Microscopic Dielectrophoresis of Single DNA in the Presence of Some Substances in Aqueous Solutions

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  • NISHIKAWA Ayaka
    Department of Chemistry, Graduate School of Science, Hiroshima University
  • TSUKAHARA Satoshi
    Department of Chemistry, Graduate School of Science, Hiroshima University
  • FUJIWARA Terufumi
    Department of Chemistry, Graduate School of Science, Hiroshima University

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  • 種々の添加物存在下における単一ＤＮＡの顕微誘電泳動挙動
  • シュジュ ノ テンカブツ ソンザイ カ ニ オケル タンイツ DNA ノ ケンビユウデン エイドウ キョドウ

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Abstract

A newly designed planar quadrupole microelectrode of gold (thickness, 50 nm) and chromium (5 nm) was fabricated by photolithography. The radius of its working area was 125 μm. Two kinds of large DNAs, λDNA (48 kbp; bp, base pair) and T4GT7DNA (166 kbp), labeled with cationic fluorophores, were taken as a sample DNA. The dielectrophoretic (DEP) behaviors of DNA in the quadrupole electrode were measured with a fluorescence microscope by applying an alternating current with a frequency of 1 kHz ~ 15 MHz and a root-mean-square voltage of 7.1 V. All of the single DNAs migrated radially to the edge of the electrode in the whole frequency range, that is, positive DEP, caused by a dynamic ion cloud around DNA. The DEP behaviors of DNAs confirmed that the fabricated quadrupole electrode made an ideal nonuniform electric field in the working area. Some aqueous substances were added and their influence on the DEP of DNA was examined. The longer T4GT7DNA migrated a little faster than λDNA, and an intercalating fluorophore slightly enhanced the DEP velocity of DNA. Aqueous polyethylene glycol (PEG) at a high concentration was known to induce a globule transition of DNA, but the viscosity of the solution at the PEG concentration was about 60-times higher than that of water. The dominant effect of PEG on the DEP of DNA was not the globule transition but the enlarged friction force that DNAs underwent from the solution, that is, a slow DEP migration. Anionic and nonionic surfactants had only a small influence on the positive DEP of DNA. A cationic surfactant (hexadecyltrimethylammonium chloride, CTAC) was strongly bound to DNA with an electrostatic interaction, but the DEP behavior of DNA was not measured because CTAC eliminated the interaction of DNA with the cationic fluorophores. Nonionic O/W emulsions showed negative DEP, independent of the DNA of positive DEP.<br>

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 54 (6), 459-465, 2005

    The Japan Society for Analytical Chemistry

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