Biomolecules for Non-Biological Things—Peptide ‘Bundlemer’ Design for Model Colloidal Particle Creation and Hierarchical Solution Assembly

A solution-assembled system comprising computationally designed coiled coil bundle motifs, also known as ‘bundlemers’, will be discussed as model colloidal particle systems for the formation of hierarchical materials. The molecules and nanostructures are non-natural amino acid sequences and provide opportunities for controlled solution behavior and arbitrary nanostructure creation with peptides. With control of the display of the amino acid side chains (both natural and non-natural) throughout the peptide bundles, desired physical and covalent (through appropriate ‘click’ chemistry) interactions are designed to control interparticle interactions in solution, which involve both individual bundlemer particles as well as polymers of connected bundlemers. With proper design of individual bundlmer particles, interbundlemer end-to-end stacking is observed between particles through physical interactions to form liquid crystal phases at low peptide concentrations. The individual bundlemer building blocks are responsive to varying salt and pH, since computational design is used to design bundlemers with different net charge character to manipulate their interactions in solution. Important for liquid crystal formation is the design of single charge bundlemer particles (e.g., with only positive/basic amino acids) that lack of opposite charges on the particle surfaces so that there are no attractive electrostatic patches to disrupt the LC alignment. The liquid crystal phases span nematic to hexagonal columnar depending on peptide concentration as well as on specific peptide design (e.g., amount of single charge, display of charge, amino acid type to create charge). Included in the discussion will be new, single charge peptide molecule design, hierarchical assembly pathway design, control of nanostructure, and liquid crystal formation and characterization wtih cryotransmission electron micorscopy, transmission electron microscopy, small-angle x-ray scattering, and molecular dynamics simulations.