The life story of hydrogen peroxide II: a periodic pH and thermochemical drive for the RNA world

Abstract

It is now accepted that primordial non-cellular RNA communities must have been subject to a periodic drive in order to replicate and prosper. We have proposed the oxidation of thiosulfate by hydrogen peroxide as this drive. This reaction system behaves as (i) a thermochemical and (ii) a pH oscillator, and in this work, we unify (i) and (ii) for the first time. We report thermally selfconsistent, dynamical simulations in which the system transitions smoothly from nearly isothermal pH to fully developed thermo-pH oscillatory regimes. We use this oscillator to drive simulated replication of a 39-bp RNA species. Production of replicated duplex under thermo-pH drive was significantly enhanced compared with that under purely thermochemical drive, effectively allowing longer strands to replicate. Longer strands are fitter, with more potential to evolve enzyme activity and resist degradation. We affirm that concern over the alleged toxicity of hydrogen peroxide to life is largely misplaced in the current context, we survey its occurrence in the solar system to motivate its inclusion as a biosignature in the search for life on other worlds and highlight that pH oscillations in a spatially extended, bounded system manifest as the fundamental driving force of life: a proton gradient.

Thiosulfate-hydrogen peroxide redox oscillator as pH driver for ribozyme activity in the RNA world

“…Since the assigned activation energy for this reaction, 50 kJ/mole, is not insignificant we suspect that this system may perform better in the high feed concentration, thermo-pH regime, which was characterised in Ball and Brindley (2015a), and in the following section we test this idea using data for another ribozyme. Table 5 Kinetic and thermochemical parameters derived from data in Hertel and Uhlenbeck (1995).…”

Implications of Microbial Thiosulfate Utilization in Red Clay Sediments of the Central Indian Basin: The Martian Analogy

“…However, hyperthermophilic autotrophs used thiosulfate much earlier as a thermochemical and pH oscillator. This astrobiologically significant reaction let the RNA world to evolve the enzyme systems (Ball & Brindley, ; Hurowitz et al, ). Significant down‐core pH oscillations were apparent in the cores examined, at a range of 6–8 occasionally extending to 5–10, replicating some of the primitive GOE‐like situations.…”

The Life Story of Hydrogen Peroxide III: Chirality and Physical Effects at the Dawn of Life

“…But overall the process works in favour of increasing the average length of D-chains, up to a limit determined by thermal and pH cycling (Ball and Brindley 2015a), and decreasing that of L-chains.…”

“…-In the dynamic thermochemical environment proposed in Ball and Brindley (2015a), thermal cycling and concentration fluctuations of hydrogen peroxide could manifest as relatively strong density gradients. Since the driver of thermophoretic motion is actually the density gradient (Brenner and Bielenberg 2005), thermophoresis would be enhanced.…”

“…Life on earth uses exclusively the D-enantiomer of ribose, the sugar moiety of the ribonucleic acids, and the L-enantiomers of the chiral amino acids. In Ball and Brindley (2014) and in parallel papers to this one (Ball and Brindley 2015a;2015b) we have developed and tested the hypothesis that hydrogen peroxide was both the power source and agent for change in the pre-cellular RNA world, through its role as the THP (thiosulfate-hydrogen peroxide) oscillator providing the essential periodic thermal and pH drive. Here we focus on the structure and properties of hydrogen peroxide and review some of its pertinent physical properties in relation to its direct physicochemical role as an agent for the emergence and evolution of a living RNA world.…”