Rod-like architecture and cross-sectional structure of an amyloid protofilament-like peptide supermolecule in aqueous solution

Abstract

Synchrotron X-ray scattering was performed on an aqueous solution containing self-assembled aggregates of a β-sheet-forming peptide conjugated with a water-soluble moiety (polyethylene glycol, PEG or an oligo-peptide comprising a transactivator of transcription, TAT, sequence). The angular dependence of the scattering intensity in the low-q region (that is, q<2.0 nm -1, where q is the magnitude of the scattering vector) indicated that the scattering objects were rod-like and completely dispersed in water without undergoing secondary aggregation. From the scattering intensity in the range of 0.5 nm -1 <5.0 nm -1), a diffraction peak was observed at q=13.4 nm -1, which could be assigned to the two neighboring α-carbons of the peptide chains of the cross-section of the β-sheet. The scattering data indicated that the β-sheet-forming peptide indeed formed stacked β-sheets in a manner similar to that observed in the case of amyloid protofilaments, and that the resultant rod-like objects could be completely dispersed in water as a result of the hydrophilic PEG or TAT moiety.