title: Self-assembly of a peptide with a tandem repeat of the Aβ16-22 sequence linked by a β turn-promoting dipeptide sequence.
abstract: Amyloid deposits have been found to be abundant in patients with Alzheimer's disease due to fibril formation by the Aβ peptides. Peptide Aβ16-22, comprising of the seven-residue segment KLVFFAE, spanning residues 16-22 of the full length Aβ42 peptide, aggregates to form fibrils or other nanostructures in isolation, depending on the conditions of dissolution and incubation. In this study, we have examined the self-assembly of PAβ, a tandem repeat peptide of the Aβ16-22 sequence, joined by a β-turn-inducing sequence Asn-Gly. To study the effect of various solvents on the self-association, hexafluoroisopropanol (HFIP), trifluoroethanol (TFE) and methanol were used. The peptide was also incubated in fibril-promoting conditions of 20% fluorinated alcohol-water mixtures which form dynamical solvent clusters, as well as in 20% MeOH-water mixture which does not form solvent clusters. Secondary structural studies suggest the presence of β-structures. Electron microscopic images indicate that fibril formation occurs in a time-dependent manner, under different conditions of solvent composition. Thioflavin-T fluorescence studies confirm the presence of amyloid fibrils in the aggregates. Although the insertion of the Asn-Gly sequence has not facilitated the formation of an ideal Type I' rigid turn, the intramolecular interactions aid the formation of a flexible β-turn conformation, with twisted β-sheets. Interactions between the intermolecular β-sheets result in the formation of amyloid fibrils. Organic solvents appear to play an important role in modulating self-assembly of peptide PAβ during fibril formation. Studies on β-hairpin engineered amyloidogenic peptides could lead to knowledge about suitable conditions for generating a diverse range of polymorphic structures.
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, 500007, India.
authors.forename: Chandrasekaran
authors.initials: C
authors.lastname: Sivakama Sundari
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, 500007, India.
authors.forename: Erugurala
authors.initials: E
authors.lastname: Bikshapathy
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad, 500007, India.
authors.forename: Ramakrishnan
authors.initials: R
authors.lastname: Nagaraj
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry*; D002942:Circular Dichroism; D004151:Dipeptides / Q000737:chemistry*; D005453:Fluorescence; D046529:Microscopy, Electron, Transmission; D010446:Peptide Fragments / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012997:Solvents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D016229:Amyloid beta-Peptides; D004151:Dipeptides; D010446:Peptide Fragments; D012997:Solvents; C417223:amyloid beta-protein (16-22)
keywords: amyloid-fibrils; aromatic interactions; beta hairpin; fluorinated alcohols; peptide self-assembly