Biological membranes play pivotal roles in the cellular activities. Transmembrane proteins are the central molecules that conduct membrane-mediated biochemical functions such as signal transduction and substance transportation. Not only the molecular functions but also the supramolecular properties of the transmembrane proteins such as self-assembly, delocalization, orientation and signal response are essential for controlling cellular activities. Here we report anisotropic ligand responses of a synthetic multipass transmembrane ion channel. An unsymmetrical molecular structure allows for oriented insertion of the synthetic amphiphile to a bilayer by addition to a pre-formed membrane. Complexation with a ligand prompts ion transportation by forming a supramolecular channel, and removal of the ligand deactivates the transportation function. Biomimetic regulation of the synthetic channel by agonistic and antagonistic ligands is also demonstrated not only in an artificial membrane but also in a biological membrane of a living cell.

Transmembrane proteins within biological membranes exhibit varieties of important functions that are vital for many cellular activities, and the development of their synthetic mimetics allows for deep understanding in related biological events. Inspired by the structures and functions of natural ion channels that can respond to multiple stimuli in an anisotropic manner, we developed multiblock amphiphile V F in this study. When V F was incorporated into the lipid bilayer membranes, V F formed a supramolecular ion channel whose ion transport property was controllable by the polarity and amplitude of the applied voltage. Microscopic emission spectroscopy revealed that V F changed its molecular conformation in response to the applied voltage. Furthermore, the ion transport property of V F could be reversibly switched by the addition of (R)-propranolol, an aromatic amine known as an antiarrhythmic agent, followed by the addition of β-cyclodextrin for its removal. The highly regulated orientation of V F allowed for an anisotropic dual-stimuli-responsiveness for the first time as a synthetic ion channel.

A miniature piezoelectric ultrasonic motor (USM) using the shear mode of (K,Na)NbO 3 (KNN)-based lead-free piezoelectric ceramics was developed. The motor can be driven in the shearing and bending vibration modes. By using the finite-element method, the motor vibration modes and driving mechanism were modeled. Both the ''soft-type'' (high-d USM) and ''hard-type'' (high-Q m USM) KNN-based lead-free piezoelectric ceramics were employed to clarify the characteristics of USMs. The experimental results reveal that the high-d USM widens the band of operational frequency in both vibration modes. In the shearing vibration mode, the high-d USM showed a revolution speed of 416 rpm, a torque of 41.5 mN m, and an efficiency of 0.6%, whereas the high-Q m USM showed the same characteristics of 313 rpm, 19.6 mN m and 1.6%, respectively. In the bending vibration mode, the characteristics of the high-Q m USM were 376 rpm, 51.4 mN m and 0.4%; however, the characters of the high-d USM deteriorated owing to the shift in resonance frequency caused by heat generation.

A chiral ligand for the rhodium‐catalyzed asymmetric 1,4‐addition of an arylboronic acid to a coumarin substrate that could markedly reduce catalyst loading was developed using interplay between theoretical and experimental approaches. Evaluation of the transition states for insertion and for hydrolysis of intermediate complexes (which were emphasized in response to the experimental results) using DFT calculations at the B97D/6‐31G(d) level with the LANL2DZ basis set for rhodium revealed that: (i) the electron‐poor nature of the ligands and (ii) CH–π interactions between the ligand and coumarin substrates played significant roles in both acceleration of insertion and inhibition of ArB(OH)2 decomposition (protodeboronation). The computationally‐designed ligand, incorporating the above information, enabled a decrease in the catalyst loading to 0.025 mol% (S/C=4,000), which is less than one one‐hundredth relative to past catalyst loadings of typically 3 mol%, with almost complete enantioselectivity. Furthermore, the gram‐scale synthesis of the urological drug, (R)‐tolterodine (l)‐tartrate, was demonstrated without the need of intermediate purification.magnified image

Inspired by mechanosensitive potassium channels found in nature, we developed a fluorinated amphiphilic cyclophane composed of fluorinated rigid aromatic units connected via flexible hydrophilic octa­(ethylene glycol) chains. Microscopic and emission spectroscopic studies revealed that the cyclophane could be incorporated into the hydrophobic layer of the lipid bilayer membranes and self-assembled to form a supramolecular transmembrane ion channel. Current recording measurements using cyclophane-containing planer lipid bilayer membranes successfully demonstrated an efficient transmembrane ion transport. We also demonstrated that the ion transport property was sensitive to the mechanical forces applied to the membranes. In addition, ion transport assays using pH-sensitive fluorescence dye revealed that the supramolecular channel possesses potassium ion selectivity. We also performed all-atom hybrid quantum-mechanical/molecular mechanical simulations to assess the channel structures at atomic resolution and the mechanism of selective potassium ion transport. This research demonstrated the first example of a synthetic mechanosensitive potassium channel, which would open a new door to sensing and manipulating biologically important processes and purification of key materials in industries.

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The morphology of corannulene molecules encapsulated in a single-walled carbon nanotube (SWCNT) is addressed using atomistic simulations. Firstly, dynamic simulation (DS) of encapsulation of corannulene molecules into a SWCNT is performed using a molecular dynamics (MD) method. It is revealed that corannulene molecules encapsulated in a SWCNT tend to form concave-concave (CC) dimers, and these dimers make stacks tilting against the SWCNT axis or take an arrangement such that their convex surfaces face the inner wall of the SWCNT. This tendency arises from the fact that the van der Waals interactions between the convex surfaces of the corannulene molecules and the inner wall of the SWCNT dominate in their dynamic encapsulation into the SWCNT, and CC dimers are favored based on the energetics. Next, conjugate gradient (CG) energy minimizations starting from two kinds of initial arrangement of corannulene molecules in a SWCNT, concave-convex (CV) and CC/convex-convex (VV) arrangements, are performed. The CG energy minimizations confirm the result of DS that CC dimers are the structural motif of corannulene molecules in a SWCNT. From the final configurations of both the simulations, the tilt angles and intermolecular distances of the stacked molecules are calculated. With increasing the SWCNT diameter, the tilt angles decrease while the intermolecular distances remain almost constant. The tilt angles of the stacked corannulene molecules are approximately expressed by a semi-analytical formula which is derived on the basis of a geometrical constraint condition.

We designed multiblock amphiphiles AmF and AmH, which consist of perfluorinated and non‐fluorinated hydrophobic units, respectively. Absorption spectroscopy revealed that both amphiphiles are molecularly dispersed in organic solvent, while they form aggregates under aqueous conditions. Furthermore, we investigated whether AmF and AmH can be incorporated into DOPC lipid bilayer membranes, and found that the maximum concentration of AmF that can be incorporated into DOPC lipid bilayer membranes is 43 times higher than that of AmH.