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Is UV-Induced Electron-Driven Proton Transfer Active in a Chemically Modified A·T DNA Base Pair?
Katharina Röttger1, Hugo J B Marroux1, Arsène F M Chemin1
1School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K.
The Journal of Physical Chemistry. B
|April 11, 2017
Summary
This study investigated UV-induced electron-driven proton transfer (EDPT) in modified adenine-thymine DNA base pairs. Researchers found no clear evidence for EDPT in 8tBA·T pairs, suggesting monomer-like dynamics dominate.
Area of Science:
- Photochemistry
- Spectroscopy
- DNA base pairing
Background:
- Understanding DNA photodynamics is crucial for photobiology and photomedicine.
- Electron-driven proton transfer (EDPT) is a proposed mechanism in DNA excited-state relaxation.
- Adenine-thymine (A·T) base pairs are fundamental to DNA structure and function.
Purpose of the Study:
- To investigate the role of EDPT in the excited-state dynamics of a chemically modified A·T DNA base pair.
- To synthesize and characterize a modified adenine derivative (8tBA) favoring Watson-Crick (WC) pairing.
- To differentiate between EDPT and other relaxation pathways in A·T base pairs.
Main Methods:
- Transient electronic and vibrational absorption spectroscopies were employed.
- A modified adenine derivative, 8-(tert-butyl)-9-ethyladenine (8tBA), was synthesized.
- Spectroscopic analysis of 8tBA and silyl-protected thymidine in chloroform.
Main Results:
- No clear spectroscopic or kinetic evidence for EDPT was found in 8tBA·T pairs.
- Ultrafast EDPT (sub-100 fs) could not be definitively ruled out.
- Monomer-like dynamics appear to dominate the excited-state relaxation of 8tBA·T.
Conclusions:
- The study suggests EDPT is not a dominant pathway in the excited-state relaxation of the investigated 8tBA·T base pair.
- The findings contrast with previous observations in guanine-cytosine (G·C) pairs.
- Further investigation may be needed to fully elucidate ultrafast EDPT contributions.
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