Protein-based materials show a great deal of potential as catalysts, sensors, and optoelectronics, where the unique efficiency, selectivity, or activity of enzymes can be captured to improve the performance of these devices.  Control over the structure and orientation of the protein in three dimensions is required to improve transport through the devices, increase the density of active sites, and optimize the stability of the protein.  We have demonstrated that self-assembly of globular protein-polymer conjugates and fusion proteins into nanostructured phases provides one route to such self-assembly obtaining high protein densities within materials that can achieve large improvements in the performance of sensors and biocatalysts. <br/> <br/>Bioconjugates or protein fusions of an enzyme or globular protein block with a coil protein or polymer block may be conceptualized as diblock copolymers, where the first block is the globular protein and the second block is the synthetic polymer or coil-like protein sequence.  Electrostatic interactions in the protein block copolymers have a large impact on their self-assembly.  To explore these effects, we studied the self-assembly of supercharged green fluorescent protein block copolymers, systematically varying the total charge on the protein.  These systems demonstrated that increasing charge promotes disassembly.  Similarly, the use of a synthetic zwitterionic polymer block or the addition of salt to copolymer systems also promotes disassembly, suggesting that charge interactions only between protein blocks are substantially contributing to the formation of nanostructured phases.  We are also able to probe electrostatic effects in fusions of globular proteins with elastin-like protein blocks, where charging of the elastin is accomplished through variation of the guest residue.  Comparison of zwitterionic and anionic blocks provides insight into the mechanism by which charge impacts assembly in these systems.<br/>

Electrostatic effects on self-assembly in protein-polymer block copolymers

253rd National Meeting (2017)

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