Biomolecules for non-biological things: Peptide ‘Bundlemer’ design for model polyelectrolyte nanoparticle creation and hierarchical solution assembly

A solution-assembled system comprised of computationally designed coiled coil bundle motifs, also known as ‘bundlemers’, will be discussed as model colloidal nanoparticle systems for the formation of hierarchical materials. The polyeletrolyte 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, target nanomaterials are being created. Interbundlemer end-to-end stacking is observed between particles through physical interactions to form lyotropic liquid crystal phases. 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 to smectic depending on peptide concentration as well as on specific peptide design (e.g., number of negative or positive charges, spatial display of charge, amino acid type to create charge). Particles with charge patches also have been designed so that liquid crystal formation is observed at extreme pHs from 1 to 14 with the bundlemer particles still folded and stable. Included in the discussion will be new, single charge peptide molecule design, hierarchical assembly pathway design, control of nanostructure, and characterization wtih cryotransmission electron micorscopy, transmission electron microscopy, small-angle x-ray scattering, and molecular dynamics simulations.