Aggregation of the amphipathic peptides (AAKA)n into antiparallel beta-sheets.
Helical wheel projections of peptides based on the repeating unit Ac-(AAKA)n-NH2 clearly illustrate an amphipathic nature. One should therefore expect these peptides to form helices if the number of residues exceeds a certain threshold value. Indeed, ECD measurements show that Ac-(AAKA)4-NH2 and, to a minor extent, also Ac-(AAKA)3-NH2 exhibit some helical content at millimolar concentrations in aqueous solution. Surprisingly, however, these peptides were found to form hydrogels with an antiparallel beta-sheet conformation at centimolar concentrations. This occurs despite the positively charged lysine side chain which would be expected to inhibit the formation of extended beta-sheet layers.
Measey
Thomas J
TJ
Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
Schweitzer-Stenner
Reinhard
R
D016880:Anisotropy; D002942:Circular Dichroism; D020100:Hydrogels / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014867:Water
D020100:Hydrogels; D010455:Peptides; D014867:Water