Starts 19 Dec 2019 14:00
Ends 19 Dec 2019 16:00
Central European Time
Leonardo Building - Luigi Stasi Seminar Room
The RNA world was a hypothetical time in the evolution of life on Earth when there was no elaborate protein synthesis and RNA emerged as both enzyme and information carrier. In the early Earth, the formation of RNA chains capable of self- copying could have enabled the transmission of genetic information from one generation to the other and, by mutations, the evolution toward more complex molecular machinery. RNA world has been suggested as the missing link between the prebiotic synthesis of biomolecules and the formation of first prokaryotic cells and DNA-based organisms. Nevertheless, this hypothesis is challenged by the fact that complex RNA structures would rapidly degrade under the conditions of the early Earth. Recently, self-copying of single-strand RNA (ssRNA) immobilized on a solid substrate has been observed experimentally at low temperatures. This suggests that prebiotic conditions associated with freezing, rather than ‘‘warm and wet’’ conditions, could have been of crucial importance in an early RNA world on ice. However, an RNA world on ice remains speculative because the interfacial mechanisms of formation and self-copying on ice are hardly accessible by experiments at atomistic resolution. Computer simulations based on atomistic molecular dynamics permit virtual experiments under plausible prebiotic conditions that are inaccessible or extremely costly in real laboratories, complementing the experimental work and driving new research and ideas. After a general overview of the RNA world hypothesis for the origin of life, I shall present results from molecular dynamics simulations of ssRNA at the air/ice interface. This work is, to the best of my knowledge, the first molecular dynamics study of an RNA world on ice surfaces. We observe that the simulated air/ice interfacial environment has an impact of the stability of ssRNA: while the backbone remains anchored to the underlying crystalline structure though long-living hydrogen bonds, the bases (hydrophobic) are solvated in the outer layers of the ice/air interface and exposed to the gas phase. This suggests the possibility of base-pairing with free nucleotide diffusing on the surface of ice or chemical reactions with adsorbed trace gases from a primordial atmosphere. Moreover, we find a smaller number of contacts between the water oxygen and 2-OH’ groups of the sugar moiety compared to supercooled liquid water at the same temperature. The anchoring of the backbone structure and the smaller number of water contacts on ice has kinetic consequences that point to lower susceptibility to hydrolysis for ssRNA on ice, supporting the feasibility of an ancient RNA world on ice as possible scenario for the emergence of life.