Amylose-grafted Curdlan: A New Class of Semi-artificial Branched Polysaccharides for Hierarchical Polymeric Superstructures Created by the Action of "Orthogonal" Binding Sites.

The semi-artificial branched-polysaccharides, amylose-grafted curdlans, were synthesized utilizing an enzymatic polymerization. Both a curdlan main chain and amylose side chains on the polysaccharides maintain the original helical structure as well as the molecular binding ability. Thanks to the difference in their molecular recognition properties between β-1,3-glucan chain and α-1,4-glucan chain, the amylose-grafted curdlans can provide two different orthogonal binding sites within one polymeric system.

Supramolecular assembly of achiral alkynylplatinum(II) complexes and carboxylic β-1,3-glucan into different helical handedness stabilized by Pt⋅⋅⋅Pt and/or π-π interactions.

Two-component ensembles of alkynylplatinum(II) terpyridine (tpy) complexes and carboxylic β-1,3-glucan (CurCOOH) have been investigated by using spectroscopic and microscopic techniques, as well as time-dependent UV/Vis absorption and circular dichroism (CD) experiments. Microscopic images of [Pt(tpy){C≡CC6 H4 (CH2 NMe3 -4)}](OTf)2 (1) have revealed spherical nanostructures, whereas helical fibrous structures of different lengths, depending on the concentration of complex 1 and CurCOOH, were observed. The helical assemblies have been found to show low-energy metal-metal-to-ligand charge transfer (MMLCT) absorption and triplet MMLCT ((3) MMLCT) emission, which are indicative of Pt⋅⋅⋅Pt and/or π-π interactions between the complex 1 molecules.

Giant amino acids designed on the polysaccharide scaffold and their protein-like structural interconversion.

Amphoteric β-1,3-glucans possessing both amino groups and carboxylic acid groups on the C6 positions of glucose units were designed and synthesized from naturally produced curdlan. The amphoteric polysaccharides showed the isoelectric point and the pH responsive interconversion between the original triple helix and single-stranded random structures. Since the pH dependences are comparable to the typical properties of proteins, the polysaccharides can be considered as a new class of giant amino acids.

Creation of circularly polarized luminescence from an achiral polyfluorene derivative through complexation with helix-forming polysaccharides: importance of the meta-linkage chain for helix formation.

A circularly polarized luminescence (CPL) material has been created by polymer-polymer complexation between a helix-forming polysaccharide, schizophyllan (SPG), and a meta-phenylene-linked polyfluorene derivative (mPFS). Computational modeling revealed that mPFS can adopt a helical structure although a conventional polyfluorene derivative with a para-phenylene linkage tends to enjoy a rigid rodlike conformation. Our detailed experimental examination showed that mPFS forms a chiral nanowire complex through cohelix formation with SPG.

Creation of chiral thixotropic gels through a crown-ammonium interaction and their application to a memory-erasing recycle system.

A unique class of oligothiophene-based organogelator bearing two crown ethers at both ends was synthesized. This compound could gelatinize several organic solvents, forming one-dimensional fibrous aggregates. From the observation of circular dichroism, it was confirmed that the helical handedness of the fibrous assembly is controllable by the chirality of 1,2-bisammonium guests, thus suggesting that one guest molecule bridges two gelator molecules through the crown-ammonium interaction.

Heat and light dual switching of a single-walled carbon nanotube/thermo-responsive helical polysaccharide complex: a new responsive system applicable to photodynamic therapy.

A thermo- and light-responsive system consisting of single-walled carbon nanotube and helical polysaccharide modified with poly(N-isopropylacrylamide) side-chains has been developed through supramolecular polymer wrapping. Coagulation of the complex can be induced by the external stimuli, which leads to a catch-and-release action of a porphyrin derivative.

A pH-responsive carboxylic β-1,3-glucan polysaccharide for complexation with polymeric guests.

The helix-forming nature of β-1,3-glucan polysaccharides is a characteristic that has potential for producing gene carriers, bio-nanomaterials and other chiral nanowires. Herein, carboxylic curdlan (CurCOOH) bearing the β-1,3-polyglucuronic acid structure was successfully prepared from β-1,3-glucan polysaccharide curdlan (Cur) by one-step oxidation using a 4-acetamido-TEMPO/NaClO/NaClO(2) system as the oxidant. The resulting high-molecular-weight CurCOOH was proved to bear the 6-COOH group in 100% purity.

New strategy for controlling the oligothiophene aggregation mode utilizing the gel-to-sol phase transition induced by crown-alkali metal interactions.

A new functional low molecular-weight gelator (LMWG) based on crown-appended quaterthiophene was synthesized and investigated as a new alkali metal cation responsive material with enhanced fluorescence emission upon gel-to-sol phase transition.

Fluidic supramolecular nano- and microfibres as molecular rails for regulated movement of nanosubstances.

Nano- and micro-sized fibrous architectures are ubiquitous in nature; in particular, microtubules have an essential role within live cells, as tracks for transporting objects to a desired place, driven by molecular motors such as dynein and kinesin. Such functions of bionanofibres motivated us to construct an artificial supramolecular rail using the fluidic property of self-assembled glycolipid nanofibres. Artificial supramolecular nanofibres constructed through molecular self-assembly of small molecules have recently attracted considerable attention for their unique properties, such as reversible formation/destruction under mild conditions and various stimuli responsiveness.

What kind of "soft materials" can we design from molecular gels?

Since their discovery, over the years, molecular gels have been constantly drawing the attention of chemists from various scientific fields. Their structural softness together with the orderliness at the molecular level provides such molecules immense potential for the amplification of their properties. Using this chemistry, one can easily realize a macroscopic outcome from a molecular level modulation.

Studies on a new class of organogelator containing 2-anthracenecarboxylic acid: influence of gelator and solvent on stereochemistry of the photodimers.

A new class of binary organogelator (G1, G2 and G3) based on 2-anthracenecarboxylic acid (2Ac), attached noncovalently with the gelator counterpart containing a 3,4,5-tris(n-dodecyloxy)benzoylamide backbone has been developed. Among the three gelators, two (G2 and G3) are chiral containing D-alanine or L-2-phenylglycine moieties, respectively. They can act as efficient gelators of organic solvents with varying polarity depending upon the gelator systems.

MCM-enzyme-supramolecular hydrogel hybrid as a fluorescence sensing material for polyanions of biological significance.

Polyanions are important sensing targets because of their wide variety of biological activities. We report a novel polyanion-selective fluorescence sensing system composed of a hybrid material of supramolecular hydrogel, enzymes, and aminoethyl-modified MCM41-type mesoporous silica particles (NH(2)-MCM41) encapsulating anionic fluorescent dyes. The rational combination of the polyanion-exchange ability of NH(2)-MCM41 and semi-wet supramolecular hydrogel matrix successfully produced three distinct domains; namely, cationic nanopores, hydrophobic nano/microfibers, and aqueous bulk gel phase, which are orthogonal to each other.

Supramolecular hydrogel exhibiting four basic logic gate functions to fine-tune substance release.

Logic-gate operations displaying macroscopic outputs are promising systems for the development of intelligent soft materials that can perform effective functions in response to various input patterns. A supramolecular hydrogel comprising the phosphate-type hydrogelator 1 exhibits macroscopic gel-sol behavior in response to four distinct input stimuli: temperature, pH, Ca(2+), and light. We characterized this performance through microscopic, spectroscopic, and rheological measurements.

Mechanical reinforcement of a supramolecular hydrogel comprising an artificial glyco-lipid through supramolecular copolymerization.

Supramolecular copolymer hydrogels were prepared by mixing 1 and the additives 2-8, and their rheological properties were evaluated. It was found that additive 3 reinforced the mechanical strength of the resultant hydrogel most efficiently, increasing the yield stress of SCH 1+3 about fourfold. The optimal mixing between the glyco-lipid hydrogelator 1 and the additive 3 sufficiently enhanced the mechanical strength of the resultant SCH, which improved the handling of the SH on the large scale.

Design of dual-emission chemosensors for ratiometric detection of ATP derivatives.

Nucleoside pyrophosphate (nucleoside PP) derivatives are widespread in living cells and play pivotal roles in various biological events. We report novel fluorescence chemosensors for nucleoside PPs that make use of coordination chemistry. The chemosensors, which contain two Zn(II)-dipicolylamine units, bind strongly to nucleoside PPs (K(app)>10(6) M(-1)) in aqueous solution and sense them by a dual-emission change.

Three distinct read-out modes for enzyme activity can operate in a semi-wet supramolecular hydrogel.

Assays of hydrolytic enzyme activity, such as of glycosidases and phosphatase, as well as several proteases, using a semi-wet supramolecular hydrogel array composed of a glycosylated amino acetate are described. It has been demonstrated that the microcavity formed by gel fibrils is suitable to immobilize native enzymes without denaturation under semi-wet conditions, and thus the nanofiber has been rationally used as a sensing domain to monitor enzymatic reactions. By using a fluorogenic substrate, reducing the size of the hydrogel can significantly improve the problem of suppressed diffusion within the gel matrix thus making the hydrogel a promising semi-wet matrix for evaluating enzyme activity.

Cooperation between artificial receptors and supramolecular hydrogels for sensing and discriminating phosphate derivatives.

This study has successfully demonstrated that the cooperative action of artificial receptors with semi-wet supramolecular hydrogels may produce a unique and efficient molecular recognition device not only for the simple sensing of phosphate derivatives, but also for discriminating among phosphate derivatives. We directly observed by confocal laser scanning microscopy that fluorescent artificial receptors can dynamically change the location between the aqueous cavity and the hydrophobic fibers upon guest-binding under semi-wet conditions provided by the supramolecular hydrogel. On the basis of such a guest-dependent dynamic redistribution of the receptor molecules, a sophisticated means for molecular recognition of phosphate derivatives can be rationally designed in the hydrogel matrix.

9-Acylation of 1-acyldipyrromethanes containing a dialkylboron mask for the alpha-acylpyrrole motif.

1,9-Diacyldipyrromethanes are important precursors to porphyrins, yet synthetic access remains limited owing to (1) poor conversion in the 9-acylation of 1-acyldipyrromethanes and (2) handling difficulties because acyldipyrromethanes typically streak upon chromatography and give amorphous powders upon attempted crystallization. A reliable means for converting a dipyrromethane to a 1-acyldipyrromethane-dialkylboron complex was recently developed, where the dialkylboron (BR(2)) unit renders the complex hydrophobic and thereby facilitates isolation. Herein a refined preparation of 1,9-diacyldipyrromethanes is presented that employs the 1-acyldipyrromethane-BR(2) complex as a substrate for 9-acylation.

Porphyrins bearing arylphosphonic acid tethers for attachment to oxide surfaces.

Synthetic molecules bearing phosphonic acid groups can be readily attached to oxide surfaces. As part of a program in molecular-based information storage, we have developed routes for the synthesis of diverse porphyrinic compounds bearing phenylphosphonic acid tethers. The routes enable (1) incorporation of masked phosphonic acid groups in precursors for use in the rational synthesis of porphyrinic compounds and (2) derivatization of porphyrins with masked phosphonic acid groups.

A tin-complexation strategy for use with diverse acylation methods in the preparation of 1,9-diacyldipyrromethanes.

The acylation of dipyrromethanes to form 1,9-diacyldipyrromethanes is an essential step in the rational synthesis of porphyrins. Although several methods for acylation are available, purification is difficult because 1,9-diacyldipyrromethanes typically streak extensively upon chromatography and give amorphous powders upon attempted crystallization. A solution to this problem has been achieved by reacting the 1,9-diacyldipyrromethane with Bu(2)SnCl(2) to give the corresponding dibutyl(5,10-dihydrodipyrrinato)tin(IV) complex.

Sol-gel polycondensation of tetraethyl orthosilicate (TEOS) in sugar-based porphyrin organogels: inorganic conversion of a sugar-directed porphyrinic fiber library through sol-gel transcription processes.

Sugar-appended porphyrins (1 a-e) with monosaccharide groups at their periphery have been rationally designed for a new class of gelating reagents. A few of these compounds have the tendancy to form one-dimensional aggregates stable enough to show successful gelation ability for DMF-alcohol mixed solvents. The aggregation mode in the specific columnar super structures has been evaluated in detail by UV-visible spectrometry (UV/Vis), circular dichroism (CD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

Double helical silica fibrils by sol-gel transcription of chiral aggregates of gemini surfactants.

Silica fibrils with a novel double stranded helical structure are prepared by sol-gel transcription of twisted bilayer ribbons formed by cationic gemini surfactants.

Circular dichroism readout of sugar recognition in the cleft of a fused-pyridine receptor.

Dicarboxamide host 2 forms 1:1 complexes with n-octyl pyranosides derived from D-glucose, D-mannose, D-galactose, D-fucose, D-lyxose, and D-arabinose. Association constants (K(a)) in the range of 77-940 M(-1) were measured in chloroform by means of induced circular dichroism and fluorescence spectroscopy. Variations in K(a) values correspond qualitatively to expected differences in hydrogen-bonding abilities of guest hydroxyl groups.