pH dependent self assembly of beta-amyloid(10-35) and beta-amyloid(10-35)PEG3000

摘要

Small angle neutron and x-ray scattering (SANS/SAXS) studies were conducted on the structure of the aggregates formed from both the truncated model peptide beta-Amyloid(10-35) (A beta(10-35)) and a block copolymer beta-Amyloid(10-35)-PEG3000 (A beta(10-35)-PEG) in D2O at pHs from 3.0 to 7.0. These studies indicate that A beta(10-35) aggregates into rodlike particles (fibril) and their radii are strongly dependent on the pH of the solution. The fibril-fibril association in A beta(10-35) solutions is less at pH < 5.6, but becomes larger at higher pH. A beta(10-35)-PEG also assembles into rod-like particles whose radius is larger by about 30 Angstrom than that for A beta(10-35) fibril at pH 4.2, while it is about 23 Angstrom larger at higher pH. Contrast matching SAXS/SANS experiments that eliminate the coherent scattering from PEG reveal that PEG moiety is located at the periphery of the fibril. Also the mass per unit length of the peptide portion is similar for both A beta(10-35) and A beta(10-35)-PEG fibrils at pH 5.6. The mass per unit length of the rods from SANS provides key information on the packing of A beta(10-35) peptides in the fibril. [References: 9]