The organization of lateral domains, called lipid rafts, in plasma membranes is essential for physiological functions, such as signaling and trafficking. In this study, we performed a systematic analysis of lateral phase separation under membrane tension. We applied osmotic pressure directed toward the outside of vesicles to induce membrane tension. Microscopic observations clarified the shifts in phase structures within bilayer membranes with change in tension and temperature. The miscibility transition temperature between one-liquid and two-liquid states was shown to increase under tension. We also observed a shift in the transition temperature between two-liquid and solid-liquid states in membranes under tension. We determined a quantitative phase diagram of phase organization with respect to the applied pressure and temperature. The results indicate that membrane tension can induce phase separation in homogeneous membranes. Our findings may provide insight into the biophysics of bilayer phase organization under tension, which is an intrinsic mechanical property of membranes.

We present a simple, rapid, and robust method for preparing asymmetric cell-sized lipid bilayer vesicles using water-in-oil (W/O) microdroplets transferred through an oil-water interface. The efficiency for producing cell-sized model membranes is elucidated in relation to the vesicular size and the weight of contained water-soluble molecules. We demonstrate the biological asymmetric nature and the formation of lipid raft microdomain structures using fluorescence microscopy.

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We fabricated and experimentally investigated a nanostructure known as a quantum-well (QW) microtube, which is a fine tube with a micron- or nanometer-order diameter fabricated by rolling a semiconductor GaAs QW. Although the wall thickness is only 40 nm, the system retains the quantum properties of a QW, and photoluminescence from the QW subband can be clearly observed. Even though the QW width is sufficiently small to make the QW subband type-II band-aligned, a type-II to type-I transition caused by uniaxial strain in the microtube allows for optical emission.

A Pt/Pd/C core−shell-structured catalyst with an extraordinarily high activity of 3625 A g −1 -Pt at 0.9 V versus a reversible hydrogen electrode (RHE) for the oxygen reduction reaction (ORR) was created by a synergistic combination of intrinsically high activity and surface decoration with melamine or tetra-(tert-butyl)-tetraazaporphyrin (tBuTAP). The intrinsically highly active Pt/Pd/C catalyst with an ORR mass activity of ca. 1000 A g −1 -Pt at 0.9 V versus RHE was synthesized by a direct displacement reaction method, and the activity was activated to ca. 1500 A g −1 -Pt via a high activation protocol (HAP) (a rectangular potential cycling of 0.05−1.0 V vs an RHE conducted in 0.1 mol dm −3 HClO 4 under an Ar atmosphere at 80 °C). The ORR activities of the Pt/Pd/C catalysts were further increased by surface decoration with melamine or tBuTAP, and the mass activity of ORR of the catalyst activated by an HAP was enhanced to 3625 A g −1 -Pt at 0.9 V versus RHE via the melamine decoration, which is about 11-fold that of a reference Pt/C catalyst (320 A g −1 -Pt). Cyclic voltammograms, linear sweep voltammograms, and CO stripping voltammograms indicated that the surface decoration further destabilized the OH species (OH ad ) adsorbed on the Pt shell and suppressed the formation of oxide on the Pt shell, which could explain the extraordinary enhancement of ORR activity. We present guidelines for creating Pt-based catalysts with extraordinarily high activity for the ORR by the synergistic combination of the intrinsically active Pt-based catalyst [improvement from the inside of Pt nanoparticles (NPs)] and surface decoration (improvement from the outside of Pt NPs).