Ester Formation and Hydrolysis during Wet–Dry Cycles: Generation of Far-from-Equilibrium Polymers in a Model Prebiotic Reaction

Biopolymers exist within living cells as far-from-equilibrium metastable polymers. Living systems must constantly invest energy for biopolymer synthesis. In the earliest stages of life on Earth, the complex molecular machinery that contemporary life employs for the synthesis and maintenance of polymers did not exist. Thus, a major question regarding the origin of life is how the first far-from-equilibrium polymers emerged from a prebiotic “pool” of monomers. Here, we describe a proof-of-principle system, in which l-malic acid monomers form far-from-equilibrium, metastable oligoesters via repeated, cyclic changes in hydration and temperature. Such cycles would have been associated with day–night and/or seasonal cycles on the early Earth. In our model system, sample heating, which promotes water evaporation and ester bond formation, drives polymerization. Even though periodic sample rehydration and heating in the hydrated state promotes ester bond hydrolysis, successive iterations of wet–dry cycles result i...