Tag Archive for: AWS SNS 000049 A

Publication on AWSensors technology

Variant-Specific Interactions at the Plasma Membrane: Heparan Sulfate’s Impact on SARS-CoV-2 Binding Kinetics

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Authors: Dario Valter Conca, Fouzia Bano, Małgorzata Graul, Julius von Wirén, Lauriane Scherrer, Hudson Pace, Himanshu Sharma, Justas Svirelis, Konrad Thorsteinsson, Andreas Dahlin, and Marta Bally

Journal: Analytical Chemistry

Abstract: The spread of SARS-CoV-2 led to the emergence of several variants of concern (VOCs). The spike glycoprotein, responsible for engaging the viral receptor, exhibits the highest density of mutations, suggesting an ongoing evolution to optimize viral entry. This study characterizes the bond formed by virion mimics carrying the SARS-CoV-2 spike protein and the plasma membrane of host cells in the early stages of virus entry. Contrary to the traditional analysis of isolated ligand-receptor pairs, we utilized well-defined biomimetic models and biochemical and biophysical techniques to characterize the multivalent interaction of VOCs with the complex cell membrane. We observed an overall increase in the binding affinity for newer VOCs. By progressively reducing the system complexity, we identify heparan sulfate (HS) as a main driver of this variation, with a 10-fold increase in affinity for Omicron BA.1 over that of the original strain. These results demonstrate the essential role of coreceptors, particularly HS, in the modulation of SARS-CoV-2 infection and highlight the importance of multiscale biophysical and biochemical assays that account for membrane complexity to fully characterize and understand the role of molecular components and their synergy in viral attachment and entry.

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Publication on AWSensors technology

Lipid packing frustration in the outer leaflet of the plasma membrane prevents scission of caveolae

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Authors: Elin Larsson, Aleksei Kabedev, Hudson Pace, Jakob Lindwall, Fouzia Bano, Robert G Parton, Christel A. S. Bergstrom, Ingela Parmryd, Marta Bally, Richard Lundmark

Journal: bioRxiv

Abstract: Lipid packing is a fundamental characteristic of bilayer membranes. It affects all membrane-associated processes ranging from curvature generation to membrane fission. Yet, we lack detailed, mechanistic understanding of how lipid packing directly affects these processes in cellular membranes. Here, we address this by focusing on caveolae, small Ω-shaped invaginations of the plasma membrane which serve as key regulators of cellular lipid sorting and mechano-responses. In addition to caveolae coat proteins, the lipid membrane is a core component of caveolae that critically impacts both the biogenesis, morphology and stability of such membrane invaginations. We show that the small compound Dyngo-4a inserts into the membrane, resulting in a dramatic dynamin-independent inhibition of caveola scission. Analysis of model membranes in combination with molecular dynamics simulations revealed that a substantial amount of Dyngo-4a was inserted and positioned at the level of cholesterol in the bilayer. Dyngo-4a-treatment resulted in decreased lipid packing in the outer leaflet of the plasma membrane preventing scission without affecting caveola morphology, caveolae- associated proteins, or the overall membrane stiffness. Artificially increasing plasma membrane cholesterol levels was found to counteract the block in caveola scission caused by Dyngo-4a-mediated lipid packing frustration. Therefore, we propose that the packing of cholesterol in the outer leaflet of the plasma membrane critically controls the confinement of caveolae to the plasma membrane.

The full article can be accessed here.

Publication on AWSensors technology

Revisiting the Charging Mechanism of α-MnO2 in Mildly Acidic Aqueous Zinc Electrolytes

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Authors: Lang Yuan Wu, ZhiWei Li, YuXuan Xiang, WenDi Dong, XiaoDong Qi, ZhenXiao Ling, YingHong Xu, HaiYang Wu, Mikhael D. Levi, Netanel Shpigel, XiaoGang Zhang

Journal: Small 

Abstract: In recent years, there have been extensive debates regarding the charging mechanism of MnO2 cathodes in aqueous Zn electrolytes. The discussion centered on several key aspects including the identity of the charge carriers contributing to the overall capacity, the nature of the electrochemical process, and the role of the zinc hydroxy films that are reversibly formed during the charging/discharging. Intense studies are also devoted to understanding the effect of the Mn2+ additive on the performance of the cathodes. Nevertheless, it seems that a consistent explanation of the α-MnO2 charging mechanism is still lacking. To address this, a step-by-step analysis of the MnO2 cathodes is conducted. Valuable information is obtained by using in situ electrochemical quartz crystal microbalance with dissipation (EQCM-D) monitoring, supplemented by solid-state nuclear magnetic resonance (NMR), X-ray diffraction (XRD) in Characterization of Materials, and pH measurements. The findings indicate that the charging mechanism is dominated by the insertion of H3O+ ions, while no evidence of Zn2+ intercalation is found. The role of the Mn2+ additive in promoting the generation of protons by forming MnOOH, enhancing the stability of Zn/α-MnO2 batteries is thoroughly investigated. This work provides a comprehensive overview on the electrochemical and the chemical reactions associated with the α-MnO2 electrodes, and will pave the way for further development of aqueous cathodes for Zn-ion batteries.

 

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Publication on AWSensors technology

Modifying last layer in polyelectrolyte multilayer coatings for capillary electrophoresis of proteins

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Authors: Sébastien Roca, Laurent Leclercq, Philippe Gonzalez, Laura Dhellemmes, Laurent Boiteau, Gaulthier Rydzek, and Hervé Cottet

Journal: Journal of Chromatography A (2023)

 

Abstract

Protein adsorption on the inner wall of the fused silica capillary wall is an important concern for capillary electrophoresis (CE) analysis since it is mainly responsible for separation efficiency reduction. Successive Multiple Ionic-polymer Layers (SMIL) are used as capillary coatings to limit protein adsorption, but even low residual adsorption strongly impacts the separation efficiency, especially at high separation voltages. In this work, the influence of the chemical nature and the PEGylation of the polyelectrolyte deposited in the last layer of the SMIL coating was investigated on the separation performances of a mixture of four model intact proteins (myoglobin (Myo), trypsin inhibitor (TI), ribonuclease a (RNAse A) and lysozyme (Lyz)). Poly(allylamine hydrochloride) (PAH), polyethyleneimine (PEI), ε-poly(L-lysine) (εPLL) and α-poly(L-lysine) (αPLL) were compared before and after chemical modification with polyethyleneglycol (PEG) of different chain lengths. The experimental results obtained by performing electrophoretic separations at different separation voltages allowed determining the residual retention factor of the proteins onto the capillary wall via the determination of the plate height at different solute velocities and demonstrated a strong impact of the polycationic last layer on the electroosmotic mobility, the separation efficiency and the overall resolution. Properties of SMIL coatings were also characterized by quartz microbalance and atomic force microscopy, demonstrating a glassy structure of the films.

 

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