Spherical Subunits Research Articles

Tuning the composition of manganese cobaltite spinel with tungsten for enhanced energy storage performance

The development of efficient and innovative energy storage devices is a necessity of the hour. Emerging nanomaterials possessing tungsten are believed to have unique physicochemical properties and their application could be extended over a wide spectrum as nanocomposite electrodes for effective high voltage energy storage applications. In the present work, a one-step hydrothermal process has been employed to prepare Tungsten (W) doped spinel oxide MnWxCo2–2xO4 (MWCO) nanostructures, where x varies from 0.01 to 0.05. The spectroscopic characterization studies proved spherical subunits embedded onto nanosheets formed by W doped bimetallic oxide with a crystalline phase. On employing the synthesized material in asymmetric supercapacitor application, it was inferred that W doping had a notable effect on the electrochemical performance. The optimized doping ratio (x=0.03) revealed an appreciable specific capacitance of 91 F g−1 at the current of 0.5 A g−1, with a retention in the capacitance of more than 80 % even after 10000 GCD cycles. Remarkable specific energy (3.17 Wh kg−1) and specific power (98 W kg−1) were also noted. Hence, the material synthesized in this study by our facile method is thought to be highly suitable as an electrode for high-performance energy storage applications.

High Voltage Asymmetric Supercapacitors Using Tungsten‐Doped Mn‐Co Spinel Ferrite Electrodes

AbstractPhysicochemical properties emerging nanomaterials possessing tungsten (W) are unique and the applications could be extended over a wide spectrum as nanocomposite electrodes for effective high voltage energy storage applications. Herewith, W doped spinel ferrite nanostructures was synthesized with facile hydrothermal strategy to get MnCo1.98W0.02O4 (MnCoW). The spectroscopic characterization studies proved spherical subunits embedded onto nanosheets formed by W doped bimetallic oxide with a crystalline phase. The resistance due to charge transfer of the electrodes was reduced which led to enhanced transfer of charge across interface of electrode and electrolyte was addressed upon W doping. Carbon based nanocomposite electrodes endowed by their unique structures and the electrochemical performance with various aqueous electrolytes were tested in an asymmetric supercapacitor application. Excellent capacitance development from 141.2 F g−1 to 203.7 F g−1 was achieved by W doping possessing an energy density of 17.9 Wh kg−1. A superior capacitance retention of 91 % was obtained from MnCoW‐based device right after 10000 cycles (charging/discharging) at 1 A g−1. The designed supercapacitor device employing MnCoW electrode exhibited better lifetime performance during lighting a LED under various angles.

Novel strategy for preparing a magnetic drawing solute for use in forward osmosis to reclaim water from the wastewater of diamond wire sawing of silicon ingots

The speedy growth of the semiconductor industries and global water scarcity issues have caused great demand for energy-saving water reclamation technologies such as forward osmosis (FO). Magnetic nanoparticles functionalized with osmotic polymer were believed to be one of the emerging materials used as the drawing solute in FO because they can be simply recovered with magnet. This study employed a novel strategy to prepare an FO drawing solute that balances the tradeoff between the amount of surface-immobilized ionic polymer for generating osmotic pressure and particle size with strong magnetization for ensuring steady recovery. The drawing solute was designed to be applied to the FO reclamation of water from the wastewater generated during the diamond wire sawing of Si ingots. Coprecipitation and polyol reduction were employed to synthesize poly(sodium acrylate)-functionalized magnetic nanoparticles (PSA-MNPs) as the drawing solute. The polyol route produced particles (PSA-MNPpolyol) sized 150–220 nm and composed of spherical subunits sized 3–5 nm. By contrast, coprecipitation resulted in irregular aggregated clusters and discrete 3–8-nm particles (PSA-MNPcp). Adding the electrostatic stabilizer sodium acetate to the precursor in the coprecipitation route (creating PSA-MNPcp+AC) significantly improved the particles’ dispersion and slightly increased their osmolality. When the optimal concentration of iron precursor was employed, the saturation magnetization and the osmolality of the PSA-MNPpolyol reached 45.89 emu/g and 258 mOsmol/kg, respectively. The average water flux generated when PSA-MNPpolyol was employed as the drawing solute was approximately 3.8 times higher than that generated when PSA-MNPcp+AC was used over a 3-h FO process on waste produced by ingot sawing. The homogeneous particle sizes of PSA-MNPpolyol are conductive to post-FO recovery through magnetic separation.

Synthesis of Ti-Ni and Zr-Ni Core–Shell Particles Using Galvanic Replacement

This article focuses on the galvanic replacement synthesis of Ti-Ni and Zr-Ni metal systems with a “core-shell” structure, which are potential precursors for intermetallics. The authors defined effective synthesis parameters and formation features of polymetallic systems characterized by granulometric, phase, and elemental composition. X-ray fluorescence and X-ray phase analysis methods showed that the deposition of nickel on dispersed titanium and zirconium leads to the production of test samples with phase composition representing a mechanical mixture of Ni and Ti, and Ni and Zr. The method of X-ray fluorescence analysis showed that the presence of hydrofluoric acid with a 0.5-1.5 M concentration results in the formation of fixed quantitative ratios of elements in the precipitate, which allows the quantitative composition of dispersed systems “titanium-nickel” and “zirconium-nickel” to be regulated within a relatively wide range. Scanning electron microscopy proved that all synthesized systems are characterized by a highly porous structure that follows the titanium and zirconium particle surface contour and the presence of spherical nanoscale subunits on the formed particle surface.

Aerosol-synthesized siliceous nanoparticles: impact of morphology and functionalization on biodistribution.

IntroductionSiliceous nanoparticles (NPs) have been extensively studied in nanomedicine due to their high biocompatibility and immense biomedical potential. Although numerous technologies have been developed, the synthesis of siliceous NPs for biomedical applications mainly relies on a few core technologies predominantly intended to produce spherical-shaped NPs.MethodsIn this context, the impact of different morphologies of siliceous NPs on biodistribution in vivo is limited. In the present study, we developed a novel technique based on an aerosol silane reactor to produce sintered silicon NPs of similar size but different surface areas due to distinct spherical subunits. Silica-converted particles were functionalized for radiolabeling with copper-64 (64Cu) to systematically analyze their behavior in the passive targeting of A431 tumor xenografts in mice after intravenous injection.ResultsWhile low nonspecific uptake was observed in most organs, the majority of particles were accumulated in the liver, spleen, and lung. Depending on the morphologies and function-alization, significant differences in the uptake profiles of the particles were observed. In terms of tumor uptake, spherical shapes with lower surface areas showed the highest accumulation and tumor-to-blood ratios of all investigated particles.ConclusionThis study highlights the importance of shape and fuctionalization of siliceous NPs on organ and tumor accumulation as significant factors for biomedical applications.

SILKS AND SILK-PRODUCING ORGANS OF NEOTROPICAL TARANTULA AVICULARIA METALLICA (ARANEAE, MYGALOMORPHAE, THERAPHOSIDAE)

Silks and silk-producing organs of the theraphosid species Avicularia metallica were studied using scanning electron microscopy. The spinning apparatus is made up of two pairs of spinnerets located at the end of the ventral side of the opisthosoma. Both pairs of spinnerets are equipped with spigots (modified setae), i.e. external outlets of silk-producing glands which, in the case of posterior lateral spinnerets, are present on all three segments.The secreted silk, which hardens when exposed to air, is processed by movements of spinnerets and the opisthosoma. An investigation of spinning activity revealed two different manners in which silk is affixed to the ground: (1) by smearing silk secretion directly onto the surface of the substratum; or (2) by attaching silken fibers onto a layer of adhesive silk of attachment fields. The fibers connecting the walls of tubular shelters to the silk of attachment fields are essentially bundles of parallel nanofibrils. The connection between multifibrillar connecting fibers and the adhesive silk of attachment fields is, in essence, “silk-to-silk” connection. Nanoglobules (spherical subunits) are the basic microstructural blocks in the studied silk materials irrespective of whether the fibrils are a part of the tube, connecting fibers, or attachment fields. SEM images showed that the liquid silk, running through spigot ducts, has two components, which do not mix as they leave the spigots. The peripheral component of the solidified protein mixture surrounds the central component, which has a granular appearance

Modelling of high-symmetry nanoscale particles by small-angle scattering

A versatile procedure to build high-symmetry objects and to calculate their corresponding small-angle scattering intensity is presented. Starting from a set of vertex positions, available from a large and extensible database, it is possible to build several types of bodies using spherical subunits. A fast implementation, based on the Debye formula using a histogram of distance, is then used to compute the theoretical scattering intensity. Since the model is built from the definition of a small set of parameters, it is possible to perform an optimization of structural parameters against experimental data. Finally, affine size polydispersities can be easily included by the rescaling of the histogram of the positions used in the calculations. Several examples of the calculations are presented, demonstrating the method and its applicability.

Small-angle scattering from generalized self-similar Vicsek fractals

An analytical approach for calculating the small-angle X-ray or neutron scattering (SAXS/SANS) from generalized self-similar Vicsek fractals (GSSVF) is presented; each fractal consists of spherical subunits. The system considered is a mass-fractal, generated iteratively from a regular 3D Vicsek fractal structure. Its fractal dimension is controllable and increases with increasing the value of the scaling factor. Small-angle scattering (SAS) intensity is determined from a set of non-interacting, randomly oriented and uniformly distributed GSSVF fractals. It is shown that in the fractal region, the curve I(q)qD is approximately log-periodic with the period equal to the scaling factor of fractal; here D and I(q) are the fractal dimension and the SAS intensity, respectively. In particular, the positions of deepest minima and highest maxima are log-periodic, and their number coincides with the number of fractal iterations. The log-periodicity of the scattering curves is a consequence of the self-similarity of GSSVF.

Silk tape nanostructure and silk gland anatomy of trichoptera

Caddisflys (order Trichoptera) construct elaborate protective shelters and food harvesting nets with underwater adhesive silk. The silk fiber resembles a nanostructured tape composed of thousands of nanofibrils (∼ 120 nm) oriented with the major axis of the fiber, which in turn are composed of spherical subunits. Weaker lateral interactions between nanofibrils allow the fiber to conform to surface topography and increase contact area. Highly phosphorylated (pSX)(4) motifs in H-fibroin blocks of positively charged basic residues are conserved across all three suborders of Trichoptera. Electrostatic interactions between the oppositely charged motifs could drive liquid-liquid phase separation of silk fiber precursors into a complex coacervates mesophase. Accessibility of phosphoserine to an anti-phosphoserine antibody is lower in the lumen of the silk gland storage region compared to the nascent fiber formed in the anterior conducting channel. The phosphorylated motifs may serve as a marker for the structural reorganization of the silk precursor mesophase into strongly refringent fibers. The structural change occurring at the transition into the conducting channel makes this region of special interest. Fiber formation from polyampholytic silk proteins in Trichoptera may suggest a new approach to create synthetic silk analogs from water-soluble precursors.

Association of the Endosomal Sorting Complex ESCRT-II with the Vps20 Subunit of ESCRT-III Generates a Curvature-sensitive Complex Capable of Nucleating ESCRT-III Filaments

The scission of membranes necessary for vesicle biogenesis and cytokinesis is mediated by cytoplasmic proteins, which include members of the ESCRT (endosomal sorting complex required for transport) machinery. During the formation of intralumenal vesicles that bud into multivesicular endosomes, the ESCRT-II complex initiates polymerization of ESCRT-III subunits essential for membrane fission. However, mechanisms underlying the spatial and temporal regulation of this process remain unclear. Here, we show that purified ESCRT-II binds to the ESCRT-III subunit Vps20 on chemically defined membranes in a curvature-dependent manner. Using a combination of liposome co-flotation assays, fluorescence-based liposome interaction studies, and high-resolution atomic force microscopy, we found that the interaction between ESCRT-II and Vps20 decreases the affinity of ESCRT-II for flat lipid bilayers. We additionally demonstrate that ESCRT-II and Vps20 nucleate flexible filaments of Vps32 that polymerize specifically along highly curved membranes as a single string of monomers. Strikingly, Vps32 filaments are shown to modulate membrane dynamics in vitro, a prerequisite for membrane scission events in cells. We propose that a curvature-dependent assembly pathway provides the spatial regulation of ESCRT-III to fuse juxtaposed bilayers of elevated curvature.

The electrorheological response of elongated particles

A particle level simulation model is proposed for investigating the effects of elongated particles on the microstructure and field-induced flow response in electrorheological fluids. The particles are modelled as a collection of spherical subunits joined by Hookean-type connectors, which enables the modelling of the particle motion through the Newtonian carrier liquid. Electrostatic polarisation of each particle leads to a torque, as well as interaction forces between the particles. The simulation results show a stress–strain response that demonstrates the yielding behaviour reported in electrorheological systems. The microstructural changes in the system are studied via a description of the orientational stress distribution in the system. The stress contribution arising from rotational effects is shown to be dependant on the average orientation vector of the particles at the commencement of the shearing.

Chromosome ultrastructure in the basidiomycete fungus Schizophyllum commune

Composition and ultrastructure of the chromosomes of the basidiomycete fungus Schizophyllum commune Fr. were studied by histochemical staining, electron microscopy and DNA-fiber auto-radiography. The histochemical reactions used for the detection of histones gave positive results in spore and dikaryotic hyphal nuclei indicating the presence of histones. Electron-microscopical localization of ammoniacal silver reaction for histones showed that silver grains, about 200–400 A in diameter, appeared only in the nuclei. This is the strongest evidence that the basic protein found by means of Fast Green and sulfaflavine is histone. In spread spore chromatin the diameter of chromatin fibers ranged from 30 A to 120 A. Fibers were found to be composed of spherical subunits, chromatinomeres (90–100 A in diameter). The linear array of silver grains in the chromatin stained with ammoniacal silver resembles chromatinomere organization. This supports earlier assumptions that chromatinomeres contain histones. Basidiospores were found to contain 0.02 pg of DNA per haploid nucleus, which divided by the chromosome number (n = 4) gives an average value of 1.6 mm of DNA per average chromosome. DNA-fiber autoradiography of labelled spore chromosomal DNA revealed molecules up to 2.2 mm in length. This is taken as evidence of “chromosome-sized” DNA molecules and a uninemic structure of eukaryotic chromosomes.

Charge and Interfacial Behavior of Short Side-Chain Heavily Glycosylated Porcine Stomach Mucin

The current accepted model for high-molecular-weight gastric mucins of the MUC family is that they adopt a polydisperse coil conformation in bulk solutions. We develop this model using well-characterized highly purified porcine gastric mucin and examine the molecules' charge and interfacial adsorption. "Orthana" mucin has short side-chains, low levels of sialic acid residues, and includes minute amounts of cystine residues that can be responsible for the self-polymerization of mucin. Atomic force microscopy and transmission electron microscopy are used to examine the interfacial behavior of the mucin and clearly demonstrate the existence of discrete spherical subunits within the mucin molecules, with sizes in agreement with static light scattering, dynamic light scattering, and zeta potential measurements. Furthermore images indicate the combs are assembled with a beads on a string conformation; the daisy chain model. Zeta potential measurements establish the polyampholyte nature of the mucin molecules, which is used to explain their adsorption behavior on similarly charged surfaces.

Expression and characterization of a Rana pipiens amelogenin protein

Amelogenin, the major protein of developing enamel matrix, controls enamel crystal growth via unique supermolecular features. While much has been contributed to our understanding of mammalian amelogenin function, little is known about how amelogenin and its unique physico-chemical features have evolved among vertebrates. Here we report, for the first time, amphibian amelogenin recombinant protein expression and characterization in Rana pipiens. In order to characterize R. pipiens amelogenin, the newly discovered amelogenin coding sequence was amplified, subcloned, and expressed in Eshcerichia coli. Our newly generated R. pipiens amelogenin-specific antisera resolved a major 19-kDa band on western blots of frog tooth extracts and revealed an enamel organ tissue-specific localization pattern using immunohistochemistry. Using mass spectroscopy, a single major compound with a molecular weight of 21.6 kDa was detected, which corresponded to the amino acid sequence-based molecular weight prediction of the His fusion recombinant protein. Dynamic light scattering studies resolved 41-nm radius subunits compared with 14-nm radius subunits from mouse recombinant amelogenin controls. Transmission electron microscopy revealed defined spherical subunits in R. pipiens matrix self-assembly in contrast with a homogeneous 'stippled' matrix in mouse amelogenin matrix self-assembly. Our data suggest that R. pipiens amelogenin is distinguished from mammalian amelogenins by a number of unique physico-chemical properties which may be related to specific modes of crystal formation in frog enamel.

A possible structure of the casein micelle based on high-resolution field-emission scanning electron microscopy

New electron micrographs, produced using the technique of Field Emission Scanning Electron Microscopy, showing the details of the micellar surface, are presented. The images show the micellar surfaces without any coating, and suggest that the surface of the micelle may have a much more complex structure than has previously been demonstrated. Although there appear to be no spherical subunits (submicelles), there is evidence for the organization of the caseins into tubular structures within the micelle. The surface is not smooth, and contains gaps between the substructures. The observations are discussed in terms of published models of micellar structure, where is it suggested how the depiction of the micellar surface can be used to explain certain factors of its reactivity and behaviour.

Dental enamel—a biological ceramic: regular substructures in enamel hydroxyapatite crystals revealed by atomic force microscopy

Hydroxyapatite crystals from developing rat incisor enamel and polished sections of mature human dental enamel were investigated using Atomic and Chemical Force Microscopy. Regular substructures were seen on crystals comprising ∼40 nm wide morphologically and chemically defined bands across the crystal long axes. Exposure to low pH resulted in selective dissolution between bands and the emergence of 2–3 spherical structures within each band. The spherical structures were chemically distinct exhibiting high friction in lateral force mode. Enamel crystals appear to comprise stacks of roughly hexagonal arrays of chemically or structurally distinct spherical subunits.

Characterization of β amyloid assemblies in drusen: the deposits associated with aging and age-related macular degeneration

Purpose. Recent studies strongly suggest that drusen, the extracellular deposits associated with age-related macular degeneration (AMD), are a manifestation of local inflammatory events. New evidence indicates that substructural elements within drusen contain activated complement components as well as amyloid β (Aβ), a major pro-inflammatory component of Alzheimer's disease plaques. We characterized the ultrastructural organization and histochemical staining properties of these Aβ-containing elements in order to further assess their significance in drusen formation and AMD pathogenesis. Methods. We used differential interference contrast optics, laser scanning confocal immunofluorescence, and immunogold electron microscopy to characterize the structural properties and molecular composition of Aβ-containing elements in drusen. We obtained estimates of their frequency from montages of electron micrographs gathered from 152 human donor eyes ranging from 9 to 91 years of age. Results. Spherical Aβ-containing elements, which are typically organized as concentric ring-like structures, are common substructural components of drusen. They stain with thioflavin T, but are not stained by Congo red; nor do they bind cationic, lipophilic, or nucleic acid-binding fluorescent dyes. Ultrastructurally, they are composed of a central core, one or more concentric inner rings with intervening electron lucent layers, and an electron dense outer shell. Immunogold labeling indicates that most Aβ immunoreactivity is associated with the outer layers that consist of densely-packed spherical subunits. No longitudinally-oriented fibril arrays, characteristic of aggregated amyloid fibrils in the brain, are evident. Other prominent drusen-associated proteins including the terminal complement complex C5b-9, vitronectin, apolipoprotein E, serum amyloid P component, and ubiquitin are excluded from the spheres. Conclusions. These structures embedded in drusen appear to represent a new type of macromolecular assembly that contains Aβ as well as activated complement components. The presence of Aβ in these extracellular deposits is an additional indication that some of the pathogenic pathways that give rise to drusen and AMD may be shared with other neurodegenerative diseases characterized by misfolded protein deposition and aggregation.

Subunit Structures in Hydroxyapatite Crystal Development in Enamel: Implications for Amelogenesis Imperfecta

Previous freeze-etching studies of developing enamel [21] revealed collinear arrays of spherical structures (~50 nM dia) of similar width to the crystals of mature tissue. Concomitant with matrix degradation/processing, spherical structures became less distinct until, coincident with massive matrix loss, only crystal outlines were seen. More recently, using Atomic force microscopy technology [22], early crystals exhibited topology reminiscent of these collinear spherical structures. After matrix loss these were replaced by similarly sized bands of positive charge density on the crystal surfaces [28]. The data suggest enamel crystals may form from mineral-matrix spherical subunits. Matrix processing may generate mineral nuclei and lead to their fusion and transformation into long apatite crystals. Support for this view derives from the appearance of short crystal segments in amelogenesis imperfecta (hypoplastic AI) or abnormally large crystals alongside 50 nM diameter spherical mineral subunits (hypomaturation AI). Mutation of matrix or processing enzymes leading to defective processing may have impaired mineral initiation, fusion, and subsequent growth.

Subunit Structures in Hydroxyapatite Crystal Development in Enamel: Implications for Amelogenesis Imperfecta

Previous freeze-etching studies of developing enamel [21] revealed collinear arrays of spherical structures (~50 nM dia) of similar width to the crystals of mature tissue. Concomitant with matrix degradation/processing, spherical structures became less distinct until, coincident with massive matrix loss, only crystal outlines were seen. More recently, using Atomic force microscopy technology [22], early crystals exhibited topology reminiscent of these collinear spherical structures. After matrix loss these were replaced by similarly sized bands of positive charge density on the crystal surfaces [28]. The data suggest enamel crystals may form from mineral-matrix spherical subunits. Matrix processing may generate mineral nuclei and lead to their fusion and transformation into long apatite crystals. Support for this view derives from the appearance of short crystal segments in amelogenesis imperfecta (hypoplastic AI) or abnormally large crystals alongside 50 nM diameter spherical mineral subunits (hypomaturation AI). Mutation of matrix or processing enzymes leading to defective processing may have impaired mineral initiation, fusion, and subsequent growth.

Xenopus laevis embryo development: arrest of epidermal cell differentiation by the chelating agent 1,10-phenanthroline.

The embryonic epidermis of stage 35 Xenopus laevis embryos is a highly differentiated structure composed of four cell types arranged in a regular architecture. Each type is distinguished by its distinct morphological characteristics. Some cells are ciliated (type 1); others have their surfaces covered by abundant, secreted vesicles of 0.1 microm diameter (type 2), or multiple linear aggregates of spherical subunits on their apical surfaces (type 3) or large secreted vesicles that emanate from prominent apical holes of 1 microm diameter (type 4). In contrast, the macroscopic appearance of embryos exposed to 10 microM 1,10-phenanthroline (OP) as well as the ultramicroscopic structure and organization of their epidermal cells are markedly altered. The most predominant cells of the embryonic epidermis are undifferentiated and of heterogeneous size. They lack any characteristic morphology and are arranged irregularly. Ghost cells are also identified. The recognizable differentiated cells are decreased in number and present in a scattered arrangement. These are identified as either type 1 or 2 cells but with ciliae that are shorter and thicker than control or with only a few vesicles larger than 0.1 microm in diameter on their surface. No cells with linear aggregates or prominent apical holes are identified. Except for the altered epidermis, the embryos do not develop any other major organs and exhibit axial abnormalities with an average dorso-anterior index of three. Thus, the chelating agent OP perturbs metal dependent processes essential for terminal differentiation that may likely account for the resultant abnormalities of embryo organogenesis and morphogenesis.