Researchers have discovered a previously unknown type of molecular movement within DNA droplets, potentially revolutionizing our understanding of cellular processes and paving the way for advanced biomaterials. This finding could lead to significant advancements in medicine and materials science.
Scientists from Johannes Gutenberg University Mainz, the Max Planck Institute for Polymer Research, and the University of Texas at Austin have observed that guest molecules, when entering droplets made of DNA polymers, don't diffuse randomly. Instead, they move through the droplets in an orderly fashion, forming a sharp, wave-like front. "This is completely unexpected behavior," explains Weixiang Chen from the Department of Chemistry at JGU. Their findings were published in the journal Nature Nanotechnology.
In the classic diffusion model, molecules in liquids spread out gradually. For example, when a drop of blue dye is added to water, the color slowly disperses. However, the guest molecules in the DNA droplets behave differently. According to Professor Dr. Andreas Walther from the Department of Chemistry at JGU, "The molecules move in a structured and controlled way that contradicts classical models, resembling a molecular wave or a moving boundary."
The research team used droplets made of thousands of single DNA strands, also known as biomolecular condensates. The unique feature of these droplets is that their properties can be precisely adjusted using the DNA structure and parameters like salt concentration. These droplets also have relevance in biological cells, which use similar condensates to organize complex biochemistry without membranes. Chen states, "Our synthetic droplets thus form an excellent model system to mimic and better understand natural processes." The researchers introduced specially designed "guest" DNA strands into the DNA droplets, which could specifically recognize and bind to the inside of the droplets. The novel movement of the guest molecules is attributed to the key-lock principle, where the added DNA and the DNA present in the droplet bind to each other. This creates a dynamic state, which is a completely new phenomenon in soft materials, according to Chen.
These findings are important not only for understanding the physics of soft materials but also for chemical processes in cells. Walther suggests, "They could be one of the missing puzzle pieces in understanding how cells regulate signals and organize molecular events." This is particularly interesting for treating neurodegenerative diseases, where proteins migrate from cell nuclei into the cytoplasm and form condensates. As these age, they transition from a dynamic to a more solid state, forming problematic fibrils. Walther concludes, "It is at least conceivable that these aging processes can be influenced with the help of our findings, which would open up a completely different treatment option for neurodegenerative diseases in the long term.”