Promoted Aggregation of Aβ on Lipid Bilayers in an Open Flowing System.

Self-assembly of amyloid-β (Aβ) peptides in nonequilibrium, flowing conditions is associated with pathogenesis of Alzheimer's disease. We examined the role of biologically relevant, nonequilibrium, flowing conditions in the desorption, diffusion, and integration of Aβ-lipid assemblies at the membrane surface using a microchannel connected with microsyringes. A 1,2-dimyristoyl--glycero-3-phosphocholine (DMPC) bilayer was formed on a glass substrate and incubated in Aβ solution under either a quiescent condition (no flow) or flowing condition for 24 h.

Interplay between two radical species in the formation of periodic patterns during a polymerization reaction.

Periodic patterns are ubiquitous in nature and spontaneously form on molecular to cosmic scales by the interplay between reaction and diffusion. Understanding how these patterns form is important to understand the construction rules of nature and apply them in the synthesis of functional artificial materials. This work clarifies how radical (R˙) species affect pattern formation in periodic precipitated and depleted zones during a polymerization process in an agarose gel.

Programmable Design of Self-Organized Patterns through a Precipitation Reaction.

Nature uses self-organized spatiotemporal patterns to construct systems with robustness and flexibility. Furthermore, understanding the principles underlying self-organization in nature enables programmable design of artificial patterns driven by chemical energy. The related mechanisms are however not clearly understood because most of these patterns are formed in reaction-diffusion (RD) systems consisting of intricate interaction between diffusion and reaction.

Role of Oxidized Lipids in Permeation of HO Through a Lipid Membrane: Molecular Mechanism of an Inhibitor to Promoter Switch.

HO permeation through a cell membrane significantly affects living organisms, and permeation is controlled by the physico-chemical nature of lipids and other membrane components. We investigated the molecular relationship between HO permeation and lipid membrane structure using three oxidized lipids. POVPC and PazePC act as intra- and inter-molecular permeation promoters, respectively; however, their underlying mechanisms were different.

Role of Electrolyte in Liesegang Pattern Formation.

Pattern formation based on the Liesegang phenomenon is considered one of the useful models for gaining a mechanistic understanding of spontaneous spatiotemporal pattern formations in nature. However, for more than a century, the Liesegang phenomenon in chemical systems has been investigated by using electrolytes as both the reaction substrate and aggregation promoter, which has obfuscated the role of the electrolyte. Here, we distinguish the electrolyte (NaSO) from the reaction substrates (Ag ion and citrate), where NaSO does not participate in the reaction step and acts as an aggregation promoter.

Liesegang Mechanism with a Gradual Phase Transition.

We report a novel and generalized chemical model for the Liesegang mechanism that involves gradual phase transitions of macromolecules, unlike previous models that involved definite and discontinuous phase transitions. As a model system, an agarose gel medium doped with an initiator was contacted with a solution containing monomer 2-methoxyethyl acrylate (MEA), in which monomers diffused into the gel medium and initiated a polymerization reaction. As there is a monomer concentration gradient along the diffusion direction, the degree of polymerization and the corresponding degree of insolubility showed a similar spatial gradient in the reaction medium because molecular solubility gradually changes from soluble to insoluble with an increase in the degree of polymerization.

One-Directional Fluidic Flow Induced by Chemical Wave Propagation in a Microchannel.

A one-directional flow induced by chemical wave propagation was investigated to understand the origin of its dynamic flow. A cylindrical injection port was connected with a straight propagation channel; the chemical wave was initiated at the injection port. Chemical waves propagated with a constant velocity irrespective of the channel width, indicating that the dynamics of the chemical waves were governed by a geometry-independent interplay between the chemical reaction and diffusion.

Propagation Behaviors of an Acid Wavefront Through a Microchannel Junction.

Waves in reaction-diffusion systems yield a wealth of dynamic self-assembling phenomena in nature. Recent studies have been devoted to utilizing these active waves in conjunction with microscale technology. To provide a compass for controlling reaction-diffusion waves in microspaces, we have investigated the propagation behavior of one specific variety of the reaction-diffusion wave: an acid wave that utilizes an autocatalytic proton-production reaction.

Liesegang patterns engineered by a chemical reaction assisted by complex formation.

Liesegang rings based on a chemical reaction, not a conventional precipitation reaction, have been developed by appropriate design of the nucleation dynamics in a system involving complex formation in a matrix. The periodic and concentric rings consisted of well-dispersed Ag nanoparticles with diameters of a few nanometers. The approach modeled here could be applied to form novel micropatterns out of inorganic salts, metal nanoparticles, organic nanocrystals, or polymeric fibers, and it could also offer a scaffold for novel models of a wide variety of reaction-diffusion phenomena in nature.

Preferential behavior on donating atoms of an ambidentate ligand 2-methylisothiazol-3(2H)-one in its metal complexes.

Five metal complexes of 2-methylisothiazol-3(2H)-one (MIO), [Co(III)(NH3)5(MIO)](3+), [Ru(II)(NH3)5(MIO)](2+), [Ru(III)(NH3)5(MIO)](3+), [Pt(II)Cl3(MIO)](-), and trans-[U(VI)O2(NO3)2(MIO)2], were synthesized, and their structures were determined by single-crystal X-ray crystallography. MIO is an ambidentate ligand and coordinates to metal centers through its oxygen atom in the cobalt(III), ruthenium(III), and uranium(VI) complexes and through its sulfur atom in the ruthenium(II) and platinum(III) complexes. This result suggests that MIO shows preferential behavior on its donating atoms.

Microchannel-induced change of chemical wave propagation dynamics: importance of ratio between the inlet and the channel sizes.

The ability to control chemical wave propagation dynamics could stimulate the science and technology of artificial and biological spatiotemporal oscillating phenomena. In contrast to the conventional chemical approaches to control the wave front dynamics, here we report a physical approach to tune the propagation dynamics under the same chemical conditions. By using well-designed microchannels with different channel widths and depths, the propagation velocity was successfully controlled based on two independent effects: (i) a transition in the proton diffusion mode and (ii) the formation of a slanted wave front.

Synthesis and some properties of binuclear ruthenocenes bridged by oligoynes: formation of bis(cyclopentadienylidene)cumulene diruthenium complexes in the two-electron oxidation.

The monoynes [Rc*C[triple bond]CRc*] and [Rc'C[triple bond]CRc'] were obtained in improved yields using [Mo(CO)6]/2-FC6H5OH as a catalyst in the alkyne metathesis of [Rc*C[triple bond]CMe] and [Rc'C[triple bond]CMe], respectively (Rc = ruthenocenyl, Rc* = 1'',2'',3'',4'',5''-pentamethylruthenocenyl, and Rc' = 2',3',4',5'-tetramethylruthenocenyl groups). The diynes [Rc*(C[triple bond]C)2Rc*] and [Rc'(C[triple bond]C)2Rc'] were synthesized by the oxidative coupling of the corresponding terminal ethynes in good yields. The triyne [Rc*(C[triple bond]C)3Rc*] and the tetrayne [Rc*(C[triple bond]C)4Rc*] were prepared by the hetero- and homocoupling of [Rc*C[triple bond]CC[triple bond]CH], which was obtained from the reaction of [Rc*C[triple bond]CCHO] with Li[N2CSiMe3], respectively.

A new redox-active coordination polymer with cobalticinium dicarboxylate.

A new two-dimensional coordination polymer with cobalticinium 1,1'-dicarboxylate (ccdc) incorporated in the framework has been prepared, the ccdc functioning as unique monoanionic dicarboxylate ligands. The compound shows a high redox activity based on the ccdc units.

Synthesis and redox behavior of ruthenocene-terminated oligoenes: characteristic and stable two-electron redox system and lower potential shift of the two-electron oxidation wave with elongating conjugation.

Ruthenocene-terminated butadienes and hexatrienes were prepared by the Wittig reaction of 3-ruthenocenyl-2-propenals with ruthenocenylmethylphosphonium salts and the Mukaiyama coupling of the propenals, respectively. Cyclic voltammetry of these complexes indicated that they were involved in a stable two-electron redox process. The oxidation potentials for ruthenocene-terminated oligoenes shifted progressively to lower potential with the increasing CH==CH units as follows: Rc--Rc (0.