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Alignment of a Model Amyloid Peptide Fragment in Bulk and at a Solid Surface

DOI: 10.1021/jp101374e DOI Help

Authors: Valeria Castelletto (University of Reading) , Claire Moulton (University of Reading) , Jose Rodriguez-perez (University of Reading) , Adam M. Squires (University of Reading) , Tugce Eralp (University of Reading) , Georg Held (University of Reading) , Matthew R. Hicks (University of Warwick) , Allison Rodger (University of Warwick) , Ian W. Hamley (University of Reading)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Physical Chemistry B , VOL 114 (24) , PAGES 8244-8254

State: Published (Approved)
Published: January 2010

Abstract: The alignment of model amyloid peptide YYKLVFFC is investigated in bulk and at a solid surface using a range of spectroscopic methods employing polarized radiation. The peptide is based on a core sequence of the amyloid beta (A beta) peptide, KLVFF. The attached tyrosine and cysteine units are exploited to yield information on alignment and possible formation of disulfide or dityrosine links. Polarized Raman spectroscopy on aligned stalks provides information on tyrosine orientation, which complements data from linear dichroism (LD) on aqueous solutions subjected to shear in a Couette cell. LD provides a detailed picture of alignment of peptide strands and aromatic residues and was also used to probe the kinetics of self-assembly. This suggests initial association of phenylalanine residues, followed by subsequent registry of strands and orientation of tyrosine residues. X-ray diffraction (XRD) data from aligned stalks is used to extract orientational order parameters from the 0.48 nm reflection in the cross-beta pattern, from which an orientational distribution function is obtained. X-ray diffraction on solutions subject to capillary flow confirmed orientation in situ at the level of the cross-beta pattern. The information on fibril and tyrosine orientation from polarized Raman spectroscopy is compared with results from NEXAFS experiments on samples prepared as films on silicon. This indicates fibrils are aligned parallel to the surface, with phenyl ring normals perpendicular to the surface. Possible disulfide bridging leading to peptide dimer formation was excluded by Raman spectroscopy, whereas dityrosine formation was probed by fluorescence experiments and was found not to occur except under alkaline conditions. Congo red binding was found not to influence the cross-beta XRD pattern.

Subject Areas: Chemistry


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