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Scanning-probe Single-electron Capacitance Spectroscopy
Published on: July 30, 2013
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Electronic spectroscopy of isolated DNA polyanions
Steven Daly1, Massimiliano Porrini1, Frédéric Rosu2
1Laboratoire Acides Nucléiques: Régulations Naturelle et Artificielle, Université de Bordeaux, Inserm & CNRS (ARNA, U1212, UMR5320), IECB, 2 rue Robert Escarpit, 33607 Pessac, France. v.gabelica@iecb.u-bordeaux.fr.
Faraday Discussions
|April 30, 2019
Summary
Action spectroscopy of DNA ions reveals fragmentation and electron detachment pathways. Electron photodetachment reveals charge state dependence and purine specificity, offering insights into photo-oxidative damage mechanisms.
Area of Science:
- Physical Chemistry
- Biophysical Chemistry
- Spectroscopy
Background:
- UV-vis spectroscopy in solution probes biomolecular structural changes via chromophore environmental shifts.
- Action spectroscopy offers potential for gas-phase ion analysis with enhanced separation capabilities.
Purpose of the Study:
- To investigate the utility of action spectroscopy for studying gas-phase DNA ions.
- To compare fragmentation and electron photodetachment (ePD) pathways in oligonucleotide polyanions.
- To elucidate the relationship between electronic structure, charge state, and photo-induced processes.
Main Methods:
- Systematic study of action spectroscopy on homo-base 6-mer DNA strands (dG6, dA6, dC6, dT6).
- Validation of gas-phase structures using ion mobility spectrometry and infrared ion spectroscopy.
- Measurement of electron binding energies via photoelectron spectroscopy.
- Calculation of electronic photo-absorption spectra.
Main Results:
- Fragmentation-based action spectra closely mirror absorption spectra, resulting from repeated photon absorption and internal conversion.
- Electron photodetachment (ePD) action spectra show charge-state dependence, influenced by electron binding energies.
- ePD is significantly more efficient for purines than pyrimidines, indicating pathway-specific relaxation dynamics.
Conclusions:
- Action spectroscopy, particularly ePD, provides insights into gas-phase DNA ion structure and excited-state relaxation.
- Charge state variations must be considered when comparing ePD spectra for structural deductions.
- The purine-specific ePD mechanism highlights pathways relevant to photo-oxidative damage in nucleic acids.
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