Structural Analyses of Designed α-Helix and ß-Sheet Peptide Nanofibers Using Solid-State Nuclear Magnetic Resonance and Cryo-Electron Microscopy and Introduction of Structure-Based Metal-Responsive Properties.

The 21-residue peptide α3, which is artificially designed and consists of three repeats of 7 residues, is known to rapidly assemble into the α-helix nanofiber. However, its molecular structure within the fiber has not yet been fully elucidated. Thus, we conducted a thorough investigation of the fiber's molecular structure using solid-state NMR and other techniques. The molecules were found to be primarily composed of the α-helix structure, with some regions near the C- and N-terminal adopting a 310-helix structure. Furthermore, it was discovered that ß-sheet hydrogen bonds were formed between the molecules at both ends. These intermolecular interactions caused the molecules to assemble parallelly in the same direction, forming helical fibers. In contrast, we designed two molecules, CaRP2 and ßKE, that can form ß-sheet intermolecular hydrogen bonds using the entire molecule instead of just the ends. Cryo-EM and other measurements confirmed that the nanofibers formed in a cross ß structure, albeit at a slow rate, with the formation times ranging from 1 to 42 days. To create peptide nanofibers that instantaneously respond to changes in the external environment, we designed several molecules (HDM1-3) based on α3 by introducing metal-binding sites. One of these molecules was found to be highly responsive to the addition of metal ions, inducing α-helix formation and simultaneously assembling into nanofibers. The nanofibers lost their structure upon removal of the metal ion. The change occurred promptly and was reversible, demonstrating that the intended level of responsiveness was attained.

Coalescence-Driven Verticality in Mesoporous TiO2 Thin Films with Long-Range Ordering.

Mesoporous semiconducting films with continuous interconnectivity and minimal tortuosity, such as densely ordered arrays of vertical channels, are ideal for ensuring a maximal surface area at the heterojunction to increase the density of charges or photons. While the design of these films with nanostructures below 50 nm using modern lithography is not feasible, continuously perpendicular pores can be obtained throughout a TiO2 film using a traditional soft-templating approach and lyotropic crystal engineering. We demonstrate here that a polystyrene-b-poly(ethylene oxide) block copolymer in a three-solvent system can self-assemble into a body-centered cubic Im3̅m template. The long-range three-dimensional periodicity of the template combined with a high degree of vertical contraction results in coalescence of the pores into orthogonal channels that are strongly interconnected with their nearest neighbors in the (011̅) plane. This work presents evidence of lateral long-range ordering with continuously transverse vertical porosity in a TiO2 material, which will enable functional applications, such as filtration, sensing, catalysis, and optoelectronics. To this end, we demonstrate the ability of the films to template and host methylammonium lead iodide perovskite nanocrystals.

Morphology Tailoring of ZnWO4 Crystallites/Architectures and Photoluminescence of the Doped RE3+ Ions (RE = Sm, Eu, Tb, and Dy).

Tartrate (Tar2-) was originally employed in this work as a chelating/structure-directing agent for hydrothermal crystallization of ZnWO4, where the decisive roles of Tar2-/Zn2+/WO42- molar ratio, solution pH (7-10), and the use of ethylene glycol (EG) cosolvent in phase/morphology evolution were deciphered in detail. It was unambiguously manifested that Tar2- may remarkably retard the intrinsically preferred [001] growth of ZnWO4, transform 1D nanorods to 0D nanoparticles and then to 2D platelets, and meanwhile induce face-to-face alignment of the platelets to form spheroidal, ellipsoidal and snowflakelike 3D architectures, where the 2D crystallites were revealed to develop via oriented attachment (colattice) of non-(00l) facets. A lower solution pH and excessive WO42- were clearly shown to enhance and offset the effect of Tar2-, which led to ellipsoidal assemblies of substantially larger 2D crystallites and suppressed 2D growth/3D assembly of ZnWO4 crystallites, respectively. With the spheroidal architectures for example, doping ZnWO4 with RE3+ yielded (Zn0.98RE0.02)WO4 phosphors (RE = Sm, Eu, Tb, and Dy, respectively) that show luminescence overlapped from the typical linelike and broad-band (∼350-700 nm) emissions of RE3+ and WO6, respectively. The luminescence color of the sample was found to drift away from the blue corner of the CIE chromaticity diagram with RE3+ doping and to be dependent on the type of RE3+.

Self-Template-Directed Metal-Organic Frameworks Network and the Derived Honeycomb-Like Carbon Flakes via Confinement Pyrolysis.

Metal-organic frameworks (MOFs) have become a research hotspot since they have been explored as convenient precursors for preparing various multifunctional nanomaterials. However, the preparation of MOF networks with controllable flake morphology in large scale is not realized yet. Herein, a self-template strategy is developed to prepare MOF networks. In this work, layered double-metal hydroxide (LDH) and other layered metal hydroxides are used not only as a scaffold but also as a self-sacrificed metal source. After capturing the abundant metal cations identically from the LDH by the organic linkers, MOF networks are in situ formed. It is interesting that the MOF network-derived carbon materials retain the flake morphology and exhibit a unique honeycomb-like macroporous structure due to the confined shrinkage of the polyhedral facets. The overall properties of the carbon networks are adjustable according to the tailored metal compositions in LDH and the derived MOFs, which are desirable for target-oriented applications as exemplified by the electrochemical application in supercapacitors.

A Glutathione-Responsive Short Sequence of Metal-Organic Complex Array.

A short metal-organic complex array (MOCA) containing a sequence of RPtRRu (1Cl ) was found to exhibit unique responses to a major biothiol, glutathione (GSH). Upon binding of GSH to 1Cl , the resultant 1:1 complex (1GS ) formed nanofibrous assemblies that suggested supramolecular polymerization through the double-salt-bridge structure formation. The binding behavior of this MOCA sequence to calf thymus DNA was also dependent on GSH; a larger conformational change of DNA was observed upon binding with 1GS , relative to that with 1Cl .

Merging Cation Exchange and Photocatalytic Charge Separation Efficiency in an Anatase/K2Ti4O9 Nanobelt Heterostructure for Metal Ions Fixation.

Efficient collection and safe disposal of toxic metals ions from aqueous solutions is critical for applications in environmental remediation. Although extensive efforts have been devoted to the synthesis of functional TiO2 materials, photocatalytic reduction (photoreduction) of aqueous metal ions into solid metals remains a challenge. We designed a TiO2 nanoparticle-decorated layered titanate (K2Ti4O9) material that retained the cation exchange ability of K2Ti4O9 but also possessed the enhanced charge separation efficiency of K2Ti4O9. Combining cation exchange with enhanced charge separation efficiency results in a heterostructured material with remarkably high activity for the photoreduction of metal ions. Initially we demonstrated how the photocatalyst can efficiently reduce aqueous Ni2+ cations, whereas the benchmark TiO2-based P25 catalyst showed little to no activity. The resulting Ni-deposited heterostructure can then be used as a catalyst for visible light-induced photocatalytic H2 evolution in water.

Selective Crystallization of Four Tungstates (La2W3O12, La2W2O9, La14W8O45, and La6W2O15) via Hydrothermal Reaction and Comparative Study of Eu3+ Luminescence.

Hydrothermal reaction at 200 °C was systematically undertaken in wide ranges of solution pH (4-13) and W/La molar ratio ( R = 0.5-2), without using any organic additive, to investigate the effect of hydrothermal parameter on product property and the underlying mechanism. Combined analysis by X-ray diffraction (XRD), inductively coupled plasma (ICP) spectroscopy, elemental mapping, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that either a decreasing pH or increasing R value yielded a product richer in W and, conversely, richer in La. The results were interpreted from the solution chemistry of La3+ and tungstate ions. As an outcome of our 40 well-designed experiments, four La tungstates-La2W3O12, La2W2O9, La14W8O45, and La6W2O15-were successfully obtained in a phase-pure form by calcining their hydrothermal precursors. Phase and morphology evolution, structure features, and properties of Eu3+ emission were, for the first time, comparatively investigated for the four compounds. Spectral analysis found that the 5 at. % Eu3+-doped La2W3O12 phosphor exhibits the highest quantum efficiency (∼47%), more red component, and the shortest fluorescence lifetime of luminescence (∼0.72 ms).

Investigation of nanoscale voids in Sb-doped p-type ZnO nanowires.

While it has multiple advantageous optoelectronic and piezoelectric properties, the application of zinc oxide has been limited by the lack of a stable p-type dopant. Recently, it was discovered that antimony doping can lead to stable p-type doping in ZnO, but one curious side effect of the doping process is the formation of voids inside the nanowire. While previously used as a signifier of successful doping, up until now, little research has been performed on these structures themselves. In this work, the effect of annealing on the size and microstructure of the voids was investigated using TEM and XRD, finding that the voids form around a region of Zn7Sb2O12. Furthermore, using Raman spectroscopy, a new peak associated with successful doping was identified. The most surprising finding, however, was the presence of water trapped inside the nanowire, showing that this is actually a composite structure. Water was initially discovered in the nanowires using atom probe tomography, and verified using Raman spectroscopy.

Stable Blue Luminescent CsPbBr3 Perovskite Nanocrystals Confined in Mesoporous Thin Films.

Creating CsPbBr3 perovskite nanocrystals with bright blue emission is challenging because their optical properties depend sensitively on structure. Growing perovskites in mesoporous templates bypasses some of these purification issues because the size of the nanocrystal is governed by the dimensions of the pores. Mesoporous silica consisting of aligned channels with tunable diameter can be easily synthesized and used as a template. When the perovskite solution evaporates and retreats, some of the liquid remains trapped in the interconnecting pores by discontinuous dewetting. The precursor crystallizes, generating stable ca. 3.1 nm blue-emitting perovskite nanocrystals. The mesoporous template also serves as a protective barrier to preserve the optical properties of the CsPbBr3 from atmospheric conditions. Compared to the bulk crystals and the powder composite, the strong blue-shift of the emission peak in the film is accompanied by a decrease in the longer lifetime component and an 8-fold increase in the external quantum efficiency.

Spatially Confined Assembly of Monodisperse Ruthenium Nanoclusters in a Hierarchically Ordered Carbon Electrode for Efficient Hydrogen Evolution.

The redox units of polyaniline (PAni) are used cooperatively, and in situ, to assemble ruthenium (Ru) nanoclusters in a hierarchically ordered carbon electrode. The oxidized quinonoid imine (QI) units in PAni bond Ru complex ions selectively, whereas reduced benzenoid amine (BA) units cannot. By electrochemically tuning the ratio of QI to BA, Ru complexes are spatially confined in the outer layer of hierarchical PAni frameworks. Carbonization of Ru-PAni hybrids induces nucleation on the outer surface of the carbon support, generating nearly monodisperse Ru nanoclusters. The optimized catalyst has a low loading of approximately 2 wt % Ru, but exhibits a mass activity for the hydrogen evolution reaction that is about 6.8 times better than commercial 20 wt % Pt/C catalyst.

Production and characterization of genetically modified human IL-11 variants.

Interleukin-11 (IL-11) has been expected as a drug on severe thrombocytopenia caused by myelo-suppressive chemotherapy. Whereas, development of IL-11 inhibitor is also expected for a treatment against IL-11 related cancer progression. Here, we will demonstrate the creation of various kinds of genetically modified hIL-11s. Modified vectors were constructed by introducing N- or O-glycosylation site on the region of hIL-11 that does not belong to the core α-helical motif based on the predicted secondary structure. N-terminal (N: between 22 to 23 aa), the first loop (M1:70 to 71 aa), the second loop (M2:114-115 aa), the third loop (M3:160-161 aa) and C-terminal (C: 200- aa) were selected for modification. A large scale production system was established and the characteristics of modified hIL-11s were evaluated. The structure was analyzed by amino acid sequence and composition analysis and CD-spectra. Glycan was assessed by monosaccharide composition analysis. Growth promoting activity and biological stability were analyzed by proliferation of T1165 cells. N-terminal modified proteins were well glycosylated and produced. Growth activity of 3NN with NASNASNAS sequence on N-terminal was about tenfold higher than wild type (WT). Structural and biological stabilities of 3NN were also better than WT and residence time in mouse blood was longer than WT. M1 variants lacked growth activity though they are well glycosylated and secondary structure is very stable. Both of 3NN and OM1 with AAATPAPG on M1 associated with hIL-11R strongly. These results indicate N-terminal and M1 variants will be expected for practical use as potent agonists or antagonists of hIL-11.

Facile synthesis of nanoporous Li1+xV1-xO2@C composites as promising anode materials for lithium-ion batteries.

Recently, a layered material with composition Li1+xV1-xO2 has been discovered as a promising alternative anode material to graphite due to its high volumetric capacity and low operation potential. Herein, we demonstrate a mild and cost-effective synthetic methodology to construct a novel nanoporous anode material (P-LVO@C), comprising Li1+xV1-xO2 nanocrystals embedded in a porous carbon matrix. The thermal decomposition of organic materials, including a triblock copolymer (P123) and citric acid, in a N2 atmosphere is the source of the nanoporous carbon in the porous composite material, while citric acid also plays a crucial role in maintaining the reductive environment of the synthetic medium. Due to the novel composition of Li1+xV1-xO2 (x ≥ 0.03), as well as its porous structure and well-integrated conductive framework, our P-LVO@C has great applicability as a high performance anode material for lithium-ion batteries. Our P-LVO@C composite electrode shows high reversible capacity with an excellent cycling performance (100 cycles) and good capacity retention (82%) at a higher rate (0.48C).

Mesoporous Semimetallic Conductors: Structural and Electronic Properties of Cobalt Phosphide Systems.

Mesoporous cobalt phosphide (meso-CoP) was prepared by the phosphorization of ordered mesoporous cobalt oxide (meso-Co3 O4 ). The electrical conductivity of meso-CoP is 37 times higher than that of nonporous CoP, and it displays semimetallic behavior with a negligibly small activation energy of 26 meV at temperatures below 296 K. Above this temperature, only materials with mesopores underwent a change in conductivity from semimetallic to semiconducting behavior. These properties were attributed to the coexistence of nanocrystalline Co2 P phases. The poor crystallinity of mesoporous materials has often been considered to be a problem but this example clearly shows its positive aspects. The concept introduced here should thus lead to new routes for the synthesis of materials with high electronic conductivity.

Observation of Quantum Confinement in Monodisperse Methylammonium Lead Halide Perovskite Nanocrystals Embedded in Mesoporous Silica.

Hybrid organic-inorganic metal halide perovskites have fascinating electronic properties and have already been implemented in various devices. Although the behavior of bulk metal halide perovskites has been widely studied, the properties of perovskite nanocrystals are less well-understood because synthesizing them is still very challenging, in part because of stability. Here we demonstrate a simple and versatile method to grow monodisperse CH3NH3PbBrxIx-3 perovskite nanocrystals inside mesoporous silica templates. The size of the nanocrystal is governed by the pore size of the templates (3.3, 3.7, 4.2, 6.2, and 7.1 nm). In-depth structural analysis shows that the nanocrystals maintain the perovskite crystal structure, but it is slightly distorted. Quantum confinement was observed by tuning the size of the particles via the template. This approach provides an additional route to tune the optical bandgap of the nanocrystal. The level of quantum confinement was modeled taking into account the dimensions of the rod-shaped nanocrystals and their close packing inside the channels of the template. Photoluminescence measurements on CH3NH3PbBr clearly show a shift from green to blue as the pore size is decreased. Synthesizing perovskite nanostructures in templates improves their stability and enables tunable electronic properties via quantum confinement. These structures may be useful as reference materials for comparison with other perovskites, or as functional materials in all solid-state light-emitting diodes.

Time-gated luminescence bioimaging with new luminescent nanocolloids based on [Mo6I8(C2F5COO)6]2- metal atom clusters.

Bioimaging and cell labeling using red or near infrared phosphors emitting in the "therapeutic window" of biological tissues have recently become some of the most active research fields in modern medical diagnostics. However, because organic and inorganic autofluorophores are omnipresent in nature, very often the background signal from fluorochromes other than targeted probes has to be eliminated. This discrimination could be available using a time-gated luminescence microscopy (TGLM) technique associated with long lifetime phosphorescent nanocomposites. Here, we report new SiO2 nanostructured particle (50 nm in diameter) embedded luminescent nanosized [Mo6I8(C2F5COO)6]2- metal atom clusters (1 nm in diameter), successfully prepared by the microemulsion technique. This combination provides new physical insight and displays red emission in biological based solution under UV-Vis excitation with long lifetimes of around 17 and 84 µs. Moreover, the nanoparticles can be internalized by cancer cells after surface functionalization by transferrin protein and clearly imaged by TGLM under excitation at 365 nm. The nanocomposites have been mainly characterized by scanning and transmission electron microscopies (SEM and HAADF-STEM), UV-Vis and photoluminescence (PL) spectroscopies.

Tunable-Sized Polymeric Micelles and Their Assembly for the Preparation of Large Mesoporous Platinum Nanoparticles.

Platinum nanoparticles with continuously tunable mesoporous structures were prepared by a simple, one-step polymeric approach. By virtue of their large pore size, these structures have a high surface area that is accessible to reagents. In the synthetic method, variation of the solvent composition plays an essential role in the systematic control of pore size and particle shape. The mesoporous Pt catalyst exhibited superior electrocatalytic activity for the methanol oxidation reaction compared to commercially available Pt catalysts. This polymeric-micelle approach provides an additional design concept for the creation of next generation of metallic catalysts.

First Synthesis of Continuous Mesoporous Copper Films with Uniformly Sized Pores by Electrochemical Soft Templating.

Although mesoporous metals have been synthesized by electrochemical methods, the possible compositions have been limited to noble metals (e.g., palladium, platinum, gold) and their alloys. Herein we describe the first fabrication of continuously mesoporous Cu films using polymeric micelles as soft templates to control the growth of Cu under sophisticated electrochemical conditions. Uniformly sized mesopores are evenly distributed over the entire film, and the pore walls are composed of highly crystalized Cu.

Coassembly-Directed Fabrication of an Exfoliated Form of Alternating Multilayers Composed of a Self-assembled Organoplatinum(II) Complex-Fullerene Dyad.

The self-assembly of covalently linked dyad 1a of cyclometalated organoplatinum(II) complex and fullerene afforded alternating multilayers of electron-rich and -deficient molecular components. On the other hand, the coassembly of 1a with organoplatinum(II) complex 2 having no fullerene moiety gave an exfoliated form of the multilayers, by inhibiting the interdigitation of organoplatinum(II) complex moieties of 1a. The coassembled 1a/2 transports both of the photogenerated holes and electrons, while the self-assembled 1a allows only the transportation of electrons under the same conditions.

Role of positions e and g in the fibrous assembly formation of an amphipathic α-helix-forming polypeptide.

We previously characterized α3, a polypeptide that has a three times repeated sequence of seven amino acids (abcdefg: LETLAKA) and forms fibrous assemblies composed of amphipathic α-helices. Upon comparison of the amino acid sequences of α3 with other α-helix forming polypeptides, we proposed that the fibrous assemblies were formed due to the alanine (Ala) residues at positions e and g. Here, we characterized seven α3 analog polypeptides with serine (Ser), glycine (Gly), or charged residues substituted for Ala at positions e and g. The α-helix forming abilities of the substituted polypeptides were less than that of α3. The polypeptides with amino acid substitutions at position g and the polypeptide KEα3, in which Ala was substituted with charged amino acids, formed few fibrous assemblies. In contrast, polypeptides with Ala replaced by Ser at position e formed ß-sheets under several conditions. These results show that Ala residues at position e and particularly at position g are involved in the formation of fibrous assemblies.

Effects of chain length of an amphipathic polypeptide carrying the repeated amino acid sequence (LETLAKA)(n) on α-helix and fibrous assembly formation.

Polypeptide α3 (21 residues), with three repeats of a seven-amino-acid sequence (LETLAKA)(3), forms an amphipathic α-helix and a long fibrous assembly. Here, we investigated the ability of α3-series polypeptides (with 14-42 residues) of various chain lengths to form α-helices and fibrous assemblies. Polypeptide α2 (14 residues), with two same-sequence repeats, did not form an α-helix, but polypeptide α2L (15 residues; α2 with one additional leucine residue on its carboxyl terminal) did form an α-helix and fibrous assembly. Fibrous assembly formation was associated with polypeptides at least as long as polypeptide α2L and with five leucine residues, indicating that the C-terminal leucine has a critical element for stabilization of α-helix and fibril formation. In contrast, polypeptides α5 (35 residues) and α6 (42 residues) aggregated easily, although they formed α-helices. A 15-35-residue chain was required for fibrous assembly formation. Electron microscopy and X-ray fiber diffraction showed that the thinnest fibrous assemblies of polypeptides were about 20 Å and had periodicities coincident with the length of the α-helix in a longitudinal direction. These results indicated that the α-helix structures were orientated along the fibrous axis and assembled into a bundle. Furthermore, the width and length of fibrous assemblies changed with changes in the pH value, resulting in variations in the charged states of the residues. Our results suggest that the formation of fibrous assemblies of amphipathic α-helices is due to the assembly of bundles via the hydrophobic faces of the helices and extension with hydrophobic noncovalent bonds containing a leucine.