Abstract
Amyloid fibrils are peptide or protein aggregates possessing a cross-β-sheet structure. They possess intrinsic fluorescence property, which is still not fully understood. Herein, we compare structural and optical properties of fibrils formed from L- and D-enantiomers of the (105–115) fragment of transthyretin (TTR) and from their racemic mixture. Our results show that autofluorescence of fibrils obtained from enantiomers differs from that of fibrils from the racemic mixture. In order to elucidate the origin of observed differences, we analyzed the structure and morphology of fibrils and showed how variations in β-sheet organization influence optical properties of fibrils. We clarified the contribution of aromatic rings and the amyloid backbone to the final blue-green emission of fibrils. This work demonstrates how enantiomeric composition of amino acids allows us to modulate the self-assembly and final morphology of well-defined fibrillar bionanostructures with optical properties controlled by supramolecular organization.
Highlights
Various peptides and proteins can undergo self-assembly into filamentous structures, commonly known as amyloid fibrils.[1,2]These species are involved in several neurodegenerative pathologies, including Alzheimer’s or Parkinson’s disease and many other disorders.[3]
We have examined the structural differences between assemblies formed by single enantiomers and the racemic mixture using atomic force microscopy (AFM), transmission electron microscopy (TEM), and attenuated total reflectance
We have performed detailed analysis of the structure and optical properties of fibrils formed from peptide fragments L, D-TTR(105−115), and their racemic mixture
Summary
Various peptides and proteins can undergo self-assembly into filamentous structures, commonly known as amyloid fibrils.[1,2]. Despite common features at the atomistic length scale, amyloids present considerable diversity at the molecular level, which gives rise to different morphologies.[19,20] In order to correlate various morphologies of amyloids with their optical properties, without any variation in the amino acid sequence, here we propose to investigate racemic mixtures of amyloidogenic peptides and to compare their properties with enantiomerically pure amyloids. We identified clear differences in the fibril morphology and β-sheet structure, for racemic amyloids We proved their peculiar intrinsic fluorescence properties. Fibrils formed from the racemic mixture exhibit blue-shifted excitation and emission spectra compared to fibrils obtained from enantiomerically pure samples. Theoretical simulation of isotopically resolved mass spectra was performed using IsoPro (v.3) software
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