Molecular rotation in self-assembled multidecker porphyrin complexes

An alkyl chain-substituted multidecker porphyrin (a cerium double-decker porphyrin (CeDDP) and a lanthanum triple-decker porphyrin (LaTDP)) complexes were arranged in a monolayer array on Au(111) substrate. By using a pulse injection deposition method, both multidecker complexes were deposited on the surface intact to form a well-defined two-dimensional array. Low-temperature scanning tunneling microscopy (STM) allowed the measurement of the topographic heights of the multidecker porphyrin complexes and visualization of their internal structures clearly. The STM images suggest that the top porphyrin ligand in CeDDP rarely rotates under nondestructive imaging condition, while the top porphyrin ligand in LaTDP exhibits flip-flop rotation even under the nondestructive imaging condition at sub-pA tunneling currents. These results provide the future applications of molecular-scale mechanical machines and single molecule storage memory.

The Design of Organic Gelators Based on a Family of Bis-Ureas

The use of organic molecules as gelators in certain organic solvents has been the target of recent research in materials science. The types of structures formed in the gel matrix have potential applications as porous solids that can be used as absorbents or in catalysis. We will present and discuss the organogelation properties of a family of bis-ureas. Studies presented will include a molecule structure activity relationship, thermodynamic properties, comparison to x-ray crystallographic data and potential functionalization of the gels formed by this class of compounds

A molecular template designed by the modification of a helix-forming β-1,3-glucan polysaccharide to fabricate one-dimensional nanostructures

We report the development of a new templating molecule designed by the modification of a helix-forming β-1,3-glucan polysaccharide to the cationic semiartificial one and its application to the fabrication of one-dimensional (1D) gold nanostructures by simple photoirradiation. Transmission electron microscopy observation showed that Au(III) ions are primarily reduced to gold nanoparticles self-assembling into the 1D array with the aid of the cationic β-1,3-glucan polysaccharide, which gradually fuse into the 1D gold nanostructure with the tapelike structure. The gold nanotape structure could not be created by neutral β-1,3-glucan polysaccharides or random coil synthetic cationic polymers. These findings consistently support the view that Au(III) ions are reduced by unmodified OH groups to gold nanoparticles under the photoirradiation, which are wrapped in the helical structure of the cationic β-1,3-glucan polysaccharide and eventually fuse into gold nanotapes. One may regard, therefore, that this cationic β-1,3-glucan polysaccharide can act as an "all-in-one" template playing three roles of reduction, 1D arrangement, and fusion of gold nanoparticles. In addition, we found an interesting phenomenon that the obtained gold nanotapes coated with cationic β-1,3-glucan polysaccharides show unique surface-enhanced Raman scattering for anionic porphyrines organized on the surface of gold nanotapes through the electrostatic interaction.

Thiourea-tagged poly(octadecyl acrylate) gels as fluoride and acetate responsive polymer gels through selective complexation

Fluoride and acetate-responsive polymer gels were prepared by incorporation of p-nitrophenylthiourea into poly(octadecyl acrylate) gels, and the colours and volumes were changed selectively in the presence of these ions by complexation in THF.

Alternate layer-by-layer adsorption of single- and double-walled carbon nanotubes wrapped by functionalized beta-1,3-glucan polysaccharides

A great deal of attention has been focused on exploiting novel methods to fabricate thin carbonaceous capsules from multiple components for advanced materials. A layer-by-layer (LbL) method is therefore being introduced to synthesize thin and multi-carbon nanotube (CNT)-based hollow capsules from CNT complexes with cationic or anionic complementarily functionalized beta-1,3-glucans as building-blocks. These ionic beta-1,3-glucans wrap around single-walled carbon nanotubes (SWNTs) and double-walled carbon nanotubes (DWNTs) to form water-soluble complexes with ionic groups on their exterior surface. Alternate self-assembly of these CNT complexes on the silica particles is demonstrated in solution by electrostatic interactions. The LbL adsorption processes were carefully monitored by zeta-potential measurements, frequency shifts of a quartz crystal microbalance (QCM), and electron micrographs. Silica particles were then dissolved away by HF acid to obtain CNT-based hollow capsules composed of SWNTs and DWNTs. We believe that these novel surface adsorption methods are useful for potential design of CNT-based advanced functional materials.

Discontinuous swelling behaviors of lipophilic polyelectrolyte gels in non-polar media

Discontinuous volume changes of lipophilic polyelectrolyte gels in non-polar organic solvent mixtures are demonstrated towards the construction of stimuli-sensitive materials in media other than water.

Desmin as a marker of proteinuria in early stages of membranous nephropathy in elderly patients

AIMS AND METHOD

Idiopathic membranous nephropathy (IMN) is the most common cause of nephrotic syndrome in adults worldwide. Many patients with IMN are elderly, but little is known about the relationship regarding the morphological stage determined by electron microscopy (EM), the amount of proteinuria, and the expression of glomerular podocyte markers such as desmin and nephrin in nephrotic glomeruli in IMN. We studied 59 patients with histopathologically proven IMN. We compared the clinical features, EM stage classification, and the immunohistochemical features of glomerular expression of podocyte markers, including desmin and nephrin, between older (age > or = 60 years) and younger (age < 60 years) patients. We also investigated these parameters in patients with minimal-change nephrotic syndrome (MCNS), minor glomerular abnormalities (MGA), and normal kidneys as age-matched controls.

RESULTS

Prevalence of nephrotic syndrome was significantly higher in the older (52.9%) than the younger group (20.0%) of IMN. The level of proteinuria was higher in early stages (Stages I + II) than in late stages (Stages III + IV) in IMN. The glomerular expression of desmin in podocytes was significantly higher in IMN as compared to MCNS, MGA, or age-matched controls. Desmin expression was significantly increased in earlier EM stages (Stages I + II) and in higher proteinuric group (daily proteinuria > or = 1 g) of older patients with IMN. Reciprocally, the reduced expression of nephrin was associated with the early EM stages (Stages I + II) of patients with IMN.

CONCLUSIONS

We conclude that the expression of desmin in podocytes is upregulated in patients with IMN as compared to other glomerular diseases including MCNS or MGA, or to controls. In elderly patients with IMN, desmin expression was associated with early EM stages and heavy proteinuria, which may reflect phenotypic alteration of the podocyte.

Lipophilic polyelectrolyte gels as super-absorbent polymers for nonpolar organic solvents

Polyelectrolyte gels that are known as super-absorbent polymers swell and absorb water up to several hundred times their dried weights and have become ubiquitous and indispensable materials in many applications. Their superior swelling abilities originate from the electrostatic repulsion between the charges on the polymer chains and the osmotic imbalance between the interior and exterior of the gels. However, no super-absorbent polymers for volatile organic compounds (VOCs), and especially for nonpolar organic solvents (epsilon<10) have been reported, because common polyelectrolyte gels collapse in such solvents owing to the formation of a higher number of aggregates of ions and ion pairs. Here, we report that a novel class of polyelectrolyte gels bearing tetra-alkylammonium tetraphenylborate as a lipophilic and bulky ionic group swell in some nonpolar organic solvents up to 500 times their dry size. Dissociation of the ionic groups even in low-dielectric media (3<epsilon<10) enhances the swelling ability by expansion of the polymer networks. This expands the potential of polyelectrolytes that have been used only in aqueous solutions or highly polar solvents, and provides soft materials that swell in a variety of media. These materials could find applications as protective barriers for VOCs spilled in the environment and as absorbents for waste oil.

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. Detailed fluorescence and UV/Vis spectral studies revealed that the emission changes of the chemosensors upon binding to nucleoside PPs can be ascribed to the loss of coordination between Zn(II) and the acridine fluorophore. This is a unique sensing system based on the anion-induced rearrangement of the coordination. Furthermore, we demonstrated the utility of these chemosensors in real-time monitoring of two important biological processes involving nucleoside PP conversion: the apyrase-catalyzed hydrolysis of nucleoside PPs and the glycosyl transfer catalyzed by beta-1,4-galactosyltransferase.

Post-polymerization of preorganized assemblies for creating shape-controlled functional materials

Combination of supramolecular chemistry with molecular recognition has been successfully applied to creating large superstructures with a wide variety of morphologies. Control of shapes and patterns of ordered molecular assemblies in nano and micro scales has attracted considerable interest as promising bottom-up technology. It is known, however, that these molecular assembling superstructures are fragile, reflecting the characteristic of the non-covalent interaction, a driving force operating in these molecular systems. In fact, they easily collapse or change by small perturbation in the environmental conditions. Thus, over the last decade, researchers have been seeking possible methods for the immobilization these superstructures. This critical review focuses on recent advances in in situ post-modification under the influence of the molecular assemblies as templates and polymerization of ordered molecular assemblies such as organogel fibers and crystals to preserve their original superstructures and intensify their mechanical strength.

Construction of superhydrophobic surfaces by fibrous aggregation of perfluoroalkyl chain-containing organogelators

Superhydrophobic surfaces, characterized by water contact angles greater than 150 degrees, can be produced by means of intermediate organogels, which were formed by perfluoroalkyl chain-containing organogelators with volatile organic solvents.