February 2013

Design Principles Revealed for a New Class of Functional Biomaterials

Ordered arrays of functional proteins with designed molecular properties created through self-assembly by combining proteins and synthetic polymers.

Click to enlarge photo. Enlarge Photo

Image courtesy Bradley D. Olsen, Massachusetts Institute of Technology, bdolsen@mit.edu.

Schematic illustration of cylinder-forming diblock copolymers, where the first block is a protein at the surface and the second block is the covalently attached synthetic polymer at the interior.

The Science

Synthetic polymers with defined molecular properties (chemical structure and molecular weight) are designed to form block copolymers with globular proteins. The self-assembly is driven by the chemical incompatibility between the proteins and the chemically linked polymers. In aqueous solution at high concentrations, these designed block copolymers exhibit a rich phase behavior that is dependent on the chemical structure of the polymer, polymer volume fraction in the block copolymer, block copolymer concentration, and temperature. By controlling these variables a variety of protein arrays with different architectures can be created.

The Impact

This discovery represents a significant step forward in our ability to control nanostructure in protein-based materials, with important applications in biocatalysis, energy conversion and nanotechnology.

Summary

If functional proteins could be organized into nanostructured arrays such as cylinders (one dimensional), lamellae (2 dimensional) and other three dimensional architectures, it could usher in new class of materials with unprecedented higher or even new functionality. Towards achieving this goal, scientists at the Massachusetts Institute of Technology designed a set of block copolymers consisting of proteins covalently bonded with synthetic polymers and explored their solution phase behavior as a function of polymer molecular weight, block copolymer composition, concentration, and temperature in the high concentration regime. The incompatibility between the protein and polymer and their chemical interaction with the solvent (water in this case) leads to novel self-assembly properties that can be controlled with the rational design of the block copolymers.  Neutron scattering experiments show that water distribution within the nanostructures drives transitions between ordered phases. Since proteins have incipient aggregating tendency in solutions, especially at higher concentrations, new routes are needed to exploit their unique function. The ability to organize functional biomaterials at high concentrations without aggregation through the block copolymer route offers new ways for the rational design of novel materials for potential applications in catalysis, sensors, nanotechnology and renewable energy.

Contact

Bradley D. Olsen, Massachusetts Institute of Technology, bdolsen@mit.edu

Funding

This work was supported by the Department of Energy Office of Science Basic Energy Sciences program.

Publications

Christopher N. Lam and Bradley D. Olsen, “Phase transitions in concentrated solution self-assembly of globular protein–polymer block copolymers”, Soft Matter, 9, 2392-2402 (2013).

C. S. Thomas, L. Xu and B. D. Olsen, “Kinetically Controlled Nanostructure Formation in Self-Assembled Globular Protein-Polymer Diblock Copolymers”, Biomacromolecules, 13, 2781–2792 (2012).

Related Links

MIT Olsen Group HomepageExternal link

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Program: BES, MSE

Performer/Facility: University

Last modified: 12/5/2013 5:18:03 PM