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Self‐Assembly of a Modified Amyloid Peptide Fragment: pH‐Responsiveness and Nematic Phase Formation
Author(s) -
Hamley Ian W.,
Castelletto Valeria,
Moulton Claire,
Myatt Daniel,
Siligardi Giuliano,
Oliveira Cristiano L. P.,
Pedersen Jan Skov,
Abutbul Inbal,
Danino Dganit
Publication year - 2010
Publication title -
macromolecular bioscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.924
H-Index - 105
eISSN - 1616-5195
pISSN - 1616-5187
DOI - 10.1002/mabi.200900217
Subject(s) - chemistry , circular dichroism , liquid crystal , aqueous solution , negative stain , crystallography , dynamic light scattering , peptide , self assembly , fourier transform infrared spectroscopy , transmission electron microscopy , organic chemistry , nanoparticle , electron microscope , materials science , chemical engineering , nanotechnology , optics , biochemistry , physics , optoelectronics , engineering
The self‐assembly of peptide YYKLVFFC based on a fragment of the amyloid beta (A β ) peptide, A β 16–20, KLVFF has been studied in aqueous solution. The peptide is designed with multiple functional residues to examine the interplay between aromatic interactions and charge on the self‐assembly, as well as specific transformations such as the pH‐induced phenol–phenolate transition of the tyrosine residue. Circular dichroism (CD) and Fourier‐transform infrared (FTIR) spectroscopies are used to investigate the conditions for β ‐sheet self‐assembly and the role of aromatic interactions in the CD spectrum as a function of pH and concentration. The formation of well‐defined fibrils at pH 4.7 is confirmed by cryo‐TEM (transmission electron microscope) and negative stain TEM. The morphology changes at higher pH, and aggregates of short twisted fibrils are observed at pH 11. Polarized optical microscopy shows birefringence at a low concentration (1 wt.‐%) of YYKLVFFC in aqueous solution, and small‐angle X‐ray scattering was used to probe nematic phase formation in more detail. A pH‐induced transition from nematic to isotropic phases is observed on increasing pH that appears to be correlated to a reduction in aggregate anisotropy upon increasing pH.