One-dimensional self-assembly of a rational designed beta-structure peptide

Fabricating various nanostructures based on the self-assembly of diverse biological molecules is now of great interest to the field of bionanotechnology. In this study, we report a de novo designed peptide (T1) with a preferential beta-hairpin forming property that can spontaneously assemble into nanofibrils in ultrapure water. The nanofibrils assembled by T1 could grow up to tens of microns in length with a left-handed helical twist and an average height of 4.9 +/- 0.9 nm. Moreover, protofilaments and nucleus structures both with a similar height of 1.4 +/- 0.2 nm were observed during fibrilization as well as via sonication of the mature nanofibrils. A typical conformational transition from random coil to beta-structure was observed in association with the fibrilization. Molecular modeling of T1 assemblies displayed that the beta-hairpin molecules organize in a parallel fashion in which the beta-strands align in an antiparallel fashion and each adjoining beta-strand runs left-handed twist at about 2.9 degrees with respect to the one located before it along the fibrillar axis. It also revealed that the maximum thickness of the assembly intermediate, the helical tape structure, is about 1.4 nm and four tapes can further assemble into a fibril with a diameter of about 4.1 nm. Taken together the results obtained by AFM, CD, and molecular modeling, T1 fibrilization probably undergoes a hierarchy approach, in which the aromatic stacking and the electrostatic interactions between the assembled structures are most likely the two major factors directing the one-dimensional self-assembly. Based on these studies, we propose T1 can be used as a model peptide to investigate the beta-sheet based self-assembly process and could be a potential bioorganic template to develop functional materials.