Renyu Zheng1,2,Mingfei Zhao3,Jingshan Du2,Yicheng Zhou2,Shuai Zhang1,Wenhao Zhou1,Andrew Ferguson4,Chun-Long Chen2
University of Washington1,Pacific Northwest National Laboratory2,Los Alamos National Laboratory3,The University of Chicago4
Renyu Zheng1,2,Mingfei Zhao3,Jingshan Du2,Yicheng Zhou2,Shuai Zhang1,Wenhao Zhou1,Andrew Ferguson4,Chun-Long Chen2
University of Washington1,Pacific Northwest National Laboratory2,Los Alamos National Laboratory3,The University of Chicago4
A long-standing challenge in biomimetic research is to create sophisticated hierarchical nanostructures that mimic the biomaterials found in living organisms. Self-assembly is a crucial process for creating these nanostructures, but the forces and dynamics governing the self-assembly of biomacromolecules, such as proteins and peptides, are complex. Developing sequence-defined synthetic polymers with simplified molecular interactions is a promising approach to synthesizing information-rich nanostructures and understanding their self-assembly mechanisms. Peptoid is a peptidomimetic molecule that moves the side group from α-carbon to nitrogen to keep the sequence programmability while simplifying the structure without backbone hydrogen donors and no backbone chirality. Previous studies have shown that amphiphilic peptoids can crystallize into highly ordered nanostructures, including nanoribbons, nanosheets, nanotubes, and nanohelices, by controlling peptoid-peptoid and peptoid-substrate interactions. However, achieving the predictable self-assembly of peptoids into designed nanostructures remains a significant challenge. In this study, we report a system of short tetramer peptoids to form crystalline peptoid helices. Due to the reduced hydrophobic interactions compared to those with six hydrophobic side chains, we showed that the self-assembly of these peptoids into nanohelices and other nanostructures are highly sensitive to the solution ionic strength and solvent condition, resulting in the formation of various nanostructures including nanohelices, nanohelix bundles, as well as nanotubes. We also demonstrate the control of supramolecular chirality of self-assembled peptoid nanohelices by using chiral polar groups with D- or L-configuration. By combining the synchrotron XRD results with molecular dynamic simulation studies, we showed the twisted form of bi-layer structures of these amphiphilic peptoids are the most stable form for those polar side chains to hide hydrophobic domains in the aqueous environment We further demonstrated that the organic cosolvent in the self-assembly could also affect the self-assembly morphology from nanohelices to nanotubes, which provides additional information on peptoid-solvent interactions as well as the self-assembly kinetics and thermodynamics. Our findings provide a facile system for controlling the twisting and stacking of peptoid amphiphiles into helical and tubular structures and suggest an approach for the precisely controlled synthesis of biomaterials.