✍ Scribed by Tureček, František
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Neutralization-reionization mass spectrometry, complemented by ab initio and density-functional theory calculations, provides a powerful tool for the investigation of polyatomic radicals relevant to transient intermediates in the process of radiation or chemically induced DNA damage. Precursor ions for analogues of DNA radicals are prepared by gas-phase protonation of nucleobases or their heterocyclic models. The proton affinity of the gas-phase acid is tuned to the topical proton affinity in the substrate molecule to achieve selective protonation. Femtosecond electron transfer imprints the structure of the precursor ion on to that of the radical. Deuterium labeling, collisional activation and variable-time measurements on a microsecond time-scale are used to study unimolecular dissociations of transient heterocyclic radicals and distinguish them from ion dissociations. Ab initio and densityfunctional theory calculations provide energies which are not available from neutralization-reionization experiments. Topical proton affinities, Franck-Condon energies pertinent to vertical electron transfer, radical stabilities and isomerization barriers are used to elucidate the structures and dissociations of isomeric heterocyclic radicals.
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