DNA ligation slows transport of semidilute DNA solutions via active entanglement

DNA ligase catalyzes the formation of phosphodiester bonds to anneal the ends of linear DNA strands, allowing DNA fragments to form long connected chains. In cells, ligation plays an essential role in replication, repair, and the formation of entangled structures. Here, we leverage in situ DNA ligation to introduce entanglements into semidilute DNA solutions with programmable time-dependence and degree of entanglement. Using fluorescence microscopy and differential dynamic microscopy, we analyze the dynamics of concentrated solutions of linear DNA strands of varying lengths as they undergo ligation. We demonstrate that DNA dynamics universally slow down as ligation continues over the course of minutes to hours. We observe sigmoidal dependence of diffusion on ligation activity time that indicates cooperativity between neighboring entangling chains. Surprisingly, we find that shorter DNA strands lead to faster and more pronounced slowing than longer strands. Future work will explore the role of DNA topology and concentration on the active mechanics, and introduce complementary enzymes that may cooperate or compete with ligation, providing a roadmap for designing dynamic, self-altering bio-based materials.