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Abstract:
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Multiple lines of evidence suggest that RNA performed all of the biological functions in the first life forms on earth . These functions included cleavage ,
ligation , polymerization , recognition , binding , and replication . In order to perform these functions , populations of RNA molecules with unevolved sequences must
have been able to fold into compact three dimensional shapes , in unregulated environments , and without the help of proteins . Folding into compact tertiary
structures is difficult because of the high charge density of RNA . Consequently , the ranges of temperature , salinity , pH , and pressure that allow RNA to fold
into functional shapes is very restricted . We use thermodynamic arguments and Brownian dynamics simulations to compute the range of these environmental parameters that will allow RNA to fold . This is a non -trivial calculation due to the formation of an ion atmosphere around RNA that reduces its electric field . The results can be used to clarify the environments in which the transition to life is possible . Our preliminary calculations suggest that environments
with low temperatures ( $0 -50^ \circ C $ ) and high salt concentrations (greater than 100mM ) are the most favorable for unassisted RNA folding and thus the
transition to RNA -based life . Applications of our results include determining the environments on early earth where life formed , assesing the habitability of
Europa , Titan , and (using modeled parameters ) extrasolar planets . |