Related Experiment Video
Updated: Mar 29, 2026

Uracil-DNA Glycosylase Assay by Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry Analysis
Published on: April 22, 2022
On the N1-H and N3-H Bond Dissociation in Uracil by Low Energy Electrons: A CASSCF/CASPT2 Study
Israel González-Ramírez1, Javier Segarra-Martí1, Luis Serrano-Andrés1
1Instituto de Ciencia Molecular, Universitat de València , P.O. Box 22085, 46071 València, Spain.
Abstract:
The dissociative electron-attachment (DEA) phenomena at the N1-H and N3-H bonds observed experimentally at low energies (<3 eV) in uracil are studied with the CASSCF/CASPT2 methodology. Two valence-bound π(-) and two dissociative σ(-) states of the uracil anionic species, together with the ground state of the neutral molecule, are proven to contribute to the shapes appearing in the experimental DEA cross sections. Conical intersections (CI) between the π(-) and σ(-) are established as the structures which activate the DEA processes. The N1-H and N3-H DEA mechanisms in uracil are described, and experimental observations are interpreted on the basis of two factors: (1) the relative energy of the (U-H)(-) + H fragments obtained after DEA with respect to the ground-state equilibrium structure (S0) of the neutral molecule (threshold for DEA) and (2) the relative energy of the CIs also with respect to S0 (band maxima). The π1(-) state is found to be mainly responsible for the N1-H bond breaking, whereas the π2(-) state is proved to be involved in the cleavage of the N3-H bond.
Related Concept Videos
UV–Vis Spectroscopy: Molecular Electronic Transitions
Radical Formation: Homolysis
Nucleotide Excision Repair
Nucleotide Excision Repair
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
IR and UV–Vis Spectroscopy of Aldehydes and Ketones
E1 Reaction: Kinetics and Mechanism

