TY - JOUR A1 - Ribar, A. A1 - Huber, S. E. A1 - Smiałek, M. A. A1 - Tanzer, K. A1 - Neustetter, M. A1 - Schürmann, Robin A1 - Bald, Ilko A1 - Denifl, S. T1 - Hydroperoxyl radical and formic acid formation from common DNA stabilizers upon low energy electron attachment N2 - 2-Amino-2-(hydroxymethyl)-1,3-propanediol (TRIS) and ethylene-diaminetetraacetic acid (EDTA) are key components of biological buffers and are frequently used as DNA stabilizers in irradiation studies. Such surface or liquid phase studies are done with the aim to understand the fundamental mechanisms of DNA radiation damage and to improve cancer radiotherapy. When ionizing radiation is used, abundant secondary electrons are formed during the irradiation process, which are able to attach to the molecular compounds present on the surface. In the present study we experimentally investigate low energy electron attachment to TRIS and methyliminodiacetic acid (MIDA), an analogue of EDTA, supported by quantum chemical calculations. The most prominent dissociation channel for TRIS is through hydroperoxyl radical formation, whereas the dissociation of MIDA results in the formation of formic and acetic acid. These compounds are well-known to cause DNA modifications, like strand breaks. The present results indicate that buffer compounds may not have an exclusive protecting effect on DNA as suggested previously. KW - DEA KW - DNA KW - Low energy electrons KW - Mass spectrometry PY - 2018 UR - http://pubs.rsc.org/en/content/articlepdf/2018/cp/c7cp07697e DO - https://doi.org/10.1039/c7cp07697e VL - 20 IS - 8 SP - 5578 EP - 5585 PB - Royal Society of Chemistry AN - OPUS4-44703 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ferreira da Silva, F. A1 - do N. Varella, M. T. A1 - Jones, N. C. A1 - Vrönning Hoffmann, S. A1 - Denifl, S. A1 - Bald, Ilko A1 - Kopyra, J. T1 - Electron-Induced Reactions in 3-Bromopyruvic Acid N2 - 3-Bromopyruvic acid (3BP) is a potential anticancer drug, the action of which on cellular metabolism is not yet entirely clear. The presence of a bromine atom suggests that it is also reactive towards low-energy electrons, which are produced in large quantities during tumour Radiation therapy. Detailed knowledge of the interaction of 3BP with secondary electrons is a prerequisite to gain a complete picture of the effects of 3BP in different forms of Cancer therapy. Herein, dissociative electron attachment (DEA) to 3BP in the gas phase has been studied both experimentally by using a crossed-beam setup and theoretically through scattering and quantum chemical calculations. These results are complemented by a vacuum ultraviolet absorption spectrum. The main fragmentation channel is the formation of Br@ close to 0 eV and within several resonant features at 1.9 and 3–8 eV. At low electron energies, Br@ formation proceeds through s* and p* shape resonances, and at higher energies through core-excited resonances. It is found that the electron-capture cross-section is clearly increased compared with that of non-brominated pyruvic acid, but, at the same time, fragmentation reactions through DEA are significantly altered as well. The 3BP transient negative ion is subject to a lower number of fragmentation reactions than those of pyruvic acid, which indicates that 3BP could indeed act by modifying the electron-transport chains within oxidative phosphorylation. It could also act as a radio-sensitiser. KW - Density functional calculations KW - Dissociative electron attachment KW - Drug discovery KW - Gas-phase reactions KW - Sensitizers PY - 2019 DO - https://doi.org/10.1002/chem.201806132 SN - 0947-6539 VL - 25 IS - 21 SP - 5498 EP - 5506 PB - WILEY-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-48003 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schürmann, Robin Mathis A1 - Tsering, Thupten A1 - Tanzer, Katrin A1 - Denifl, Stephan A1 - Kumar, S.V.K. A1 - Bald, Ilko T1 - Resonant Formation of Strand Breaks in Sensitized Oligonucleotides Induced by Low-Energy Electrons (0.5–9 eV) N2 - Halogenated nucleobases are used as radiosensitizers in cancer radiation therapy, enhancing the reactivity of DNA to secondary low-energy electrons (LEEs). LEEs induce DNA strand breaks at specific energies (resonances) by dissociative electron attachment (DEA). Although halogenated nucleobases show intense DEA resonances at various electron energies in the gas phase, it is inherently difficult to investigate the influence of halogenated nucleobases on the actual DNA strand breakage over the broad range of electron energies at which DEA can take place (<12 eV). By using DNA origami nanostructures, we determined the energy dependence of the strand break cross-section for oligonucleotides modified with 8-bromoadenine ((8Br)A). These results were evaluated against DEA measurements with isolated (8Br)A in the gas phase. Contrary to expectations, the major contribution to strand breaks is from resonances at around 7 eV while resonances at very low energy (<2 eV) have little influence on strand breaks. KW - Dissociative electron attachment KW - DNA damage KW - DNA nanotechnology KW - Low energy electrons PY - 2017 DO - https://doi.org/10.1002/anie.201705504 SN - 1433-7851 SN - 1521-3773 VL - 56 IS - 36 SP - 10952 EP - 10955 PB - Wiley AN - OPUS4-41850 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schürmann, Robin A1 - Tsering, Thupten A1 - Tanzer, Katrin A1 - Denifl, Stephan A1 - Kumar, S.V.K. A1 - Bald, Ilko T1 - Resonante Bildung von Strangbrüchen in sensibilisierten Oligonukleotiden induziert durch niederenergetische Elektronen (0.5–9.0 eV) N2 - In der Krebs-Strahlentherapie werden halogenierte Nukleinbasen als Radiosensibilisatoren eingesetzt, um die Reaktivität der DNA gegenüber niederenergetischen Elektro- nen (NEEs) zu erhöhen. NEEs erzeugen DNA-Strangbrüche bei spezifischen Energien (Resonanzen) durch dissoziative Elektronenanlagerung (DEA). Obwohl halogenierte Nukle- inbasen intensive DEA-Resonanzen bei verschiedenen Elek-tronenenergien in der Gasphase aufweisen, kann der Einfluss der halogenierten Nukleinbasen auf tatsächliche DNA-Strangbrüche grundsätzlich nur schwer über den Energiebereich, in dem DEA stattfindet (< 12 eV), untersucht werden. Mithilfe von DNA-Origami-Nanostrukturen haben wir die Energieabhängigkeit der Wirkungsquerschnitte für DNA-Strangbrüche von Oligonukleotiden bestimmt, die mit 8- Bromadenin (8BrA) modifiziert wurden. Diese Ergebnisse wurden mit DEA-Messungen an isoliertem 8BrA in der Gas-phase verglichen. Entgegen der Erwartungen wird der Großteil der Strangbrüche durch Resonanzen um 7 eV hervorgerufen, wohingegen der Einfluss von Resonanzen bei sehr niedrigen Energien (< 2eV) auf die Strangbrüche gering ist. KW - DNA Schäden KW - Niederenergetische Elektronen KW - DNA Nanotechnologie KW - Dissoziative Elektronen Anlagerung PY - 2017 DO - https://doi.org/10.1002/ange.201705504 SN - 1521-3757 SN - 0044-8249 VL - 129 IS - 36 SP - 11094 EP - 11098 PB - Wiley AN - OPUS4-41851 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -