This account discusses construction strategies for various functional biomaterials based on the designed self-assembly of biomolecules. Novel glycoclusters with regular intervals were developed by self-assembly of carbohydrate-conjugated oligodeoxyribonucleotides (ODNs) with the half-sliding complementary ODNs. Complexes of carbohydrate-modified DNA and lectin afforded a new regulation system for gene expression. DNA three-way junctions bearing self-complementary sticky-ends were self-assembled into nanometer-to-micrometer-sized spherical structures depending on the concentration. The three-way component design was extended to the design of an artificial trigonal peptide conjugate. The trigonal peptide conjugates bearing β-sheet-forming peptides or glutathione self-assembled into nano-sized spherical assemblies. Self-assembly of β-annulus peptide derived from tomato bushy stunt virus afforded artificial viral capsids, which can encapsulate and be modified with various molecules.
We have prepared visible-light-sensitive tungsten oxide (WO3) nanoparticle photocatalysts by a thermal plasma method and subsequent annealing treatment. The WO3 photocatalysts effectively decomposed acetaldehyde under visible-light irradiation and the activity increased with the annealing temperature. The WO3 annealed at 600 °C exhibited fivefold higher photocatalytic activity than nitrogen-doped TiO2 and commercial WO3. The high photocatalytic activity of the WO3 nanoparticles was attributed to their high crystallinity and large surface area. It was also found that the acetaldehyde decomposition rate over the WO3 nanoparticles was significantly enhanced by the addition of metal oxides such as ZrO2. The ZrO2 additive functions as an adsorbent of the acetic acid (reaction intermediate) to remove the acetic acid from the WO3 surface. Furthermore, the complete oxidation of acetaldehyde into CO2 and H2O was achieved using a Ru (0.02 wt%)-loaded WO3-ZrO2 mixed oxide under visible-light irradiation, and this catalyst exhibited excellent durability for the reaction.
This article describes the full details of our reductive approach to nitrones from amides. Reduction of N-siloxyamides with the Schwartz reagent [Cp2ZrHCl], followed by addition of an acid provided functionalized nitrones. The developed conditions were then extended to a catalytic version with the Vaska complex [IrCl(CO)(PPh3)2] and (Me2HSi)2O starting from N-hydroxyamides. 1H NMR studies of the Ir-catalyzed reaction revealed that the developed conditions promoted two different types of catalytic reactions including dehydrosilylation of an N-hydroxyl group and subsequent hydrosilylation of an amide carbonyl. A salient feature of our methods is their high chemoselectivity in the presence of a variety of functional groups. In addition, our reductive methods enabled concise synthesis of cyclic and macrocyclic nitrones, which are known to be challenging compounds to access by conventional methods.
Thermoluminescence spectra of gamma-irradiated shells of oysters, scallops, mussels, littleneck clams, and freshwater clams are measured with a multichannel Fourier-transform luminescence spectrometer. Oysters, scallops, and mussels isothermally heated at 200 °C show strong luminescence due to the electronic transition of Mn2+, which is included as an impurity in shells and excited to a metastable state by gamma-ray irradiation. Littleneck clams and freshwater clams show very weak thermoluminescence under the same experimental conditions and show strong thermoluminescence owing to phase transition when they are heated at 450 °C before gamma-ray irradiation. The phase transition of the crystal structures from aragonite to calcite is monitored by infrared spectroscopy.
We have synthesized a series of chiral π-conjugated polymers bearing glucose-linked biphenyl units in the main chain through copolymerizations of a key diethynyl compound (GLB-1), containing the structural element of naturally-occurring ellagitannin, with various diiodoaryls. The circular dichroism and circularly polarized luminescence properties of the obtained polymers were investigated in solution and the solid state. Based on a comparative study using the corresponding unimer model compounds, poly-3 and poly-4 bearing (oligo)thiophene-type comonomer units are considered to be able to fold into an excess one-handed helical conformation in solution and the solid state under an appropriate exterior environment. In contrast, analogous polymers bearing p- and m-phenylene residues as comonomer units did not form regular higher-ordered structures. We also observed that poly-3 and poly-4 efficiently emitted left-handed circularly polarized light with a corresponding fluorescence region arising from their helical chirality, and possessed dissymmetry factors of approximately 1.0 × 10−2 for the film state.
We demonstrated that the aggregation behavior of hyperbranched amphiphilic protic poly(ionic liquid)s (HBP-ILs) can be controlled by varying not only the number of peripheral hydrophobic arms and nature of counterions. Additionally, increasing the hydrophobicity of the HBP-ILs led to a condensed monolayer phase at the air-water interface. The balance of intermolecular interactions mediated by the presence of the ionic liquid component in the inner shell of micelles determines the final morphology in solution and at interfaces.
HutB is a putative heme transport protein located in the periplasmic space in Vibrio cholerae. Here, we purified HutB and characterized its heme binding properties. An analysis of the Soret band showed that there are two types of heme binding geometries depending on the heme concentration: 404-nm species are dominant at lower concentrations of heme, and 394-nm species dominate at higher concentrations. Moreover, a mutational study revealed that either Tyr65 or Tyr198 binds heme with the help of histidine, a property shared with another V. cholerae heme transport protein, HutX, despite the absence of sequence similarity, indicating that HutB acts as a heme transport protein in the periplasm.
A series of oxygen- and sulfur-bridged bianthracene V-shaped π-electronic cores are facilely synthesized. We clarify their fundamental properties and aggregated structures in single crystals as well as measure their transistor performances in single crystal field-effect transistors. Both V-shaped molecules possess bent structures induced by the intermolecular interaction in a herringbone-packing manner. A theoretical calculation study reveals that the driving force of the bent structures originates from the strong dispersion energy. Additionally, the bent conformation plays a crucial role in the formation of a dense packing structure, resulting in an attractive intermolecular overlap. An examination of the charge transport indicates that the hole mobility is up to 2.0 cm2/Vs. Finally, to understand the anisotropies of the mobility in single crystals, the transistors are evaluated when the channel direction is either parallel or orthogonal to the column direction in the herringbone packing along with their band structure calculations. Sulfur-bridged V-shaped π-electronic cores are more suitable for two-dimensional carrier-transport than oxygen-bridged analogs.
Here we have prepared ZIF-67 derived nanoporous carbons (NPCs) under different carbonization temperatures ranging from 800 to 1000 °C, and investigated the effect of the temperature on the porous structure. Raman analysis confirms that the graphitic degree of the obtained samples increases as the applied carbonization temperature is increased. With the gradual increase of the graphitic degree, the surface area is decreased.
Polystyrene-cross-linking triphenylphosphines having methyl groups as ortho substituents were synthesized. Coordination of the polymer-bound tri(o-tolyl)phosphine-type ligand toward a Pd(II) complex was investigated by 31P CP/MAS NMR spectroscopies. Effects of the ortho-methyl-substituent were evaluated in the Pd-catalyzed cross-coupling of aryl chlorides.
In contrast to monofunctional electrocatalysts for oxygen evolution reaction (OER), hydrogen evolution reaction (HER) or oxygen reduction reaction (ORR), trifunctional catalysts for simultaneously generating H2, O2 and H2O provide a crucial means for improving the overall efficiency of water electrolysis. Herein we present a series of nonnoble metal [M = Fe(III), Co(II), Ni(II)]-nitrogen co-doped oxidized graphite rods (M-N/OGRs) that function as in situ working electrodes for tri-functional OER, HER and ORR electrocatalysis. The enhanced performance of the hybrid catalysts appear mostly associated with dual active site mechanisms originating from the synergic effects of M-N/Co-doped on the surface of the OGR. Our findings suggest that, the development of multifunctional electrocatalysts with optimal catalytic activity using transition metals and nitrogen doped OGR opens new doors for in situ synthesized electrocatalysts for use in clean electrochemical energy storage and conversion technologies.
Binary nanocomposite materials comprised of cobalt oxide (Co3O4) nanocrystals embedded in reduced graphene oxide (RGO) sheet were fabricated using one-pot hydrothermal synthetic route without using any structure guiding surfactant. We succeeded to visualize a 1/8 corner of a single cubic shape Co3O4 crystal under transmission electron microscopy (TEM). Shape and size of Co3O4 crystals varies from particle-type (size ∼10 nm), octahedral (size ∼20 nm) and aggregates of particles (size in the range of 50–80 nm) with increase in concentration of Co3O4 in the Co3O4/RGO composite. Cyclic voltammetry and charge/discharge measurements in aqueous KOH electrolyte (2 M) revealed that the Co3O4/RGO composite material exhibits electrochemical supercapacitive performance giving specific capacitance of 487 F g−1 at scan rate of 5 mV s−1 followed by outstanding cyclic stability sustaining 96.6% of capacitance after 2000 cycles.
XANES spectra were measured on Ca K-edge for Ca2N, Ca3N2, Ca2NH, CaNH, and Ca(NH2)2. Ca2N and Ca3N2 show the lowest edge positions, while Ca(NH2)2 the highest. The relationship between the edge positions and electron biasing around Ca in the compounds is discussed and the oxidation numbers are estimated.