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Understanding the mechanisms underlying amyloid‐β (Aβ) aggregation is pivotal in the context of Alzheimer's disease. This study aims to elucidate the secondary nucleation process of Aβ42 peptides by combining experimental and computational methods. Using a newly developed nanopipette‐based amyloid seeding and translocation assay, confocal fluorescence spectroscopy, and molecular dynamics simulations, the influence of the seed properties on Aβ aggregation is investigated. Both fragmented and unfragmented seeds played distinct roles in the formation of oligomers, with fragmented seeds facilitating the formation of larger aggregates early in the incubation phase. The results show that secondary nucleation leads to the formation of oligomers of various sizes and structures as well as larger fibrils structured in β‐sheets. From these findings a mechanism of secondary nucleation involving two types of aggregate populations, one released and one growing on the mother fiber is proposed. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) and, by extension, fluoropolymers are ubiquitous in science, life, and the environment as perfluoroalkyl pollutants (PFAS). In all cases, it is difficult to transform these materials due to their chemical inertness. Herein, we report a direct amination process of PTFE and some fluoropolymers such as polyvinylidene fluoride (PVDF) and Nafion by lithium alkylamide salts. Synthesizing these reactants extemporaneously between lithium metal and an aliphatic primary di- or triamine that also serves as a solvent leads to the rapid nucleophilic substitution of fluoride by an alkylamide moiety when in contact with the fluoropolymer. Moreover, lithium alkylamides dissolved in suitable solvents other than amines can react with fluoropolymers. This highly efficient one-pot process opens the way for further surface or bulk modification if needed, providing an easy, inexpensive, and fast experiment protocol on large scales. [ABSTRACT FROM AUTHOR]

Solid-state nanopores are a promising platform for characterizing proteins. In order to improve their lifetime and prevent fouling, Polyethylene Glycol (PEG) grafting is one of the most efficient and low-cost solutions. Different models to calculate the PEG thickness do not consider their interaction with the nanopore inner surface nor the effect of confinement. Here, we investigate by molecular dynamic simulation the PEG conformation inside a nanopore in the case of hydrophobic and hydrophilic nanopores. Our results reveal that the nanopore inner surface plays a role in the PEG organization and, thus, in the speed of the salt constituent. The resulting pair interaction between PEG and its environment clearly shows a more important affinity for K+ compared to Li+ cations. [ABSTRACT FROM AUTHOR]

Oxidative addition of aliphatic amine on monocyclic 2‐R‐1,3,2‐dioxaphospholane (R = methyl or phenyl) leading to phosphoranes bearing a PH axial bond was investigated using a combined theoretical and experimental approach. The reaction followed first order kinetics for both reactants. The activation parameters were consistent with a concerted mechanism exhibiting stereo, enantio, and regio specificities. Systematic density functional theory studies including reactivity descriptors, structural parameters, determination of all possible phosphorane isomers, their transition states and their formation mechanisms were carried out to delineate the reaction pathway. Depending on the nature of the atom in the final apical position (H, N of the amine, or C of the methyl), three types of phosphoranes were identified. Energy profiles, using the intrinsic reaction coordinate technique for the formation of each isomer, were established. It was shown that the phosphorus biphilicity acts in three consecutive sequences, namely nitrogen nucleophilic attack leading to a supermolecule structure, nucleophilic behavior of phosphorus in the transition state zone of influence, and electrophilic approach of the nitrogen atom to complete the reaction. Phosphorane with an equatorial PH bond was found to be a kinetic product that transforms rapidly to the thermodynamically stable isomer with axial PH via two consecutive Berry pseudo‐rotations. A new tool, referred to reactive internal reaction coordinates, was introduced to represent the reaction path more clearly. [ABSTRACT FROM AUTHOR]

Solid‐state nanopores are an emerging technology used as a high‐throughput, label‐free analytical method for the characterization of protein aggregation in an aqueous solution. In this work, we used Levodopamine to coat a silicon nitride nanopore surface that was fabricated through a dielectric breakdown in order to reduce the unspecific adsorption. The coating of inner nanopore wall by investigation of the translocation of heparin. The functionalized nanopore was used to investigate the aggregation of amyloid‐β and α‐synuclein, two biomarkers of degenerative diseases. In the first application, we demonstrate that the α‐synuclein WT is more prone to form dimers than the variant A53T. In the second one, we show for the Aβ(42)‐E22Δ (Osaka mutant) that the addition of Aβ(42)‐WT monomers increases the polymorphism of oligomers, while the incubation with Aβ(42)‐WT fibrils generates larger aggregates. [ABSTRACT FROM AUTHOR]