Search

Poly-N-isopropylacrylamide colloidal arrays are exploited for site-selective self-assembly of gold nanoparticles on large areas. The soft colloids host the drying process of gold nanoparticle dispersion droplets and leave room for capillary convection and Marangoni convection flow paving the road to a simple bottom-up fabrication strategy for nanostructure arrays.

3-Bromopyruvic acid (3BP) is a potential anti-cancer 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 σ* and π* 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.

High-energy radiation is used in combination with radiosensitizing therapeutics to treat cancer. The most common radiosensitizers are halogenated nucleosides and cisplatin derivatives, and recently also metal nanoparticles have been suggested as potential radiosensitizing agents. The radiosensitizing action of these compounds can at least partly be ascribed to an enhanced reactivity towards secondary low-energy electrons generated along the radiation track of the high-energy primary radiation, or to an additional emission of secondary reactive electrons close to the tumor tissue. This is referred to as physico-chemical radiosensitization. In this Concept article we present current experimental methods used to study fundamental processes of physico-chemical radiosensitization and discuss the most relevant classes of radiosensitizers. Open questions in the current discussions are identified and future directions outlined, which can lead to optimized treatment protocols or even novel therapeutic concepts.

During cancer radiation therapy high‐energy radiation is used to reduce tumour tissue. The irradiation produces a shower of secondary low‐energy (

In der Krebs-Strahlentherapie werden halogenierte Nukleinbasen als Radiosensibilisatoren eingesetzt, um die Reaktivitat der DNA gegenuber niederenergetischen Elektro- nen (NEEs) zu erhohen. NEEs erzeugen DNA-Strangbruche 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 tatsachliche DNA-Strangbruche grundsatzlich nur schwer uber den Energiebereich, in dem DEA stattfindet (< 12 eV), untersucht werden. Mithilfe von DNA-Origami-Nanostrukturen haben wir die Energieabhangigkeit der Wirkungsquerschnitte fur DNA-Strangbruche 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 Grosteil der Strangbruche durch Resonanzen um 7 eV hervorgerufen, wohingegen der Einfluss von Resonanzen bei sehr niedrigen Energien (< 2eV) auf die Strangbruche gering ist.

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 (

DNA-Origami-Nanostrukturen sind vielseitig anwendbare Hilfsmittel, die genutzt werden konnen, um Funktionalitaten mit hoher lokaler Kontrolle anzuordnen. Hier zeigen wir, dass DNA-Origami-Substrate genutzt werden konnen, um die Faltung bestimmter Guanin(G)-Quadruplex-Strukturen zu unterdrucken. Die Faltung von Telomer-DNA zu G-Quadruplexen in Gegenwart einwertiger Kationen (z. B. Na+ und K+) wird derzeit zur Detektion von K+-Ionen genutzt, allerdings mit ungenugender Selektivitat gegenuber Na+. Mithilfe von FRET zwischen zwei organischen Farbstoffen, die am 3′- und 5′-Ende der Telomer-DNA immobilisiert werden, zeigen wir, dass die G-Quadruplex-Faltung auf DNA-Origami-Strukturen in Gegenwart von Natriumionen sterisch gehindert wird. Dadurch stellt die an DNA-Origami-Strukturen gebundene Telomer-DNA ein hochempfindliches und selektives Detektionssystem fur Kaliumionen dar, sogar in Gegenwart hoher Natriumionenkonzentration.

Udgivelsesdato: 2009