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<p>Intrinsically disordered protein polymers (IDPPs) are repetitive biopolymers that,
when enriched with prolines, glycines, and aliphatic amino acids, have observable
lower critical solution temperature (LCST) phase transition behavior at physiologically
relevant temperature and concentration ranges. This behavior is a striking feature
of disordered proteins in nature, where chemical or physical stimuli lead to sharp
conformational or phase transitions. Accordingly, protein-based polymers have been
designed to mimic these behaviors, leading to a broad range of biotechnological applications.
This work is driven by two approaches. In our science focused approach, we developed
a polymer-physics based framework for understanding IDPP hydrophobicity using the
relationship between phase transition temperature and globule surface tension. This
physics-based framework has allowed us to better understand the unified contributions
of chain length, concentration, temperature, and individual amino acid side chains
to IDPP hydrophobicity by studying phase transition data. In our engineering focused
approach, we developed novel tools that enable the high throughput discovery of new
proteins that exhibit phase transitions, in order to increase the number of known
stimuli responsive peptide sequence motifs beyond the limits of bioinspired design.
The exhaustive discovery of new proteins that exhibit phase transitions consists of
gene synthesis and protein screening. We developed two key technologies that has enabled
(1) the scalable synthesis of repetitive gene libraries using a novel graph theoretic
gene optimization approach (Codon Scrambling) and (2) the pooled synthesis of large
complex gene libraries from libraries of oligonucleotides. Combined with pipelines
for the screening of phase transition behavior, these technologies have enabled us
to generate a diverse library of protein sequences necessary to validate our theoretical
models. Finally, we developed an algorithm for the de novo design of nonrepetitive
protein sequences that exhibit phase transition behavior, further broadening the sequence
space of stimuli responsive synthetic IDPPs.</p>
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