STUDYING THE REACTIVITY OF URACIL IN THE GAS PHASE: STATISTICAL vs. NON-STATISTICAL APPROACH

International audienceØ RRKM and KINETIC MONTE CARLO (KMC) SIMULATIONS : statistical reactivity. Ø INTRODUCTION-NH 3-HNCO Ensemble of trajectories V = V ion + V Ar-ion QM MM Potential energy function Ø QM-MM CHEMICAL DYNAMICS SIMULATIONS [1] : non-statistical mechanisms Collision system Ø RESULTS • Studying the reactivity of biomolecules in the gas phase allows to get rid of the effects of the environment: intrinsic properties of the molecule. • System: Uracil in DNA has cytotoxic and mutagenic potential. AM1, PM3 and DFT Collision gas Fragment ion Fragments ions (product ions) Activated fragment ion (continues to fragment) Fragmenting ion Activated ion Precursor ion Neutral loss Ø ESI-MS/MS: mass of the fragments. Collision cell Ø Our AIM • Explain non-statistical and statistical reactivity of protonated Uracil in the gas phase and obtain predictive MS-MS spectra. • For trajectories that did not react before IVR (intramolecular vibrational relaxation) takes place but have enough energy to react later on. • Following automatic protocol [3] to find all fragmentation pathways, TSs and minima. Then this is used as input fot RRKM and KMC simulations. (1) (6)-CO loss (m/z 85) (2) (3) (4) (5) from RRKM analysis: H + transfer ns (out of simulation time) NH 3 loss H 2 O loss React.