Key requirements for the first cells on Earth include the ability to compartmentalize and evolve. Compartmentalization spatially localizes biomolecules from a dilute pool and an evolving cell, which, as it grows and divides, permits mixing and propagation of information to daughter cells. Complex coacervate microdroplets are excellent candidates as primordial cells with the ability to partition and concentrate molecules into their core and support primitive and complex biochemical reactions. However, the evolution of coacervate protocells by fusion, growth and fission has not yet been demonstrated. In this work, a primordial environment initiated the evolution of coacervate-based protocells. Gas bubbles inside heated rock pores perturb the coacervate protocell distribution and drive the growth, fusion, division and selection of coacervate microdroplets. Our findings provide a compelling scenario for the evolution of membrane-free coacervate microdroplets on the early Earth, induced by common gas bubbles within heated rock pores.

Microscale thermophoresis (MST) is av ersatile technique to measure binding affinities of binder-ligand systems,b ased on the directional movement of molecules in atemperature gradient. We extended MST to measure binding kinetics as well as binding affinity in as ingle experiment by increasing the thermal dissipation of the sample.T he kinetic relaxation fingerprints were derived from the fluorescence changes during thermodynamic re-equilibration of the sample after local heating.U sing this method, we measured DNA hybridization on-rates and off-rates in the range 10 4 -10 6 m À1 s À1 and 10 À4 -10 À1 s À1 ,r espectively.W eo bserved the expected exponential dependence of the DNAh ybridization off-rates on salt concentration, strand length and inverse temperature. The measured on-rates showed al inear dependence on salt concentration and weak dependence on strand length and temperature.F or biomolecular interactions with large enthalpic contributions,t he kinetic MST technique offers ar obust, cost-effective and immobilization-free determination of kinetic rates and binding affinity simultaneously,e ven in crowded solutions.

Key requirements for the first cells on Earth include the ability to compartmentalize and evolve. Compartmentalization spatially localizes biomolecules from a dilute pool and an evolving cell which grows and divides permits mixing and propagation of information to daughter cells. Complex coacervate microdroplets are excellent candidates as primordial cells with the ability to partition and concentrate molecules into their core and support primitive and complex biochemical reactions. However, the evolution of coacervate protocells by fusion, growth and fission has not yet been demonstrated. In this work, a primordial environment initiated the evolution of coacervate-based protocells. Gas bubbles inside heated rock pores perturb the coacervate protocell distribution and drive the growth, fusion, division and selection of coacervate microdroplets. This setting provides a primordial non-equilibrium environment. Our findings describe how common gas bubbles within heated rock pores induce the early evolution processes of coacervate-based protocells, providing a compelling scenario for the evolution of membrane-free coacervate microdroplets on the early Earth.

Microscale thermophoresis (MST) is a versatile technique to measure binding affinities of binder–ligand systems, based on the directional movement of molecules in a temperature gradient. We extended MST to measure binding kinetics as well as binding affinity in a single experiment by increasing the thermal dissipation of the sample. The kinetic relaxation fingerprints were derived from the fluorescence changes during thermodynamic re‐equilibration of the sample after local heating. Using this method, we measured DNA hybridization on‐rates and off‐rates in the range 104–106 m−1 s−1 and 10−4–10−1 s−1, respectively. We observed the expected exponential dependence of the DNA hybridization off‐rates on salt concentration, strand length and inverse temperature. The measured on‐rates showed a linear dependence on salt concentration and weak dependence on strand length and temperature. For biomolecular interactions with large enthalpic contributions, the kinetic MST technique offers a robust, cost‐effective and immobilization‐free determination of kinetic rates and binding affinity simultaneously, even in crowded solutions.