Self-assembly and liquid crystal behavior of computationally designed peptide coiled-coil bundlemers with parallel symmetry*

Computationally designed α-helical peptides formed by 29 amino acids can assemble into the homotetrameric, parallel coiled coils in the aqueous solution, which are also called ‘bundlemers’. Bundlemers have a hydrophobic interior core and multiple amino acid side-chain residues on the exterior as possible modification positions for targeted solution behavior. The exposed N-termini additionally provide potential sites for ‘click’ chemistry functional pairs to form multibundlemer chains by covalent linkages. Parallel folding coiled coil bundlemers offer the unique possibility for monodisperse, rigid, dimer bundlemer rods when linked together in a head-to-head fashion. Short rods are observed with transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS).  Results show the monodisperse rod length and diameter consistent with the computationally designed parallel, homotetrameric bundlemer building block connected into dimer rods. Optical birefringence phenomenon is observed in concentrated rod solution under the polarized optical microscopy (POM). Different exterior surface modification strategies will be discussed to produce liquid crystals formed by different mechanisms.