Solvation and Stabilization of Single Strand RNA at the Air/ice Interface Support a Primordial RNA World on Ice

Outstanding questions about the RNA world hypothesis for the emergence of life
on Earth concern the stability and self-replication of prebiotic aqueous RNA.
Recent experimental work has suggested that solid substrates and low
temperatures could help resolve these issues. Here, we use classical molecular
dynamics simulations to explore the possibility that the substrate is ice itself. We
find that at -20 C, a quasi-liquid layer at the air/ice interface solvates a short (8-
nucleotide) RNA strand such that phosphate groups tend to anchor to specific
points of the underlying crystal lattice, lengthening the strand. Hydrophobic bases,
meanwhile, tend to migrate to the air/ice interface. Further, contacts between
solvent water and ribose 2-OH’ groups are found to occur less frequently for RNA
on ice than for aqueous RNA at the same temperature; this reduces the likelihood
of deprotonation of the 2-OH’ and its subsequent nucleophilic attack on the
phosphate diester. The implied enhanced resistance to hydrolysis, in turn, could
increase opportunities for polymerization and self-copying. These findings thus
offer the possibility of a role for an ancient RNA world on ice distinct from that
considered in extant elaborations of the RNA world hypothesis. This work is, to the
best of our knowledge, the first molecular dynamics study of RNA on ice