Hyperuniform Phase-separated DNA Droplets

Many recent studies of phase separation in biology focus on phase separation as a dynamic control mechanism for cellular function, but it can also result in complex mesoscopic structures. Here, we investigate the long-range structures formed by a model phase-separating DNA system. We use DNA nanostars, a system of finite-valence, attractive particles roughly 10nm in size whose sequence is designed such that they self-assemble into liquid droplets on the micron scale via a binodal phase transition. We acquire images of fluorescent DNA nanostar droplets, and calculate from the images the scattering function χ(q)=<ρ(q)ρ(-q)>. We find that the structure is hyperuniform, corresponding to a disordered structure with anomalously small long range density fluctuations, χ(q→0)∼q^α with α=2. Droplet diffusion tends to erase this structure, while measurements of multi-phase nanostar systems show hyperuniformity only occurs within, but not across, liquid species. Overall, our observations are consistent with a hyperuniform structure that is driven by spinodal decomposition, and modulated by Brownian motion. We expect the hyperuniformity exhibited by the model phase separating system of DNA nanostars will provide insight into certain phase-separated structures seen in nature.