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Bridging the Gap between Natural and Synthetic Polymers

In using polymeric materials, we live with the fact that chemical polymerization processes give rise to complex mixtures of molecular chains.  The extent of this complexity is astonishing; in a typical gram-scale sample of a familiar synthetic polymer (e.g., polyethylene), every molecule is unique, structurally distinct from every other. Despite their complexity, and in some respects because of it, synthetic polymers are enormously interesting and important.  They exhibit an extraordinary range of physical and mechanical properties, and can be used to prepare materials that range from soft elastomers to fibers stronger than steel.  They can be fluids at room temperature, or they can protect spacecraft from the intense heat of atmospheric re-entry.  Their versatility arises in large part from the diversity of monomeric starting materials that are amenable to chemical polymerization.

Proteins, like synthetic polymers, consist of long molecular chains.  But because their molecular architectures and folding properties are well defined, proteins have acquired functions (e.g., catalysis and molecular recognition) that are not readily engineered into synthetic polymers.  At the same time, the physical properties of proteins are often problematic; many proteins unfold at relatively low temperatures, and they are notoriously sensitive to proteases and denaturants.