| Autor: |
Chomicz-Mańka L; Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland., Czaja A; Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland., Falkiewicz K; Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland., Zdrowowicz M; Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland., Biernacki K; Department of Organic Chemistry, Faculty of Chemistry, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland., Demkowicz S; Department of Organic Chemistry, Faculty of Chemistry, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland., Izadi F; Institut für Ionenphysik und Angewandte Physik and Center for Biomolecular Sciences Innsbruck, Leopold-Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria., Arthur-Baidoo E; Institut für Ionenphysik und Angewandte Physik and Center for Biomolecular Sciences Innsbruck, Leopold-Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria., Denifl S; Institut für Ionenphysik und Angewandte Physik and Center for Biomolecular Sciences Innsbruck, Leopold-Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria., Zhu Z; Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States., Tufekci BA; Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States., Harris R; Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States., Bowen KH; Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States., Rak J; Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland. |
| Abstrakt: |
Single-strand breaks (SSBs) induced via electron attachment were previously observed in dry DNA under ultrahigh vacuum (UHV), while hydrated electrons were found not able to induce this DNA damage in an aqueous solution. To explain these findings, crossed electron-molecular beam (CEMB) and anion photoelectron spectroscopy (aPES) experiments coupled to density functional theory (DFT) modeling were used to demonstrate the fundamental importance of proton transfer (PT) in radical anions formed via electron attachment. Three molecular systems were investigated: 5'-monophosphate of 2'-deoxycytidine (dCMPH), where PT in the electron adduct is feasible, and two ethylated derivatives, 5'-diethylphosphate and 3',5'-tetraethyldiphosphate of 2'-deoxycytidine, where PT is blocked due to substitution of labile protons with the ethyl residues. CEMB and aPES experiments confirmed the cleavage of the C3'/C5'-O bond as the main dissociation channel related to electron attachment in the ethylated derivatives. In the case of dCMPH, however, electron attachment (in the aPES experiments) yielded its parent (intact) radical anion, dCMPH - , suggesting that its dissociation was inhibited. The aPES-measured vertical detachment energy of the dCMPH - was found to be 3.27 eV, which agreed with its B3LYP/6-31++G(d,p)-calculated value and implied that electron-induced proton transfer (EIPT) had occurred during electron attachment to the dCMPH model nucleotide. In other words, EIPT, subduing dissociation, appeared to be somewhat protective against SSB. While EIPT is facilitated in solution compared to the dry environment, the above findings are consistent with the stability of DNA against hydrated electron-induced SSB in solution versus free electron-induced SSB formation in dry DNA. |
