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      Hydrogen peroxide thermochemical oscillator as driver for primordial RNA replication

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          Abstract

          This paper presents and tests a previously unrecognised mechanism for driving a replicating molecular system on the prebiotic earth. It is proposed that cell-free RNA replication in the primordial soup may have been driven by self-sustained oscillatory thermochemical reactions. To test this hypothesis a well-characterised hydrogen peroxide oscillator was chosen as the driver and complementary RNA strands with known association and melting kinetics were used as the substrate. An open flow system model for the self-consistent, coupled evolution of the temperature and concentrations in a simple autocatalytic scheme is solved numerically, and it is shown that thermochemical cycling drives replication of the RNA strands. For the (justifiably realistic) values of parameters chosen for the simulated example system, the mean amount of replicant produced at steady state is 6.56 times the input amount, given a constant supply of substrate species. The spontaneous onset of sustained thermochemical oscillations via slowly drifting parameters is demonstrated, and a scheme is given for prebiotic production of complementary RNA strands on rock surfaces.

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          Most cited references 13

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          The "strong" RNA world hypothesis: fifty years old.

          This year marks the 50(th) anniversary of a proposal by Alex Rich that RNA, as a single biopolymer acting in two capacities, might have supported both genetics and catalysis at the origin of life. We review here both published and previously unreported experimental data that provide new perspectives on this old proposal. The new data include evidence that, in the presence of borate, small amounts of carbohydrates can fix large amounts of formaldehyde that are expected in an environment rich in carbon dioxide. Further, we consider other species, including arsenate, arsenite, phosphite, and germanate, that might replace phosphate as linkers in genetic biopolymers. While linkages involving these oxyanions are judged to be too unstable to support genetics on Earth, we consider the possibility that they might do so in colder semi-aqueous environments more exotic than those found on Earth, where cosolvents such as ammonia might prevent freezing at temperatures well below 273 K. These include the ammonia-water environments that are possibly present at low temperatures beneath the surface of Titan, Saturn's largest moon.
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            Pyrite-induced hydrogen peroxide formation as a driving force in the evolution of photosynthetic organisms on an early earth.

            The remarkable discovery of pyrite-induced hydrogen peroxide (H2O2) provides a key step in the evolution of oxygenic photosynthesis. Here we show that H2O2 can be generated rapidly via a reaction between pyrite and H2O in the absence of dissolved oxygen. The reaction proceeds in the dark, and H2O2 levels increase upon illumination with visible light. Since pyrite was stable in most photic environments prior to the rise of O2 levels, this finding represents an important mechanism for the formation of H2O2 on early Earth.
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              Exponential DNA replication by laminar convection.

              It is shown that laminar thermal convection can drive a chain reaction of DNA replication. The convection is triggered by a constant horizontal temperature gradient, moving molecules along stationary paths between hot and cold regions. This implements the temperature cycling for the classical polymerase chain reaction (PCR). The amplification is shown to be exponential and reaches 100,000-fold gains within 25 min. Besides direct applications, the mechanism might have implications for the molecular evolution of life.
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                Author and article information

                Journal
                16 February 2014
                2014-03-05
                Article
                10.1098/rsif.2013.1052
                1402.3875

                http://arxiv.org/licenses/nonexclusive-distrib/1.0/

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                Submitted 14 Nov 2013 to J. Roy. Soc. Interface, accepted in final form 25 Feb 2014. An article on this paper appears on https://theconversation.com/au. A new recipe for primordial soup on the pre-biotic earth may help answer questions about the origin of life, and explain why new life does not emerge from non-living precursors on the modern earth
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                Comments

                IN THE beginning, there were no living cells and no proteins in the primordial soup on the pre-biotic earth. The ‘RNA World’ hypothesis holds that cell-free RNA communities grew in rock pores around hydrothermal vents and replicated and evolved, before the evolution of DNA, proteins and cell membranes. But cell-free RNA replication requires thermal cycling - heating to separate base-paired double strands and a cooling phase to anneal complementary strands into newly replicated double helixes. This fact seems to have been completely overlooked in most hypotheses about the origin of life. In this paper we proposed and tested the hypothesis that thermal cycling to drive cell-free RNA replication and amplification in this environment may have been provided by a natural hydrogen peroxide thermochemical oscillator. This also provides a mechanism for natural selection and molecular evolution. Hydrogen peroxide is believed also to occur abundantly on Jupiter’s moon Europa, and formerly on Mars, which is suggestive that these planetary bodies may have evolved their own RNA worlds! Our results also may answer the (previously unanswerable) question of why new life does not emerge from non-living precursors on the modern earth: Quite simply there are no longer the amounts of hydrogen peroxide around that were there in the good old days! The breakthrough of this research was obtained by applying insights gained from applied mathematics and chemical engineering to a fundamental problem of the origin of life. It demonstrates that an interdisciplinary approach can make game-changing advances in this field, one of the biggest open problems.
                2014-05-20 14:19 UTC
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