The proposed work in this MIRA application leverages my long-standing interest and expertise in the design of genetically encoded stimulus-responsive peptide polymers. My group pioneered the development of recombinant elastin-like polypeptides (ELPs) that exhibit lower critical solution temperature (LCST) phase behavior. We have also, in parallel, pioneered the development of high-throughput methods for the assembly of highly repetitive genes that we used to create the largest extant library of recombinant peptide polymers. Characterization of their aqueous phase behavior led to the discovery of sequence heuristics that can be used for the de novo used design of peptide polymers that exhibit LCST phase behavior and a class of resilin-like polypeptides (RLPs) that exhibit the converse ? upper critical solution phase transition (UCST) phase behavior. Building upon this work, we will explore two new areas in this proposal. First, we will investigate how we can recapitulate the hierarchical structure and properties exhibited by biological materials by the design of partially ordered polymers (POPs) ?that consist of disordered polypeptides embedded with a periodically recurring secondary structure motif? that exhibit temperature triggered hierarchical self-assembly into macroscopic materials that mimic the in vivo organization of structural proteins like elastin networks. We will carry out a systematic exploration of the design of new POPs, to verify that the combination of order and disorder at the chain segment level is a new and robust design principle that will yield materials with hierarchical self- assembly across many length scales. Second, we will develop a new line of investigation on genetically encoded biohybrid polymers via post-translational modifications (PTMs) that precisely combine peptide and non-peptide components to create biomaterials that exhibit triggered, hierarchical self-assembly into macroscopic materials. In this aim, we will expand upon our initial work on in vivo myristoylation of ELPs and UCST exhibiting RLPs to investigate if we can convert structure-directing peptides into myristoylation substrates, to create myristoylated polypeptides where the myristoylated segment can direct hierarchical self-assembly of the entire construct. We will also investigate modification of ELPs and RLPs with cholesterol that has the potential to direct self-assembly, and phosphorylation, which will provide a unique trigger of self-assembly. Much remains to be done in both areas, as our preliminary foray into these new areas only hint at the enormous possibilities in the molecular design of new biomaterials enabled by these approaches. The work we propose herein promises to yield new biomaterials with interesting structures and properties with a host of applications in biotechnology and medicine.
We will create the next generation of polypeptide biomaterials that exploit two principles ubiquitous in biology: first, they combine ordered and disordered components to yield materials that self-organize into bulk materials with a unique internal structure. Second, we will exploit post-translational modifications ?a class of reactions carried out on proteins after they are made inside a cell? to decorate the polypeptides with non-peptide moieties to create new biohybrid polymers. All these materials will be designed to respond to a thermal trigger, such as a small elevation or depression in temperature, to self-organize into bulk materials with useful properties that will make them useful for a range of applications in medicine and biotechnology.