Journal
BIOPHYSICAL CHEMISTRY
Volume 158, Issue 2-3, Pages 96-103Publisher
ELSEVIER
DOI: 10.1016/j.bpc.2011.05.017
Keywords
Alzheimer's disease; Amyloid-beta peptide; Ultraviolet resonance Raman; Circular dichroism; Thioflavin T; Myricetin
Funding
- University of Missouri Research Council
- University of Missouri Research Board
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The mechanism by which flavonoids prevent formation of amyloid-beta (A beta) fibrils, as well as how they associate with non-fibrillar A beta is still unclear. Fresh, un-oxidized myricetin exhibited excitation and emission fluorescence maxima at 481 and 531 nm, respectively. Introduction of either A beta(1-42) or A beta(25-40) resulted in a fluorescence decrease, when measured at 481 nm, suggesting formation of a myricetin-A beta complex. Circular dichroism (CD) and ultraviolet resonance Raman (UVRR) studies indicate that the association of myricetin with the A beta peptide or its hydrophobic fragment, A beta(25-40), leads to subtle changes in each peptide's conformation. A beta(25-40) formed amyloid fibrils at a similar rate, when compared to the full-length peptide, A beta(1-42), using thioflavin T (ThT) fluorescence. Studies also indicated that myricetin was equally effective at preventing the formation of both A beta(1-42) and A beta(25-40) fibrils. Although ThT assays indicated that A beta(1-16) did not form amyloid fibrils, CD studies of the hydrophilic fragment, A beta(1-16), suggest possible interactions between myricetin and aromatic side chains. UVRR studies of the full-length peptide and A beta(1-16) showed increases in the intensity of the aromatic modes upon introduction of myricetin. Our findings suggest that myricetin interacts with soluble A beta via two mechanisms, association with the hydrophobic C-terminal region and interactions with the aromatic side chains. (C) 2011 Elsevier B.V. All rights reserved.
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