"There are cases here that by changing the sequence by just a single monomer (a single link in that chain), it can drastically change how these things are able to form. We have also proven that we can predict the outcome."Charles Sing, University of Illinois at Urbana-Champaign

Thanks to a team of researchers from the University of Illinois at Urbana-Champaign and the University of Massachusetts Amherst, scientists are now able to read patterns on long chains of molecules to understand and predict the behavior of disordered strands of proteins and polymers. These results could, among other things, pave the way for the development of new materials from synthetic polymers.

The lab of Charles Sing, assistant professor of chemical and biomolecular engineering at Illinois, provided the theory behind the discovery, which was then verified through experiments. These were conducted in the lab of Sarah Perry, assistant professor of chemical engineering at the University of Massachusetts Amherst, and an Illinois alumnus. The researchers report their findings in a paper in ACS Central Science.

They set out to understand the physics behind the precise sequence of charged monomers along the polymer chain and how it affects the polymer's ability to create self-assembling liquid materials called complex coacervates.

"The thing that I think is exciting about this work is that we're taking inspiration from a biological system," Sing said. "The typical picture of a protein shows that it folds into a very precise structure. This system, however, is based around intrinsically disordered proteins."

This paper builds on earlier findings by Perry and Sing from 2017. "Our earlier paper showed that these sequences matter, this one shows why they matter," Sing explained. "The first showed that different sequences give different properties in complex coacervation. What we're able to now do is use a theory to actually predict why they behave this way."

Unlike structured proteins, which interact with very specific binding partners, most synthetic polymers do not. "They are fuzzier, in that they will react with a wide range of molecules in their surroundings," Sing explained.

They found that, despite this fact, the precise sequence of the monomers (amino acids) along a protein really does make a difference. "It has been obvious to biophysicists that sequence makes a big difference if they are forming a very precise structure," Sing said. "As it turns out, it also makes a big difference if they are forming imprecise structures."

Even unstructured proteins have a precision associated with them. Monomers, the building blocks of complex molecules, are the links in the chain. What Sing's group theorized is that by knowing the sequence of polymers and monomers and the charge (positive, negative or neutral) associated with them, one can predict the physical properties of the complex molecules.

"While researchers have known that if they put different charges different places in one of these intrinsically disordered proteins, the actual thermodynamic properties change," Sing said. "What we are able to show is that you can actually change the strength of this by changing it on the sequence very specifically. There are cases here that by changing the sequence by just a single monomer (a single link in that chain), it can drastically change how these things are able to form. We have also proven that we can predict the outcome."

Sing adds that this information is valuable to biophysicists, bioengineers and material scientists alike. The discovery will help bioengineers to understand a broad class of proteins, and to tune these proteins to modify their behavior. It gives them a new way to put information into molecules for building new materials and make a better guess as to how these materials will behave.

Materials scientists can, for example, use this information to have sufficient control over a material to cause it to assemble into very complicated structures or make membranes that precisely filter out contaminants in water. Their hope is that scientists, inspired by biopolymers, can take this ability to predict physical behaviors by simply reading the sequence and use it to design new smart materials.

"This in some sense is bringing biology and synthetic polymers closer together," Sing said. "For example, at the end of the day, there is not a major difference in the chemistry between proteins and nylon. Biology is using that information to instruct how life happens. If you can put in the identity of these various links specifically, that's valuable information for a number of other applications."

This story is adapted from material from the University of Illinois at Urbana-Champaign, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.