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In this O-alkyl­ated sulfonyl­pyrazolone, the sulfur atom lies 0.558 (1) Å out of the pyrazole ring plane. The NH2 group is involved in an intra­molecular hydrogen bond to a sulfonyl oxygen atom and in a three-centre system with the two oxygen atoms of the side chain at C3, forming a ribbon structure., In the title compound, C18H17N3O4S, the pyrazole ring is planar, with the sulfur atom lying 0.558 (1) Å out of the ring plane. The NH2 group is involved in an intra­molecular hydrogen bond to a sulfonyl oxygen atom; its other hydrogen atom forms an asymmetric three-centre hydrogen bond to the two oxygen atoms of the —O—CH2—C=O— grouping, via the 21 screw axis, forming a ribbon structure parallel to the b axis. Translationally adjacent, coplanar ribbons form a layer parallel to (10).

A recently developed bottom-up synthesis strategy enables the fabrication of graphene nanoribbons with well-defined width and non-trivial edge structures from dedicated molecular precursors. Here we discuss the synthesis and properties of zigzag nanoribbons (ZGNRs) modified with periodic cove-cape-cove units along their edges. Contrary to pristine ZGNRs, which show antiferromagnetic correlation of their edge states, the edge-modified ZGNRs exhibit a finite single particle band gap without localized edge states. We report the on-surface synthesis of such edge-modified ZGNRs and discuss tunneling conductance dI/dV spectra and dI/dV spatial maps that reveal a noticeable localization of electronic states at the cape units and the opening of a band gap without presence of edge states of magnetic origin. A thorough ab initio investigation of the electronic structure identifies the conditions under which antiferromagnetically coupled, edge-localized states reappear in the electronic structure. Further modifications of the ribbon structure are proposed that lead to an enhancement of such features, which could find application in nanoelectronics and spintronics.

We report a unique dynamic morphology transformation of a Ag+-coordinated supramolecular nanostructure accompanying the conversion of complex structures in aqueous solution. In the presence of AgNO3 (1.0 equiv), the achiral bipyridine-based ligand 1G, possessing hydrazine and glycine moieties, preferentially generated a 1D needle-like structure (nanostructure I) based on the 1GAgNO3 complex (1G:Ag+ = 1:1) as a metastable product. Nanostructure I was then transformed into nanostructure II, which was composed of the 1G3Ag2(NO3)2 complex (1G:Ag+ = 3:2) as the thermodynamically stable product. This nanostructure exhibited a 1D helical tubular structure with a uniform diameter via a 2D ribbon as an intermediator, which led to the generation of a circular dichroism (CD) signal with right-handed (P-type) helicity. The observed dynamic transformation was attributed to formation of the thermodynamically favored helical 1G3Ag2(NO3)2 complex. In addition, the helical 1G3Ag2(NO3)2 complex acted as an initiator in the transformation from the 1D needle-like structure to the 1D helical tube via a 2D ribbon. The enhanced ΔG° value of nanostructure II compared to that of nanostructure I confirmed that nanostructure II is thermodynamically stable. More importantly, the transformation of supramolecular nanostructure I to nanostructure II occurred via an "on" pathway, even though the 1GAgNO3 complex was converted to the 1G3Ag2(NO3)2 complex, which did not involve dissociation from nanostructure I into the monomeric 1GAgNO3 complex species. In the kinetic study, the NO3- anion was found to act as an accelerator for the dynamic transformation from nanostructure I to nanostructure II. This result provides the first example of a dynamic transformation of a 1D needle-like structure into a 1D tubular structure via a 2D ribbon structure, accompanied by the conversion of a complex structure and the generation of a large CD signal for the metallo-supramolecular nanostructure. This study may open up new avenues to the understanding of a dynamic morphology transformation process in biological systems.

Birefringent crystals can modulate and detect the polarization of light, and have been widely used in the field of optoelectronic devices. The combination of a d10 transition metal cation and π-conjugated (H2C3N3O3)− group is a feasible approach for the synthesis of new crystal structures possessing large birefringence and short cutoff edges. Herein, a new hydroisocyanurate birefringent material Zn(H2C3N3O3)2·3H2O (ZHCY) was synthesized by a mild hydrothermal method. ZHCY featured a 2D layered ribbon structure constituted by coplanar π-conjugated (H2C3N3O3)− hydroisocyanurates, and displayed a wide band gap (5.24 eV) and a large birefringence (Δnexp ∼ 0.323, Δncal = 0.283 at 800 nm). Theoretical calculations revealed that its optical properties mainly originated from the π-conjugate coplanar (H2C3N3O3)− groups, which contribute to the enhancement of birefringence.

Structure evolutions of rapidly quenched Al65Ni10Si25 alloy were investigated using DTA, X-ray diffraction, SEM, and EDX methods. The processes of structural transformation from the as-quenched state into a nanocrystalline state were studied. The common and distinctive features of structural transformation processes induced by heating, isothermal annealing, and laser irradiation were observed. The formation of the nanoscale structure was observed in all ways of treatment. Two metastable phases that were formed at different temperatures were observed: hexagonal H-phase and Al9Ni2. The phase composition in the equilibrium state was observed as Al + Si + Al3Ni. A high-temperature phase of Al6Ni3Si was found in the alloy after laser heating that shows the possibility of “freezing” the high-temperature phases in the ribbon structure using laser treatment. The fractal structure was observed on the ribbon surface after irradiation.

An inorganic-organic hybrid complex [Cd7Cl14L2(EtOH)2]n (L = 4-Aminoantipyrine) was synthesised by solvothermal reaction and characterised by X-ray single-crystal diffraction analyses. It has unusual seven-nuclear cadmium chloride structure, which extends along the a-axis to form an infinite flat ribbon structure with the thickness of 3 A and the width of 18 A. The flat inorganic ribbon is wrapped in the two edge sides by organic molecules to form a sandwich structure. The MTT assay result displayed that the synthesised complex possessed antiproliferative activity potentials against the HCT-116, HepG2 and MCF-7 cancer cell lines. After 72 h treatment, the complex had a potent inhibitory effect on HCT-116 cells, and the IC50 value was 1.05 ± 0.06 (μg/mL). The cell cycle and apoptosis experiments showed that the complex remarkably induced apoptosis and arrested the HCT-116 cancer cell lines in the G1/G0 phase related to the concentration.

The structures of the two isomeric hydrogen-bonded 1:1 cocrystals of 5-nitro­quinoline with 2-chloro-4-nitro­benzoic acid and 5-chloro-2-nitro­benzoic acid have been determined at 190 K. In each crystal, the acid and base mol­ecules are linked by a short O—H⋯N hydrogen bond., The structures of two isomeric com­pounds of 5-nitro­quinoline with chloro- and nitro-substituted benzoic acid, namely, 2-chloro-4-nitro­benzoic acid–5-nitro­quinoline (1/1), (I), and 5-chloro-2-nitro­benzoic acid–5-nitro­quinoline (1/1), (II), both C7H4ClNO4·C9H6N2O2, have been determined at 190 K. In each com­pound, the acid and base mol­ecules are held together by an O—H⋯N hydrogen bond. In the crystal of (I), the hydrogen-bonded acid–base units are linked by a C—H⋯O hydrogen bond, forming a tape structure along [10]. The tapes are stacked into a layer parallel to the ab plane via N—O⋯π inter­actions between the nitro group of the base mol­ecule and the quinoline ring system. The layers are further linked by other C—H⋯O hydrogen bonds, forming a three-dimensional network. In the crystal of (II), the hydrogen-bonded acid–base units are linked into a wide ribbon structure running along [10] via C—H⋯O hydrogen bonds. The ribbons are further linked via another C—H⋯O hydrogen bond, forming a layer parallel to (110). Weak π–π inter­actions [centroid–centroid distances of 3.7080 (10) and 3.7543 (9) Å] are observed between the quinoline ring systems of adjacent layers. Hirshfeld surfaces for the 5-nitro­quinoline mol­ecules of the two com­pounds mapped over shape index and d norm were generated to visualize the weak inter­molecular inter­actions.

The silicon-based 1D photonic structure is proposed in this research to realize an intermediate layer, which could be used in tandem solar cell, where 1 D photonic structure deals with a silicon ribbon with having 10 number of circular periodic air hole on it. Further, the principle of realization of the present intermediate layer is based on the generation of photonic band gap with respect to the visible light, which is evaluated with the help of the plane wave expansion method. Finally, photonic band gap analysis confirms that the proposed one-dimensional photonic ribbon structure can be a suitable layer to introduce in a tandem solar cell to envisage better efficiency.

We demonstrated the morphology transformation of co-assemblies based on terpyridine-based ligands (1R and 1S) possessing R- or S-alanine analogues and their platinum(II) complex (2R-Pt and 2S-Pt). The right-handed helical ribbon of the co-assembly formed with 0.5 equivalents of 2R-Pt to 1R was converted into the left-handed helical ribbon with 0.6 equivalents of 2R-Pt. The left-handed helical ribbon structure of the co-assembly became a tubular structure in the presence of 0.8-1.0 equivalents of 2R-Pt. The morphology transformation via helical inversion at the supramolecular level was due to an orientation change of the amide groups caused by non-covalent Pt⋅⋅⋅Pt interactions between the terpyridine of 2R-Pt and that of 2R-Pt. This study provides insights into controlling the morphology of the transformation of helical ribbons into tubular structures through helicity inversion in co-assembled supramolecular nanostructures based on platinum(II) complexes.

Ni-Mn-Ga-Co-Cu melt spun ribbons were investigated in the as-cast and annealed states. The initial microstructure of the ribbons was highly anisotropic along the growing direction and was characterized by three different regions of equiaxed, columnar and dendritic grains. At ambient temperature, the microstructure was composed of two martensitic phases, i.e. non-modulated and seven-layer modulated, and the high temperature L21 austenite phase. The stabilization of the austenite phase was a consequence of a strong grain size reduction, especially close to the “contact” side of the ribbons. Subsequent annealing at 823 K triggered atomic ordering, which promoted an improvement in the magnetization. Additional annealing at 1173 K brought about a substantial refinement of the microstructure. The ribbon structure changed to a single non-modulated martensite phase, whereas on a microstructural level, the grains and martensitic plates coarsened considerably. The annealed ribbons resembled oligo-crystalline materials and may cause interest for magnetic field-induced strain applications.

Using photoelectron diffraction (XPD), photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED), we investigate the structure of silicon nano-ribbons grown on Au(1 1 0). We find that silicon forms two zigzag-terminated hexagonal chains along the [ 1 ‾ 1 0]-substrate direction, while the gold substrate forms a bulk-typed surface reconstruction after silicon evaporation. Only two missing rows along the [ 1 ‾ 1 0]-direction remain partially in their original structure at the Si/Au interface. Unlike silicon nano-ribbon formation on Ag(1 1 0), nano-ribbon growth on Au(1 1 0) is strongly substrate influenced by Van-der-Waals interaction and by AuSi bonding formation. This strong interaction leads to a substrate-driven hexagon formation, where the gold atoms are partially integrated into the ribbon structure. Besides the determination of the internal silicon nano-ribbon structure, we identify the origin of the two chemically shifted silicon components in the XPS spectra by deconvolving the diffraction pattern.

Hydrothermal reaction of cadmium nitrate, 2,5-thiophenedicarboxylic acid (H2tdc) and one of the conformationally flexible dipyridylamide ligands N,N′-(heptane-1,7-diyl)dinicotinamide (hedn), N,N′-(hexane-1,6-diyl)diisonicotinamide (hdin), N,N′-(hexane-1,6-diyl)dinicotinamide (hdn), N,N′-(propane-1,3-diyl)dinicotinamide (pdn), N,N′-(propane-1,3-diyl)diisonicotinamide (pdin) produced five new coordination polymers which were structurally characterized by single-crystal X-ray diffraction. {[Cd(tdc)(hedn)(H2O)]·3H2O}n (1) manifests looped (4,4) grid motifs with two-fold parallel interpenetration. {[Cd(tdc)(hdin)(H2O)]·H2O}n (2) shows stacked (4,4) grid motifs. {[Cd2(tdc)2(hdn)(H2O)4]·H2O}n (3) exhibits herringbone (6,3) grid motifs. In contrast to the 2D topologies seen in 1–3, {[Cd2(tdc)2(pdn)(H2O)2]·4H2O}n (4) displays a 3D self-penetrated net with 6482 nbo topology and [Cd(tdc)(pdin)]n (5) shows a 1D ribbon structure constructed from staple-conformation pdin ligands and {Cd2O2} dimer-containing [Cd(tdc)]n chains. Thermal decomposition and nitrobenzene detection properties of these five new materials are discussed.

In this work, a novel Cu(I) coordination polymer, Cu2LBr2 (1) based on a pyridyl-functionalized resorcin[4]arene [L = (2,8,14,20-tetraethyl-4,10,16,22-tetra kis((2-pyridylmethylene)oxy)-6,12,18,24-tetramethoxy-resorcin[4]arene)] has been synthesized under solvothermal condition. 1 was characterized by various physicochemical analyses and it shows a ribbon structure. Notably, 1 exhibits an outstanding thermal stability. 1 possesses strong luminescent property, and can selectively probe Cr2O72−, MnO4− and nitrobenzene via luminescent quenching. In addition, 1 is an efficient catalyst for azide–alkyne cycloaddition reaction.

The naked DNA inside the nucleus interacts with proteins and RNAs forming a higher order chromatin structure to spatially and temporally control transcription in eukaryotic cells. The 30 nm chromatin fiber is one of the most important determinants of the regulation of eukaryotic transcription. However, the transition of chromatin from the 30 nm inactive higher order structure to the actively transcribed lower order nucleosomal arrays is unclear, which limits our understanding of eukaryotic transcription. Using a method to extract near-native eukaryotic chromatin, we revealed the chromatin structure at the transitional state from the 30 nm chromatin to multiple nucleosomal arrays by cryogenic electron tomography (cryo-ET). Reproducible electron microscopy images revealed that the transitional structure is a branching structure that the 30 nm chromatin hierarchically branches into lower order nucleosomal arrays, indicating chromatin compaction at different levels to control its accessibility during the interphase. We further observed that some of the chromatin fibers on the branching structure have a helix ribbon structure, while the others randomly twist together. Our finding of the chromatin helix ribbon structure on the extracted native chromatin revealed by cryo-ET indicates a complex higher order chromatin organization beyond the beads-on-a-string structure. The hierarchical branching and helix ribbon structure may provide mechanistic insights into how chromatin organization plays a central role in transcriptional regulation and other DNA-related biological processes during diseases such as cancer.

The morphological transformation of an arched ribbon driven by torsion is a scientific problem that is connected with daily life and requires thorough analysis. An arched ribbon can achieve an instantaneous high speed through energy transformation and then return to the original shape of the structure. In this paper, based on the characteristics of the ribbon structure, the dynamic mathematical model of the arched ribbon driven by torsion is established from the Kirchhoff rod equation. The variations of the Euler angle of each point on the center line of the ribbon with the arc coordinate s and the rotation angle of the supports ϕ was examined. The relationship between the internal force distribution of each point in the direction of d ˆ a and the material, cross-sectional properties, and rotation angle of the supports was obtained. We used ABAQUS, a nonlinear finite element analysis tool, to simulate the morphological transformations of the ribbons, verified our theory with simulation results, and reproduced the experimental results of Sano. Furthermore, we redefined the concept of the “critical flipping point” of Sano. In this paper, the dimensional analysis method was used to fit the simulation data. The following relationship between the critical width w ∗ , thickness h , and the radius R of the ribbon with different cross sections was obtained: w ∗ = A ⋅ R h / R 0 . 6 , where A is 3.19 for rectangular cross sections and 3.06 for elliptical cross sections. By analyzing the simulation data, we determined the variation behavior of the out-of-plane deflection of the center point of the ribbon with the radius R , width w , and thickness h . Our research has guiding significance for understanding and designing arched ribbons driven by torsion, and the results can be applied to problems of different scales.

We provide a pair of ribbon graphs that have the same rotor routing and Bernardi sandpile torsors, but different topological genus. This resolves a question posed by M. Chan [Cha]. We also show that if we are given a graph, but not its ribbon structure, along with the rotor routing sandpile torsors, we are able to determine the ribbon graph's genus., Reformatted for DMTCS

Two new complexes, [Zn(tp)(RdmB)(H2O)] (I) and [Cd(tp)(RdmB)] (II) (tp = terephthalate, RdmB = rhodamine B), are obtained by similar hydrothermal synthesis reactions. X-ray crystallography reveals that both compounds are one-dimensional (1D) polymeric solids, in which I (C36H36N2O8Zn) ascribes to monoclinic C2/m space group, Z = 4 (a = 18.834(5) A, b = 16.859(5) A, c = 10.111(3) A, β = 97.638(4)°), while II (C108H102N6O21Cd3) crystallizes in monoclinic P21/n, 4 (a = 12.2309(1) A, b = 61.5661(7) A, c = 12.5852(1) A, β = 93.951(1)°). Owing to the difference in the coordination sphere around the metal center, four-coordinated zinc centers for I bridged by linear tp molecules associated with RdmB ligands result in an interesting 1D infinite zigzag tape-like structure, whereas six-/seven-coordinated cadmium centers for II bridged by the same ligands generate a novel 1D infinite biserrated edge ribbon structure with a 2,3,3-linked {62.10}{63}{6} network or a simplified 2,4-linked {43.62.8}{4} topological networ...

Three coordination assemblies, 1–3, [Ce(NO3)6]·[(H-phen)6·(NO3)3], [Pr(NO3)6]·[(H-phen)6·(NO3)3,] and [Sm(NO3)3·(phen)·(H2O)2]·[(H-phen)·(NO3)·H2O], respectively, wherein (H-phen = 1,10-phenanthroline), have been reported. In the complexes of 1 and 2, secondary coordination spheres yield a host-network, into which primary coordination sphere is encapsulated. In the complex, 3, however, both primary and secondary coordination spheres direct the formation of crossed ribbon structure, with voids being filled by water molecules. Nevertheless, acid molecules did not present in any of the complexes 1–3. Three-dimensional structures are determined by single crystal X-ray diffraction method and the analysis of packing of the molecules within the crystal lattices has been discussed in detail.

Low-field magnetocaloric effect occurred in itinerant metamagnetic materials is at core for magnetic cooling application. This works reports the magnetocaloric responses obtained at 1.35 T for the silicon-doped iron-based binary alloy La(Fe 0.88 Si 0.12 ) 13 in the bulk and ribbon form. Both samples possess a same symmetry but with different crystallite sizes and lattice parameters. The ribbon sample shows a larger maximum entropy change (nearly 8.5 times larger) and a higher Curie temperature (5 K higher) in comparison with that of the bulk sample. The obtained relative cooling power for the ribbon is also larger and very promising for application (RCP = 153 J/kg versus 25.2 J/kg for the bulk). The origin of the effect observed is assigned to the occurrence of negative magnetovolume effect in the ribbon structure with limit crystallization, caused by rapid cooling process at the preparation, which induced smaller crystallite size and large lattice constant at the overall weaker local crystal field.

Mirabilite (Na2SO4⋅10H2O) is one of the representative phase change materials. Temperature dependent structural behavior of mirabilite was investigated by using single-crystal X-ray diffraction (XRD) technique in the temperature range between 213 and 303 ​K. Thermal expansion of mirabilite was mainly ascribed to the expansion of two Na(H2O)6 octahedra constituting the ribbon structure along the c-axis. Three O atoms out of four apices of SO4 tetrahedron were split into two partially occupied O sites. The resulting disordered arrangement gave two orientations (major and minor) for the SO4 tetrahedron. The SO4 tetrahedron of the major orientation had the smaller volume than that of the minor orientation. The volume of the major SO4 tetrahedron showed a decreasing trend as increasing temperature. This shrinkage of the major SO4 tetrahedron would induce oxygen diffusion from the major SO4 tetrahedron to the minor SO4 tetrahedron. As a result, the O site occupancies belonging to the minor SO4 tetrahedron increased from 0.17 to 0.27. Crystal structure of mirabilite consists of infinite ribbons of edge-sharing Na(H2O)6 octahedra alternating with chains composed of SO4 tetrahedra and two H2O molecules to form sheets parallel to the b-c plane. Since the fundamental structure of mirabilite is essentially the same as that of thenardite (Na2SO4), phase change from mirabilite to thenardite immediately occurs after dehydration without formation of any intermediate phase.

The structure, conformation and configuration of the n -propyl 3-azido-2,3-dideoxy-β- d - arabino -hexopyranoside ( BAra-nPr ) were determined by 1 H NMR, 13 C NMR, and IR spectroscopy, as well as by optical rotation. The crystal structure was confirmed by single-crystal X-ray diffraction studies at room temperature. The compound crystallizes in P 2 1 space group symmetry of the monoclinic system. The molecule has a 4 C 1 chair conformation with azide group in the equatorial position both in a solution as well as in the crystal. The spatial arrangement of azide group is compared to other previously determined azidosugars. The hydrogen bonds between the hydroxyl group of sugar molecules lead to a ribbon structure observed also for the ethyl homolog. The packing of ribbons is dependent on the alkyl substituent length and with the elongation changes from pseudohexagonal to lamellar. Acidity constants for the n -propyl 3-azido-2,3-dideoxy-β- d - arabino -hexopyranoside ( BAra-nPr ) in an aqueous solution were evaluated by the spectrophotometric and potentiometric titrations methods. Title compound exhibit blue absorption with the maximum wavelengths in the range of 266 nm and 306 nm. Based on these measurements we showed equilibria existing in a particular solution and a distribution of species which have formed during the titration. We also investigated interactions between Cu(II), Ni(II) and VO(II) and title compound (as ligand L) during complexometric titration. On these bases we identified that in [Cu II - BAra-nPr ] 2+ the ratio of the ligand L to metal ion M(II) was 3:1, while in [Ni II - BAra-nPr ] 2+ and [VO II - BAra-nPr ] 2+ complexes 2:1 ratios were found. The cumulative stability constants (as log β) occurring in an aqueous solution for the complexes of BAra-nPr with Cu(II), Ni(II) and VO(IV) were 14.57; 11.71 and 4.20, respectively.

Li2C2 has the highest theoretical capacity (1400 mA·h·g–1) as the electrode material for Li-ion battery, but suffers from low conductivity. Here we found that under external pressure its conductivity was irreversibly enhanced by 109-fold. To explain that, we performed X-ray diffraction, Raman, IR, gas chromatography–mass spectrometry, and theoretical investigations under external pressure. We found that the C22– anions approached to each other and polymerized upon compression, which is responsible for the irreversible enhancement of conductivity. The polymer has a ribbon structure and disproportionates into Li3C4 (Li2–0.5C2) ribbon structure, Li6C3 (Li propenide) and Li4C3 (Li allenide) upon decompression, implying that the carbon skeletal is highly electrochemically active. Our work reported polymerized Li2C2 for the first time, demonstrated that applying pressure is an effective method to prepare novel Li–C frameworks, and hence shed light on the search for novel carbon-based electrode materials.

The molecule of the title compound, C9H8F3N, adopts an E configuration with respect to the C=C double bond. The dihedral angle between the benzene ring and the prop-1-enyl group is 25.4 (3)°. In the crystal, molecules are linked via pairs of N—H...F hydrogen bonds into inversion dimers with an R 2 2(16) ring motif. The dimers are linked by C—H...N hydrogen bonds, forming a ribbon structure along the b-axis direction. The ribbons are linked by N—H...π and C—H...π interactions, generating a three-dimensional network.

The effects of turbulence in the very local interstellar medium (VLISM) have been proposed by Giacalone & Jokipii (2015) to be important in determining the structure of the Interstellar Boundary Explorer (IBEX) ribbon via particle trapping by magnetic mirroring. We further explore this effect by simulating the motion of charged particles in a turbulent magnetic field superposed on a large-scale mean field, which we have considered to be either spatially-uniform or a mean field derived from a 3D MHD simulation. We find that the ribbon is not double-peaked, in contrast to Giacalone & Jokipii (2015). However, the magnetic mirror force still plays an important role in trapping particles. Furthermore, the ribbon$'$s thickness is considerably larger if the large-scale mean field is draped around the heliosphere. Voyager 1 observations in the VLISM show a turbulent field component that is stronger than previously thought, which we test in our simulation. We find that the inclusion of turbulent fluctuations at scales ${\gtrsim}$100 au and power consistent with Voyager 1 observations produces a ribbon whose large-scale structure is inconsistent with IBEX observations. However, restricting the fluctuations to ${\sim}$10 au or smaller produces a smoother ribbon structure similar to IBEX observations. Different turbulence realizations produce different small-scale features ${\lesssim}10��$ in the ribbon, but its large-scale structure is robust if the maximum fluctuation size is ${\sim}$10 au. This suggests that the magnetic field structure at scales ${\lesssim}$10 au is determined by the heliosphere$'$s interaction with the VLISM and cannot entirely be represented by homogeneous interstellar turbulence., Submitted to the Astrophysical Journal

The model peptides A8K and A10K self-assemble in water into ca. 100 nm long ribbon-like aggregates. These structures can be described as β-sheets laminated into a ribbon structure with a constant elliptical cross-section of 4 by 8 nm, where the longer axis corresponds to a finite number, N ≈ 15, of laminated sheets, and 4 nm corresponds to a stretched peptide length. The ribbon cross-section is strikingly constant and independent of the peptide concentration. High-contrast transmission electron microscopy shows that the ribbons are twisted with a pitch λ ≈ 15 nm. The self-assembly is analyzed within a simple model taking into account the interfacial free energy of the hydrophobic β-sheets and a free energy penalty arising from an increased stretching of hydrogen bonds within the laminated β-sheets, arising from the twist of the ribbons. The model predicts an optimal value N, in agreement with the experimental observations.

The interplay between topology and correlation lies at the forefront of modern condensed matter physics. In this paper, we study the extended fermion-Hubbard model, including the on-site as well as the nearest-neighbor repulsive interactions, on a topological square lattice that supports the Chern insulator. Within the mean-field method, we find that the spontaneous symmetry breaking (SSB) charge-density wave or antiferromagnetic insulator dominates the system when the onsite or nearest-neighbor interactions are strong enough. It is interesting that the antiferromagnetic Chern insulator will appear in the phase diagram when there is an explicitly nonvanishing sublattice potential. In addition, we explore how a finite-size ribbon structure affects the phase diagram and point out that the critical interaction for SSB occurs with weaker strength than the bulk system.

Active zones at chemical synapses are highly specialized sites for the regulated release of neurotransmitters. Despite a high degree of active zone protein conservation in vertebrates, every type of chemical synapse expresses a given set of protein isoforms and splice variants adapted to the demands on neurotransmitter release. So far, we know little about how specific active zone proteins contribute to the structural and functional diversity of active zones. In this study, we explored the nanodomain organization of ribbon-type active zones by addressing the significance of Piccolino, the ribbon synapse-specific splice variant of Piccolo, for shaping the ribbon structure. We followed up on previous results, which indicated that rod photoreceptor synaptic ribbons lose their structural integrity in a knockdown of Piccolino. Here, we demonstrate an interaction between Piccolino and the major ribbon component RIBEYE that supports plate-shaped synaptic ribbons in retinal neurons. In a detailed ultrastructural analysis of three different types of retinal ribbon synapses in Piccolo/Piccolino-deficient male and female rats, we show that the absence of Piccolino destabilizes the superstructure of plate-shaped synaptic ribbons, although with variable manifestation in the cell types examined. Our analysis illustrates how the expression of a specific active zone protein splice variant (e.g., Piccolino) contributes to structural diversity of vertebrate active zones.SIGNIFICANCE STATEMENTRetinal ribbon synapses are a specialized type of chemical synapse adapted for the regulated fast and tonic release of neurotransmitter. The hallmark of retinal ribbon synapses is the plate-shaped synaptic ribbon, which extends from the release site into the terminals' cytoplasm and tethers hundreds of synaptic vesicles. Here, we show that Piccolino, the synaptic ribbon specific splice variant of Piccolo, interacts with RIBEYE, the main component of synaptic ribbons. This interaction occurs via several PxDLS-like motifs located at the C terminus of Piccolino, which can connect multiple RIBEYE molecules. Loss of Piccolino disrupts the characteristic plate-shaped structure of synaptic ribbons, indicating a role of Piccolino in synaptic ribbon assembly.

Ferritin, a soluble and highly robust protein with subunits packed into well-defined helices, is a key component of the iron regulatory system in the brain and thus is widely recognized as a crucial protein for iron metabolism, but may also bear possible implications in some neurodegenerative disorders. Here, we present evidence of how human recombinant apoferritin can convert into an unusual structure from its folded native state; that is, amyloid fibrils analogue to those found in pathological disorders such as Alzheimer's and Parkinson's diseases. An extensive combination of advanced microscopy, spectroscopy and scattering techniques concur to reveal that apoferritin fibrils possess a common double stranded twisted ribbon structure which can result in a mesoscopic right-handed chirality. We highlight a direct connection between the chirality and morphology of the resulting amyloid fibrils, and the initial protein subunits composition, advancing our understanding on the possible role of misfolding in some ferritin-related pathologies and posing new bases for the design of chiral 1D functional nanostructures.

A novel 1D-Linear coordination polymer [CaII(4–ABA)(CH3COO)(H2O)(DMF)]n (4-ABA = 4-aminobenzoic acid, DMF= Dimethyl formamide) has been synthesized successfully using DMF as one of the solvent by solvothermal synthesis. A single crystal X-ray studies of [CaII(4–ABA)(CH3COO)(H2O)(DMF)]n complex confirms the octa-coordinated calcium center with 4-ABA, DMF and water. It crystallizes in orthorhombic space group Pnma and has a 1D polymeric ribbon structure containing Ca(II) structure with distorted bicapped trigonal prismatic geometry. The complex was successfully employed as a homogenous catalyst in bicarbonate mediated epoxidation of cyclohexene and the complex was found to be selective in oxidation as only one product was formed i.e. cyclohexene oxide.

The present work describes the synthesis and rystallographic analysis of ga hybrid peptides, Boc-g4 -L-Phe-L-Pro-NHMe (P1) and Boc-(g4 -L-Phe-L-Pro)2-NHMe (P2). Peptide P1 adopts twelve membered (C12) helical turn over ga segment, while P2 folds into twisted ribbon structure involving two expanded C12 helical turns

The present study describes the synthesis and crystallographic analysis of αγ hybrid peptides, Boc-Gpn-L-Pro-NHMe (1), Boc-Aib-Gpn-L-Pro-NHMe (2), and Boc-L-Pro-Aib-Gpn-L-Pro-NHMe (3). Peptides 1 and 2 adopt expanded 12-membered (C12 ) helical turn over γα segment. Peptide 3 promotes the ribbon structure stabilized by type II β-turn (C10 ) followed by the expanded C12 helical γα turn. Both right-handed and left-handed helical conformations for Aib residue are observed in peptides 2 and 3, respectively.

Aycan, Tugba/0000-0002-5313-7807 WOS: 000366238100029 Two mixed-ligand coordination dimers, [Ni-2(pm) (ina)(2)(H2O)(4)] (1) and [Mn-2(Hpm)(2)(ina)(2)(H2O)(21)center dot H2O (2) (pm = tetraanion of pyromellitic acid, Hpm = trianion of pyromellitic acid and ma = isonicotinamide), were comparatively investigated by focusing on their supramolecular architectures. Their structural properties were characterized by X-ray diffraction technique (XRD) and Fourier transform infrared spectroscopy (FT-IR). In 1, each pm(4-) anion adopts mu(2)-bridging mode to connect two Ni(II) ions through carboxylate groups while in 2 Hpm(3-) anion bridges Mn(II) ions with tridentate coordination mode of carboxylate groups in cis positions. In I, D-1 H-bonded linear chain consists of R3(8) synthons. Linear chains are inter-connected by O-H center dot center dot center dot O bonds with DA:AD type organization of aqua ligands, resulting in Ri(Ei) synthons to form 2D structure. The increase in the dimensionality of the network is achieved by the involvement of aqua ligands in H-bonds with DD:AA fashion. In 2, the amide group of ma ligand and the aqua ligand involve in DD:AA type H-bond with COO- group of Hpm(3)(-) in the formation of ribbon structure. The ribbon structures are inter-connected by H-bonds between the aqua ligands and carboxylate groups, forming 2D supramolecular sheet through Ri (4) synthons. Unlike the case of I, the pyridinium plays an important role to form 3D network of 2 by connecting 2D sheets through Ri(22) and 121(30) synthons. The FT-IR investigation of the complexes was performed within the mid-IR region, mainly focusing on the characteristic vibrations of pyromellitic acid and isonicotinamide moieties by considering their free states and ligand behavior in the case of complex formation. (C) 2015 Elsevier B.V. All rights reserved. Ondokuz Mayis UniversityOndokuz Mayis University [PYO.FEN.1904.10.07] This study has been supported financially by Ondokuz Mayis University (Project No: PYO.FEN.1904.10.07). The authors sincerely thank to Prof. Dr. Orhan Buyukgungor for data acquisition.

The green microalga, Pyramimonas parkeae (Prasinophyceae) has an ejective organelle containing a coiled ribbon structure resembling the ejectisome in Cryptophyta. This structure is discharged from the cell by a stimulus and extends to form a tube-like structure, but the molecular components of the structure have not been identified. Tricine-SDS-PAGE analysis indicated that the ribbon-like structure of P. parkeae contains some proteins and low molecular acidic polymers. Edman degradation, LC/MS/MS analyses and immunological studies demonstrated that their proteins are core histones (H3, H2A, H2B and H4). In addition, monosaccharide composition analysis of the ribbon-like structures and degradation by lysozyme strongly indicated that the ribbon-like structure consist of β (1-4) linked polymers containing N-acetyl-glucosamine. Purified polymers and recombinant histones formed glob-like or filamentous structures. Therefore we conclude that the ribbon-like structure of P. parkeae mainly consists of a complex of core histones (H3, H2A, H2B and H4) and polymers containing N-acetyl-glucosamine, and suggest to name the ejective organelle in P. parkeae the "histrosome" to distinguish it from the ejectisome in Cryptophyta.

In the context, using solvo-thermal method, three isostructural lanthanide coordination polymers with viologen as linker ([m-H2bpybdc], m-bpybdc = 1,1′–bis(3-carboxyphenyl)-4,4′-bipyridinium), whose basic frameworks are formulated as [Ln(m-bpybdc)(H2O)3NO3] (Ln-CP, Ln = Sm, Eu and Gd). Among the crystal structures of Eu-CP and Gd-CP are determined, which belong to the one-dimensional ribbon structure. The physical characterization and especially the luminescence properties of them are studied in details. Furthermore, it is found that the coordinated water molecules can hinder the photo-induced electron transfer process (PET) of these viologen based lanthanide coordination polymers. So Eu-CP is selected to try to check water molecule in solvents for its photo response. These results show useful data for the structure, luminescence and photo response application of viologen based lanthanide coordination polymers.

The bottom-up fabrication graphene nanoribbons (GNRs) has opened new opportunities to specifically control their electronic and optical properties by precisely controlling their atomic structure. Here, we address excitations in GNRs with periodic structural wiggles, so-called Chevron GNRs. Based on reflectance difference and high-resolution electron energy loss spectroscopies together with ab-initio simulations, we demonstrate that their excited-state properties are dominated by strongly bound excitons. The spectral fingerprints corresponding to different reaction stages in their bottom-up fabrication are also unequivocally identified, allowing us to follow the exciton build-up from the starting monomer precursor to the final ribbon structure.

The asymmetric unit of the title compound, C22H14O6, consists of two independent molecules differing in the orientations of the ester groups. In one molecule, the two terminal benzene rings are inclined to the central benzene ring by 4.99 (13) and 77.46 (13)°, while in the other the corresponding angles are 11.03 (13) and 88.09 (12)°. In the crystal, molecules are connected into a ribbon structure running along [101]viaC—H...O and C—H...π interactions. Adjacent ribbons are further linked by additional C—H...O and C—H...π interactions. The crystal studied was a non-merohedral twin [twin law (0.986 − 0.073 − 0.008, 0.323 1.036 0.148, −0.121 − 0.102 0.942)], the ratio of components being 0.937 (4):0.063 (4).

In present study, we have investigated electronic and temperature dependent transport properties of carbyne like linear chain and ribbon like zigzag structures of Boron (B) nanowire. The linear chain structure showed higher electric and thermal conductivity, as it is sp-hybridized, than its counterpart ribbon (R) structure. However the conductivity of ribbon structure increases with increases in width due to edge geometry effect. The ribbon (3R) structure showed high electric and thermal conductivity of 8.0×1019 1/Ω m s and 0.59×1015 W/ m K respectively. Interestingly we have observed that B linear chain showed higher thermal conductivity of 0.23×1015 W/ m K than its ribbon R and 2R structure above 600K. Because of high Seebeck co-efficient of boron chain and ribbon (R) structures at low temperature, they could find applications in thermoelectric sensors. Our results show that tuning conductivity property of boron nanowire could be of great interest in research for future electric connector in nanodevices.