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Insight into the internal structure of amyloid- oligomers by isotope-edited Fourier transform infrared spectroscopy
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.ORCID iD: 0000-0001-5784-7673
Number of Authors: 32019 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 16, p. 8587-8597Article in journal (Refereed) Published
Abstract [en]

The internal structure of amyloid- (A) oligomers was investigated with isotope-edited Fourier transform infrared spectroscopy. Homo-oligomers of A(40) and A(42) were prepared from unlabeled and C-13, N-15-labeled monomeric A and from mixtures of these. For the unlabeled peptides, two main bands were observed in (H2O)-H-2 at 1685 and 1622 cm(-1) for A(40) and at 1685 and 1626 cm(-1) for A(42). These band positions indicate that the number of strands per sheet is at least four. The obtained experimental amide I spectra were simulated using a number of structural models (antiparallel -sheets, -barrels and a dodecamer structure). According to experiments and calculations, the main C-13-band shifts down at increasing molar ratio of labeled peptides. This shift occurs when vibrational coupling becomes possible between C-13-amide groups in close-by strands. It is small, when intervening C-12-strands increase the distance between C-13-strands; it is large, when many neighboring strands are labeled. The shift depends on the internal structure of the peptides within the oligomers, i.e. on the building block that each peptide molecule contributes to the -sheets of the oligomers. The shift is largest, when individual peptides contribute just a single strand surrounded by strands from other peptide molecules. It is smaller when each molecule forms two or three adjacent strands. As indicated by a comparison between experiment and computation, the number of adjacent -strands per peptide molecule is two for A(40) oligomers and two or more for A(42) oligomers. Our results are well explained by regular, antiparallel -sheets or -barrels.

Place, publisher, year, edition, pages
2019. Vol. 21, no 16, p. 8587-8597
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Chemical Sciences Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-170149DOI: 10.1039/c9cp00717bISI: 000465603200036PubMedID: 30964131OAI: oai:DiVA.org:su-170149DiVA, id: diva2:1331143
Available from: 2019-06-26 Created: 2019-06-26 Last updated: 2019-06-26Bibliographically approved

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Baronio, Cesare M.Baldassarre, MaurizioBarth, Andreas
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