• Title/Summary/Keyword: high molecular weight

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High Level Production of Supra Molecular Weight Poly(3-Hydroxybutyrate) by Metabolically Engineered Escherichia coli

  • Park, Jong-il;Lee, Sang-Yup
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.9 no.3
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    • pp.196-200
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    • 2004
  • The supra molecular weight poly(〔R〕-3-hydroxybutyrate) (PH B), having a molecular weight greater than 2 million Da, has recently been found to possess improved mechanical properties compared with the normal molecular weight PHB, which has a molecular weight of less than 1 million Da. However, applications for this PHB have been hampered due to the difficulty of its production. Reported here, is the development of a new metabolically engineered Escherichia coli strain and its fermentation for high level production of supra molecular weight PHB. Recombinant E. coli strains, harboring plasm ids of different copy numbers containing the Alcaligenes latus PHB biosynthesis genes, were cultured and the molecular weights of the accumulated PHB were compared. When the recombinant E. coli XL1-Blue, harboring a medium-copy-number pJC2 containing the A. latus PHB biosynthesis genes, was cultivated by fed-batch culture at pH 6.0, supra molecular weight PHB could be produced at up to 89.8 g/L with a productivity of 2.07 g PHB/L-h. The molecular weight of PHB obtained under these conditions was as high as 22 MDa, exceeding by an order of magnitude the molecular weight of PHB typically produced in Ralstonia eutropha or recombinant E. coli.

A Comparative Coagulopathic Study for Treatment of Vasospasm by Using Low- and High-molecular Weight Hydroxyethyl Starches

  • Hwang, Sung-Ho;Won, Yu-Sam;Yu, Jang-Sun;Yang, Jae-Young;Choi, Chun-Sik
    • Journal of Korean Neurosurgical Society
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    • v.42 no.5
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    • pp.377-381
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    • 2007
  • Objective : High-molecular-weight hydroxyethyl starch (HES) compromises blood coagulation more than does low-molecular-weight HES. We compared the effects of low- and high-molecular-weight HES for the treatment of vasospasm and investigated the dose relationship with each other. Methods : Retrospectively, in a series of consecutive 102 patients with subarachnoid hemorrhage (SAH), 35 patients developed clinical symptoms of vasospasm of these fourteen patients were treated with low-molecular weight HES for volume expansion while the other 21 received high-molecular-weight HES as continuous intravenous infusion. Prothrombin time (PT), partial thromboplastin time (PIT), fibrinogen level, and platelet count were all measured prior to initiation, during treatment and after termination of therapy for symptomatic vasospasm. The total dose of HES ranged from 5 L to 14 L and median infusion duration was 10 days. Results : A more pronounced PTT prolongation was observed in high-molecular-weight HES group compared with low-molecular-weight HES group. No other coagulation parameters were altered. Dosage (=duration) shows a positive correlation with PTT. Clinically, significant bleeding episodes were noted in four patients who received high-molecular-weight HES. Conclusion : Coagulopathy was developed in direct proportion to molecular weight of starch and dosages. We propose the extreme caution in the administration of HES solution for the vasospasm treatment.

Preparation and Characterization of High Molecular Weight Poly(butylene succinate)

  • Han, Yang-Kyoo;Kim, Sung-Rim;Kim, Jinyeol
    • Macromolecular Research
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    • v.10 no.2
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    • pp.108-114
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    • 2002
  • Poly(butylene succinate) (PBS) prepolymers were prepared by the condensation polymerization of 1,4-butanediol (1,4-BD) and succinic atid (SCA) in the presence of titanium (VI) isoproxide(TPI) catalyst. The PBS prepolymers reacted with 1,4-BD or SCA to obtain hydroxyl or carboxylic acid group terminated PBS. High molecular weight linear or branched PBS was synthesized by a coupling reaction between hydroxyl and carboxylic acid group terminated PBS, or by a branching reaction between carboxylic acid group terminated PBS and glycerol as a branching agent. The weight average molecular weight of the prepared linear or branched PBS was in the range of 100,000-220,000. Both melting point and thermal stability of the high molecular weight linear and branched PBSs were somewhat higher than those of general PBS. From a tensile behavior by Instron test, modulus, tensile strength and elongation at break improved with increase in the molecular weight of the prepared PBS through the coupling or the branching reaction. In particular, the high molecular weight linear PBS had about 2.5 times higher value in modulus than the branched one.

Production and characterization of ultra-high-molecular weight poly(3-hydroxybutyrate) by recombinant Escherichia coli

  • Park, Jong-Pil;Park, Si-Jae;Lee, Sang-Yeop
    • 한국생물공학회:학술대회논문집
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    • 2001.11a
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    • pp.731-734
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    • 2001
  • An efficient fermentation strategy for the high level production of ultra-high-molecular weight poly(3-hdyroxybutyrate) (PHB) was developed. Although the cell and PHA concentrations obtained by flask cultures at different initial pH (6.0 or 6.9) were almost same level, the molecular mass of PHB produced were quite different along with the initial pH. When a recombinant Escherichia coli XL1-Blue harboring pJC2 containing the Alcaligenes latus PHB biosynthesis genes was cultivated in flask culture (pH 6.0), the PHB having a very high molecular weight of 22 MDa could be produced while only below 1 MDa at initial pH 6.9. The ultra-high-molecular weight PHB could be synthesized to high concentration of 89.8 g/L resulting in the PHB productivity of 2.07 g/L-h by simple fed-batch culture. In this study, we report that PHB having various molecular mass can be produced by employing metabolically engineered E. coli strains harboring the plasmids of different copy numbers containing the A. latus phbCAB genes.

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The efect of freeness and paper physical properties treated with high and low molecular weight cellulase in the different surface pore sized fibers (Cellulase의 분자량과 섬유소의 표면공극 상이성이 여수도 및 종이의 강도적 특성에 미치는 영향)

  • 김병현;신종순;강영립;어영호
    • Journal of the Korean Graphic Arts Communication Society
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    • v.18 no.1
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    • pp.141-155
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    • 2000
  • To examine how the difference of molecular weight distribution of cellulase influenced the beating process according to surface pore size of the fiber, high molecular weight enzyme and low one were applied to soft wood pulp, hard wood pulp, cotton linter pulp. Some enzymes with the distribution of low molecular weight penetrated into cellulose in the proportion of surface pore size and the results were negative as like : the low viscosity, decrease of refining Yield, decrease of fine fibers content and so on. But in cotton linter pulp in the small surface area, the fiber softness was increased and it had a positive result that the paper intensity was high. Other enzymes with the distribution of high molecular weight had an enzyme reaction on the most surfaces of cellulose. They were effective in eliminating the fuzz of hydrophile fine fibers and the freeness was increased.

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High Performance Phenoxytitanium-Based Catalysts for Olefin Polymerization

  • Miyatake, Tatsuya
    • Proceedings of the Polymer Society of Korea Conference
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    • 2006.10a
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    • pp.159-160
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    • 2006
  • We developed novel catalyst, PHENICS composed of the combination of a cyclopentadienyl group to perform a high catalytic activity and a bulky phenoxy group, which performs the production of high molecular weight polyolefin. The polymerization activity of PHENICS at high temperature is higher than well-known CGC catalyst. PHENICS showed the excellent ability of comonomer incorporation into polymer chain. The obtained copolymer had a high molecular weight. The PHENICS catalyst is also active to the copolymerization of ethylene and several vinyl comonomers such as styrene, norbornen, and conjugated dienes. We will discuss new cocatalysts for PHENICS to improve activity and the ability of molecular weight control.

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Size Characterization of Sodium Hyaluronate by Field Programming Frit Inlet Asymmetrical Flow Field-Flow Fractionation/Multiangle Light Scattering

  • Kim, Hoon-joo;Lee, Hee-jeong;Moon, Myeong-Hee
    • Bulletin of the Korean Chemical Society
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    • v.27 no.3
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    • pp.413-418
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    • 2006
  • Sodium hyaluronate (NaHA), water soluble polymer having ultra-high molecular weight, is characterized by using on-line frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) and multiangle light scattering (MALS). This study demonstrates the capability of power programming FI-AFlFFF for the separation of NaHA and the applicability of FI-AFlFFF with MALS for the characterization of molecular weight distribution and their structural information. Since sample injection and relaxation in FI-AFlFFF are achieved by using hydrodynamic relaxation, separation of high molecular weight polymers can be achieved smoothly without halting the separation flow. Experiments are carried out with the two different NaHA products (a raw NaHA sample and a thermally degraded NaHA product) and molecular weight distribution and conformations in solution are determined. Influence of sample filtration on the change of molecular weight distribution is also discussed.

Molecular Weight Distribution Characterization of Organics for the Dongbok Lake Water by Coagulation and Adsorption of Activated Carbon (동복 호소수의 응집침전 및 활성탄 흡착에 의한 용존유기물 분자량 분포 특성)

  • 정경훈;최형일
    • Journal of Environmental Science International
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    • v.7 no.1
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    • pp.104-111
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    • 1998
  • The Dongbok lake water before and after alum coagulation and activated carbon adsorption were analyzed in terms of organic contents, molecular weight distributuin (MWD), and UV-absorbance. Dissolved organic compounds in the Dongbok lake were fractionated into three molecular size classes by gel permeation chromatography. The fractionation was reasonably successful in isolating compounds with The bulk of the dissolved carbon was present in compounds of molecular weight in the range of 3,000~10,000. Alum coagulation preferentially treated molecules of high molecular weight, which has molecules larger than 10,000. The dissolved organic carbon (DOC) removal after activated carbon adsorption was high in the Fraction B , IR . The $A_{260}$/DOC ratio after alum and activated carbon treatment the Fraction II, III. This results suggest that the organics remaining after each treatment has a trihalomethane formation potential

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Effects of Molecular Weight of PC on Mechanical Properties of PC/ABS Blends using High-Shear Rate Processing

  • Lee, Eun Ju;Park, Hee Jung;Kim, Se Mi;Lee, Seung Goo;Lee, Kee Yoon
    • Korean Chemical Engineering Research
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    • v.56 no.3
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    • pp.343-348
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    • 2018
  • Each of the two polycarbonates (PC) of different molecular weights was blended with acrylonitrile-butadiene-styrene (ABS) under high-shear rate processing to afford PC/ABS. Sizes of ABS dispersed phases and mechanical properties of PC/ABS blends were investigated and high-shear rate processing of PC/ABS was carried out by changing screw speed and processing time. Prepared specimens were examined by scanning electron microscope (SEM) to observe morphology changes. Sizes of ABS dispersed phases in PC/ABS blends were observed to decrease gradually as screw speeds increased. Tensile strengths and elongations of specimens were investigated by universal testing method (UTM) to study the influence of molecular weight of PC exerting on PC/ABS blends. As a result, PC1/ABS blends (PC1: higher molecular weight PC) exhibited more strengthened properties than PC2/ABS (PC2: lower molecular weight PC). The tensile strength of PC1/ABS showed an increasing tendency when the screw speed increased, and the elongation did not show a significant decrease, but increased slightly with increasing shear time at a constant screw speed of 1000 rpm.