Institute for Integrated Cell Material science WPI iCeMS


Institute for Integrated Cell Material science WPI iCeMS

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Nagata K.O.,Institute for Integrated Cell Material science WPI iCeMS | Nakada C.,Institute for Integrated Cell Material science WPI iCeMS | Nakada C.,Instruments Company | Kasai R.S.,Kyoto University | And 4 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2013

The generation of high-density lipoprotein (HDL), one of the most critical events for preventing atherosclerosis, is mediated by ATP-binding cassette protein A1 (ABCA1). ABCA1 is known to transfer cellular cholesterol and phospholipids to apolipoprotein A-I (apoA-I) for generating discoidal HDL (dHDL) particles, composed of 100-200 lipid molecules surrounded by two apoA-I molecules; however, the regulatory mechanisms are still poorly understood. Here we observed ABCA1-GFP and apoA-I at the level of single molecules on the plasma membrane via a total internal reflection fluorescence microscope. We found that about 70% of total ABCA1-GFP spots are immobilized on the plasma membrane and estimated that about 89% of immobile ABCA1 molecules are in dimers. Furthermore, an ATPase-deficient ABCA1 mutant failed to be immobilized or form a dimer. We found that the lipid acceptor apoA-I interacts with the ABCA1 dimer to generate dHDL and is followed by ABCA1 dimer-monomer interconversion. This indicates that the formation of the ABCA1 dimer is the key for apoA-I binding and nascent HDL generation. Our findings suggest the physiological significance of conversion of the ABCA1 monomer to a dimer: The dimer serves as a receptor for two apoA-I molecules for dHDL particle generation. © PNAS 2013.

Shibata A.C.E.,Institute for Integrated Cell Material science WPI iCeMS | Shibata A.C.E.,Kyoto University | Fujiwara T.K.,Institute for Integrated Cell Material science WPI iCeMS | Fujiwara T.K.,Kyoto University | And 16 more authors.
Cytoskeleton | Year: 2012

The focal adhesion (FA) is an integrin-based structure built in/on the plasma membrane, mechanically linking the extracellular matrix with the termini of actin stress fibers, providing key scaffolds for the cells to migrate in tissues. The FA was considered as a micron-scale, massive assembly of various proteins, although its formation and decomposition occur quickly in several to several 10 s of minutes. The mechanism of rapid FA regulation has been a major mystery in cell biology. Here, using fast single fluorescent-molecule imaging, we found that transferrin receptor and Thy1, non-FA membrane proteins, readily enter the FA zone, diffuse rapidly there, and exit into the bulk plasma membrane. Integrin β3 also readily enters the FA zone, and repeatedly undergoes temporary immobilization and diffusion in the FA zone, whereas approximately one-third of integrin β3 is immobilized there. These results are consistent with the archipelago architecture of the FA, which consists of many integrin islands: the membrane molecules enter the inter-island channels rather freely, and the integrins in the integrin islands can be rapidly exchanged with those in the bulk membrane. Such an archipelago architecture would allow rapid FA formation and disintegration, and might be applicable to other large protein domains in the plasma membrane. © 2012 Wiley Periodicals, Inc.

Pathak P.,University of Nevada, Reno | Gupta S.,University of Nevada, Reno | Grosulak K.,University of Nevada, Reno | Imahori H.,Institute for Integrated Cell Material science WPI iCeMS | And 2 more authors.
Journal of Physical Chemistry C | Year: 2015

A nature-inspired "tree"-like 3D hierarchical titania/TiO2 architecture was prepared as a façade to strategically assemble reduced graphene oxide/RGO (a facile charge transporter) and cadmium sulfide/CdS (a visible light harvester) is presented for the first time. The core 3D TiO2 heterostructure was prepared using a TiCl3 mediated surface treatment of titania nanorods on fluorine-doped tin oxide (FTO) coated glass-slides. The performance of the 3D TiO2, which varies as a function of the treatment time, was first examined to achieve optimal photoelectrochemical response. Subsequently, the architecture was tested for its (i) theoretical water-splitting potential and (ii) ability to immobilize chalcogenide nonocrystals (CdS) with and without RGO. The best "applied bias to photoconversion efficiency" (% ABPE) was noted to be 0.36% (-0.15 V vs Ag/AgCl) for the TiO2 architecture. A 140% increase with CdS deposition on the branched TiO2 indicated the structures' ability to effectively immobilize the chalcogenide. The effect of RGO on the photoelectrochemical response was explored and an optimum loading (1 mg.mL-1) of RGO was noted to boost the photoresponse by an additional 150% compared to "CdS-only" photoanodes. Further, stability analysis performed over 3 h showed that the presence of RGO significantly delays CdS corrosion-driven deactivation. Finally, the fundamental insights on the impact of RGO in the 3D TiO2/RGO/CdS photoanode and its effect on the charge transportation mechanism were examined using electrochemical impedance spectroscopy. © 2015 American Chemical Society.

Kusumi A.,Institute for Integrated Cell Material science WPI iCeMS | Kusumi A.,Kyoto University | Fujiwara T.K.,Institute for Integrated Cell Material science WPI iCeMS | Chadda R.,Institute for Integrated Cell Material science WPI iCeMS | And 7 more authors.
Annual Review of Cell and Developmental Biology | Year: 2012

The recent rapid accumulation of knowledge on the dynamics and structure of the plasma membrane has prompted major modifications of the textbook fluid-mosaic model. However, because the new data have been obtained in a variety of research contexts using various biological paradigms, the impact of the critical conceptual modifications on biomedical research and development has been limited. In this review, we try to synthesize our current biological, chemical, and physical knowledge about the plasma membrane to provide new fundamental organizing principles of this structure that underlie every molecular mechanism that realizes its functions. Special attention is paid to signal transduction function and the dynamic aspect of the organizing principles. We propose that the cooperative action of the hierarchical three-tiered mesoscale (2300 nm) domains actin-membrane-skeleton induced compartments (40300 nm), raft domains (220 nm), and dynamic protein complex domains (310 nm) is critical for membrane function and distinguishes the plasma membrane from a classical Singer-Nicolson-type model. Copyright © 2012 by Annual Reviews. All rights reserved.

Tanaka K.,Institute for Integrated Cell Material science WPI iCeMS | Tanaka K.,Japan Science and Technology Agency
EPJ Web of Conferences | Year: 2013

We present novel generation methods of intense terahertz single cycle pulses. The Cherenkov scheme with tilted wave-front technique in the LiNbO 3 crystal gives us the maximum electric field larger than 1 MV/cm, which ponderomotive energy is as large as 10 eV. The ponderomotive energy is strong enough to ionize bound electronic states in solids such as donors and accepters and easy to induce nonlinear optical effects in solids. © Owned by the authors, published by EDP Sciences, 2013.

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