Kaori Sugihara

In this Communication, we introduce transmembrane anion transport with pnictogen-bonding compounds and compare their characteristics with chalcogen- and halogen-bonding analogues. Tellurium-centered chalcogen bonds are at least as active as antimony-centered pnictogen bonds, whereas iodine-centered halogen bonds are 3 orders of magnitude less active. Irregular voltage-dependent single-channel currents, high gating charges, and efficient dye leakage support for the formation of bulky, membrane-di

Young plants of the common Okinawa mangrove species Bruguiera gymnorrhiza were transferred from freshwater to a medium with seawater salt level (500 mM NaCl). Two-dimensional gel electrophoresis revealed in the leaf extract of the plant a 33 kDa protein with pI 5.2, whose quantity increased as a result of NaCl treatment. The N-terminal amino acids sequence of this protein had a significant homology with mature region of oxygen evolving enhancer protein 1 (OEE1) precursor. The cloning of OEE1 pre

Polydiacetylenes (PDAs) are a family of mechanochromic polymers that change color from blue to red and emit fluorescence when exposed to external stimuli, making them extremely popular materials in biosensing. Although several informative reviews on PDA biosensing have been reported in the last few years, their mechanochromism, where external forces induce the color transition, has not been reviewed for a long time. This mini review summarizes recent progress in PDA mechanochromism, with a speci

Quantitative and anisotropic mechanochromism of polydiacetylene over nanoscale distances remains unaddressed even after 50 years of extensive research. This is because its anisotropic structure on substrates necessitates the application of both vertical and lateral forces (shear forces) to characterize it, whereas atomic force microscopy, which is the usual technique used to investigate nanoscale forces, is only capable of quantifying vertical forces. In this study, we address this lacuna by uti

A lipid bilayer with gigaohm resistance was fabricated over a single 800 nm pore in a Si3N4 chip using 50 nm liposomes. The nanopore was prefilled with a polyelectrolyte multilayer (PEM) that triggered the spontaneous fusion of the lipid vesicles. Pore-forming peptide melittin was incorporated in the bilayer, and single channel activities were monitored for a period of 2.5 weeks. The long lifetime of the system enabled the observation of the time-dependent stabilization effect of the melittin op

Thermochromic temperature of polydiacetylene has been reported to coincide with the melting temperature of its lipidic monomers, indicating that the solid-to-liquid phase transition of monomers is linked to the color change. In this work, we study a hypothesis that peptide-induced chromism is similarly mediated by the lipid phase transition as many antimicrobial peptides are known to modulate the melting temperature of lipids.

Conventional lipid-tube formation is based on either a tube phase of certain lipids or the shape transformation of lamellar structures by applying a point load. In the present study, lipid blocks in inverted hexagonal phase made of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) were shown to protrude lipid nanotubes upon a fluid-dynamic flow on polyelectrolyte-functionalized surfaces in physiological buffer solution. The outer diameter of the tubes is 19.1 ± 4.5 nm and their lengths are up

A procedure based on freezing and thawing was developed to induce the rupture of adsorbed lipid vesicles on solid surfaces into supported lipid bilayers (SLBs). The SLB assembly exploits the phase transition of both lipids and water during freezing. It enables SLB formation independent of the type of substrates and lipids as long as the vesicles spontaneously adsorb onto the surface. The created SLB is a single bilayer, and has a diffusion coefficient of (0.6–4) × 10−8 cm2 s−1 on TiO2, which is

We have demonstrated colorimetric and fluorescence detection of a peptide, melittin, based on polydiacetylene (PDA) made of 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC(8,9)PC). The PDA used in this work has a phosphocholine headgroup, which mimics peptide–cell membrane interactions better than the conventional PDAs with carboxyl headgroups. The dose curve (colorimetric response vs. melittin concentration) showed a half maximum response at the melittin concentration of 0.1 mg ml

Horizontal black lipid membranes (BLMs) enable optical microscopy to be combined with the electrophysiological measurements for studying ion channels, peptide pores, and ionophores. However, a careful literature review reveals that simultaneous fluorescence and electrical recordings in horizontal BLMs have been rarely reported for an unclear reason, whereas many works employ bright-field microscopy instead of fluorescence microscopy or perform fluorescence imaging and electrical measurements one

The wedge calibration method is the most popular calibration technique in friction force microscopy for converting raw lateral laser deflection signals (in volt) into forces (in newton). Recent trends in nanotribology demand the use of the method at nanonewton (nN) force ranges; however, this method fails at these small forces. The objective of the present work is to identify the reason why the conventional wedge calibration method fails at nN force ranges. We found that the equation used in the

A mechanochromic polymer, polydiacetylene, changes color upon ligand binding, being a popular material in biosensing. However, whether it can also detect ligand functions in addition to binding is left understudied. In this work, we report that the polydiacetylene can be used to determine the net charges and the mode of actions (carpet model, toroidal pore model, etc.) of antimicrobial peptides and detergents via EC₅₀ and Hill coefficients from the colorimetric response-dose curves. T