imperfect. New methods and improvements to existing methods are being studied and some of the results will be discussed. In addition, comprehensive two-dimensional liquid chromatography allows the complete characterization of two mutually dependent distributions. LCxSEC chromatograms provide a very good qualitative impression of the distributions, but calibration is not straightforward. Finally, progress in mass spectrometry allows much better information to be obtained.

  • PDF

Removal of Natural Organic Matter by Mixing Coagulants in Coagulation Process (응집공정에서 혼합응집제 주입에 의한 자연유기물질의 제거)

  • 명복태;우달식;최종현;이윤진;남상호
    • Journal of Environmental Health Sciences
    • /
    • v.27 no.2
    • /
    • pp.60-66
    • /
    • 2001
  • Natural organic matters(NOMs) are found everywhere such as soil, surface and ground waters and consist of both humic and nonhumic components, and their heterogeneith makes each source unique. This study was carried to evaluate the removal characteristics of NOMs by mixing coagulants and the variation of apparent molecular weight distribution(AMWD) in coagulation process. Ratio of optimum coagulants dosage for removal of DOC and turbidity by mixing coagulants was 1.83 mM F $e^{3+}$/mM $Al^{3+}$. DOC removal increased at lower pH. The pH6 control focused on the removal of organic matters could reduce the amount of coagulant consumption by 2 to 3 times based on the pH8.5 of natural water. The dissolved organic matters in the natural water from the mid-stream of Han River were composed of the low molecular weight(LMW,<1 K) of 59.7%, and the medium and high molecular weight(M.HMW, 1~30 K) of 40.3%, respectively. At pH6, the DOC removal efficiencies of LMW(<1 K) and M.HMW(1~30 K) in coagulation process were 27~35%, 62~72%, respectively. The fraction smaller than 1 K was not eliminated to a noticeable degree, while the fraction of 1~30 K was relatively well removed. In conclustion, mixing coagulants were fairly effective in the removal of natural organic matter.r.

  • PDF

Interaction of Oxygen and Chlorine Dioxide in Pulp Bleaching (II) - Studies on the Degradation of Carbohydrates - (펄프 표백시 산소와 이산화염소의 상호작용 (제2보) - 탄수화물의 분해에 관한 연구 -)

  • 윤병호;김세종;최경화;김영훈
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.36 no.1
    • /
    • pp.37-42
    • /
    • 2004
  • ECF and TCF bleaching methods are favored in bleaching plants over the world due to the increasing environment constraints. However, interaction of main stages(D and O stage) in ECF bleaching have not been understood completely yet. The degradation of holocellulose as a carbohydrate model compound was investigated by SEC(size exclusive chromatography) to estimate the change of its molecular weight distribution after O and D stage combination treatment. The molecular weight distribution of holocellulose was observed in two divisions(higher and lower molecular portions). It was also shown that DO sequence was more effective than OD, and DOD or ODO was more effective than DO. D stage had a little effect on the degradation of holocellulose, while the degradation of holocellulose increased as the time of the first O stage increased.

Evaluation of Granular Activated Carbon Process Focusing on Molar mass and size distribution of DOM (DOM의 분자량과 크기분포에 따른 입상활성탄 공정의 평가)

  • Chae, Seon H.;Lee, Kyung H .
    • Journal of Korean Society of Water and Wastewater
    • /
    • v.22 no.1
    • /
    • pp.31-38
    • /
    • 2008
  • The primary objective of this study was to evaluate the variation of the molecular size distribution by granular activated carbon (GAC) adsorption. GAC adsorption was assessed by using the rapid small-scale column test (RSSCT) and high-performance size-exclusion chromatography (HPSEC) was used to analyze the molecular size distribution (MSD) in the effluent of GAC column. RSSCT study suggested that GAC adsorption exhibited excellent interrelationship between dissolved organic carbon (DOC) breakthrough and MSD as function of bed volumes passed. After GAC treatment, the nonadsorbable fraction which was about 25percents of influent DOC corresponded to the hydrophilic (HPI) natural organic carbon (NOM) of NOM fractions and was composed entirely of <300 molecular weight (MW) in the HPSEC at the initial stage of the RSSCT operation. The dominant MW fraction in the source water was 1,000~5,000daltons. At the bed volumes 2,500, MW <500 of GAC treated water was risen rather than it of source water. After the bed volumes 7,300 of operation, the MW 1,000~3,000 fraction was closed to about 80percents of DOC found in the GAC influent. The Number-average molecular weight (Mn) value determined using HPSEC for the effluent of GAC column was gently increased as DOC breakthrough progress. The quotient p(Mw/Mn) can be used to estimate the degree of polydispersity was shown greatest value for the GAC effluent at the initial stage of the RSSCT operation.