Temperature, surface morphology and biochemical cues: A combined approach to influence the molecular conformation of Alpha-synuclein

• μFTIR investigation of two α-synuclein proteins involved in Parkinson's disease
• High temperature and fluid phase of lipid systems favor β-sheet configuration.
• Hydrophilic nanostructured surfaces hinder the formation of β-sheet material.

Here we report an investigation on conformational changes of Alpha-synuclein (α-syn) and one of its mutations (E46K), whose fibrillar assemblies in neural cells are the molecular hallmark of Parkinsons' disease. By varying the environmental conditions of the two peptides in terms of temperature (21–60 °C), the presence of lipid systems (in homogeneous fluid phase or presenting raft-like domains) and nanostructured surfaces, we observed significant secondary structure alterations in both proteins. In order to probe such transitions, we exploited synchrotron μFTIR directly on solid ring-like residues formed immediately upon evaporation. We concluded that high temperatures and the presence of a lipid fluid phase induce a transition from α-helical materials to β-sheet ones (the characteristic conformation of α-syn fibrils) on pristine flat substrates. The presence of lipid rafts hindered this transition. On the other hand, the inclination to form β-sheet phases in the presence of high temperatures or lipid systems was sensitively lowered by drying the proteins on top of nanostructured highly hydrophilic supports which allow a more homogeneous distribution of the analyte throughout the residue. These results and the presented protocol can indeed pave the basis for the structural characterization of this controversially debated protein and of other neurodegenerative peptides.

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