Liquid Crystal\nBehavior of Uniform Short Rods Made\nfrom Computationally Designed Parallel Coiled Coil Building Blocks

Parallel, homotetrameric coiled coils were computationally\ndesigned\nusing 29 amino acid peptides. These parallel coiled coils, called\n“bundlemers”, have <i>C</i><sub>2</sub> symmetry,\nwith all N-termini displayed from one end of the nanoparticle and\nall C-termini from the opposite end. This anisotropic display of the\npeptide termini allowed for the functionalization of two sets of nanoparticles\nwith either maleimide or thiol functionality at the N-terminal region\nof the constituent peptides. The thiol-Michael conjugation reaction\nbetween the N-terminal end of complementary bundlemer nanoparticles\nformed monodisperse, rigid bundlemer dimer, called “dibundlemer”,\nrods. The constituent, individual bundlemer nanoparticles were characterized\nwith small-angle X-ray scattering (SAXS), Förster resonance\nenergy transfer (FRET), and circular dichroism (CD) spectroscopy to\nconfirm the parallel assembly of the coiled coils, consistent with\nthe computational design. The dibundlemer rods were characterized\nwith SAXS to reveal the uniform dibundlemer nature of the rods. Optical\nbirefringence is observed in concentrated samples of the rods, with\npolarized optical microscopy (POM) revealing a nematic liquid crystalline\nbehavior.