TY - JOUR A1 - Kreye, Oliver A1 - Türünc, Oguz A1 - Sehlinger, Ansgar A1 - Rackwitz, Jenny A1 - Meier, Michael A. R. T1 - Structurally diverse polyamides obtained from monomers derived via the Ugi multicomponent reaction JF - Chemistry - a European journal N2 - The combination of the Ugi four-component reaction (Ugi-4CR) with acyclic diene metathesis (ADMET) or thiolene polymerization led to the formation of poly-1-(alkylcarbamoyl) carboxamides, a new class of substituted polyamides with amide moieties in the polymer backbone, as well as its side chains. 10-Undecenoic acid, obtained by pyrolysis of ricinoleic acid, the main fatty acid of castor oil, was used as the key renewable building block. The use of different primary amines, as well as isonitriles (isocyanides) for the described Ugi reactions provided monomers with high structural diversity. Furthermore, the possibility of versatile post-modification of functional groups in the side chains of the corresponding polymers should be of considerable interest in materials science. The obtained monomers were polymerized by ADMET, as well as thiolene, chemistry and all polymers were fully characterized. Finally, ortho-nitrobenzylamide-containing polyamides obtained by this route were shown to be photoresponsive and exhibited a dramatic change of their properties upon irradiation with light. KW - metathesis KW - polyamides KW - polymerization KW - renewable resources KW - Ugi reaction KW - thiol-ene reactions Y1 - 2012 U6 - https://doi.org/10.1002/chem.201103341 SN - 0947-6539 VL - 18 IS - 18 SP - 5767 EP - 5776 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Prinz, Julia A1 - Schreiber, Benjamin A1 - Olejko, Lydia A1 - Oertel, Jana A1 - Rackwitz, Jenny A1 - Keller, Adrian A1 - Bald, Ilko T1 - DNA origami substrates for highly sensitive surface-enhanced raman scattering JF - The journal of physical chemistry letters N2 - DNA nanotechnology holds great promise for the fabrication of novel plasmonic nanostructures and the potential to carry out single-molecule measurements using optical spectroscopy. Here, we demonstrate for the first time that DNA origami nanostructures can be exploited as substrates for surface-enhanced Raman scattering (SERS). Gold nanoparticles (AuNPs) have been arranged into dimers to create intense Raman scattering hot spots in the interparticle gaps. AuNPs (15 nm) covered with TAMRA-modified DNA have been placed at a nominal distance of 25 nm to demonstrate the formation of Raman hot spots. To control the plasmonic coupling between the nanoparticles and thus the field enhancement in the hot spot, the size of AuNPs has been varied from 5 to 28 nm by electroless Au deposition. By the precise positioning of a specific number of TAMRA molecules in these hot spots, SERS with the highest sensitivity down to the few-molecule level is obtained. Y1 - 2013 U6 - https://doi.org/10.1021/jz402076b SN - 1948-7185 VL - 4 IS - 23 SP - 4140 EP - 4145 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Keller, Adrian A1 - Rackwitz, Jenny A1 - Cauet, Emilie A1 - Lievin, Jacques A1 - Körzdörfer, Thomas A1 - Rotaru, Alexandru A1 - Gothelf, Kurt V. A1 - Besenbacher, Flemming A1 - Bald, Ilko T1 - Sequence dependence of electron-induced DNA strand breakage revealed by DNA nanoarrays JF - Scientific reports Y1 - 2014 U6 - https://doi.org/10.1038/srep07391 SN - 2045-2322 VL - 4 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Vogel, Stefanie A1 - Rackwitz, Jenny A1 - Schuerman, Robin A1 - Prinz, Julia A1 - Milosavljevic, Aleksandar R. A1 - Refregiers, Matthieu A1 - Giuliani, Alexandre A1 - Bald, Ilko T1 - Using DNA origami nanostructures to determine absolute cross sections for UV photon-induced DNA strand breakage JF - The journal of physical chemistry letters N2 - We have characterized ultraviolet (UV) photon-induced DNA strand break processes by determination of absolute cross sections for photoabsorption and for sequence-specific DNA single strand breakage induced by photons in an energy range from 6.50 to 8.94 eV. These represent the lowest-energy photons able to induce DNA strand breaks. Oligonudeotide targets are immobilized on a UV transparent substrate in controlled quantities through attachment to DNA origami templates. Photon-induced dissociation of single DNA strands is visualized and quantified using atomic force microscopy. The obtained quantum yields for strand breakage vary between 0.06 and 0.5, indicating highly efficient DNA strand breakage by UV photons, which is clearly dependent on the photon energy. Above the ionization threshold strand breakage becomes clearly the dominant form of DNA radiation damage, which is then also dependent on the nucleotide sequence. Y1 - 2015 U6 - https://doi.org/10.1021/acs.jpclett.5b02238 SN - 1948-7185 VL - 6 IS - 22 SP - 4589 EP - 4593 PB - American Chemical Society CY - Washington ER - TY - THES A1 - Rackwitz, Jenny T1 - A novel approach to study low-energy electron-induced damage to DNA oligonucleotides BT - Influence of DNA sequence, topology and nucleobase modification Y1 - 2016 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 - TY - JOUR A1 - Rackwitz, Jenny A1 - Ranković, Miloš Lj. A1 - Milosavljević, Aleksandar R. A1 - Bald, Ilko T1 - A novel setup for the determination of absolute cross sections for low-energy electron induced strand breaks in oligonucleotides BT - the effect of the radiosensitizer 5-fluorouracil* JF - The European physical journal : D, Atomic, molecular, optical and plasma physics N2 - Low-energy electrons (LEEs) play an important role in DNA radiation damage. Here we present a method to quantify LEE induced strand breakage in well-defined oligonucleotide single strands in terms of absolute cross sections. An LEE irradiation setup covering electron energies <500 eV is constructed and optimized to irradiate DNA origami triangles carrying well-defined oligonucleotide target strands. Measurements are presented for 10.0 and 5.5 eV for different oligonucleotide targets. The determination of absolute strand break cross sections is performed by atomic force microscopy analysis. An accurate fluence determination ensures small margins of error of the determined absolute single strand break cross sections sigma SSB. In this way, the influence of sequence modification with the radiosensitive 5-Fluorouracil (U-5F) is studied using an absolute and relative data analysis. We demonstrate an increase in the strand break yields of U-5F containing oligonucleotides by a factor of 1.5 to 1.6 compared with non-modified oligonucleotide sequences when irradiated with 10 eV electrons. Y1 - 2017 U6 - https://doi.org/10.1140/epjd/e2016-70608-4 SN - 1434-6060 SN - 1434-6079 VL - 71 PB - Springer CY - New York ER - TY - JOUR A1 - Rackwitz, Jenny A1 - Bald, Ilko T1 - Low-energy electron-induced strand breaks in telomere-derived DNA sequences BT - influence of DNA sequence and topology JF - Chemistry - a European journal N2 - During cancer radiation therapy high-energy radiation is used to reduce tumour tissue. The irradiation produces a shower of secondary low-energy (<20 eV) electrons, which are able to damage DNA very efficiently by dissociative electron attachment. Recently, it was suggested that low-energy electron-induced DNA strand breaks strongly depend on the specific DNA sequence with a high sensitivity of G-rich sequences. Here, we use DNA origami platforms to expose G-rich telomere sequences to low-energy (8.8 eV) electrons to determine absolute cross sections for strand breakage and to study the influence of sequence modifications and topology of telomeric DNA on the strand breakage. We find that the telomeric DNA 5′-(TTA GGG)2 is more sensitive to low-energy electrons than an intermixed sequence 5′-(TGT GTG A)2 confirming the unique electronic properties resulting from G-stacking. With increasing length of the oligonucleotide (i.e., going from 5′-(GGG ATT)2 to 5′-(GGG ATT)4), both the variety of topology and the electron-induced strand break cross sections increase. Addition of K+ ions decreases the strand break cross section for all sequences that are able to fold G-quadruplexes or G-intermediates, whereas the strand break cross section for the intermixed sequence remains unchanged. These results indicate that telomeric DNA is rather sensitive towards low-energy electron-induced strand breakage suggesting significant telomere shortening that can also occur during cancer radiation therapy. KW - DNA damage KW - DNA strand breaks KW - low-energy electron KW - radiation therapy KW - telomeric DNA Y1 - 2018 U6 - https://doi.org/10.1002/chem.201705889 SN - 0947-6539 SN - 1521-3765 VL - 24 IS - 18 SP - 4680 EP - 4688 PB - Wiley-VCH CY - Weinheim ER -