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Edited by Paul E. FraserThe aggregation of amyloid-␤ (A␤) on lipid bilayers has been implicated as a mechanism by which A␤ exerts its toxicity in Alzheimer's disease (AD). Lipid bilayer thinning has been observed during both oxidative stress and protein aggregation in AD, but whether these pathological modifications of the bilayer correlate with A␤ misfolding is unclear. Here, we studied peptide-lipid interactions in synthetic bilayers of the shortchain lipid dilauroyl phosphatidylcholine (DLPC) as a simplified model for diseased bilayers to determine their impact on A␤ aggregate, protofibril, and fibril formation. A␤ aggregation and fibril formation in membranes composed of dioleoyl phosphatidylcholine (DOPC) or 1-palmitoyl-2-oleoyl phosphatidylcholine mimicking normal bilayers served as controls. Differences in aggregate formation and stability were monitored by a combination of thioflavin-T fluorescence, circular dichroism, atomic force microscopy, transmission electron microscopy, and NMR. Despite the ability of all three lipid bilayers to catalyze aggregation, DLPC accelerates aggregation at much lower concentrations and prevents the fibrillation of A␤ at low micromolar concentrations. DLPC stabilized globular, membrane-associated oligomers, which could disrupt the bilayer integrity. DLPC bilayers also remodeled preformed amyloid fibrils into a pseudo-unfolded, molten globule state, which resembled on-pathway, protofibrillar aggregates. Whereas the stabilized, membrane-associated oligomers were found to be nontoxic, the remodeled species displayed toxicity similar to that of conventionally prepared aggregates. These results provide mechanistic insights into the roles that pathologically thin bilayers may play in A␤ aggregation on neuronal bilayers, and pathological lipid oxidation may contribute to A␤ misfolding.

A covalently assembled monolayer of 61-(p-hydroxyphenylmethano)fullerene [C60] molecules has been synthesized. Both static and dynamic contact angle measurements show that the hydrophobic character increases upon the fullerene linkage. Atomic force microscopy lithography shows that the depth of the monolayer is about 19 Å. UV−vis spectra are well-tuned with the presence of the fullerene on the silica surfaces. The surface atomic composition, investigated by angle-resolved X-ray photoelectron spectra, shows a monotonic increase of the carbon signal upon decreasing the photoelectron takeoff angles, thus confirming the upper layer nature of this signal. Room-temperature photoluminescence spectra, under controlled atmosphere, show that the oxygen presence influences considerably the luminescence quantum yield.

The repeated use of conventional synthetic pesticides in crop protection leads to resistance development by pests along with a negative impact on the environment, particularly non-target arthropods. Plant-derived active compounds, such as essential oils (EOs), play a key role in sustainably controlling pests. The lethal and sublethal activity of citrus peel EOs as emulsions and included in polyethylene glycol (PEG) nanoparticles (EO-NPs) was determined against the invasive tomato pest Tuta absoluta. Their effects on the plants were also assessed. The results showed an overall good insecticidal activity of the compounds tested, with a higher mortality through contact on eggs and larvae by EO emulsions and through ingestion on larvae by EO-NPs. The nanoformulation also significantly reduced the visible toxic effects on the plants. The data collected suggest that these natural compounds, especially when nanoformulated, could be successfully used in integrated pest management programs for T. absoluta.

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