For the First Time, New Study Reveals the Structure of Polyelectrolyte Complexes that Help Organize Your Cells
Does the Internal Structure of Polyelectrolyte Complex Look Like a Scrambled Egg?
For decades, no one knew exactly how the regions looked inside a polyelectrolyte complex. How do they line up? Were they arranged in neat alternating lines, or more like what a Russian scientist termed “scrambled eggs”?
A new study from the University of Chicago’s Pritzker School of Molecular Engineering reveals the internal structure of polyelectrolyte complexes.
For a significant period, it has been understood that a distinctive molecular construct known as a “polyelectrolyte complex” plays a vital role in maintaining cell organization. These complexes excel at forming barriers between two liquid substances, a feature cells utilize to establish compartments. Scientists have identified this unique attribute as potentially useful in a range of technological applications such as water filtration, improved batteries, underwater adhesive, and even in the enhancement of pharmaceutical medications.
However, for a long time, the precise internal structure of these polyelectrolyte complexes remained a mystery. These complexes contain chains carrying both positive and negative charges, but how they align was unknown. Did they form organized, alternating lines, or did they resemble the disordered state described by a Russian scientist as “scrambled eggs”?
A breakthrough study led by the Pritzker School of Molecular Engineering at the University of Chicago has shed light on the internal architecture of polyelectrolyte complexes for the very first time.
According to study co-author Juan de Pablo, the Liew Family Professor of Molecular Engineering and senior scientist at Argonne National Laboratory, “understanding the molecular structure enables more precise synthesis and preparation. This newfound knowledge opens the door to new applications.”
The multi-faceted study led by de Pablo and Matt Tirrell, Dean of the Pritzker School of Molecular Engineering, involved the concerted efforts of numerous researchers over several years. Initial work by postdoctoral researchers Artem Rumyantsev and Heyi Liang involved developing molecular models and performing thousands of simulations along with theoretical computations based on statistical mechanics. Their goal was to comprehend how these molecules most likely assemble.
The baton was then passed to a team led by graduate student Yan Fang and postdoctoral researcher Angelika Neitzel. They were tasked with creating precise molecular copies in the lab and utilizing an advanced method to decipher their structure.
A technique known as neutron scattering was employed to examine the finer details of these molecules. This process involves firing beams of neutrons at the molecules and reconstructing their patterns based on how the neutrons scatter. However, this method couldn’t distinguish between the positively and negatively charged chains.
To overcome this, the team swapped out the hydrogen atoms in the positively charged chains with deuterium, a slightly different version of hydrogen that reacts differently during neutron scattering.
Through this process, the team determined that these chains exhibit distinct, repeated patterns at a microscale level, though these patterns weren’t uniformly distributed over extensive distances.
According to the researchers, once the molecular structure of these molecules is comprehended, the possibility for new applications arises. Besides their fundamental role in understanding biological functions, the unique capabilities of polyelectrolyte complexes make them highly valuable to scientists and engineers.
“These droplets still have a lot of water with them, which makes their interfacial tension low—so they tend to encapsulate objects or spread over surfaces and adhere, which are both very useful behaviors,” as explained by Tirrell. “You can use this to deliver drugs in the body, or for things like designing an underwater adhesive.”
“It’s a very powerful combination of these two approaches. It wouldn’t have happened with either group working in isolation,” Tirrel added.
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