Features of the mechanical treatment of rice husk for the performance of the solid-phase reaction of silicon dioxide with polyphenols

The distinguishing features of rice husk are high strength properties, chemical stability, high ash content, and low nutritional value, which are determined by the composition and structure of this type of raw material. The goal of the study was to determine optimal methods of mechanical treatment for the performance of a solid-phase reaction of silicon dioxide from rice husk with polyphenol compounds. Different regimes of the treatment of plant raw material have been compared. It has been shown that, for the solid-phase reaction of silicon dioxide from plant raw material with polyphenol compounds to occur, both the destruction of the supramolecular complex of silicon dioxide with the lignocellulose matrix, which is accomplished by fine grinding, and the plastic deformation of the silicon dioxide phase with the formation of reaction centers are necessary. These operations can be brought about using grinders with the attrition and shear modes of operation, including roller mills. It is preferable that silicon dioxide is in the composition of plant raw material since the reaction between silicon dioxide and polyphenols with the formation of surface complexes requires the presence of silanol groups. If silicon dioxide is derived from rice husk by conventional methods, most hydroxyl groups are eliminated, which significantly decreases the reactivity.     

Analysis of the mechanism of intensification of fermentation process using yeast cells in a suspension of high-dispersed oxides

The differential microcalorimetry was used to explore an influence of particles of silicon dioxide, and also other high-dispersed oxides (0.05% of masses.) in water suspension of yeast cells on intensification of the process of their fermentation in endogenous metabolic conditions. It was shown that intensification of the processes of the vital activity of yeast microorganisms was observed in the specified interval of the concentration of silicon dioxide hydrosol particles. Mechanisms of interaction between SiO₂ particles and a surface of a cellular organism, as well as interaction between SiO₂ particles and one of metabolism products — carbon dioxide were studied. It was found out, that Al₂O₃, TiO₂ hydrosols also had a stimulating effect, but it is lower compared to that of SiO₂.     

Proteomic characterization of hierarchical megacomplex formation in Arabidopsis thylakoid membrane

Conversion of solar energy into chemical energy in plant chloroplasts concomitantly modifies the thylakoid architecture and hierarchical interactions between pigment–protein complexes. Here, the thylakoids were isolated from light‐acclimated Arabidopsis leaves and investigated with respect to the composition of the thylakoid protein complexes and their association into higher molecular mass complexes, the largest one comprising both photosystems (PSII and PSI) and light‐harvesting chlorophyll a/b‐binding complexes (LHCII). Because the majority of plant light‐harvesting capacity is accommodated in LHCII complexes, their structural interaction with photosystem core complexes is extremely important for efficient light harvesting. Specific differences in the strength of LHCII binding to PSII core complexes and the formation of PSII supercomplexes are well characterized. Yet, the role of loosely bound L‐LHCII that disconnects to a large extent during the isolation of thylakoid protein complexes remains elusive. Because L‐LHCII apparently has a flexible role in light harvesting and energy dissipation, depending on environmental conditions, its close interaction with photosystems is a prerequisite for successful light harvesting in vivo. Here, to reveal the labile and fragile light‐dependent protein interactions in the thylakoid network, isolated membranes were subjected to sequential solubilization using detergents with differential solubilization capacity and applying strict quality control. Optimized 3D‐lpBN‐lpBN‐sodium dodecyl sulfate–polyacrylamide gel electrophoresis system demonstrated that PSII–LHCII supercomplexes, together with PSI complexes, hierarchically form larger megacomplexes via interactions with L‐LHCII trimers. The polypeptide composition of LHCII trimers and the phosphorylation of Lhcb1 and Lhcb2 were examined to determine the light‐dependent supramolecular organization of the photosystems into megacomplexes.     

Experimental Colonization and Alteration of Orthopyroxene by the Pleomorphic Bacteria Ramlibacter tataouinensis

The colonization of orthopyroxene crystals by a pleomorphic bacterium and the mineralogical products resulting from a prolonged interaction have been studied. We used Ramlibacter tataouinensis (strain TTB310), which is an aerobic β-Proteobacterium moving over surfaces by gliding motility and whose life cycle includes rods and spherical cysts. Analysis of cultures grown on solid media with micrometer-sized pyroxene and quartz crystals scattered over the surface revealed a taxis of the bacteria toward the crystals. Given the mineralogical non-specificity of the interaction, a mechanism of elasticotaxis is inferred. After the rods had adhered to the pyroxene surface, they differentiated into cysts leading to the formation of microcolonies that were centered on a crystal grain. This suggests an original coupling between the life cycle of R. tataouinensis and the interaction with the crystals. The alteration of orthopyroxene was studied by high-resolution transmission electron microscopy at the interface between cysts and pyroxene crystals. The pyroxene surface showed an amorphous layer that was more developed than that of abiotic control samples processed under the same conditions. Moreover, chemical analyses showed that the dissolution of pyroxene was reduced in the presence of R. tataouinensis. The origin and the significance of the amorphous layers is discussed.     

Electrical properties and interaction with silicon dioxide particles of Bacillus subtilis cells

It was shown that, depending on the quantity of phosphate in cultivation media, the surface layer of the Bacillus subtilis cell wall can mainly consist of either teichoic or teichuronic acids. It was found that the addition of silicon dioxide particles to the bacterial suspension induces an increase in the negative charge of the cell. This cell response to contact interaction with solid particles is observed in bacteria whose surface components are teichoic acids.     

Differential binding of wild-type and a mutant RepA protein to oriR sequence suggests a model for the initiation of plasmid R1 replication.

DNA replication of the enterobacterial plasmid R1 is initiated by RepA protein. We have developed a new procedure for the purification of RepA from inclusion bodies, which involves CHAPS-mediated solubilization. This method has been also used for the thermosensitive mutant protein RepA2623. The nucleoprotein complexes obtained with both proteins and oriR, the origin of replication, are studied in this paper. DNaseI and hydroxyl-radical footprinting suggest the presence in oriR of two sites with different affinity for RepA separated by eight helical turns. The pattern of hypersensitive sites in the footprints indicates that the oriR sequence, when complexed with RepA, is curved. The binding of RepA molecules to oriR is co-operative and this co-operativity is defective in the thermosensitive protein. Band-shift analysis of RepA-oriR complexes revealed the existence of a species with an anomalously high electrophoretic mobility that appears after formation of the first RepA-oriR complex and requires the sequential interaction of RepA with its two distal binding sites. These features lead us to propose that protein-protein interactions between RepA bound to both distal sites could be responsible for oriR looping. This model represents a novel mechanism that results in activation of an origin in a replicon that does not contain iterons.     

Measurement of the rate of O2 consumption by peritoneal macrophages using electron paramagnetic resonance

To study the process of activation of macrophages by silicon dioxide particles, use was made of an electrode-free method for measuring the O2 consumption rate. It was discovered that within the first minute of interaction with silicon dioxide particles the rate of O2 consumption by peritoneal macrophages rose 3-4-fold.     

A LB film morphological study with reference to biopolymer–surfactant interaction taking gelatin–CTAB system as a model

The interaction of gelatin with cetyltrimethylammonium bromide (CTAB) studied at pH 9 and an ionic strength of 0.005, produces an interfacial surface active gelatin–CTAB (monomer) complex (GS_n^I), a surface inactive gelatin–CTAB (micelle) complex in bulk (GS_m^B), followed by coacervation, and its solubilization in micellar solution of CTAB. We have herein attempted to probe the interfacial morphological changes of gelatin and its CTAB complexes, and not the bulk properties like coacervation and/or micellar solubilization. The morphologies of pure gelatin and CTAB films and that of gelatin–CTAB interacted complex at the interface have been investigated using LB, SEM, AFM and ellipsometric techniques. The stability of the gelatin monolayer at varied concentrations with and without CTAB has been examined. The SEM images of stabilized films of gelatin and gelatin–CTAB complex have witnessed compact smooth as well as rough surfaces with formation of distinct domains. Drastic morphological change in the film before the critical aggregational concentration of CTAB (T₂) has been in line with an initial abrupt decrease in surface tension. This has been corroborated by AFM measurements, which along with morphology demonstration has provided information on the diameter of the ensembles formed and roughness of the LB films constituted of pure components and their complexes. Thickness of the film was at its maximum in the domain region, as corroborated by ellipsometric technique. Such an elaborate interfacial monolayer and film morphology study of biopolymer-amphiphile system has been rarely documented in literature.     

Isolation of coronavirus envelope glycoproteins and interaction with the viral nucleocapsid.

The two envelope glycoproteins and the viral nucleocapsid of the coronavirus A59 were isolated by solubilization of the viral membrane with Nonidet P-40 at 4 degrees C followed by sucrose density gradient sedimentation. Isolated E2 consisted of rosettes of peplomers, whereas E1, the membrane glycoprotein, was irregular and amorphous. Under certain conditions significant interactions occurred between components of Nonidet P-40-disrupted virions. Incubation of the Nonidet P-40-disrupted virus at 37 degrees C resulted in formation of a complex between one of the viral glycoproteins, E1, and the viral nucleocapsid. This was caused by a temperature-dependent conformational change in E1, resulting in aggregation of E1 and interaction with the viral RNA in the nucleocapsid. E1 also bound rRNA. The E1-nucleocapsid complexes can be distinguished on sucrose and Renografin density gradients from native viral nucleocapsids. The separation of the membrane glycoprotein E1 from the peplomeric glycoprotein E2 permitted preparation of antisera against these isolated proteins. A model is proposed for the arrangement of the three major structural proteins in the coronavirus A59 virion in relation to the viral envelope and RNA.     

In Situ Measurement of Solid Electrolyte Interphase Evolution on Silicon Anodes Using Atomic Force Microscopy

In situ measurements of the growth of solid electrolyte interphase (SEI) layer on silicon and the lithiation‐induced volume changes in silicon in lithium ion half‐cells are reported. Thin film amorphous silicon electrodes are fabricated in a configuration that allows unambiguous separation of the total thickness change into contribution from SEI thickness and silicon volume change. Electrodes are assembled into a custom‐designed electrochemical cell, which is integrated with an atomic force microscope. The electrodes are subjected to constant potential lithiation/delithiation at a sequence of potential values and the thickness measurements are made at each potential after equilibrium is reached. Experiments are carried out with two electrolytes—1.2 m lithium hexafluoro‐phosphate (LiPF₆) in ethylene carbonate (EC) and 1.2 m LiPF₆ in propylene carbonate (PC)—to investigate the influence of electrolyte composition on SEI evolution. It is observed that SEI formation occurs predominantly during the first lithiation and the maximum SEI thickness is ≈17 and 10 nm respectively for EC and PC electrolytes. This study also presents the measured Si expansion ratio versus equilibrium potential and charge capacity versus equilibrium potential; both relationships display hysteresis, which is explained in terms of the stress–potential coupling in silicon.     

Hydrogen plasma surface activation of silicon for biomedical applications

Silicon has gradually been recognized to be an essential trace element in the normal metabolism of higher animals, and the role of silicon in the human body has aroused interests in the biomedical community. In fact, the interactions between silicon-based devices and the human body such as biosensors and microelectromechanical systems (MEMS) often suffer from poor biocompatibility. In this work, hydrogen plasma immersion ion implantation (H-PIII) is conducted to improve the bioactivity or bone conductivity of silicon. In order to investigate the formation mechanism of bone-like apatite on the surface of the hydrogen implanted silicon wafer, two comparative experiments, hydrogenation and argon bombardment, are performed. The H-PIII sample exhibits an amorphous surface consisting of Si-H bonds. After immersion in simulated body fluids, a negatively charged surface containing the functional group ([triple bond]Si-O-) is produced and bone-like apatite is observed to nucleate and grow on the surface. The surface of the H-PIII silicon wafer favors the adhesion and growth of osteoblast cells and good cytocompatibility may be inferred.     

Is plant ecology more siliceous than we realise?

Although silicon occurs in all plants, it is an element that is largely overlooked by many plant ecologists and most plant-related research on silicon comes from agronomy, archaeology, palaeontology and biogeochemistry. Plant silicon has many functions, acting biochemically as silicic acid and physically as amorphous silica. It contributes to cell and plant strength and enables plants to respond adaptively to environmental stresses. Consequently, plant silicon can increase plant fitness in many fundamental aspects of ecology, including plant-herbivore interactions, light interception, pathogen resistance and alleviation of abiotic stresses. Here, we provide an ecological perspective to research outcomes from diverse disciplines, showing that silicon is an important element in plant ecology that is worthy of greater attention.     

Sugar-specific Attachment of Pseudomonas syringae pv. glycinea to Isolated Single Leaf Cells of Resistant Soybean Cultivars

Phase-contrast and scanning electron microscopy showed races of P. synngae pv. glycinea uniformly distributed over and attached to the whole surface of isolated single leaf cells of resistant soybean cultivars, as early as 30 to 180 min after inoculation. On the contrary, attachment in the compatible interaction did not occur within 10—15 h. In a later period, compatibility was characterized by the formation of adherent bacterial clusters. Early attachment of races 1 and 6 to cv. Harosoy and that of race 5 to cv. Flambeau leaf cells, each representing incompatible interaction, could be inhibited by L-rhamnose and D-glucose, respectively. Furthermore, the lack of Mn²⁺ and Fe²⁺ and heat-treatment of plant cells also affected the early attachment in incompatible combinations and resulted in cluster formation, suggesting incompatibility rather than compatibility to be the active phenomenon. Pre-inoculation of cells with an incompatible race induced changes that caused compatible bacteria also to distributively attach to plant cell surface indicating that a transfer of information or surface alterations occur upon attachment in incompatible interaction.     

Quantitative characterization of agglomerates and aggregates of pyrogenic and precipitated amorphous silica nanomaterials by transmission electron microscopy

ABSTRACT: BACKGROUND: The interaction of a nanomaterial (NM) with a biological system depends not only on the sizeof its primary particles but also on the size, shape and surface topology of its aggregates andagglomerates. A method based on transmission electron microscopy (TEM), to visualize theNM and on image analysis, to measure detected features quantitatively, was assessed for itscapacity to characterize the aggregates and agglomerates of precipitated and pyrogenicsynthetic amorphous silicon dioxide (SAS), or silica, NM. RESULTS: Bright field (BF) TEM combined with systematic random imaging and semi-automatic imageanalysis allows measuring the properties of SAS NM quantitatively. Automation allows measuring multiple and arithmetically complex parameters simultaneously on high numbersof detected particles. This reduces operator-induced bias and assures a statistically relevantnumber of measurements, avoiding the tedious repetitive task of manual measurements.Access to multiple parameters further allows selecting the optimal parameter in function of aspecific purpose.Using principle component analysis (PCA), twenty-three measured parameters wereclassified into three classes containing measures for size, shape and surface topology of theNM. CONCLUSION: The presented method allows a detailed quantitative characterization of NM, like dispersionsof precipitated and pyrogenic SAS based on the number-based distributions of their meandiameter, sphericity and shape factor.     

Fluorinated End‐Groups in Electrolytes Induce Ordered Electrolyte/Anode Interface Even at Open‐Circuit Potential as Revealed by Sum Frequency Generation Vibrational Spectroscopy

Fluorine‐based additives have a tremendously beneficial effect on the performance of lithium‐ion batteries, yet the origin of this phenomenon is unclear. This paper shows that the formation of a solid‐electrolyte interphase (SEI) on the anode surface in the first five charge/discharge cycles is affected by the stereochemistry of the electrolyte molecules on the anode surface starting at open‐circuit potential (OCP). This study shows an anode‐specific model system, the reduction of 1,2‐diethoxy ethane with lithium bis(trifluoromethane)sulfonimide, as a salt on an amorphous silicon anode, and compares the electrochemical response and SEI formation to its fluorinated version, bis(2,2,2‐trifluoroethoxy) ethane (BTFEOE), by sum frequency generation (SFG) vibrational spectroscopy under reaction conditions. The SFG results suggest that the ? CF₃ end‐groups of the linear ether BTFEOE change their adsorption orientation on the a‐Si surface at OCP, leading to a better protective layer. Supporting evidence from ex situ scanning electron microscopy and X‐ray photoelectron spectroscopy depth profiling measurements shows that the fluorinated ether, BTFEOE, yields a smooth SEI on the a‐Si surface and enables lithium ions to intercalate deeper into the a‐Si bulk.     

Iron oxide solubilization by organic matter and its effect on iron availability

The solubility of Fe in soils is largely controlled by Fe oxides; ferrihydrite, amorphous ferric hydroxide, and soil-Fe are generally believed to exert the major control. Fe(III) hydrolysis species constitute the major Fe species in solution. Other inorganic Fe complexes are present, but their concentrations are much less than the hydrolysis species. Organic complexes of Fe including those of organic acids like citrate, oxalate, and malate contribute slightly to increased Fe solubility in acid soils, but not in alkaline soils.The most important influence that organic matter has on the solubilization of Fe is through reduction. Respiration of organic matter creates reduction microsites in soil where Fe²⁺ concentrations increase above those of the Fe(III) hydrolysis species. Fluctuating redox conditions in these microsites are conducive to the formation of a mixed valency ferrosic hydroxide. This metastable precipitate maintains an elevated level of soluble inorganic Fe for prolonged periods and increases Fe availability to plants. The release of reducing agents and acids next to roots, as well as the production of siderophores by microorganisms within the rhizosphere, contribute to the solubilization and increased availability of Fe to plants.     

Direct observation of poly(3-hydroxybutyrate) depolymerase adsorbed on polyester thin film by atomic force microscopy

Poly[(R)-3-hydroxybutyrate] (PHB) depolymerases adsorbed on poly(L-lactide) (PLLA) thin film were directly observed by atomic force microscopy (AFM). A PLLA thin film of 100 nm thickness was prepared on a silicon wafer by spin-cast method. The PLLA thin film was treated at 220 degrees C and quenched to room temperature, resulting in the formation of a completely amorphous film with a smooth surface. Then, the PHB depolymerases from Pseudomonas stutzeri YM1006 and Ralstonia pickettii T1 were dispersed on the amorphous PLLA thin film. Direct AFM observation has revealed that the PHB depolymerases bind in an elliptic shape on the surface of the PLLA thin film and that a small ridge is created around each enzyme molecule. After removal of the enzymes with 40% ethanol aqueous solution, small hollows were found on the PLLA thin film. These results suggest that a PHB depolymerase interacts with polyester molecules during their adsorption to make a hollow on the substrate surface.     

Emerging facets of plastid division regulation

Plastids are complex organelles that are integrated into the plant host cell where they differentiate and divide in tune with plant differentiation and development. In line with their prokaryotic origin, plastid division involves both evolutionary conserved proteins and proteins of eukaryotic origin where the host has acquired control over the process. The plastid division apparatus is spatially separated between the stromal and the cytosolic space but where clear coordination mechanisms exist between the two machineries. Our knowledge of the plastid division process has increased dramatically during the past decade and recent findings have not only shed light on plastid division enzymology and the formation of plastid division complexes but also on the integration of the division process into a multicellular context. This review summarises our current knowledge of plastid division with an emphasis on biochemical features, the functional assembly of protein complexes and regulatory features of the overall process.     

the stability in various detergents of transferrin-transferrin receptor complexes from reticulocyte plasma membranes

Transferrin-membrane protein complexes were solubilized either with 0.4% sodium dodecyl sulfate (SDS), 1% Triton X-100 or 0.5% sulfobetaine 3-14 from the plasma membranes of rabbit reticulocytes previously labeled with 125I and then incubated with 131-labeled transferrin. When the solubilized membranes were analyzed by gel filtration fractionation, marked variation in the preservation of transferrin-transferrin receptor interaction was noted between the three detergents. After SDS solubilization, more than 80% of the 131I-labeled transferrin remained associated with membrane proteins with apparent molecular weight of the transferrin-receptor complexes of 1400 000 and 240 000. In contrast, after Triton X-100 solubilization only 40% of the transferrin was still complexed to membrane proteins with an apparent molecular weight of the complex of 450 000. Dissociation of transferrin from its receptor was most marked following sulfobetaine solubilization, with less than 30% of the transferrin still complexed. Following gel filtration 131I-labeled transferrin-125I-labeled membrane protein complexes were immunoprecipitated with goat specific anti-rabbit transferrin antibodies. The immunoprecipitates were analyzed under stringent dissociating conditions by two SDS-polyacrylamide gel electrophoretic techniques. In a linear 5-25% polyacrylamide gradient the 125I-labeled receptor obtained after membrane solubilization with all three detergents had an apparent molecular weight of 80 000. In contrast, in a different system using 10% polyacrylamide gel two 125I-labeled receptor components were detected wih apparent molecular weights of 90 000 and 80 000. These results demonstrate that estimates of the molecular weight of the transferrin receptor depended on the conditions of electrophoresis and suggest that the transferrin receptor is partially modified, perhaps by glycosylation.     

Differential detergent-solubilization of integral thylakoid membrane complexes in spinach chloroplasts. Localization of photosystem II, cytochrome b6-f complex and photosystem I

Progressive solubilization of spinach chloroplast thylakoids by Triton X-100 was employed to investigate the domain organization of the electron transport complexes in the thylakoid membrane. Triton/chlorophyll ratios of 1:1 were sufficient to disrupt fully the continuity of the thylakoid membrane network, but not sufficient to solubilize either photosystem I (PSI), photosystem II (PSII) or the cytochrome b6-f(Cyt b6-f) complex. Progressive with the Triton concentration increase (Triton/Chl greater than 1:1), a differential solubilization of the three electron transport complexes was observed. Solubilization of the Cyt b6-f complex from the thylakoid membrane preceded that of PSI and apparently occurred early in the solubilization of stroma-exposed segments of the chloroplast lamellae. The initial removal of chlorophyll (up to 40% of the total) occurred upon solubilization of PSI from the stroma-exposed lamella regions in which PSI is localized. The tightly appressed membrane of the grana partition regions was markedly resistant to solubilization by Triton X-100. Thus, solubilization of PSII from this membrane region was initiated only after all Cyt b6-f and PSI complexes were removed from the chloroplast lamellae. The results support the notion of extreme lateral heterogeneity in the organization of the electron transport complexes in higher plant chloroplasts and suggest a Cyt b6-f localization in the membrane of the narrow fret regions which serve as a continuum between the grana and stroma lamellae.