29 Novembre 2018 - 11h
Marco Saitta, Sorbonne Université, Paris, France
Lieu : LCQB Kitchen, Bâtiment C, 4ème étage.
Résumé : Computational approaches are nowadays a full, self-standing branch of chemistry, both for their quantum-based (“ab initio”) accuracy, and for its multiscale extent. In prebiotic chemistry, however, due to the instrinsic complexity of the chemical problems, ab initio atomistic simulations have so far had a limited impact, with the exception of a few relevant studies, including the elucidation of the chemical interactions between biomolecules with surfaces, such as ice and minerals, or the simulation of the effect of the pressure/temperature shock waves induced by meteorite impacts in the early Earth. Surprisingly, even the celebrated Miller experiments, which historically reported on the spontaneous formation of amino-acids from a mixture of simple molecules reacting under an electric discharge, have never been studied at the quantum atomistic level.
Here we set the general problem of chemical networks within new topology-based concepts, using search algorithms and social network data analysis. This allows a very efficient definition of reaction coordinates even in the complex chemical environments which are typical of likely prebiotic scenarii. We thus report on the first ab initio computer simulations, based on quantum physics and a fully atomistic approach, of Miller-like experiments in the condensed phase. Our study  shows that glycine spontaneously form from mixtures of simple molecules once an electric field is switched on. We identify formic acid and formamide  as key intermediate products of the early steps of the Miller reactions, and the crucible of formation of complex biological molecules, as confirmed by our recent experimental and theoretical study on high-energy chemistry of formamide . From a broader chemical perspective, we show that formamide plays the role of hub of a complex reaction network in both the gas and the condensed phase . We are now going on a larger scale, studying the atomistic mechanisms of RNA nucleotides synthesis , meteoritic amino acids  and sugars  in fully realistic prebiotic solution environments. All these results pave the way to novel computational approaches in the research of the chemical origins of life.
Pour plus d'informations, voir la page du labo.
 Saitta AM and Saija F (2014) Proceedings of the National Academy of Sciences USA 111:13768-13773.
 Saitta AM, Saija F, Pietrucci F, and Guyot F (2015) Proceedings of the National Academy of Sciences USA 112, E343-E343.
 Ferus M et al. (2017) Proceedings of the National Academy of Sciences USA, 114:4306-4311.
 Pietrucci F and Saitta AM (2015) Proceedings of the National Academy of Sciences USA 112, 15030-15035.
 Perez-Villa A et al. (2018) J. Phys. Chem. Lett. 9, 4981–4987.
 Pietrucci F et al. (2018) ACS Earth Space Chem 2, 588-598.
 Cassone G et al. (2018) Chem Comm 54, 3211.