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Featured researches published by Daichi Yamaura.


Scientific Reports | 2017

Mechanically stable solvent-free lipid bilayers in nano- and micro-tapered apertures for reconstitution of cell-free synthesized hERG channels

Daisuke Tadaki; Daichi Yamaura; Shun Araki; Miyu Yoshida; Kohei Arata; Takeshi Ohori; Kenichi Ishibashi; Miki Kato; Teng Ma; Ryusuke Miyata; Yuzuru Tozawa; Hideaki Yamamoto; Michio Niwano; Ayumi Hirano-Iwata

The self-assembled bilayer lipid membrane (BLM) is the basic component of the cell membrane. The reconstitution of ion channel proteins in artificially formed BLMs represents a well-defined system for the functional analysis of ion channels and screening the effects of drugs that act on them. However, because BLMs are unstable, this limits the experimental throughput of BLM reconstitution systems. Here we report on the formation of mechanically stable solvent-free BLMs in microfabricated apertures with defined nano- and micro-tapered edge structures. The role of such nano- and micro-tapered structures on the stability of the BLMs was also investigated. Finally, this BLM system was combined with a cell-free synthesized human ether-a-go-go-related gene channel, a cardiac potassium channel whose relation to arrhythmic side effects following drug treatment is well recognized. Such stable BLMs as these, when combined with a cell-free system, represent a potential platform for screening the effects of drugs that act on various ion-channel genotypes.


Langmuir | 2018

Amphiphobic Septa Enhance the Mechanical Stability of Free-Standing Bilayer Lipid Membranes

Daichi Yamaura; Daisuke Tadaki; Shun Araki; Miyu Yoshida; Kohei Arata; Takeshi Ohori; Kenichi Ishibashi; Miki Kato; Teng Ma; Ryusuke Miyata; Hideaki Yamamoto; Ryugo Tero; Masao Sakuraba; Toshio Ogino; Michio Niwano; Ayumi Hirano-Iwata

Artificial bilayer lipid membranes (BLMs) provide well-defined systems for investigating the fundamental properties of membrane proteins, including ion channels, and for screening the effect of drugs that act on them. However, the application of this technique is limited due to the low stability and low reconstitution efficiency of the process. We previously reported on improving the stability of BLM based on the fabrication of microapertures having a tapered edge in SiO2/Si3N4 septa and efficient ion channel incorporation based on vesicle fusion accelerated by a centrifugal force. Although the BLM stability and incorporation probability were dramatically improved when these approaches were used, some BLMs were ruptured when subjected to a centrifugal force. To further improve the BLM stability, we investigated the effect of modifying the surface of the SiO2/Si3N4 septa on the stability of BLM suspended in the septa. The modified surfaces were characterized in terms of hydrophobicity, lipophobicity, and surface roughness. Diffusion coefficients of the lipid monolayers formed on the modified surfaces were also determined. Highly fluidic lipid monolayers were formed on the amphiphobic substrates that had been modified with long-chain perfluorocarbons. Free-standing BLMs formed in amphiphobic septa showed a much higher mechanical stability, including tolerance to water movement and applied centrifugal forces with and without proteoliposomes, than those formed in the septa that had been modified with a short alkyl chain. These results demonstrate that highly stable BLMs are formed when the surface of the septa has amphiphobic properties. Because highly fluidic lipid monolayers that are formed on the septa seamlessly connect with BLMs in a free-standing region, the high fluidity of the lipids contributes to decreasing potential damage to BLMs when mechanical stresses are applied. This approach to improve the BLM stability increases the experimental efficiency of the BLM systems and will contribute to the development of high-throughput platforms for functional assays of ion channel proteins.


Japanese Journal of Applied Physics | 2018

Micro- and nanofabrication methods for ion channel reconstitution in bilayer lipid membranes

Daisuke Tadaki; Daichi Yamaura; Kohei Arata; Takeshi Ohori; Teng Ma; Hideaki Yamamoto; Michio Niwano; Ayumi Hirano-Iwata

The self-assembled bilayer lipid membrane (BLM) forms the basic structure of the cell membrane and serves as a major barrier against ion movement. Ion channel proteins function as gated pores that permit ion permeation across the BLM. The reconstitution of ion channel proteins in artificially formed BLMs represents a well-defined system for investigating channel functions and screening drug effects on ion channels. In this review, we will discuss our recent microfabrication approaches to the formation of stable BLMs containing ion channel proteins as a potential platform for next-generation drug screening systems. BLMs formed in a microaperture having a tapered edge exhibited highly stable properties, such as a lifetime of ~65 h and tolerance to solution changes even after the incorporation of the human ether-a-go-go-related gene (hERG) channel. We also explore a new method of efficiently incorporating human ion channels into BLMs by centrifugation. Our approaches to the formation of stable BLMs and efficient channel incorporation markedly improve the experimental efficiency of BLM reconstitution systems, leading to the realization of a BLM-based high-throughput platform for functional assays of various ion channels.


Journal of Electroanalytical Chemistry | 2019

Photomodulation of electrical conductivity of a PCBM-doped free-standing lipid bilayer in buffer solution

Kensaku Kanomata; Takafumi Deguchi; Teng Ma; Takumi Haseyama; Masanori Miura; Daichi Yamaura; Daisuke Tadaki; Michio Niwano; Ayumi Hirano-Iwata; Fumihiko Hirose


The Japan Society of Applied Physics | 2018

Light-induced current response of PCBM-embedded lipid bilayer membrane

Takafumi Deguchi; Ma Teng; Kensaku Kanomata; Daichi Yamaura; Daisuke Tadaki; Fumihiko Hirose; Ayumi Hirano


The Japan Society of Applied Physics | 2018

Quantification of Drug Side Effects on Cell-Free Synthesized Ion-Channels in Solvent-Free Lipid Bilayers Based on Microfabricated Silicon Chips

Miki Kato; Miyu Yoshida; Daichi Yamaura; Kohei Arata; Daisuke Tadaki; Hideaki Yamamoto; Yuzuru Tozawa; Michio Niwano; Ayumi Hirano


The Japan Society of Applied Physics | 2017

Enhance stability of free-standing lipid bilayer by surface modification

Daichi Yamaura; Tadaki Daisuke; Araki Shun; Yoshida Miyu; Arata Kohei; Ohori Takeshi; Yamamoto Hideaki; Ogino Toshio; Niwano Michio; Hirano-Iwata Ayumi


The Japan Society of Applied Physics | 2017

Recording Ion-Channel Currents at Artificial Lipid Bilayers Formed in Microfabricated Silicon Chips

Kohei Arata; Ayumi Hirano-Iwata; Daisuke Tadaki; Daichi Yamaura; Shun Araki; Miyu Yoshida; Takeshi Ohori; Hideaki Yamamoto; Michio Niwano


The Japan Society of Applied Physics | 2017

Optimization of edge structures of micro-apertures fabricated in semiconductor silicon chips for formation of stable artificial bilayer lipid membranes

Daisuke Tadaki; Ayumi Hirano-Iwata; Daichi Yamaura; Shun Araki; Miyu Yoshida; Kohei Arata; Takeshi Ohori; Hideaki Yamamoto; Michio Niwano


The Japan Society of Applied Physics | 2017

Fabrication of silicon chips for evaluation of electrical characteristics of bilayer lipid membranes

Takeshi Ohori; Ayumi Hirano-Iwata; Daisuke Tadaki; Daichi Yamaura; Shun Araki; Miyu Yoshida; Kohei Arata; Hideaki Yamamoto; Michio Niwano

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Toshio Ogino

Yokohama National University

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