Computer modeling of polyelectrolyte systems.A new study has devised a strategy for modeling polyelectrolytes, such as DNA and RNA. With polyelectrolytes having a range of uses, such as in thickeners, emulsifiers, and soaps, as well as biomedical and nanomaterial applications in implant coatings and drug delivery systems, this breakthrough offers an improved understanding of polyelectrolyte systems, especially as it allows much larger and more complex systems to be modeled and investigated.
Polyelectrolytes, chains of molecules that are positively or negatively charged when in water, are sensitive to change. Computational modeling to simulate the behavior of polyelectrolyte systems – a change in charge influences how the polyelectrolytes interact with each other – helps to identify which polyelectrolytes are most likely to have suitable characteristics for specific applications. It is difficult to model such complex systems due to the number of ions that can interact with the polyelectrolytes, altering their charge, shape, properties, and behaviors, vastly increasing the required computing power.
However, this research developed a way to explain the effect of the ions but with less computing power and quicker results. Rather than accounting for each ion, scientists from North Carolina State University used an implicit solvent ionic strength method with a single parameter to control for the effect of the ions in a dissipative particle dynamics model. As reported in Macromolecular Theory and Simulations [Li et al. Macromol. Theory Simul. (2014) DOI: 10.1002/mats.201400043], this allows for possible candidates to be analyzed, before their behavior can be varied due to the number of ions in the system by increasing the concentration of salts, which are ionic in an aqueous solution.
“The model can be used to help researchers understand the behavior of biological polyelectrolyte systems such as DNA–protein binding structures, RNA, and antibodies in aqueous environment.”Yaroslava Yingling, senior author.
The method was applied to two test cases: a long, single polyelectrolyte chain, and the self-assembly of polyelectrolyte block copolymers. Block polyelectrolytes can often help to create “smart” carriers for drug delivery through self-assembly in solution that can respond to physical stimuli. Responses can include changes in shape, volume, and mechanical properties. As senior author Yaroslava Yingling said, “The model can be used to help researchers understand the behavior of biological polyelectrolyte systems such as DNA–protein binding structures, RNA, and antibodies in aqueous environment.”
The team is now applying the model to the study of the self-assembled systems of block polyelectrolyte copolymers in aqueous solutions, as the self-assembled form various morphologies in response to changes in salt concentration. It is hoped the model can also be further applied to self-assembly systems of more complex polyelectrolyte-based materials.