The formation of amyloid fibrils by the intrinsically disordered protein α-synuclein is a hallmark of Parkinson disease. To characterize the microscopic steps in the mechanism of aggregation of this ...protein we have used in vitro aggregation assays in the presence of preformed seed fibrils to determine the molecular rate constant of fibril elongation under a range of different conditions. We show that α-synuclein amyloid fibrils grow by monomer and not oligomer addition and are subject to higher-order assembly processes that decrease their capacity to grow. We also find that at neutral pH under quiescent conditions homogeneous primary nucleation and secondary processes, such as fragmentation and surface-assisted nucleation, which can lead to proliferation of the total number of aggregates, are undetectable. At pH values below 6, however, the rate of secondary nucleation increases dramatically, leading to a completely different balance between the nucleation and growth of aggregates. Thus, at mildly acidic pH values, such as those, for example, that are present in some intracellular locations, including endosomes and lysosomes, multiplication of aggregates is much faster than at normal physiological pH values, largely as a consequence of much more rapid secondary nucleation. These findings provide new insights into possible mechanisms of α-synuclein aggregation and aggregate spreading in the context of Parkinson disease.
•Self-assembly of two polysaccharides into polyelectrolyte complex hydrogel film.•The electrostatic interactions existing in hydrogel film were studied in detail.•Hydrogel film was effective in Pb2+ ...removal with the maximum adsorption of 418.4 mg/g.•Adsorption occurs via the models of Crank kinetic and Langmuir isotherm.•Hydrogel film can be regenerated and adsorption capacity is over 95% after 5 cycles.
Herein, a novel polyelectrolyte complex (PEC) hydrogel film has been fabricated through self-assembly of two oppositely charged polysaccharides salecan and carboxymethyl chitosan (CMCS) for Pb2+ removal. The formation of PEC network structure via electrostatic interactions was confirmed by FT-IR, XRD, XPS and TGA. The change of salecan/CMCS ratio had obvious influence on the swelling capacity, morphology and rheological properties of the hydrogel films. The adsorption capacity of Pb2+ was specifically investigated by tuning the salecan/CMCS ratio, other ions, pH, ion concentration and contact time. Furthermore, the equilibrium isotherms were better fitted with Langmuir model, indicating monolayer adsorption behaviour. The maximum adsorption capacity of Pb2+ according to Langmuir model was 418.4 mg/g, higher than that of some other adsorbents. The adsorption kinetics was well modelled by pseudo-second-order and Crank model, suggesting chemisorption and internal diffusion control mechanism. The PEC hydrogel film also exhibited excellent reusability after 5 adsorption/desorption cycles without obvious changes in the adsorption capacity. Overall, these results not only highlight a new idea for the utilization of salecan, but also provide a green method for the rational design of highly efficient adsorbent for Pb2+ removal.
This study investigates the effects of bovine serum albumin (BSA) on blueberry anthocyanins and their interaction. Findings showed that BSA could protect blueberry anthocyanins against degradation ...and retain their antioxidant activity at an ideal concentration of 0.15 mg/mL under three deteriorating treatments: illumination, vitamin C + illumination, and sucrose + illumination. The fluorescence and UV absorption spectra showed that malvidin-3-o-galactoside (M3G), the major monomer in blueberry anthocyanins, led to a static quenching of BSA and the binding site of M3G to BSA was approximately one. Further, the interaction was a spontaneous process with electrostatic interactions being the main force. CD spectra and synchronous fluorescence spectra presented alterations in the secondary structure and microenvironment of Trp and Tyr residues of BSA, respectively, upon interaction with M3G. Finally, molecular docking analysis showed that M3G mainly bound the II and III domains of BSA by hydrogen bonds and electrostatic interaction. In conclusion, our study highlights the protective effects of BSA on the stability and anti-oxidant activity of blueberry anthocyanins and their interaction analysis.
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•BSA protects blueberry anthocyanins against the degradation and loss of antioxidant capacity under illumination treatments.•Interaction between M3G and BSA is spontaneous and mainly attributed to electrostatic forces.•Secondary structural and microenvironments around tyrosine and tryptophan residues of BSA are influenced by M3G.•Molecular docking shows that M3G mainly bound II and III domains of BSA by hydrogen bonds and electrostatic interaction.
Here we report that negatively charged polysulfates can bind to the spike protein of SARS‐CoV‐2 via electrostatic interactions. Using a plaque reduction assay, we compare inhibition of SARS‐CoV‐2 by ...heparin, pentosan sulfate, linear polyglycerol sulfate (LPGS) and hyperbranched polyglycerol sulfate (HPGS). Highly sulfated LPGS is the optimal inhibitor, with an IC50 of 67 μg mL−1 (approx. 1.6 μm). This synthetic polysulfate exhibits more than 60‐fold higher virus inhibitory activity than heparin (IC50: 4084 μg mL−1), along with much lower anticoagulant activity. Furthermore, in molecular dynamics simulations, we verified that LPGS can bind more strongly to the spike protein than heparin, and that LPGS can interact even more with the spike protein of the new N501Y and E484K variants. Our study demonstrates that the entry of SARS‐CoV‐2 into host cells can be blocked via electrostatic interactions, therefore LPGS can serve as a blueprint for the design of novel viral inhibitors of SARS‐CoV‐2.
Negatively charged polysulfates can bind to the positively charged patches of RBD of SARS‐CoV‐2 and block viral interaction with host cells for infection inhibition. The synthetic linear polyglycerol sulfate (LPGS) exhibits higher virus inhibitory activity than heparin, but lower anticoagulant activity. Therefore, it is considered to be a promising substitute for heparin in clinical applications.
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► High pressure adsorption of industrially relevant gases on Cu-BTC and MIL-101. ► Open metal sites and polarity of the gas govern adsorption in low pressure region. ► The effect of ...polarity of the adsorbate decreases with temperature. ► Pore volume governs adsorption in high pressure region. ► Several other interesting features in isotherms CH
4, CO
2 and CO are discussed.
A comparative adsorption study of three gases
viz. CO, CO
2 and CH
4 on two adsorbents
viz. Cu-BTC (or HKUST-1) and Cr-BDC (or MIL-101) is reported in this article. The gravimetric adsorption equilibrium measurements on the samples were performed in a Rubotherm magnetic suspension balance at three different temperatures: 295, 318 and 353
K and pressures ranging between 0 and 100
bar. Virial-Langmuir model was used to model the experimental data on Cu-BTC, whereas Dual Site Langmuir (DSL) model was used for adsorption on MIL-101. For all gases the enthalpy of adsorption at low loading was higher on MIL-101 than that on Cu-BTC, indicating the availability of open metal sites in case of MIL-101. Moreover, a sharp decrease in enthalpy of adsorption is observed in case of MIL-101, whereas only a moderate decrease is observed in case of Cu-BTC. CO has a large Henry’s constant on MIL-101, whereas at higher pressures, the solid exhibits better capacity for CO
2. In case of Cu-BTC, CO
2 has a higher capacity on the adsorbent as compared to the other two gases throughout the entire range of pressures studied. All the experimental data is critically analyzed by examining the role of open metal centers, adsorbate polarity and the effect of temperature on the electrostatic interactions.
The Cover Feature shows an electrostatic‐assisted catalysis of carbon dioxide molecule at an iron porphyrin decorated with cationic functions in the second coordination sphere. Such functions ...significantly lower the overpotential of the reaction while maintaining high catalytic efficiency. This provides a new way to vault the reactivity pattern of molecular catalysts. More information can be found in the Full Paper by A. Khadhraoui et al.
Polysaccharide-based biopolymer particles are known as biocompatible, sustainable and easy to be modified, and widely used in food and biomedical fields. In this study, a novel polysaccharide-based ...particle as curcumin (Cur) carrier was developed through self-assembly driven by electrostatic interactions between carboxymethylated corn fiber gum (CMCFG) and chitosan (Cs). Firstly, the chemical structure of synthesized CMCFG was characterized to prove successful carboxymethylation. Then Cur-loaded CMCFG/Cs particles (Cur-CMCsPs) with different mass ratios of CMCFG to Cs (1:3, 1:2, 1:1, 2:1 and 3:1) were prepared and their particle size, zeta-potential, crystalline structure and micro-morphology were determined. Smaller particle size was observed when the mass ratio of CMCFG to Cs exceeded 1:1, among which the lowest hydrodynamic diameter was less than 300 nm, as uniform spherical particles. Furthermore, the highest encapsulation efficiency of the resulting Cur-CMCsPs surpassed 93% and the Cur loaded in particles showed the excellent photo/thermal stability. Besides, the particles could significantly improve the bioaccessibility of Cur reaching 74.94%. This study provides strategy support for suitably designing biopolymer particles as delivery vehicles of hydrophobic nutrients in food and biomedical fields.
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•The carboxymethylation of CFG raised its initial decomposition temperature.•Spherical nanoparticle was formed by electrostatic assembly of CMCFG and chitosan.•The encapsulation efficiency of curcumin in Cur-CMCsPs was over 90%.•The bioaccessibility and stability of encapsulated curcumin were improved.
The objective of this study was to synthesize a novel, efficient and economical bio-adsorbent with three dimensions (3D) structure using a direct assembly method for removal of methylene blue (MB) ...from aqueous solution. The raw materials were corn straw core (CSC) and graphene oxide (GO). The variables that affected adsorption capacity were tested. GO loading could facilitate the removal rate. When 5wt% GO was added (CSC-5GO), the removal rate was increased by 21.62% compared to pure CSC (64.58%). Furthermore, the adsorption by CSC-5GO fitted pseudo-second-order kinetic model (R2>0.998) and Temkin model (R2>0.955). The maximum adsorption capacity was 414.03mgg−1 for MB at pH=12, 298K and MB concentration of 1000mgL−1. The adsorption thermodynamic test results suggested that the adsorption was a spontaneous, exothermic and randomness decrease process. Furthermore, after five cycles of adsorption-desorption test, the adsorbent removal rate was >90%, which implied that CSC-5GO had an excellent reproducibility.
The schematic illustration of assembling CSC-GO and adsorption MB process. Display omitted
•The highly efficient 3D bio-adsorption was synthesized using a sample assembly method.•The maximum adsorption capacity was 414.03mgg−1 for MB.•The adsorption performance obeyed the pseudo-second-order and Temkin models.•CSC-5GO had an excellent reproducibility and environmental protection.
A newly introduced Na−B bond in NaBH3− has been a challenge for the chemical bonding community. Here, a series of MBH3− (M=Li, Na, K) species and NaB(CN)3− are studied within the context of quantum ...chemical topology approaches. The analyses suggest that M–B interaction cannot be classified as an ordinary covalent, dative, or even simple ionic interaction. The interactions are controlled by coulombic forces between the metals and the substituents on boron, for example, H or CN, more than the direct M–B interaction. On the other hand, while the characteristics of the (3, −1) critical points of the bonds are comparable to weak hydrogen bonds, not covalent bonds, the metal and boron share a substantial sum of electrons. To the best of the author's knowledge, the characteristics of these bonds are unprecedented among known molecules. Considering all paradoxical properties of these bonds, they are herein described as ionic‐enforced covalent bonds.
Ionic‐enforced covalency in M−B bonds of MBX3− species originates from strong electrostatic interaction between the metals and boranes. This interaction keeps the atoms within proximity of each other through strong coulombic forces but causes non‐negligible degrees of electron sharing.
Mesenchymal stem cell (MSC) therapy can attenuate organ damage and reduce mortality in sepsis; however, the detailed mechanism is not fully elucidated. In this study, it is shown that MSC‐derived ...apoptotic vesicles (apoVs) can ameliorate multiple organ dysfunction and improve survival in septic mice. Mechanistically, it is found that tail vein‐infused apoVs mainly accumulate in the bone marrow of septic mice via electrostatic charge interactions with positively charged neutrophil extracellular traps (NETs). Moreover, apoVs switch neutrophils NETosis to apoptosis via the apoV‐Fas ligand (FasL)‐activated Fas pathway. In summary, these findings uncover a previously unknown role of apoVs in sepsis treatment and an electrostatic charge‐directed target therapeutic mechanism, suggesting that cell death is associated with disease development and therapy.
Apoptotic vesicles (ApoVs) are recruited by neutrophil extracellular traps (NETs) via electrostatic charge interaction in the bone marrow. ApoVs can mediate the cell death pattern switch of neutrophils from NETosis to apoptosis via the Fas/Fas ligand pathway, then inhibit the migration of neutrophils from bone marrow to distal organs, alleviating the organ injury, and improving the survival of septic mice.
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