• Title/Summary/Keyword: Cross linking

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Immobilization of Thermolysin for Synthesis of Aspartame Precursor (아스파탐 전구체의 합성을 위한 Thermolysin의 고정화)

  • Han, Min-Su;Kim, Woo-Jung
    • Korean Journal of Food Science and Technology
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    • v.27 no.5
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    • pp.753-756
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    • 1995
  • Optimum conditions for immobilization of thermolysin, a metalloendopeptidase catalyzing synthesis of aspartame precursors, were investigated with using Amberlie XAD-7 as carrier and glutaraldehyde as cross-linking agent. Adsorption of thermolysin onto the carrier was rapid at the initial stage and 96% of the enzyme was adsorbed after 24 hours at $5^{\circ}C$. There was a linear relationship between amount of thermolysin adsorbed and thermolysin loaded upto 300g per liter of carrier. The effective range of cross-linking time, concentration of glutaraldehyde and pH for immobilization of the enzyme were $3{\sim}7\;hours,\;6{\sim}12.5%\;and\;pH\;6.0{\sim}7.0$, respectively. Degree of cross-linking and residual enzyme activity were high when cross-linked for 7 hours with 6% glutaraldehyde or for 3 hours with 12.5% glutaraldehyde. The residual enzyme activity was over 30% under these conditions.

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The Schizosaccharomyces pombe Proteins that Bind to the Human HnRNPA1 Winner RNA

  • Kim, Jeong-Kook
    • Journal of Microbiology
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    • v.35 no.4
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    • pp.327-333
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    • 1997
  • Although extensively characterized in human cells, no heterogeneous nuclear ribonucleoprotein(hnRNP) has been found in the fission yeast Schizosaccharomyces pombe which is amenable to genetic studies and more similar to mammals than Saccharomyces cerevisiae is in terms of RNA processing. As a first step to characterize hnRNPs from S. pombe, attempt was made to find human hnRNP A1 homologs from S. pombe. The RNA molecule (A1 winner) containing the consensus high-affinity hnRNP A1 binding site (UAGGGA/U) was synthesized in vitro and used in an ultraviolet(UV) light-induced protein-RNA cross-linking assay. A number of S, pombe proteins bound to the A1 winner RNA. An approximately 50-kDa protein(p50) cross-linked more efficiently to the A1 winner RNA than other proteins. The p50 protein did not cross-link to a nonspecific RNA, but rather to the A1-5’ SS RNA in which the consensus 5’ splice junction sites of S. pombe introns were abolished. This suggests that the p50 protein, however, did not bind to the single-stranded DNA to shich the human hnRNP A1 could bind and be eluted with 0.5M NaCl. Further analysis should reveal more features of this RNA-binding protein.

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The Effects of Annealing on Resistant Starch Contents of Cross-linked Maize Starches (Annealing 처리가 가교결합 옥수수전분의 저항전분 수율에 미치는 영향)

  • Mun, Sae-Hun;Shin, Mal-Shick
    • Korean Journal of Food Science and Technology
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    • v.34 no.3
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    • pp.431-436
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    • 2002
  • To develop a method for increasing RS level in maize starch, cross-linked resistant starches treated with annealing were prepared. Maize starch and amylomaize VII were used in the study and annealed at $40{\sim}60^{\circ}C$ before cross-linking modification. To compare effect of annealing below gelatinization temperature, starches were heat treated at 70 and $100^{\circ}C$. RS contents were assayed by pancreatin-gravimetric (P/G) method. When maize starch and amylomaize VII were cross-linked at $45^{\circ}C$ and pH 11.0 by slurrying the starch on a solution of STMP(sodium trimetaphosphate), STPP(sodium tripolyphosphate), and sodium sulfate, RS content was 14.7% and 45.3%, respectively. Annealing below gelatinization temperature before cross-linking increased RS contents of prepared cross-linked starches but did not affect the swelling power. Heat treatment above gelatinization temperature increased the swelling power of cross-linked starch prepared from maize starch. The characteristics by X-ray diffractometry and scanning electron microscopy of cross-linked resistant starch were not changed by annealing.

Citing Pattern Analysis based on Cited-by Linking Data of DOI Journals in the Field of Natural Sciences & Engineering (Cited-by Linking 데이터 기반 자연과학 및 공학 분야 학술논문 인용 패턴 분석)

  • Seo, Sun Kyung;Choi, Ho Nam;Kim, Byung-Kyu;Choi, Seon-Heui;Kim, Jeong Hwan
    • Journal of the Korean Society for information Management
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    • v.33 no.2
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    • pp.157-176
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    • 2016
  • Cited-by Linking Service is one of the CrossRef's information services that allows you to discover how your publications are being cited and to incorporate that information into your online publication platform. This study tries to investigate citation patterns in the field of both Natural Science and Engineering using all of DOI assigned articles and Cited-by Linking data which are accumulated and managed by KISTI. The investigating approach is designed to verify the theory of 1) cognitive accessibility, 2) 'perceived quality and significance' and 3) 'subject relativity'. For cognitive accessibility verification the fulltext language portion of Korean and English between "Cited DOI Source Data" and "NOT Cited DOI Source Data" was compared. For perceived quality and significance verification the availability of the "Cited DOI Source Data" and "NOT Cited DOI Source Data" from SCIE and SCOPUS was employed. For subject relativity DOI data were classified and analysed on the basis of OECD subject classification scheme. Findings are that global citability is closely related to the fulltext language of the articles and their quality and significance. And in the natural science field most of citations are from the same subject categories, while relatively more citations are from other subject categories in the engineering field.

A Study on Effects of Vulcanization Systems on Cross-linking and Degradation Reactions of NR/CR Blends Using Dynamic DSC and TGA (Dynamic DSC와 TGA를 이용한 NR/CR 고무블렌드의 가황시스템이 가교 및 열화반응에 미치는 영향 연구)

  • Min, Byung-kwon;Park, DongRyul;Ahn, WonSool
    • Korean Chemical Engineering Research
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    • v.47 no.2
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    • pp.169-173
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    • 2009
  • Effects of variations sulfur/accelerator ratio on cross-linking and thermal degradation behavior of NR/CR rubber compounds were studied using both dynamic DSC and non-isothermal TGA. DSC thermograms of the given samples were obtained with several different heating rates, and after cross-liked in DSC, TGA thermograms with the same samples also obtained. Kissinger analysis was applied to assess the activation energies for the cross-linking and thermal decomposition processes. Results showed that the formation and thermal decomposition reaction of the samples occurred in the overall temperature range of $120{\sim}180^{\circ}C$ and $350{\sim}450^{\circ}C$, respectively, exhibiting that data could be well-fittable by Kissinger method. Furthermore, formation activation energy by DSC was estimated as $83.0{\pm}5.0kJ/mol$, which was much smaller than that of degradation by TGA, $147.0{\pm}2.0kJ/mol$. From these results, it was considered that, although variations of sulfur/accelerator ratio in the present experiments affected little on the formation mechanism and/or thermal degradation, they could play roles as the catalysts which lower the activation energy of formation. Because of stabilization after formation reaction, however, they have no more effects on the lowering the activation energy, showing higher values when decomposition, caused by main-chain scissions.

Characteristics of porous Chitosan-Alginate-Gelatin Scaffold Cross-linked by Heat-treatment (열처리에 의해 가교된 다공성 키토산-알지네이트-젤라틴 지지체의 특성)

  • Sin, Byeong-Cheol;Choe, Min-Su;Han, Hui-Dong;Seong, Ha-Su
    • Journal of the Korean Chemical Society
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    • v.50 no.3
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    • pp.224-231
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    • 2006
  • agents used for enhancing mechanical properties of porous natural scaffolds, reduces biocompatability of the scaffolds, due to their inherent cytotoxicity. In this study, scaffolds which was composed of chitosan, alginate and gelatin were cross-linked by using heat treatment instead of cross-linking agent and mechanical properties of the cross-linked scaffold were investigated. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that cross-linking of heat-treated scaffold was formed via amide or ester linkage between the polymer chains. The heat-treated scaffold had interconnected pores with mean diameter of 100~200 m and showed more than two fold increase of water uptake in comparison with chemically cross-linked scaffold. Tensile strength of the heat-treated scaffold increased up to 130% compared to non cross-linked scaffold and average maximum elongation was 11.3%. The porous cross-linked scaffold with the improved mechanical property may be suitable as a biocompatable scaffold for tissue engineering.