Protometabolically generated NADH mediates material properties of aqueous dispersions to coacervate microdroplets

Macromolecular assembly between biomolecules dictates the material state of aqueous dispersions like the cytoplasm. The formation of protein precipitates, fibres, or liquid droplets have been associated with the regulation of biochemical function and disease. However, the effect of small molecules and metabolites on tuning phase behaviour remains underexplored. Here we use the protometabolic reduction of NAD ⁺ to NADH by pyruvate to study the effect of NADH production on the phase properties of polyarginine in bicarbonate buffer. Our results show that reduction of NAD ⁺ in the presence of polyarginine can tune the material properties of the dispersion between precipitates, homogeneous solution and liquid droplets depending on the buffer concentration. In-situ droplet formation results in 2-3 times higher reaction rate and NADH yield, compared to homogeneous solution. Our results demonstrate how small molecules can significantly impact material properties in aqueous dispersions and the positive effect of heterogeneous dispersions on primitive metabolic reactions.