Researchers Yeseul Lee and Murugappan Muthukumar have made a groundbreaking discovery regarding polyzwitterions, revealing that these seemingly neutral molecules can exhibit unexpected behaviors in biochemical environments. A new study has discovered some particularly exciting properties of polyzwitterions. Under a restricted set of conditions these substances can ultimately perform as charged species, upending deeply entrenched assumptions of molecular behavior in biochemistry.
Polyzwitterions are multispecies polymers made of zwitterions, or special molecules that are neutral overall but have strong positive and negative character. Usually, these positive and negative charges offset, leading to a zwitterion with an overall net neutral charge. A recent work by Lee and Muthukumar showed that polyzwitterions can nonetheless display directionally coherent motion. Their studies seek to advance the understanding of the basic biochemical energetic forces at work and the mechanisms by which these complicated molecules operate.
The early researchers performed their experiments with polyzwitterions like PSBMA and PMPC, and examined their behavior under an EP setup. PSBMA unexpectedly moved in the opposite direction, towards the deep end of the experimental apparatus, acting as if it had a net positive charge. In the meantime, PMPC was drifting further into the shallow end, behaving as though it had a net positive charge. This unexpected observation exposes a marvelous phenomenon known as charge symmetry breaking. It occurs when one end of a molecule becomes more positively charged relative to the other end.
Understanding Polyzwitterions
Polyzwitterions contain only neutral repeating units but can exhibit remarkable properties. The researchers selected these small molecules as a model polymer to use in their study. Specifically, they have been captivated by their strange, fascinating properties and their important relevance to biochemistry.
Yeseul Lee emphasized her interest in understanding the building blocks of proteins and amino acids within cells. She stated, “My interest is in the proteins and amino acids, which are the building blocks for protein, inside our body’s cells.” This study doesn’t just lay the groundwork for polyzwitterions but provides a better understanding of biochemical interactions at play with many different biopolymers.
Murugappan Muthukumar helped frame their work in even deeper context by explaining how biopolymers are ubiquitous in cellular contexts. He explained, “Proteins are biopolymers and a biopolymer is a series of charged and neutral elements. Biopolymers are crowded throughout the cellular environment. It is of great significance to understand how these molecules move from one location to another and communicate in such crowded environments, because we cannot live without their movement and communication.”
The Experiment and Its Findings
The study’s novel approach included single-molecule electrophoresis in a home-built nanohole with a diameter of only 3.5 nanometers. Such a size restriction meant that only one polymer strand could march through at a time. Consequently, we were able to comprehensively and rigorously track their movement and responses to electrical stimulation.
The next step for the researchers is to size the system up. This allowed them to assess how polyzwitterions were moving through their environment. That was the missing piece of the puzzle, Lee explained, because researchers had thought the dielectric constant surrounding polyzwitterions was much higher than reality. “It has long been thought that the cellular electrolyte solution surrounding the polyzwitterions and biopolymers has a uniform dielectric constant,” she remarked.
Muthukumar highlighted the significance of their findings, stating, “This is a new contribution to our understanding of fundamental forces in biochemistry.” He elaborated on the importance of understanding how neutral parts of biopolymers interact within crowded environments, noting that “we know a good deal about the movement of the charged parts of biopolymers,” but until now, “there hasn’t been much interest in the neutral parts.”
Implications for Biochemical Research
The outcome from Lee and Muthukumar’s research is a ground-breaking leap forward in the biochemistry field. Their research uncovers how some polyzwitterions can carry one charge at one extremity and the opposite charge near the middle. This unexpected finding has far-reaching consequences for scientists investigating the molecular underpinnings of cellular interactions in health, development and disease.
Muthukumar emphasized the novelty of their findings by stating, “No one knew that the dielectric constant varied as one moves away from the polymer backbone. Here we could quantify its consequences.” This realization opens up new research directions towards understanding biomolecules in a more complex, relevant environment. It has the potential to make monumental leaps in design drug delivery systems and molecular engineering.
The study demonstrates that even neutral molecules can play a key role in driving biochemical processes. This revolutionizes and upends existing interpretations of molecule stability. Lee and Muthukumar upend standard assumptions about neutrality in biochemistry. Their innovative research opens the door for new explorations into the complexities of molecular dynamics.