Polymers constructed from the self-assembly of computationally designed coiled-coil peptide via designed assembly pathways*

A series of net positively charged 29 amino-acids peptides were computationally designed to self-assemble into tetrameric, anti-parallel coiled-coil peptide bundles, or 'bundlemers'. Specifically, peptides with a net +4 charge were synthesized with either a thiol or maleimide present at the peptide N-terminus.  In order to form polymer chains, peptides are firstly self-assembled into coiled-coil bundlemer particles. Then the thiol and maleimide bundles are subsequently chemically conjugated to form rigid peptide bundle chains. This pathway is called a physical-chemical pathway to chain formation. Another chemical-physical pathway is possible to fabricate the rod-like chains where the two peptides are first dissolved in organic solvent and conjugated together. Subsequent water addition causes the peptides to self-assemble into coiled-coil bundlemer chains. Transmission electron microscopy (TEM) was used to investigate the length distribution of peptide rods, and Small-angle X-ray scattering (SAXS) was utilized to characterize the size and structure of the nanostructure at different solvent conditions. The merits of both pathways in the control of chain formation and the control of amino acid sequence that constitutes the resultant chains will be discussed.