Publications (17)44.88 Total impact
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Article: Rotary motion driven by a direct current electric field
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ABSTRACT: We report the rotary motion of an aqueous microdroplet in an oil phase under a stationary direct current electric field. A droplet exhibits rotary motion under a suitable geometrical arrangement of positive and negative electrodes. Rotary motion appears above a certain critical electric potential and its frequency increases with an increase in the potential. A simple theoretical model is proposed to describe the occurrence of this rotary motion, together with an argument for the future expansion of this micro rotary motor system.Applied Physics Letters 04/2010; · 3.84 Impact Factor -
Article: Hyaluronic acid and its derivative as a multi-functional gene expression enhancer: protection from non-specific interactions, adhesion to targeted cells, and transcriptional activation.
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ABSTRACT: Hyaluronic acid (HA), a natural anionic mucopolysaccharide, can be deposited onto the cationic surface of DNA/polyethyleneimine (PEI) complexes to recharge the surface potential and reduce nonspecific interactions with proteins. HA can also be used as a ligand to target specific cell receptors. Furthermore, HA-coating enhanced the transcriptional activity of the plasmid/PEI complexes, probably by loosening the tight binding between DNA and PEI, which facilitated the approach of transcription factors. Amphoteric HA derivative having spermine side chains (Spn-HA) with a structure similar to HMG protein showed higher transcription-enhancing activity than HA. Plasmid/PEI/Spn-HA ternary complex exhibited 29-fold higher transgene expression efficiency than naked plasmid/PEI complexes in CHO cells.Journal of Controlled Release 06/2006; 112(3):382-8. · 5.73 Impact Factor -
Article: A design of nanosized PEGylated-latex mixed polymer solution for microchip electrophoresis.
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ABSTRACT: We report here advanced microchip electrophoresis using a nanoparticle doped polymer solution that enables greater separation of DNA. The proposed system is simple and effective without any new apparatus or complicated procedures. Various amounts and sizes (80 nm, 110 nm, and 193 nm) of polymer nanoparticle solutions (PEGylated-latex) were mixed with a conventional polymer solution for microchip electrophoresis. When a 0.49 wt% hydroxyl propyl methyl cellulose (HPMC) buffer solution was mixed with a 2.25 wt% 80 nm-PEGylated-latex a higher separation efficiency and a higher mobility of a wider molecular range of dsDNA (10 bp to 2 kbp) was achieved under low viscosity conditions (<5.5 cP) than in conventional 0.7% HPMC. The separation performance was dependent on the particle size and concentration. Furthermore, the effectiveness of the larger PEGylated-latex (193 nm) was not as high as the smaller one (80 to 110 nm). The observed separation improvement by polymer solution with latex-nanoparticles seems to derive from the balance between wider polymer mesh size and the structural obstacles of particles in the buffer.Lab on a Chip 03/2005; 5(2):199-204. · 5.67 Impact Factor -
Article: Nanospheres for DNA separation chips.
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ABSTRACT: We report here a technology to carry out separations of a wide range of DNA fragments with high speed and high resolution. The approach uses a nanoparticle medium, core-shell type nanospheres, in conjunction with a pressurization technique during microchip electrophoresis. DNA fragments up to 15 kilobase pairs (kbp) were successfully analyzed within 100 s without observing any saturation in migration rates. DNA fragments migrate in the medium while maintaining their characteristic molecular structure. To guarantee effective DNA loading and electrofocusing in the nanosphere solution, we developed a double pressurization technique. Optimal pressure conditions and concentrations of packed nanospheres are critical to achieve improved DNA separations.Nature Biotechnology 04/2004; 22(3):337-40. · 23.27 Impact Factor -
Article: PEG−PLL Block Copolymers Induce Reversible Large Discrete Coil−Globule Transition in a Single DNA Molecule through Cooperative Complex Formation
07/2003; -
Article: Direct observation of brownian motion of macromolecules by fluorescence microscope
Journal of Polymer Science Part B Polymer Physics 03/2003; 30(7):779 - 783. · 1.53 Impact Factor -
Article: Periodic behavior of DNA molecules during steady field gel electrophoresis
04/2002; -
Article: Periodic Motion of Large DNA Molecules during Steady Field Gel Electrophoresis
04/2002; -
Article: Motion of large DNA molecules traveling from solution to gel under steady field
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ABSTRACT: Direct observation of individual T4 DNA molecules at the interface between gel and pure solvent under steady electric field was carried out with fluorescence microscopy. Statistical analyses of the image data show that (1) when a DNA arrives at the gel surface, it remains there for a short time before the DNA stretches its arms to enter the gel, and (2) the time spent on the gel surface increases with an increase of the agarose percentage in the gel. © 1996 John Wiley & Sons, Inc.Journal of Polymer Science Part B Polymer Physics 12/1998; 34(6):1105 - 1111. · 1.53 Impact Factor -
Article: Higher Order Structure of DNA Controlled by the Redox State of Fe2+/Fe3+
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ABSTRACT: We performed fluorescence microscopic observation of the conformational change of individual T4DNAs (166 kbp) induced by Fe2+/Fe3+. Individual DNAs undergo a marked discrete transition from an elongated coil into a collapsed globule with an increase in the Fe3+ concentration at around 1−2 μM. On the other hand, DNAs remained in the elongated coil state with the addition of Fe2+ up to a concentration of 30 μM. Using these experimental results we tried to control the transition of DNA by the redox reaction of Fe2+/Fe3+. We found that collapsed globule DNA unfolds with the reduction of Fe3+. The results have been analyzed theoretically in terms of the double minima in the free energy profile of a single DNA molecule, indicating that the change in the translational entropy of the counterions is the main reason why high-valency ions are more effective in inducing the collapse.11/1997; -
Article: Reorientation of large DNA molecules in concentrated polyacrylamide solution during crossed‐field electrophoresis
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ABSTRACT: Recently, we found that, in concentrated neutral solutions, DNA molecules migrate in linear conformation under steady electric field. In this paper, we report the conformational change of DNA during 120° crossed-field electrophoresis in the same polymer solution. We found that, in concentrated polyacrylamide solutions, the reorientation process of DNAs becomes simple: the DNA goes back along the previous track and the reorientation time is longer motion for the separation of DNA fragments in pulsed field gel electrophoresis. We expect that this phenomenon is useful for a more efficient separation technique of large DNAs than the current pulsed field gel electrophoresis.Electrophoresis 12/1996; 18(11):1912 - 1915. · 3.30 Impact Factor -
Article: Change of the higher order structure of DNA induced by the complexation with intercalating synthetic polymer, as is visualized by fluorescence microscopy.
Nucleic Acids Research. 01/1993; 21:37-40. -
Article: Controlling Topological Defect in Nematic Liquid Crystal with Focuesed Laser(Poster session 2, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)
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ABSTRACT: この論文は国立情報学研究所の電子図書館事業により電子化されました。 シュリーレンテクスチャを擁するネマチック液晶試料中に、集光レーザーを位置を変えながら連続照射することで多重のリング状wall構造をつくり出した。このwall構造はその中心から動径方向にダイレクタが回転している秩序構造であると考えられるが、実際に時計回りと反時計回りの二種類が存在することを実験的に確認した。また輝度解析によりリングの半径が等比数列になっていることを発見し、それを数理モデルにより説明した。 Liquid crystal has an anisotropic optical property that gives huge ordered and disorderd spatio-temporal patterns through a polarizing microscopy. Here, we report a new orderd structure formation mediated by a defect of liquid crystal together with a convergent linearly polarized laser beam Lnearly polarized laser beam have an ability to reorient illuminated liquid crystalline molecules along the laser polarization direction. -
Article: Formation of multiple ring-like wall in Nematic Liquid Crystal with focused laser beam
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ABSTRACT: この論文は国立情報学研究所の電子図書館事業により電子化されました。 研究会報告 シュリーレン組織状のネマチック状態に、集光したYAGレーザーを照射した。その結果クロスニコル観察下で、レーザーの照射地点を中心として明暗が交互に現れる同心円状のパターンを生じる事を見いだした。この配向は一種のwall構造であり、隣接するリング半径の比は一定であることがわかった。 -
Article: Electrophoresis of long DNA molecules in linear polyacrylamide solutions
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ABSTRACT: Electrophoresis of long DNA (T4 DNA; 166 kb, S. pombe chromosomal DNA; 3–6 Mb) in linear polyacrylamide solutions was investigated by fluorescence microscopy and capillary electrophoresis. In the past studies on electrophoresis of long DNA in a polymer solution, it was reported that DNA migrates in `U-shape conformation'. We found that at higher polymer concentrations, the shape of the migrating DNA changes from U shape to linear shape (`I-shape conformation'). In the migration mode with the I-shape conformation, the DNA moves with almost constant velocity and constant shape. However, the migration velocity does depend on the DNA size, and it is possible to separate DNAs under this I-shape motion. Actually, Mb-sized DNAs are well separated within 5 min in the region for the I-shape motion by means of capillary electrophoresis with a DC field. Considering that it takes 20 h to separate Mb-sized DNAs by standard pulsed-field gel electrophoresis (PFGE), this results will be useful for the separation of giant DNAs.Biophysical Chemistry. -
Article: Dissociation of DNA–polycation complexes by polyanions and polyampholytes
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ABSTRACT: Both polyanions and polyampholytes cause the dissociation of DNA–polycation complexes in experiments. To elucidate their mechanisms, Monte Carlo simulations have been conducted on a simple model, with DNA modeled as an infinite charged cylinder and other polyions treated as charged Shish–Kebab rods. Our results show that a highly charged polyanion is required to separate a polycation from a DNA. However, for a diblocked polyampholyte, its net dipole induces a higher probability to bridge a DNA and a polycation. Thus, the loosening mechanisms are found to be markedly different between polyanions and polyampholytes. -
Article: Opposite effect between intercalator and minor groove binding drug on the higher order structure of DNA as is visualized by fluorescence microscopy
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ABSTRACT: Fluorescence microscopy is applied to obtain the information on the change of the higher-order structure of giant DNA molecules in an aqueous solution. Using T4 DNA, it becomes clear that ethidium bromide, an intercalator, tends to extend the DNA, whereas minor groove binding drugs such as 4′,6-diamidino-2-phenylindole and Hoechst 33258 tend to contract the DNA. These changes of higher-order structure have been quantitatively evaluated as the changes in persistent length together with the change of contour length. It is also confirmed that the persistent length obtained by use of fluorescence microscopy is reliable enough comparing with those reported for the shorter DNA by use of light scattering.Biochemical and Biophysical Research Communications.
Top co-authors
Top Journals
Institutions
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2006–2010
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Kyoto University
- Department of Physics II
Kyoto, Kyoto-fu, Japan
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1996–2003
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Nagoya University
Nagoya-shi, Aichi-ken, Japan
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