Salt-dependent properties of a coacervate-like, self-assembled DNA liquidElectronic supplementary information (ESI) available: Experimental results showing negligible effects of the overall NS concentration and YOYO-1 dye on NS-liquid DNA concentrations. NS-liquid densities measured from sedimentation velocities of NS-liquid droplets. Bulk-rheology of NS-liquids. A representative plot showing recovery of the radial averaged intensity in a FRAP experiment. Microrheology of a NS-liquid with a stro

Liquid-liquid phase separation of a polymer-rich phase from a polymer-dilute solution, known generally as coacervation, has been observed in a variety of biomolecular systems. Understanding of this process, and the properties of the resulting liquid, has been hampered in typical systems by the complexity of the components and of the intermolecular interactions. Here, we examine a single-component system comprised entirely of DNA, in which tetravalent DNA nanostar particles condense into liquids through attractive bonds formed from basepairing interactions. We measure the density, viscosity, particle self-diffusion, and surface tension of NS-liquid droplets. The sequence- and salt-dependent thermodynamics of basepairing accounts for most properties, particularly indicating that particle transport is an activated process whose barrier is the breaking of a single bond, and that very few bonds are broken at the surface. However, more complex effects are also seen. The relation of density to salt shows that electrostatic screening compacts the NS particles. Further, the interrelation of the transport properties indicates a breakdown of the Stokes-Einstein relation. This observation, in concert with the low surface tension and single-bond transport barrier, suggests this DNA liquid has a heterogeneous, clustered structure that is likely enabled by internal NS particle flexibility. We discuss these results in comparison to other coacervate systems. Liquid DNA droplets, made of self-assembled DNA particles ('nanostars'), show salt-dependent viscosity, self-diffusion, and surface tension due mainly to basepairing thermodynamics. Yet, certain aspects indicate a heterogeneous liquid structure. These results are compared to other coacervate systems.