• Journal of the Korean Applied Science and Technology
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• v.17 no.1
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• pp.37-42
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• 2000

Drug delivery system(DDS) have been actively studied for the past twenty years. Dual action agents are unique chemical entities comprised of two different types of antibacterial compounds covalently linked together in a single molecule in such a way that both components are able to exert their bactericidal properties. In spite of the advent of the antibacterial agent the sulfa agents are the most widely used antibacterial agent today. In this study, new antibacterials derivative was synthesized using glutaraldehyde such as crosslinking agent for the purpose of dual-action as DDS study. Antibacterial activity of these new synthetic derivative between their structures and activities were examined by disc diffusion method. As a result, new synthetic derivative exhibited the broad antibacterial activities against Gram(+) and Gram(-) bacilli. Especially, the antibacterial effect of new synthetic derivative against Gram negative(Esherichia. coli) was much stronger than that against Gram positive.

• Journal of Microbiology and Biotechnology
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• v.22 no.5
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• pp.628-636
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• 2012

Raw-starch-digesting enzyme (RSDA) was immobilized on Amberlite beads by conjugation of glutaraldehyde/polyglutaraldehyde (PG)-activated beads or by crosslinking. The effect of immobilization on enzyme stability and catalytic efficiency was evaluated. Immobilization conditions greatly influenced the immobilization efficiency. Optimum pH values shifted from pH 5 to 6 for spontaneous crosslinking and sequential crosslinking, to pH 6-8 for RSDA covalently attached on polyglutaraldehyde-activated Amberlite beads, and to pH 7 for RSDA on glutaraldehyde-activated Amberlite. RSDA on glutaraldehyde-activated Amberlite beads had no loss of activity after 2 h storage at pH 9; enzyme on PG-activated beads lost 9%, whereas soluble enzyme lost 65% of its initial activity. Soluble enzyme lost 50% initial activity after 3 h incubation at $60^{\circ}C$, whereas glutaraldehyde-activated derivative lost only 7.7% initial activity. RSDA derivatives retained over 90% activity after 10 batch reuse at $40^{\circ}C$. The apparent $K_m$ of the enzyme reduced from 0.35 mg/ml to 0.32 mg/ml for RSDA on glutaraldehyde-activated RSDA but increased to 0.42 mg/ml for the PG-activated RSDA derivative. Covalent immobilization on glutaraldehyde Amberlite beads was most stable and promises to address the instability and contamination issues that impede the industrial use of RSDAs. Moreover, the cheap, porous, and non-toxic nature of Amberlite, ease of immobilization, and high yield make it more interesting for the immobilization of this enzyme.

• Journal of Hydrogen and New Energy
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• v.22 no.1
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• pp.1-12
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• 2011

To improve the mechanical properties, such as durabilities and antioxidative characteristics, the covalently cross-linked (CL-) SPEEK (sulfonated polyether ether ketone)/Cs-substituted HPA (heteropoly acid) organic-inorganic composite membranes (CL-SPEEK/Cs-HPAs), have been intensively investigated. The composite membrane were prepared by blending cesium-substituted HPAs (Cs-HPAs), including tungstophosphoric acid (TPA), molybdophosphoric acid (MoPA), and tungstosilicic acid (TSiA) with cross-linking agent content of 0.01 mL. And composite electrolytes composed of Cs-HPAs, prepared by immersion (imm.) and titration (titr.) methods to increase the stability of HPAs in water, were applied to polymer electrolyte membrane electrolysis (PEME). As a result, the proton conductivity of Cs-substituted composite membranes increased rapidly over $60^{\circ}C$ but mechanical properties, such as tensile strength, decreased in accordance with added Cs content. The bleeding-out of Cs-TPA membranes by titration method (50 vol.% Cs) decreased steadily to 2.15%. In the oxidative stability test by Fenton solution, the durability of membranes with Cs-HPA significantly increased. In case of CL-SPEEK/ Cs-TPA membrane, duration time increased more than 1200 hours. It is expected that even though CL-SPEEK/Cs-MoPA membrane shows the high proton conductivity, electrocatalytic activity and cell voltage of 1.80 V for water electrolysis, the CL-SPEEK/Cs-TPA (imm.) is more suitable as an alternative membrane in real system with the satisfactory proton conductivity, mechanical properties, anti-oxidative stability and cell voltage of 1.89 V.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.112-117
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• 2021

In this study, a method of self-assembly of peptides based on irreversible covalent bonds was studied by mimicking a biological covalent bond, dityrosine bond. A tyrosine-rich short peptide monomer having the sequence of Tyr-Tyr-Leu-Tyr-Tyr (YYLYY) was selected to achieve a high-density of dityrosine bond. The peptide nanoparticles covalently self-assembled with dityrosine bonds were synthesized by one-step photo-crosslinking of a peptide using a ruthenium catalyst under visible light. The effect of the concentration of each component for the size of the peptide nanoparticle was studied using dynamic light scattering, UV-Vis spectroscopy, and transmission electron microscopy. As a result, the synthesis conditions for size of the peptide nanoparticles ranging from 130 nm to 350 nm were optimized.

• Korean Journal of Food Science and Technology
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• v.16 no.3
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• pp.267-272
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• 1984

${\beta}-Fructofuranosidase$ was immobilized covalently on the oxidized microbial wall of a Penicillium spp. 'PS-8', which is totally different from the conventional whole cell immobilization in concept. The immobilization of ${\beta}-fructofuranosidase$ by a series of treatments; oxidation of microbial cells with sodium metaperiodate, enzyme loading on the oxidized cells, extrusion, and crosslinking induced by glutaradehyde, were carried out. The final product had a good mechanical strength and showed 26% of the applied enzyme activity. The specific activity was 750 units per g of the dry cell product. The immobilized enzyme showed the kinetic parameters as follows; optimum pH at 5, optimum temperature at $55^{\circ}C$, activation energy of 19 kJ $mol^{-1}$, and apparent Km of 55 mM.