Investigating the Coassembly of Enantiomeric Amyloid Peptides

Amyloid proteins refer to misfolded proteins that have become dysfunctional in the body and aggregate to form insoluble fibrils, resulting in deposits in many organs throughout the body. These proteins have been of great interest in the medicinal community, due to linkage of amyloid proteins to various pathologies including Alzheimer’s disease. However, the assembly properties of these amyloid proteins are being explored in the field of biomaterials, due to its potential for biomedical applications in biological scaffolding, cell delivery, and regenerative medicine. Amphipathic amyloid peptides composed of hydrophobic and hydrophilic amino acids self-assemble into amyloidogenic pleated β-sheet fibrils. Previous studies on the amphipathic peptide (FKFE)₂ composed of alternating hydrophobic and hydrophilic groups have shown that equimolar mixtures of the enantiomers coassemble to form fibrils in a rippled β-sheet orientation. To further study necessary conditions for coassembly of amphipathic peptides, the amyloid beta peptide 16-22 fragment (Aβ [16-22]), which contains hydrophilic ends with a hydrophobic core, was utilized as a model. Spectroscopic analysis indicated that equimolar mixtures of enantiomeric peptide Aβ (16-22) did not self-sort and assemble into amyloidogenic fibrils of only L-peptide and D-peptide, but rather coassembled into crystalline-like structures consisting of alternating L- and D-peptides. Further studies in the packing methodology of these peptides are being conducted to better understand the assembly properties and potential for medicinal purposes.