Related Experiment Video
Updated: Oct 27, 2025
08:22
Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
7.0K
A theoretical study on the excited-state deactivation paths for the A-5FU dimer
Xue-Fang Yu1, Ting-He Fu, Bo Xiao
1The Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Yantai University, Yantai 264005, People's Republic of China. yuxuefang2008@gmail.com.
Physical Chemistry Chemical Physics : PCCP
|July 22, 2021
Summary
DNA photostability is crucial for organisms. The adenine-5-fluorouracil (A-5FU) dimer
Area of Science:
- Photochemistry
- Molecular Biophysics
- Quantum Chemistry
Background:
- DNA photostability is essential for biological function.
- Adenine-5-fluorouracil (A-5FU) is a modified DNA base pair, replacing a methyl group with fluorine.
- Understanding excited-state decay pathways is key to DNA photostability.
Purpose of the Study:
- To investigate the excited-state decay mechanisms of the A-5FU dimer.
- To explore the roles of proton transfer and out-of-plane twisting in A-5FU excited-state dynamics.
- To compare decay pathways in the 1ππ* and 1nπ* states.
Main Methods:
- Time-Dependent Density Functional Theory (TDDFT) calculations for static properties.
- Non-adiabatic dynamic simulations for excited-state decay.
- Coupled-Cluster (CC2) calculations to validate TDDFT accuracy.
Main Results:
- Double bond deformation (C=C or C=N) in A and 5FU offers an efficient depopulation pathway for excited states.
- These deformation pathways compete effectively with excited-state proton transfer.
- Monomer-like decay mechanisms are significant in weakly hydrogen-bonded DNA base pairs.
Conclusions:
- Out-of-plane twisting and double bond deformations are critical for A-5FU excited-state decay.
- These monomer-like pathways contribute significantly to the photostability of DNA base pairs.
- Provides novel insights into the excited-state dynamics of DNA base pairs and analogues.
Related Concept Videos
01:25Deactivation Processes: Jablonski Diagram
1.1K
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
1.1K
02:13Bond Dissociation Energy and Activation Energy
9.9K
Bond energy is the energy required to break a bond homolytically. These values are usually expressed in units of kcal/mol or kJ/mol and are referred to as bond dissociation energies when given for specific bonds or average bond energies when indicated for a given type of bond over many compounds. Firstly, the bond dissociation energy for a single bond is weaker than that of a double bond, which in turn is weaker than that of a triple bond. Secondly, hydrogen forms relatively strong bonds with...
9.9K
01:11Radical Reactivity: Overview
2.2K
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired...
2.2K
01:24ortho–para-Directing Deactivators: Halogens
6.1K
Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...
6.1K
01:29Atomic Fluorescence Spectroscopy
580
Atomic fluorescence spectroscopy (AFS) is an analytical technique that involves the electronic transitions of atoms in a flame, furnace, or plasma being excited by electromagnetic (EM) radiation. When these atoms absorb energy, they become excited and subsequently release energy as they return to their original state. This emitted light, or "fluorescence," is observed at a right angle to the incident beam. Both absorption and emission processes transpire at distinct wavelengths, which...
580
03:18Nuclear Stability
20.8K
Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together...
To hold positively charged protons together...
20.8K