Significant examples have demonstrated the successful constructions of various nanoarchitectures via the self-assembly of amphiphilic molecules, such as surfactants and block co-polymers. However, the intrinstic polydispersities in chemical structures and chain conformations limit the nanostructure complexity that can be achieved with the use of only these types of molecules. Synthetic peptides with the high sequence- and shape-specificity determined by the precise primary sequences and the encoded secondary-structures can serve as the assembly building blocks for the construction of highly controllable and complex nanoarchitectures. Computational design was employed to design peptides that can form antiparallel, alpha-helical tetrameric coiled-coil bundles in solution that then further assemble into higher order structures with targeted organization. The designed hydrophobic core ensures the structure stability of the bundles in the aqueous solution to tolerate non-physiological condtions. It is found that in a specific solution conditoin, the bundles self-assemble into homogenous nanotubes at pH 4.5. As analyzed by cryo-TEM, SAXS and STEM mass-mapping, a mono-layer tilted-bundle model is proposed to explain the nanotube structure. The charged state and distribution of the peptide bundles associated with the acidic solution condition are believed to be the reason triggering certain inter-bundle interactions and leading to the formation of nanotubes. Rational sequence modifications were applied to control the dimensions of the nanotubes or to completely disrupt the tube nanostructure or to add metal-binding functionality to the system. Moreover, kinetic control was applied in the multi-step assembly process to produce a branched nanotube morphology. Further fixation or crosslinking treatment can be applied to the branched nanotube system for the development of stable hyper-branched materials with potential applications such as filtering, catalyst/drug carrier and implantable materials.

Controlled self-assembly of peptide nanotubes via sequence modification and kinetic control

2019 Spring National Meeting

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