Masaki Kogiso

Self-assembled peptide fibers from valylvaline bola-amphiphiles by a parallel β-sheet network

A series of dipeptide-based bola-amphiphiles, bis(N-alpha-amide-L-valyl-L-valine) 1, n-alkane dicarboxylate (n=4-12), have been synthesized. The bola-amphiphiles with n=4 and 6 self-assembled to form crystalline solids in water, whereas those with n=7-12 produced peptide fibers. FT-IR spectroscopy and X-ray diffraction patterns revealed that the peptide fibers have parallel-type beta-sheet networks between the valylvaline units. FT-IR deconvolution study of carboxyl regions indicated that these crystalline solids and peptide fibers are stabilized by interlayer bifurcated and intralayer lateral hydrogen-bond networks between the end carboxylic acid groups, respectively.

Necklace-like Chains of Hybrid Nanospheres Consisting of Pd Nanocystals and Peptidic Lipids

In this Communication, we report one-pot, high yield formation of unprecedented 1-D necklace-like chains consisting of hybrid Pd nanocrystals (NCs) embedded in spheres of a peptidic lipid. We employed the synthetic peptidic lipid, 2-(2-tetradecanamidoacetamido)acetic acid (1). We found that in the presence of palladium acetate [Pd(OAc)(2)] 1 can self-assemble into structured spheres which connect each other one by one to form the necklace chains in ethanol solutions by coordination of negatively charged carboxylic (COO(-)) groups with Pd(II). Upon reduction of ethanol, the coordinated Pd(II) are reduced into Pd atoms, which subsequently initiate the generation of Pd nuclei, and finally grow into Pd NCs embedded in the sphere chain of 1.

Organic nanotubes for drug loading and cellular delivery

Organic nanotubes made of synthetic amphiphilic molecules are novel materials that form by self-assembly. In this study, organic nanotubes with a carboxyl group (ONTs) at the surface were used as a carrier for the anticancer drug doxorubicin, which has a weak amine group. The IC(50) values of ONT for cells were higher than that of conventional liposomes, suggesting that ONTs are safe. The results showed that the drug loading of ONTs was susceptible to the effect of ionic strength and H(+) concentration in the medium, and drug release from ONTs was promoted at lower pH, which is favorable for the release of drugs in the endosome after cellular uptake. ONTs loaded with the drug were internalized, and the drug was released quickly in the cells, as demonstrated on transmission electron microscopy images of ONTs and the detection of a 0.05% dose of ONT chelating gadolinium in the cells. Moreover, ONT could be modified chemically with folate by simply mixing with a folate-conjugate lipid. Therefore, these novel, biodegradable organic nanotubes have the potential to be used as drug carriers for controlled and targeting drug delivery.

Cross‐Section Molecular Imaging of Supramolecular Microtubes with Contact Atomic Force Microscopy

Bent molecules, distorted layers, columnar domains, and tube membranes (shown schematically in the picture): These hierarchical layers were directly visualized by contact atomic force microscopy along the long axes of the molecules aligned within microtubes made up of bolaamphiphile 1 by self-assembly.

Highly efficient production of various organic nanotubes with different surfaces and their application to an adsorbent

Self-assembly of simple glycyl–glycine-containing peptide lipids, both in water and alcohol, gave various organic nanotubes covered with different functional surfaces in a facile production manner. Especially, the self-assembly in alcohol media increased the yield of nanotube by more than 5 times and decreased the production time by less than one-tenth when compared with conventional self-assembly in water. The glycyl–glycine residue proved to be critical to afford a tubular morphology stabilized by the polyglycine-II-type hydrogen-bond networks. Therefore, the glycyl–glycine-containing peptide lipids can give nanotubes with desired surfaces by connecting an appropriate functional moiety to the glycyl–glycine residue. In addition, the adsorption ability of gold nanoparticles to the specific nanotube surface showed the high potentiality of the nanotubes as an adsorbent.

One-dimensional organization of copper nanoparticles by chemical reduction of lipid-copper hybrid nanofibers

One-dimensional organization of copper nanoparticles has been achieved by chemical reduction using lipid-copper hybrid nanofibers as a template; the reduction of copper ions and the resulting formation of copper clusters occurred at intervals of 2–5 nm along the nanofibers.

Supramolecular Polyglycine II-Type Structure of Glycylglycine Bolaamphiphile

Abstract Bolaamphiphile with a glycylglycine unit at each end, N,N′-bis(carboxymethylcarbamoylmethyl)decane-1, 10-dicarboxamide, has been synthesized. The crystal structure was determined by single-crystal X-ray analysis. The space group is P21/a with unit cell parameters: a = 8.678(3), b = 4.873(4), c = 27.161(3) A, β = 92.68(2)°, Z = 2, Dc = 1.33g/cm3, and R = 0.051 for 2095 data. The two halves of the molecule are related by a center of symmetry and have a folded [sbnd] CH2 [sbnd] CH2 [sbnd] CO [sbnd] conformation (TGS or TGS). The molecules are arranged in a layered structure along the c-axis, forming a linear polymolecular chain stabilized by acid-acid dimerization at each end. Each chain is arranged in a pseudo-hexagonal lattice stabilized by three-dimensional hydrogen-bond networks between amide groups. This supramolecular crystal structure provides the first example of polyglycine II-type structure made of noncovalent polymolecular chains.

Single bilayered organic nanotubes: anchors for production of a reusable catalyst with nickel ions

Organic nanotubes self-assembled from lipid compounds facilitate the synthesis of a new nano-catalyst with nickel ions. The nickel ions were fixed on the surface of the organic nanotubes through coordination. The nanotubes catalyzed oxidation of a wide range of organic compounds with hydrogen peroxide without organic solvent, and are reusable in at least five cycles without loss of activity.

Solvent-chirality selective organogelation by chiral aspartame lipids

We examined supramolecular gelation of propylene carbonate enantiomers with novel chiral aspartame lipids. Different gelation ability and stability were observed based on the combination of gelator and the solvent enantiomers. This work demonstrates that gelator–solvent chirality matching can determine self-assembled nanostructures and gelation efficiency.

A hydro/organo/hybrid gelator: a peptide lipid with turning aspartame head groups.

This work presents a novel bola-type peptide lipid which can gelate water, organic solvents, and water/organic-solvent mixtures. In its molecular structure, an amphiphilic dipeptide aspartame (L-α-aspartyl-L-phenylalanine methyl ester) is connected at both ends of an alkylene linker. The different morphologies in the hydrogel (helical nanotapes) and the organogel (tape-like nanostructures) were visualized by energy-filtering transmission electron microscopy (EF-TEM) and energy-filtering scanning electron microscopy (FE-SEM), and the molecular arrangement was examined using X-ray diffraction (XRD), infrared (IR) spectroscopy, and circular dichroism (CD) spectroscopy. Possessing a hydrophilic aspartic acid group and a (relatively) hydrophobic phenylalanine methyl ester group, the dipeptide head group can turn about in response to solvent polarity. As a consequence, the solvent condition changed the molecular packing of the gelator and affected the overall supramolecular structure of the gel. It is noted that the peptide lipid gelated mixed solvents of water and organic solvents such as dichloromethane, liquid-paraffin, olive-oil, silicone-oils, and so on. The present hybrid gel can simultaneously hold hydrophilic and hydrophobic functional materials.