Polymer chains via control of intermolecular assembly pathway of peptide bundlemers

Peptides were computationally designed to self-assemble into homotetrameric, anti-parallel coiled coils, or 'bundlemers'. Specifically, peptides with a net +4 charge per peptide, or +16 per tetrameric bundlemer, were synthesized and modified with a thiol (via incorporation of cysteine as the N-terminal amino acid) or maleimide (via incorporation at the N-terminus). When in water, the respective thiol or maleimide functionalized peptide assembled into coiled-coil bundlemer particles. When the thiol and maleimide functionalized bundlers were subsequently mixed, a thiol-Michael 'click' reaction created polymer chains with extreme rigidity from bundlemer building blocks. Utilizing organic solvent, the same rigid polymer chains can form with a separate, unique assembly pathway. The thiol and maleimide functionalized chains were first dissolved in organic solvent and conjugated together. Subsequent water titration causes the peptides to physically self-assemble into the same coiled-coil rigid chains. This alternate pathway provides direct insight into the stability of the coiled-coil bundles in organic solvent as well as kinetic control of the rigid rod polymer formation on physical assembly with water titration.