[Show abstract][Hide abstract] ABSTRACT: The electronic structure of DNA is determined by its nucleotide sequence, which is for instance exploited in molecular electronics. Here we demonstrate that also the DNA strand breakage induced by low-energy electrons (18 eV) depends on the nucleotide sequence. To determine the absolute cross sections for electron induced single strand breaks in specific 13 mer oligonucleotides we used atomic force microscopy analysis of DNA origami based DNA nanoarrays. We investigated the DNA sequences 59-TT(XYX) 3 TT with X 5 A, G, C and Y 5 T, BrU 5-bromouracil and found absolute strand break cross sections between 2.66 ? 10 214 cm 2 and 7.06 ? 10 214 cm 2 . The highest cross section was found for 59-TT(ATA) 3 TT and 59-TT(ABrUA) 3 TT, respectively. BrU is a radiosensitizer, which was discussed to be used in cancer radiation therapy. The replacement of T by BrU into the investigated DNA sequences leads to a slight increase of the absolute strand break cross sections resulting in sequence-dependent enhancement factors between 1.14 and 1.66. Nevertheless, the variation of strand break cross sections due to the specific nucleotide sequence is considerably higher. Thus, the present results suggest the development of targeted radiosensitizers for cancer radiation therapy. D NA exhibits nucleotide sequence dependent electronic properties, which affect its charge transport prop-erties, UV stability, and sensitivity toward radiation 1–3 . These properties manifest themselves in quantities such as the ionization potential 4,5 , in the dynamics of the electronic states (excitonic coupling, lifetime of excited states) 1,6 , but also in the reactivity for instance towards low-energy electrons 3,7,8 . A large number of secondary electrons is formed along the radiation track of high-energy radiation, which is routinely applied in radiation therapy to kill tumor tissue. These low-energy electrons (LEEs) have a most probable energy around 10 eV 9 and are able to directly induce DNA single and double strand breaks (SSBs and DSBs) via dissociative electron attachment through the formation of negative ion resonances 10–12
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: The combination of the Ugi four-component reaction (Ugi-4CR) with acyclic diene metathesis (ADMET) or thiol-ene 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 thiol-ene, 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.
Chemistry - A European Journal 03/2012; 18(18):5767-76. · 5.93 Impact Factor