Light-Responsive Mononucleotide Coacervates.

Liquid-liquid phase separation (LLPS) is central to the formation of biomolecular condensates in modern cells and is also explored as a mechanism for assembling protocells. Phase-separated droplets provide dynamic micro-environments that concentrate reactants, enhance reactions, and allow molecular exchange, essential for both cellular regulation, and adaptive compartmentalization. While modern cells achieve dynamic LLPS through enzymatic and metabolic pathways, protocells may be designed to harness external stimuli such as pH, temperature, redox potential, or light. However, existing studies of light-responsive coacervates rely on complex biomolecules, limiting their use as minimal platforms of energy-driven phase separation. Here, we develop a minimal system of light-responsive coacervates composed of low-molecular-weight species: mononucleotides and azobenzene-based amphiphiles with varying charge valency. These coacervates undergo reversible phase transitions through azobenzene photoisomerization, with their behavior governed by charge valency and nucleotide structure. We demonstrate that coacervates formed with high-valency azobenzenes remain stable under UV irradiation but exhibit significant property changes, while those with low-valency azobenzenes dissolve, enabling light-controlled nucleotide release. Additionally, we achieved hierarchical droplet organization and light-actuated biomolecular localization within multiphase systems. Overall, these findings establish a minimal platform for designing light-responsive synthetic protocells, providing insights into dynamic compartmentalization in de novo life-like systems.