UMass Amherst Chemical Engineer Sarah L. Perry Helps Decode How Charge Patterns Instruct Polymer Chain Functions

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AMHERST, Mass. – Researchers at the University of Massachusetts Amherst and the University of Illinois Urbana-Champaign say they have discovered how to read patterns of charges on long molecules that determine its function and direct its shape. The findings, published in ACS Central Science, allow scientists to quickly and accurately predict how the polymer will act and will help them design new materials using specific charge sequences.

Sarah L. Perry, assistant professor of chemical engineering at UMass Amherst, says this research builds on previous work she has conducted with her collaborator Charles E. Sing at Illinois Urbana-Champaign.

Perry says nature uses long-chain molecules called polymers for a diverse array of applications. Proteins are used to build tissues, enzymes perform chemistry, and DNA encodes the information of life. In most of these examples, the polymer is folded into a complex shape that defines its function. It is that process that Perry and her colleagues set out to understand, she says.

That’s because the polymers found in nature are in stark contrast to most applications of polymers or plastics that we see in our everyday life. However, scientists are increasingly discovering new examples where biology makes use of unstructured, or intrinsically disordered proteins or polymers. “In these examples, the function of the protein is still defined by the sequence of chemistry encoded along the polymer chain, but we need a new way of understanding how this molecular-level information is translated into function,” Perry says.

“In the current article, which builds on the results of our earlier Nature Communications paper, researchers in my lab collaborated with the group of Charles Sing to understand how the sequence of charge along a model polymer affected its ability to create self-assembling liquid materials. These self-assembled liquids, also known as ‘complex coacervates’ are directly analogous to increasing numbers of liquid granules being discovered in cells,” Perry says.

“Our experimental results, coupled with theory and simulation results from the Sing lab has firmly identified the ways in which charge patterning can affect these materials. Furthermore, we have demonstrated a new method for quickly predicting the phase behavior of these materials to aid in future materials design efforts,” Perry says.

Perry says the next step is to incorporate other molecular interactions into this new theoretical framework. That may open the door to engineering new materials out of synthetic polymers, she says.