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Gladytz A.,Leibniz Institute of Surface Modification | Wagner M.,Leibniz Institute of Surface Modification | Haupl T.,Wilhelm Ostwald Institute for Physical and Theoretical Chemistry | Elsner C.,Leibniz Institute of Surface Modification | And 2 more authors.
Particle and Particle Systems Characterization | Year: 2015

There is growing concern that nanoparticles (NPs) may accelerate amyloid protein aggregation and thus cause amyloid-related diseases. Here, the potential of silver and gold NPs is explored (diameter 20 nm) on the aggregation of the amyloid peptide sequences NNFGAIL from human islet amyloid polypeptide and the yeast prion protein sequence GNNQQNY, which are both the sequences of the full systems, which are able to aggregate into characteristic amyloid cross-beta sheet fibrillar structures. Here, it is shown that silver and gold NPs in physiological aqueous solution at ambient temperatures accelerate the aggregation kinetics of both peptides significantly (in vitro). Scanning electron microscopy and X-ray diffraction provide solid evidence for a "structure-making" effect of the NPs. In particular, we are able to image the initial peptide corona and measure its structural reorganization in time-resolved kinetic experiments. After a conversion time Δt, the coated NPs appear to act as templates or seeds for rapid fibrillation. Interestingly, cross-fibrillation experiments with different peptide-coated NPs (pcNPs) reveal that they can efficiently induce aggregation of similar peptides once the pcNPs are structurally converted. It is discussed that these structurally converted pcNPs may display similar kinetic features as toxic and aggregation inducing oligomers/protofibrils in normal amyloid aggregation, without being transient and very low-concentration species. Finally, we suggest and discuss a simple mechanistic picture with the biomolecule corona of NPs being central to the function of the coated NPs in amyloid fibrillation. Although they are a useful material, there is concern that metal nanoparticles (NPs) may accelerate amyloid protein aggregration, leading to amyloid-related diseases. The effect of silver and gold NPs is explored on two amyloid protein sequences: one human and one from yeast. Scanning electron microscopy and X-ray diffraction show strong evidence for a "structure-making" effect of the NPs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Raz Y.,Ben - Gurion University of the Negev | Adler J.,University of Leipzig | Vogel A.,University of Leipzig | Scheidt H.A.,University of Leipzig | And 5 more authors.
Physical Chemistry Chemical Physics | Year: 2014

Tau is a microtubule-associated protein and is involved in microtubule assembly and stabilization. It consists of four repeats that bind to the microtubule. The ΔK280 deletion mutation in the tau R2 repeat region is directly associated with the development of the frontotemporal dementia parkinsonism linked to chromosome 17 (FTDP-17). This deletion mutation is known to accelerate tau R2 repeat aggregation. However, the secondary and the tertiary structures of the self-assembled ΔK280 tau R2 repeat mutant aggregates are still controversial. Moreover, it is unclear whether extensions by one residue in the N- or the C-terminus of this mutant can influence the secondary or the tertiary structure. Herein, we combine solid-state NMR, atomic force microscopy, electron microscopy and all-atom explicit molecular dynamics simulations to investigate the effects of the deletion mutation and the N- and the C-terminal extension of this mutant on the structure. Our main findings show that the deletion mutation induces the formation of small aggregates, such as oligomers, and reduces the formation of fibrils. However, the extensions in the N- or the C-terminus revealed more fibril formation than small aggregates. Further, in the deletion mutation only one structure is preferred, while the N- and the C-terminal extensions strongly lead to polymorphic states. Finally, our broad and combined experimental and computational techniques provide direct structural information regarding ΔK280 tau R2 repeat mutant aggregates and their extensions in the N- and C-terminii by one residue. © 2014 the Partner Organisations.

Abel B.,Leibniz Institute of Surface Modification | Abel B.,Wilhelm Ostwald Institute for Physical and Theoretical Chemistry
Annual Review of Physical Chemistry | Year: 2013

Charged particles such as hydrated ions and transient hydrated electrons, the simplest anionic reducing agents in water, and the special hydronium and hydroxide ions at water interfaces play an important role in many fields of science, such as atmospheric chemistry, radiation chemistry, and biology, as well as biochemistry. This article focuses on these species near hydrophobic interfaces of water, such as the air or vacuum interface of water or water protein/membrane interfaces. Ions at interfaces as well as solvated electrons have been reviewed frequently during the past decade. Although all species have been known for some time with seemingly familiar features, recently the picture in all cases became increasingly diffuse rather than clearer. The current account gives a critical state-of-the art overview of what is known and what remains to be understood and investigated about hydrated interfacial ions and electrons. © 2013 by Annual Reviews. All rights reserved.

Abel B.,Leibniz Institute of Surface Modification | Abel B.,Wilhelm Ostwald Institute for Physical and Theoretical Chemistry
AIP Conference Proceedings | Year: 2014

Nanoparticles (NPs) are used in many products of our daily life, however, there has been concern that they may also be harmful to human health. Recently NPs thave been found to accelerate the fibrillation kinetics of amyloid systems. In the past this has been preliminarily attributed to a nucleation effect. Nanoparticle surfaces and interfaces appear to limit the degrees of freedom of amyloid systems (i.e., peptides and proteins) due to a phase space constraint such that rapid cross-beta structures are formed faster than without interface interactions and in turn fibril formation is enhanced significantly. Here we explore if lipid bilayers in the form of liposomes (140nm) also accelerate fibril formation for amyloid systems. We have investigated a fragment NNFGAIL of the Human islet amyloid polypeptide (hIAPP) in contact with 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) liposomes in aqueous solution. We found that the lipid bilayer vesicles do accelerate fibril formation in time-resolved off-line detected atomic force microscopy experiments. Characteristic Thioflavine-T fluorescence on the same structures verify that the structures consist of aggregated peptides in a typical cross-β-structure arrangement. © 2014 AIP Publishing LLC.

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