TY  - JOUR
A1  - Vogel, Stefanie
A1  - Ebel, Kenny
A1  - Schürmann, Robin Mathis
A1  - Heck, Christian
A1  - Meiling, Till
A1  - Milosavljevic, Aleksandar R.
A1  - Giuliani, Alexandre
A1  - Bald, Ilko
T1  - Vacuum-UV and Low-Energy Electron-Induced DNA Strand Breaks
BT  - Influence of the DNA Sequence and Substrate
JF  - ChemPhysChem : a European journal of chemical physics and physical chemistry
N2  - DNA is effectively damaged by radiation, which can on the one hand lead to cancer and is on the other hand directly exploited in the treatment of tumor tissue. DNA strand breaks are already induced by photons having an energy below the ionization energy of DNA. At high photon energies, most of the DNA strand breaks are induced by low-energy secondary electrons. In the present study we quantified photon and electron induced DNA strand breaks in four different 12mer oligonucleotides. They are irradiated directly with 8.44 eV vacuum ultraviolet (VUV) photons and 8.8 eV low energy electrons (LEE). By using Si instead of VUV transparent CaF2 as a substrate the VUV exposure leads to an additional release of LEEs, which have a maximum energy of 3.6 eV and can significantly enhance strand break cross sections. Atomic force microscopy is used to visualize strand breaks on DNA origami platforms and to determine absolute values for the strand break cross sections. Upon irradiation with 8.44 eV photons all the investigated sequences show very similar strand break cross sections in the range of 1.7-2.3x10(-16) cm(2). The strand break cross sections for LEE irradiation at 8.8 eV are one to two orders of magnitude larger than the ones for VUV photons, and a slight sequence dependence is observed. The sequence dependence is even more pronounced for LEEs with energies <3.6 eV. The present results help to assess DNA damage by photons and electrons close to the ionization threshold.
KW  - DNA origami
KW  - DNA radiation damage
KW  - DNA strand breaks
KW  - low-energy electrons
KW  - vacuum-UV radiation
Y1  - 2019
U6  - https://doi.org/10.1002/cphc.201801152
SN  - 1439-4235
SN  - 1439-7641
VL  - 20
IS  - 6
SP  - 823
EP  - 830
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Rackwitz, Jenny
A1  - Kopyra, Janina
A1  - Dabkowska, Iwona
A1  - Ebel, Kenny
A1  - Rankovic, MiloS Lj.
A1  - Milosavljevic, Aleksandar R.
A1  - Bald, Ilko
T1  - Sensitizing DNA Towards Low-Energy Electrons with 2-Fluoroadenine
JF  - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition
N2  - 2-Fluoroadenine ((2F)A) is a therapeutic agent, which is suggested for application in cancer radiotherapy. The molecular mechanism of DNA radiation damage can be ascribed to a significant extent to the action of low-energy (<20 eV) electrons (LEEs), which damage DNA by dissociative electron attachment. LEE induced reactions in (2F)A are characterized both isolated in the gas phase and in the condensed phase when it is incorporated into DNA. Information about negative ion resonances and anion-mediated fragmentation reactions is combined with an absolute quantification of DNA strand breaks in (2F)A-containing oligonucleotides upon irradiation with LEEs. The incorporation of (2F)A into DNA results in an enhanced strand breakage. The strand-break cross sections are clearly energy dependent, whereas the strand-break enhancements by (2F)A at 5.5, 10, and 15 eV are very similar. Thus, (2F)A can be considered an effective radiosensitizer operative at a wide range of electron energies.
KW  - ab initio calculations
KW  - dissociative electron attachment
KW  - DNA origami
KW  - DNA radiation damage
KW  - fludarabine
Y1  - 2016
U6  - https://doi.org/10.1002/anie.201603464
SN  - 1433-7851
SN  - 1521-3773
VL  - 55
SP  - 10248
EP  - 10252
PB  - Wiley-VCH
CY  - Weinheim
ER  -