Regulation of β-Sheet Structures within Amyloid-Like β-Sheet Assemblage from Tripeptide Derivatives

Abstract

N-(11-Trimethylammonioundecanoyl)-O,O‘-didodecyl tripeptide bromides and N-(11-trimethylammonioundecanyl)-O-dodecyl tripeptide bromides formed a parallel β-sheet structure when they aggregated in water and in CCl4. The parallel β-sheet was distinguished from the antiparallel counterpart by Fourier transform infrared spectroscopy because the former lacks a weak band at about 1690 cm-1 that is characteristic for the latter. The FT-IR spectra of the aggregate in CCl4 remained unchanged if the solution was diluted to 0.01 mM, condensed to dryness, or heated to 60 °C, and hence, the β-sheet was easily formed and thermodynamically stable. The parallel β-sheet was also possible to transform into an antiparallel β-sheet, for example, by mixing with another tripeptide-containing amphiphile whose tripeptide part had an opposite direction. Transmission electron microscope (TEM) and atomic force microscope (AFM) pictures revealed that the aggregate in CCl4 is a bundle of small filaments whose diameters are 70−80 Å. Developed interpeptide hydrogen bonding should be formed along the long axis of the filament. The morphological structures and stable peptide arrangements of the present assemblages are similar to those of the amyloid fiber whose accumulation causes fatal diseases.