Fig. 1: Active droplets scheme.
From: Active coacervate droplets are protocells that grow and resist Ostwald ripening
The pyruvate kinase-catalyzed (PyK) conversion of ADP to ATP, combined with the liquid–liquid phase separation of ATP-K72 complexes, is a minimal translation of an active droplet. In this system, ADP is the substrate, and ATP (together with the lysine-rich protein K72) is the droplet material. We fuel the droplets by manual addition of the second substrate, PEP. The waste, pyruvate, is not re-used in our setup. The local increase in the amount of ATP inside the droplets causes the recruitment of more protein, leading to droplet growth. Growth may compete with other active (nucleation) and passive (coalescence, Ostwald ripening) processes that need to be distinguished experimentally.
