• Title/Summary/Keyword: very high molecular weight

Search Result 121, Processing Time 0.026 seconds

A study on the Condition of Pyrolysis of Coal Tar Pitch to Form the Mesophase as a Matrix Precursor of Carbon/Carbon Composites (탄소/탄소 복합재 매트릭스 전구체인 이방성 메조페이스 형성을 위한 콜타르 핏치의 열분해 조건 연구)

  • 정형진;정윤중;조동환;임연수;김기원
    • Journal of the Korean Ceramic Society
    • /
    • v.34 no.9
    • /
    • pp.963-968
    • /
    • 1997
  • Coal tar pitch was used to study the effect of the pyrolysis conditions to produce mesophase pitch used as a matrix precursor for carbon/carbon composites. The pyrolysis conditions were presented in all cases that the total pressure was 1 atm and the first stage temperature was changed from 25$0^{\circ}C$ to 34$0^{\circ}C$ to remove the low molecular weight compounds in the pitch, and then, heated to 40$0^{\circ}C$ to form anisotropic mesophase as the second stage temperature. The first stage temperature was very affected to form resulting anisotropic mesophase pitch. The resulting mesophase pitches show a significantly increased anisotropic contents upto 30$0^{\circ}C$. However, the contents of mesophase were decreased above 30$0^{\circ}C$. It was the reason that the first stage temperature had been control the number of free radicals to react the aromatic compounds in the pitch to form high molecular weight compound. Therefore, the two stage pyrolysis method could be very effectively used to control various contents of anisotropic polyaromatic mesophase compared to continuous to continuous heating method.

  • PDF

Food application of enzymes derived from microorganisms degrading chitin and chitosan (키틴과 키토산 분해 미생물 유래 효소의 식품에의 이용)

  • Park, Jae Kweon
    • Food Science and Industry
    • /
    • v.53 no.1
    • /
    • pp.43-55
    • /
    • 2020
  • Most reports demonstrated the substrate specificity-based kinetic properties of chitin or chitosan degrading enzymes. However, there is virtually less information on the high quality and quantity production of chitin or chitosan hydrolysates having a larger than (GlcN)7 from the hydrolysis of high molecular weight chitosan using specific enzymes and their biological activity. Therefore, the production of such molecules and the discovery of such enzyme sources are very important. Fortunately, the author has established a mass production method of chitosan hydrolysates (GlcN)n, n=2-13 that have been characterized as a potent antioxidant substance, as well as antifungal and antibacterial activities against Penicillium species and highly selective pathogenic bacteria. In addition, preclinical studies using (GlcN)n, n=5-25 demonstrated that these molecules played a very important role in maintaining biometric balance. Collectively, it is implicated that the application of these mixed substances to foods with significant biological activity is very encouraging.

A Study on the Impact Behavior of Bulletproof Materials According to the Combining Method

  • Jihyun Kwon;Euisang Yoo
    • Elastomers and Composites
    • /
    • v.57 no.4
    • /
    • pp.157-164
    • /
    • 2022
  • Representative bulletproof materials, such as aramid or ultra-high molecular weight polyethylene(UHMWPE), have excellent strength and modulus in the plane direction but are very vulnerable to forces applied in the thickness direction. This paper reports a study on the effects of reinforcement in the thickness direction when bulletproof composite fabrics are prepared to improve their performance. Aramid and UHMWPE fabrics were combined using the film-bonding, needle-punching, or stitching methods and then subjected to low-velocity projectile and ball-drop impact tests. The results of the low-velocity projectile test indicated that the backface signature(BFS) decreased by up to 29.2% in fabrics obtained via the film-bonding method. However, the weight of the film-bonded fabric increased by approximately 23% compared with that obtained by simple lamination, and the fabric stiffened on account of the binder. Flexibility, light weight for wearability, and excellent bulletproof performance are very important factors in the development of bulletproof materials. When the needle-punching method was used, the BFS increased as the fibers sustained damage by the needle. When the composite fabrics were combined by stitching, no significant difference in weight and thickness was observed, and the BFS showed similar results. When a diagonal stitching pattern was employed, the BFS decreased as the stitching density increased. By contrast, when a diamond stitching pattern was used, the fabric fibers were damaged and the BFS increased as the stitching density increased.

Structure function relationships amongst the purple acid phosphatase family of binuclear metal-containing enzymes

  • Hamilton, Susan
    • Proceedings of the Korean Society for Bioinformatics Conference
    • /
    • 2003.10a
    • /
    • pp.5-5
    • /
    • 2003
  • The purple acid phosphatases comprise a family of binuclear metal-containing enzymes. The metal centre contains one ferric ion and one divalent metal ion. Spectroscopic studies of the monomeric, ${\sim}$36 kDa mammalian purple acid phosphatases reveal the presence of an Fe(III)Fe(II) centre in which the metals are weakly antiferromagnetically coupled, whereas the dimeric, ${\sim}$110 000 kDa plant enzymes contain either Fe(III)Zn(II) or Fe(III)Mn(II). The three dimensional structures of the red kidney bean and pig enzymes show very similar arrangements of the metal ligands but some significant differences beyond the immediate vicinity of the metals. In addition to the catalytic domain, the plant enzyme contains a second domain of unknown function. A search of sequence databases was undertaken using a sequence pattern which includes the conserved metal-binding residues in the plant and animal enzymes. The search revealed the presence in plants of a 'mammalian-type' low molecular weight purple acid phosphatase, a high molecular weight form in some fungi, and a homologue in some bacteria. The catalytic mechanism of the enzyme has been investigated with a view to understanding the marked difference in specificity between the Fe-Mn sweet potato enzyme, which exhibits highly efficient catalysis towards both activated and unactivated phosphate esters, and other PAPs, which hydrolyse only activated esters. Comparison of the active site structures of the enzymes reveal some interesting differences between them which may account for the difference. The implications fur understanding the physiological functions of the enzymes will be discussed.

  • PDF

Biochemical Characteristics of a Palmitoyl Acyl Carrier Protein Thioesterase Purified from Iris pseudoacorus

  • Kang, Han-Chul;Hwang, Young-Soo
    • BMB Reports
    • /
    • v.29 no.5
    • /
    • pp.436-441
    • /
    • 1996
  • The palmitoyl acyl carrier protein (ACP) specific thioesterase (EC 3.1.2.14) from Iris pseudoacorus was purified and characterized. The thioesterase which was very unstable in relatively high salt concentrations was eluted using a co-gradient of Triton X-100 and low concentration of KCl or Na-phosphate from Q-Sepharose, DEAE-Sepharose, and hydroxyapatite chromatography. SDS-PAGE analysis showed a single band with a molecular weight of 35,000. The native molecular weight of approximately 37,000 was estimated by Sephacryl S-200 chromatography, indicating that the enzyme is a monomer. The thioesterase activity was inhibited about 75% and 50% by N-ethylmaleimide (2 mM) and phenylmethylsulfonyl fluoride (2 mM). respectively. The N-ethylmaleimide-inactivation was protected by sodium palmitate but the inactivation with phenylmethylsulfonyl fluoride was not protected. Oxidation of thiols by 2 mM 5.5'-dithio-bis-(2-nitrobenzoic acid) resulted in 65% inactivation of the enzyme. These results suggest that a cysteinyl residue is essential to the catalytic reaction of the enzyme. The enzyme activity was increased by sodium citrate and also by $Cu^{2+}$

  • PDF

Synthesis of High Molecular Weight Poly(Hexafluoropropylene Oxide) by Anionic Polymerization (음이온 중합에 의한 고분자량 헥사플루오르프로필렌 옥사이드 중합제의 합성)

  • Lee, Sang-Goo;Ha, Jong-Wook;Park, In-Jun;Lee, Soo-Bok;Lee, Jong-Dae
    • Polymer(Korea)
    • /
    • v.32 no.4
    • /
    • pp.385-389
    • /
    • 2008
  • Chain propagation and chain transfer in anionic polymerization of hexafluoropropylene oxide were investigated under various reaction conditions such as the stabilization of reaction temperature, the amount of hexafluoropropylene solvent, and the feeding rate of hexafluoropropylene oxide monomer. Anionic initiator for the polymerization was synthesized from cesium fluoride and hexafluoropropylene oxide in tetraethyleneglycol dimethylether. It was possible to obtain a high molecular weight poly(HFPO) ($M_w$ 14800) using the anionic initiator in conditions of stabilized reaction temperature, and optimized addition of solvent and monomer feeding (HFP/initiator mole ratio=31.5 and HFPO feeding rate=11.67 g/hr). Otherwise, chain transfer reaction in anionic polymerization was increased. From the results of molecular weight in various reaction conditions, it was found that chain propagation and chain transfer in anionic polymerization of HFPO were very sensitive to reaction conditions.

Changes in Specific Protein Profiles during Initiation of Adventitious Roots in Soybean (Glycine max L.) Cotyledons (대두 (Glycine max L.)의 자엽 부정근 형성시 특이단백질의 변화 양상)

  • 한태진
    • Korean Journal of Plant Tissue Culture
    • /
    • v.21 no.2
    • /
    • pp.123-129
    • /
    • 1994
  • The potency of adventitious root initiation was investigated in relation with germination days and ike end of culture days healed with root induction medium on the initiation of adventitious roots from explants of soybean (Glycine max L.) cotyledon. Also, the changes in the pattern of protein profiles related with adventitious mot initiation have been examined by two-dimensional polyauyl-amide gel elecoophoresis during the germination and the initiation of adventitious roots. The potency of adventitious root initiation from germinated cotyledons was high after 4 days, and adventitious roots were initiated from after 4 days and very high after 6 days healed with mot induction medium There was a reproducible quantitative change in 34 specific protein spots during germination and adventitious root initiation. A necessary basic protein for adventitious root initiation with rotative molecular weight of 27 kD was induced during the germination. And three basic protein groups with relative molecular weight 22 kD, 23 kD and 33 kD, and two acidic protein groups with relative molecular weight 27kD and 29 kD were induced during the initiation of adventitious roots.

  • PDF

Transfersomes-mediated gene transfer into organs in mice by direct application on intact skin

  • Lee, Eun;Kim, Adele;Kim, Chong-Kook
    • Proceedings of the PSK Conference
    • /
    • 2002.10a
    • /
    • pp.416.2-416.2
    • /
    • 2002
  • Transfersomes are highly detormable hydrophilic lipid vesicles that are able to penetrate the skin barrier so that they can be used to carry low- and high-molecular weight molecules into the body. Until recently. it has been reported that molecules such as insulin. interleukin-2 and several other large molecules have been transported into the body using Transfersomes as a delivery system. Here however, for the very first time, genes (GFP) have been transported into the mice non-invasively using the Transtersomes as a delivery vehicle. (omitted)

  • PDF

Comparison of the Properties of Molecular Composites Blends of Poly(vinyl alcohol)/Conducting Polymer (폴리비닐알콜/전도성고분자 분자복합체와 블렌드의 물성 비교)

  • Kwon, Ji-Yun;Kim, Young-Hee;Kim, Han-Do
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 2001.10a
    • /
    • pp.29-32
    • /
    • 2001
  • Conductive polymers(CPs) are a relatively new class of organic materials displaying as their foremost property a high conductivity combined with very light weight, flexibility and reasonably facile processability[1]. Due to their high conductivity/weight ratio, they have recently evinced much interest in potential application as EMI shielding screens, coatings or jackets for flexible conductors, rechargeable batteries and as possible substitutes for metallic conductors or semiconductors in wide variety of electrical devices[2]. (omitted)

  • PDF

Molecular Characterization of Seaweeds Using RAPD and Differential Display

  • HONG Yong-Ki;KIM Yong-Tae;KIM Se-Kwon
    • Korean Journal of Fisheries and Aquatic Sciences
    • /
    • v.29 no.6
    • /
    • pp.770-778
    • /
    • 1996
  • A rapid and economical method of simultaneous extraction of DNA and RNA from seaweeds has been developed by the use of lithium chloride. Lithium chloride facilitates the softening of cell walls resulting in a decrease in both compressive and tensile modulus of elasticity. The DNA was characterized by high molecular weight larger than 27 kb and a relative lack of carbohydrate and protein contamination. The DNA and RNA extracted by the method from many seaweeds were of sufficient quality to be used as a template for per amplification with a plant intergenic gene primer set, for RAPD analysis with arbitrary primers, and for differential display with arbitrary primers in the morphologically distinct regions of the matured Porphyra thallus. The cDNA polymorphism indicated that the reproductive tissue types (male, female, patch) had a relatively high degree of similarity; the vegetative tissue types (dividing, non-dividing) also showed a similar pattern with respect to each other. Holdfast tissue had very low similarity with the other tissues, but appeared most similar to vegetative non-dividing tissue type.

  • PDF