Polycondensation in the primordial world: A hypothesis for the evolution of the first biopolymers
May 10-15, 2015
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 α-hydroxy 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 in polymer yields and molecular weight distributions in excess of that observed after a single drying cycle. We term this phenomenon a “polymerization ratchet. A mathematical model was developed based on a polycondensation kinetics scheme that takes into the account the effects of different reaction parameters. Using this model, conditions for ratcheting kinetics were predicted and verified experimentally. These results provide insights regarding the potential for very simple systems to exhibit features that would have been necessary for initiation of polymer evolution, before the emergence of genomes or enzymes.
Joseph Schork, Martha Grover, Nicholas Hud, Facundo Fernandez, Sheng Yu, Jay Forsythe, and Ramanarayanan Krishnamurthy, "Polycondensation in the primordial world: A hypothesis for the evolution of the first biopolymers" in "Polymer Reaction Engineering IX", E. Vivaldo-Lima, UNAM; J. Debling, BASF; F. Zaldo-Garcia, CP-COMEX; J. Tsavalas, Univ. of New Hampshire Eds, ECI Symposium Series, (2015). http://dc.engconfintl.org/polymer_rx_eng_IX/42