Much of our research in this area focuses on artificial intrinsically disordered proteins (A-IDPs). One class —Elastin-like Polypeptides (ELPs)— are polymers of a Val-Pro-Gly-Xaa-Gly motif found in tropoelastin that display lower critical solution temperature (LCST) phase behavior. A second class that we have more recently focused on are Resilin-like polypeptides (RLPs) that show the mirror image —upper critical solution temperature (UCST)— phase behavior. A primary focus of our research in ELPs and RLPs is the development of applications in biotechnology and medicine that exploit their phase transition behavior. These applications include the purification of proteins, viruses, and cells, the delivery of anticancer therapeutics to solid tumors by self-assembled nanoparticles of ELPs and RLPs, and the development of ELPs as injectable depots for sustained delivery of biologics.
More recently, we have expanded our tool-box of biomolecular materials beyond RLPs and ELPs by scanning across sequence space to identify a large class of peptide motifs, that when polymerized show LCST or UCST phase behavior. We have also developed genetically encoded variants that encode noncanonical amino acids into these polymers that provide new opportunities for biorthogonal reactions in vitro and in vivo. Other variants encode post-translational modifications into these polymers that greatly diversity their chemical complexity and drive their hierarchical self-assembly into macroscopic materials.