4.7 Article

Tuning self-assembled morphology of the Aβ(16-22) peptide by substitution of phenylalanine residues

Journal

COLLOIDS AND SURFACES B-BIOINTERFACES
Volume 147, Issue -, Pages 116-123

Publisher

ELSEVIER SCIENCE BV
DOI: 10.1016/j.colsurfb.2016.07.052

Keywords

Amyloid peptides; Self-assembly; Aromatic interaction; Steric hindrance; Morphology

Funding

  1. National Natural Science Foundation of China [21573287, 21076231]
  2. Fundamental Research Funds for the Central Universities [14CX05040A]
  3. Natural Science Funds of Shandong Province of China for Distinguished Young Scholar [JQ201105]
  4. UK and Engineering and Physical Sciences Research Council
  5. Engineering and Physical Sciences Research Council [1540614] Funding Source: researchfish

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The effects of the two phenylalanine (Phe) residues in the blocked A beta(16-22) peptide on its self-assembly have been investigated by replacing both of them with two cyclohexylalanines (Chas) or two phenyl-glycines (Phgs). TEM and SANS studies revealed that the flat and wide nanoribbons of A beta(16-22) were transformed into thin nanotubes when replaced with Chas, and thinner and twisted nanofibrils when replaced with Phgs. The red-shifting degree of characteristic CD peaks suggested an increased twisting in the self-assembly of the derivative peptides, especially in the case of Ac-KLV(Phg)(Phg)AE-NH2. Furthermore, molecular dynamics (MD) simulations also indicated the increasing trend in twisting when Chas or Phgs were substituted for Phes. These results demonstrated that the hydrophobic interactions and spatial conformation between Cha residues were sufficient to cause lateral association of beta-sheets to twisted/helical nanoribbons, which finally developed into nanotubes, while for Phg residue, the loss of the rotational freedom of the aromatic ring induced much stronger steric hindrance for the lateral stacking of Ac-KLV(Phg)(Phg)AE-NH2 beta-sheets, eventually leading to the nanofibril formation. This study thus demonstrates that both the aromatic structure and the steric conformation of Phe residues are crucial in A beta(16-22) self-assembly, especially in the significant lateral association of beta-sheets. (C) 2016 Elsevier B.V. All rights reserved.

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