Soft and Living Matter Seminar Series: Monday March 16th, 2020 -- Computationally designed coiled coil bundlemers as modular building blocks for supramolecular self-assembly

Event Date: 

Monday, March 16, 2020 - 11:00am

Event Location: 

  • MRL 2053
  • Soft and Living Matter

Utilization of biomacromolecules to engineer self-assembled materials that display target structure and function at the nanoscale is an active area of new materials research. Peptides that are short sequences of amino acids are excellent candidates for this purpose. Computational prediction of peptide sequences has further enabled faster screening and deterministic design of peptide-based biomaterials. In my talk, I will discuss the utility of artificial peptides that were computationally designed to form coiled coils aka bundlemers. Short α-helical peptides tetramerize to form a bundlemer with a hydrophobic core and displaying side chains that are strategically chosen to drive their assembly under mild solution conditions.

Via a feedback cycle between experiments and sequence-optimization algorithms, we have tested multiple peptide designs for successful bundlemer formation. Specifically, small angle neutron scattering (SANS) measurements confirmed that all bundlemers are robust 4 nm x 2 nm cylinders. These bundlemers behave as colloids exhibiting short-range attraction and long-range repulsion (SALR) interactions wherein the solution structure is uniquely impacted by sequence-specific charge patterns on their surface.

Taking advantage of their structural robustness, we modified the bundlemers to incorporate thiol or maleimide groups at the N-termini that yielded tetra-functional ‘monomers’. The decorated bundlemers were reacted via Thiol-Michael click reaction, resulting in end-to-end polymerization of bundlemers. Short linkers between bundlemers yielded rigid rod-like polymers, whereas longer flexible linkers resulted in semi-rigid polymers, both having a cross-section of ≈ 2 nm (confirmed via SANS) that can be viewed under a Transmission Electron Microscope.  The difference in bending dynamics of rigid rod-like versus semi-rigid polymers was further corroborated by Neutron Spin Echo measurements.

Due to the step-growth polymerization kinetics of Thiol-Michael click reaction, the average length of rigid rod-like polymers was readily tunable. SANS studies of the inter-rod interactions showed that the rod-like polymers behave like polyelectrolytes in solution with a large intrinsic persistence length. Furthermore, lyotropic liquid crystal formation in concentrated solutions was dependent on constituent bundlemer design. Thus, the bundlemer-based rigid rod-like polymers are also excellent model systems to study sequence-driven structure-property relationships in proteinaceous 1D assemblies.

THIS MEETING WILL BE AVAILABLE VIA ZOOM:

Topic: SPECIAL SOFT/LIVING MATTER SEMINAR -Nairiti Sinha - Computationally designed coiled coil bundlemers as modular building blocks for supramolecular self-assembly
Time: Mar 16, 2020 11:00 AM Pacific Time (US and Canada)

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Meeting ID: 701 205 404