title: Abeta(1-28) fragment of the amyloid peptide predominantly adopts a polyproline II conformation in an acidic solution.
abstract: To structurally characterize the nonaggregated state of the amyloid beta peptide, which assembles into the hallmark fibrils of Alzheimer disease, we investigated the conformation of the N-terminal extracellular peptide fragment Abeta(1-28) in D(2)O at acidic pD by utilizing combined FTIR and isotropic and anisotropic Raman spectra measured between 1550 and 1750 cm(-1). Peptide aggregation is avoided under the conditions chosen. The amide I' band was found to exhibit a significant noncoincidence effect in that the first moment of the anisotropic Raman and of the IR band profile appears red-shifted from that of the isotropic Raman scattering. A simulation based on a coupled oscillator model involving all 27 amide I' modes of the peptide reveals that the peptide adopts a predominantly polyproline II conformation. Our results are inconsistent with the notion that the monomeric form of Abeta(1-28) is a totally disordered, random-coil structure. Generally, they underscore the notion that polyproline II is a characteristic motif of the unfolded state of proteins and peptides.
authors.affiliation: Department of Biology, University of Puerto Rico, Río Piedras Campus, P.O. Box 23346, San Juan PR00931.
authors.forename: Fatma
authors.initials: F
authors.lastname: Eker
authors.forename: Kai
authors.initials: K
authors.lastname: Griebenow
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schweitzer-Stenner
mesh_terms: D000143:Acids / Q000737:chemistry; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D000143:Acids; D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D010455:Peptides; C084358:amyloid beta-protein (1-28); C011083:polyproline