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

Here we report an investigation on conformational changes of Alpha-synuclein (alpha-syn) and one of its mutations (E46K), whose fibrillar assemblies in neural cells are the molecular hallmark of Parlcinsons' disease. By varying the environmental conditions of the two peptides in terms of temperature (21-60 degrees 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 mu FTIR 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 alpha-helical materials to beta-sheet ones (the characteristic conformation of alpha-syn fibrils) on pristine flat substrates. The presence of lipid rafts hindered this transition. On the other hand, the inclination to form beta-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. (C) 2016 Elsevier B.V. All rights reserved.