• Title/Summary/Keyword: chemical binding

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Surface modification of polymeric membranes for low protein binding

  • Higuchi, Akon;Tamai, Miho;Tagawa, Yoh-Ichi;Chang, Yung;Ling, Qing-Dong
    • Membrane and Water Treatment
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    • v.1 no.2
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    • pp.103-120
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    • 2010
  • Surface modification of microfiltration and ultrafiltration membranes has been widely used to improve the protein adsorption resistance and permeation properties of hydrophobic membranes. Several surface modification methods for converting conventional membranes into low-protein-binding membranes are reviewed. They are categorized as either physical modification or chemical modification of the membrane surface. Physical modification of the membrane surface can be achieved by coating it with hydrophilic polymers, hydrophilic-hydrophobic copolymers, surfactants or proteins. Another method of physical modification is plasma treatment with gases. A hydrophilic membrane surface can be also generated during phase-inverted micro-separation during membrane formation, by blending hydrophilic or hydrophilic-hydrophobic polymers with a hydrophobic base membrane polymer. The most widely used method of chemical modification is surface grafting of a hydrophilic polymer by UV polymerization because it is the easiest method; the membranes are dipped into monomers with and without photo-initiators, then irradiated with UV. Plasma-induced polymerization of hydrophilic monomers on the surface is another popular method, and surface chemical reactions have also been developed by several researchers. Several important examples of physical and chemical modifications of membrane surfaces for low-protein-binding are summarized in this article.

Binding affinity of some herbal extracts on the muscarinic acetylcholine receptor subtype 1 $(mAChR-M_1)$ (수종 생약추출물의 muscarin성$(M_1\;type)$ acetylcholine 수용체$(mAChR-M_1)$에 대한 친화력 검색)

  • Kim, Young-Sup;Kim, Jeoung-Seob;Kim, Seong-Kie;Heor, Jung-Hee;Lee, Byung-Eui;Ryu, Shi-Yong
    • Korean Journal of Pharmacognosy
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    • v.32 no.3 s.126
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    • pp.219-225
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    • 2001
  • The water extracts of 82 Korean medicinal herbs were examined for the binding affinity on the recombinant human muscarinic acetylcholine receptor subtype 1 $(mAChR-M_1)$ produced from the CHO (Chinese Hamster Ovary) cell line. Of those tested, the extracts of Coptidis Rhizoma, Phellodendri Cortex, Hedyotis Herba and of Terminariae Fructus were found to exhibit a significant competition with $[^3H]$ N-methyl-scopolamine for the specific binding to $mAChR-M_1$ in a dose dependent manner, respectively.

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Presteady State Kinetics of ATP Hydrolysis by Escherichia coli Rho Protein Monitors the Initiation Process

  • Jeong, Yong-Ju;Kim, Dong-Eun
    • Bulletin of the Korean Chemical Society
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    • v.27 no.2
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    • pp.224-230
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    • 2006
  • Escherichia coli transcription termination factor Rho catalyzes the unwinding of RNA/DNA duplex in reactions that are coupled to ATP binding and hydrolysis. We report here the kinetic mechanism of presteady state ATP binding and hydrolysis by the Rho-RNA complex. Presteady state chemical quenched-flow technique under multiple turnover condition was used to probe the kinetics of ATP binding and hydrolysis by the Rho-RNA complex. The quenched-flow presteady state kinetics of ATP hydrolysis studies show that three ATPs are bound to the Rho-RNA complex with a rate of $4.4\;{\times}\;10^5M^{-1}s^{-1}$, which are subsequently hydrolyzed at a rate of $88s^{-1}$ and released during the initiation process. Global fit of the presteady state ATP hydrolysis kinetic data suggests that a rapid-equilibrium binding of ATP to Rho-RNA complex occurs prior to the first turnover and the chemistry step is not reversible. The initial burst of three ATPs hydrolysis was proposed to be involved in the initialization step that accompanies proper complex formation of Rho-RNA. Based on these results a kinetic model for initiation process for Rho-RNA complex was proposed relating the mechanism of ATP binding and hydrolysis by Rho to the structural transitions of Rho-RNA complex to reach the steady state phase, which is implicated during translocation along the RNA.