A directed attractive interaction between predefined “patchy” sites on the surfaces of anisotropic microcolloids can provide them with the ability to self‐assemble in a controlled manner to build ...target structures of increased complexity. An important step toward the controlled formation of a desired superstructure is to identify reversible electrostatic interactions between patches which allow them to align with one another. The formation of bipatchy particles with two oppositely charged patches fabricated using sandwich microcontact printing is reported. These particles spontaneously self‐aggregate in solution, where a diversity of short and long chains of bipatchy particles with different shapes, such as branched, bent, and linear, are formed. Calculations show that chain formation is driven by a combination of attractive electrostatic interactions between oppositely charged patches and the charge‐induced polarization of interacting particles.
Bipatchy microparticles with two oppositely charged patches are prepared using sandwich microcontact printing. These particles spontaneously self‐aggregate in solution forming a plurality of different shapes. Statistics of interactions between oppositely charged patches is compared with calculations of many‐body‐approach. Shape formation is driven by a combination of electrostatic interactions between charged patches and the charge‐induced polarization of interacting particles.
Eukaryotic cells are complex biological systems that depend on highly connected molecular interaction networks with intrinsically disordered proteins as essential components. Through specific ...examples, we relate the conformational ensemble nature of intrinsic disorder (ID) in transcription factors to functions in plants. Transcription factors contain large regulatory ID-regions with numerous orphan sequence motifs, representing potential important interaction sites. ID-regions may affect DNA-binding through electrostatic interactions or allosterically as for the bZIP transcription factors, in which the DNA-binding domains also populate ensembles of dynamic transient structures. The flexibility of ID is well-suited for interaction networks requiring efficient molecular adjustments. For example, Radical Induced Cell Death1 depends on ID in transcription factors for its numerous, structurally heterogeneous interactions, and the JAZ:MYC:MED15 regulatory unit depends on protein dynamics, including binding-associated unfolding, for regulation of jasmonate-signaling. Flexibility makes ID-regions excellent targets of posttranslational modifications. For example, the extent of phosphorylation of the NAC transcription factor SOG1 regulates target gene expression and the DNA-damage response, and phosphorylation of the AP2/ERF transcription factor DREB2A acts as a switch enabling heat-regulated degradation. ID-related phase separation is emerging as being important to transcriptional regulation with condensates functioning in storage and inactivation of transcription factors. The applicative potential of ID-regions is apparent, as removal of an ID-region of the AP2/ERF transcription factor WRI1 affects its stability and consequently oil biosynthesis. The highlighted examples show that ID plays essential functional roles in plant biology and has a promising potential in engineering.
•TMP and TBP were used as activating agents to produce activated carbons.•TMP and TBP activations enhanced the SBET and total acidic groups of final carbons.•AC-TMP and AC-TBP contained much more ...surface functional groups than AC-PPA.•AC-TMP and AC-TBP showed much higher Pb(II) sorption capacities than AC-PPA.•Sorption mechanisms: complexation, cation exchange and electrostatic attraction.
The present research explored the feasibility of preparation of activated carbons from lotus stalks (LS) by trimethyl phosphate (TMP) and tributyl phosphate (TBP) activations (producing AC-TMP and AC-TBP) and compared their physiochemical and Pb(II) adsorptive properties with the activated carbon (AC-PPA) obtained from phosphoric acid (PPA) activation of LS. The carbons were characterized by N2 adsorption/desorption, Boehm’s titration, FTIR and XPS. Physical and chemical analysis results indicated that activations with TMP and TBP dramatically enhanced the SBET and concentrations of O-containing surface functional groups of the AC-TMP and AC-TBP compared to the carbon (LS-C) derived from pyrolysis of LS. AC-TMP and AC-TBP displayed much less SBET than AC-PPA, but they contained much higher acidic groups on their surfaces. The Pb(II) adsorption capacities of the carbons were also investigated at different contact times, pHs, ionic strengths and initial Pb(II) concentrations. The adsorption equilibrium data of the carbons were well fitted to the Freundlich model. The maximum Pb(II) adsorption capacities of AC-TMP (240.6mg/g) and AC-TBP (229.1mg/g) were much higher than that of AC-PPA (139.0mg/g), resulting from their higher content of O-containing functional groups that could adsorb more Pb(II) species by electrostatic attraction, cation exchange and surface complexation.
Staphylococcal γ-hemolysin is a bicomponent pore-forming toxin composed of LukF and Hlg2. These proteins are expressed as water-soluble monomers and then assemble into the oligomeric pore form on the ...target cell. Here, we report the crystal structure of the octameric pore form of γ-hemolysin at 2.5 Å resolution, which is the first high-resolution structure of a β-barrel transmembrane protein composed of two proteins reported to date. The octameric assembly consists of four molecules of LukF and Hlg2 located alternately in a circular pattern, which explains the biochemical data accumulated over the past two decades. The structure, in combination with the monomeric forms, demonstrates the elaborate molecular machinery involved in pore formation by two different molecules, in which interprotomer electrostatic interactions using loops connecting β2 and β3 (loop A: Asp43-Lys48 of LukF and Lys37-Lys43 of Hlg2) play pivotal roles as the structural determinants for assembly through unwinding of the N-terminal β-strands (amino-latch) of the adjacent protomer, releasing the transmembrane stem domain folded into a β-sheet in the monomer (prestem), and interaction with the adjacent protomer.
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► A novel approach on recycle of waste phosphogypsum was exploited. ► Phosphogypsum was utilized to prepare hydroxyapatite nanoparticles with high purity. ► nHAp derived from PG ...exhibits excellent adsoprtion capacity for fluoride. ► Fluoride adsorbs onto nHAp mainly by electrostatic interaction and hydrogen bond.
In the present study, waste phosphogypsum (PG) was utilized firstly to prepare hydroxyapatite nanoparticles (nHAp) via microwave irradiation technology. The nHAp derived from PG exhibited a hexagonal structure with the particle size about 20nm×60nm and high purity. Meanwhile, the adsorption behaviour of fluoride onto the nHAp derived from PG was investigated to evaluate the potential application of this material for the treatment of the wastewater polluted with fluoride. The results indicate that the nHAp derived from PG can be used as an efficient adsorbent for the removal of fluoride from aqueous solution. The maximum adsorption capacities calculated from Langmuir–Freundlich model were 19.742, 26.108, 36.914 and 40.818mgF−/g nHAp for 298, 308, 318 and 328K, respectively. The pseudo-second order kinetic model was found to provide the best correlation of the used experimental data compared to the pseudo-first order and the adsorption isotherm could be well defined by Langmuir–Freundlich equation. The adsorption mechanism investigation shows that electrostatic interaction and hydrogen bond are the main driving force for fluoride uptake onto nHAp derived from waste PG.
•α-Fe2O3 NPs were produced without surfactants.•α-Fe2O3 NPs showed good physicochemical properties.•CA/α-Fe2O3 composite membranes were produced by NIPS methodology.•The composite membranes showed ...better properties than CA membrane.•Antibacterial activity is explained by electrostatic interactions.
Polymer nanoparticles (NPs) composites are rapidly gaining attention due to their high potential for application in several technological fields. On one hand, polymers contribute to balance the attractive magnetic and van der Waals forces that act on NPs and thus reduce their agglomeration. On the other hand, NPs can bring into the composites their inherent properties as nanosized objects. In this work, hematite NPs were blended with cellulose acetate (CA) polymer and thin nanocomposite films were produced by the non-solvent induced phase separation technique. A full physicochemical characterization of these composite materials confirmed its superior character in terms of structure, thermal stability, electronic/optical and antibacterial properties when compared to the polymer on its own and opens the door to its further validation in adsorptive and photocatalytic applications.
The interaction of photosensitizer methylene blue (MB) with single stranded oligonucleotides of composition AAA-AAA-AAA (A9), CCC-CCC-CCC (C9), GGG-GGG-GGG (G9), and TTT-TTT-TTT (T9) has been studied ...using UV–vis and fluorescence spectroscopies. The quenching effect of single stranded G9 over MB is favored over the other sequences. The analysis of the fluorescence data by Benesi–Hildebrand plot shows that MB forms 1:1 complex with G9. Results from spectroscopic experiments, Stern-Volmer and van’t Hoff plots are consistent with a principal contribution of the static quenching on the overall quenching mechanism and with the electrostatic binding mode of MB-single stranded G9 system. A quantum chemical modeling at DFT//B3LYP/6-31G(d,p) level confirms the experimental results. Asides from providing an insight into the underlying mechanism of the interaction between methylene blue and DNA, these results can be exploited for the design of novel DNA sensors using photoactive labels.
► The NaA membrane of 8Å non-zeolitic pore diameter showed excellent salts rejection (more than 99.9%) and high water flux (1.9kg/m2h at 69°C) in seawater. ► The excellent salts rejection was ...attributed to a joint size exclusion/charge exclusion/surface evaporation mechanism. ► The high water flux was explained by the reduced electrostatic interaction between the positively charged surface and the polar water. ► The positive charge was incurred by the adsorption of metal species, especially sodium ions. ► Evidently, the surface charge was an important distinction governing the water flux.
The pervaporative salts rejection and water flux characteristics of the NaA zeolite membrane in seawater were investigated. The upper limit of the non-zeolitic pore diameter was 8Å. High salts rejection (more than 99.9%) was shown for all of the ions in the seawater, even, and to a considerable extent, for boron (79.2% at 69°C). The high rejections were attributed to a joint size exclusion/charge exclusion/surface evaporation mechanism. High water flux in the seawater (1.9kg/m2h at 69°C) also was manifested, and was much higher than that in pure water at temperatures lower than 100°C. Moreover, the apparent activation energy of the water permeation in seawater was always lower than that in pure water (37.39kJ/mol). The higher water flux and low activation energy were explained by the reduced electrostatic interaction between the positive surface charge and the polar water. The positive surface charge was induced by the charge reversal that was incurred by the adsorption of metal species on the zeolite surface. The water flux in the NaOH, NaCl, NaNO3 and Na2SO4 solutions also was investigated, and could be understood as a function of the surface charge. It was clear that the surface charge was an important distinction governing the water flux. The excellent salts rejection and water flux data indicated that the pervaporation process incorporating the NaA zeolite membrane is a promising candidate for desalination applications.
The mechanism of SO2 removal from a CO2/SO2 gas mixture in a copper benzene-1, 3, 5-tricarboxylate (Cu-BTC) material is investigated at the molecular level by the grand canonical Monte Carlo method. ...The effects of seven kinds of force-field relationships among CO2, SO2 and Cu-BTC on the selectivity for a SO2/CO2 gas mixture at different temperatures are studied in detail. The accuracy of the simulation model is validated by the experimental data. The results show that more SO2 molecules are adsorbed than CO2, and the electrostatic interactions involving SO2 are more sensitive to temperature than CO2 is. The multilayer desorption for SO2 and CO2 occurs in large-square channels. The effect of the electrostatic interactions involving SO2 is stronger than the interactions of CO2. The forms of CO2 and SO2 adsorption in Cu-BTC with electrostatic interactions are Cu2+∙∙∙OCO and Cu2+∙∙∙OSO, respectively.
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•Selectivity for SO2 to CO2 decreases with increasing temperature.•Competitive adsorption between SO2 and CO2 exists in the mixture adsorption.•Electrostatic interactions of SO2 are more sensitive to the temperature.•Multilayer desorption occurs in large-square channels.
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