ÐãÉ«Ö±²¥

Abstract:

A solution-assembled system comprised of computationally designed coiled coil bundle motifs, also known as ‘bundlemers’, will be discussed as model colloidal nanoparticle systems for the formation of hierarchical materials. The molecules and nanostructures are non-natural amino acid sequences and provide opportunities for controlled solution behavior and arbitrary nanostructure creation with peptides. With control of the display of the amino acid side chains (both natural and non-natural) throughout the peptide bundles, desired physical and covalent (through appropriate ‘click’ chemistry) interactions are designed to control interparticle interactions in solution, which involve both individual bundlemer particles as well as polymers of connected bundlemers. With proper design of individual bundlmer particles, two target nanomaterials are being created. First, interbundlemer end-to-end stacking is observed between particles through physical interactions to form lyotropic liquid crystal phases. Important for liquid crystal formation is the design of single charge bundlemer particles (e.g., with only positive/basic amino acids) that lack of opposite charges on the particle surfaces so that there are no attractive electrostatic patches to disrupt the LC alignment. The liquid crystal phases span nematic to hexagonal columnar to smectic depending on peptide concentration as well as on specific peptide design (e.g., number of negative or positive charges, spatial display of charge, amino acid type to create charge). Second, nanoporous lattices can be formed through simply solution mixing. The lattices display crystalline-like structure but with regular pores on the nanoscale. The lattice structures are formed through two different assembly mechanisms; the functionalization of bundlemer paritcles with hydrophobic side chains on their exterior for lattice formation through interparticle hydrophobic interactions or through the mixing of oppositely charged, single charged bundlemers through electrostatic complexation. Included in the discussion will be new, single charge peptide molecule design, hierarchical assembly pathway design, control of nanostructure, and characterization wtih cryotransmission electron micorscopy, transmission electron microscopy, small-angle x-ray scattering, and molecular dynamics simulations.

Ìý

Bio:

Darrin Pochan is currently Distinguished Professor in the Materials Science and Engineering Department as well as having appointments in the Delaware Biotechnology Institute, Department of Chemistry & Biochemistry, and the Department of Biomedical Engineering at the University of Delaware. Since joining the MSE department in 1999 after a Ph.D. in Polymer Science and Engineering at the University of Massachusetts-Amherst and a National Research Council Post-doctoral fellowship at the National Institute of Standards and Technology in Gaithersburg, MD, he has developed a research program around the construction of new materials and nanostructures via molecular solution assembly mechanisms. Areas of focus are biomolecular and polymer self-assembly, biomaterials, and materials for nanotechnology and sustainable materials. His honors include an NSF Career Award, the DuPont Young Faculty Award, the Dillon medal from the American Physical Society and Fellowship in the American Physical Society, American Chemical Society, Royal Society of Chemistry, American Institute of Medical and Biological Engineering, and the National Academy of Inventors. Darrin recently served as Chair of MSE at UD from 2014-2022 and as Editor in Chief of Soft Matter from 2017-2022 published by the Royal Society of Chemistry in the United Kingdom.