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First aid kit in some living organisms helps fix DNA after lengthy sun exposure (Vol. 48, No. 5-6)
New study unveils the binding mechanisms of enzymes capable of repairing DNA damaged by UV light before any risk of cellular malfunction sets in
Sunburn in living organisms is caused by ultraviolet (UV) light from the sun damaging the DNA in the cells. Many organisms, however, have an in-built mechanism for repairing the sun damage. This is possible thanks to an enzyme called DNA photolyase, which is so specialised that cryptochrome, a structurally similar molecule, is unable to do the same job. By comparing both types of molecule, physicists can understand precisely how the ability of our enzymes to repair DNA boils down to the most minute structural details. In a study published recently, the authors pinpoint the mechanism by which repair enzymes bind to the damaged site.
K. Aalbæk Jepsen and I. A. Solov'yov, On binding specificity of (6-4) photolyase to a T(6-4)T DNA photoproduct, Eur. Phys. J. D 71, 155 (2017)
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Monodisperse magnetic nanoparticles prepared from block copolymer template (Vol. 48, No. 5-6)
Magnetic nanoparticles are playing an increasing role in biomedical applications, both for diagnosis (e.g. contrast agent in MRI (Magnetic resonance imaging) or for MPI (magnetic particles imaging)) and for therapy thanks to their ability to exert forces and torques on biological species allowing for instance cancer cells destruction or oriented growth of biological tissue.
In order to fabricate magnetic nanoparticles with high monodispersity, required in particular in biomedical imaging, we have developed a new preparation method based on the use of self-assembled block copolymer template.
Such techniques have already been explored for the preparation of patterned media for ultra-high density magnetic recording. However, our requirements substantially differ from those for storage media. A sacrificial layer has to be introduced between the substrate and the diblock copolymer to allow the release of the nanoparticles in solution. For that purpose, an optimized germanium oxide layer was used. The obtained superparamagnetic particles do not agglomerate in solution. They can be made of biocompatible material (magnetite) and exhibit very narrow size dispersion (≈7%). They can be good contrast agents for medical imaging.
M. Morcrette, G. Ortiz, S. Tallegas, H. Joisten, R. Tiron, T. Baron, Y. Hou, S. Lequien, A. Bsiesy and B. Dieny, Fabrication of monodisperse magnetic nanoparticles released in solution using a block copolymer template, J. Phys. D: Appl. Phys. 50, 295001 (2017)
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Astronauts to bring asteroid back into lunar orbit (Vol. 48, No. 5-6)
Italian Space Agency presents plans to develop a robotic solar-powered spacecraft capable of displacing a near-Earth asteroid towards lunar orbit for ease of study
Future space exploration aims to fly further from Earth than ever before. Now, Italian Space Agency scientists have expressed an interest in contributing to the development of robotic technologies to bring an asteroid from beyond lunar orbit back into closer reach in order to better study it. In a paper published recently, the authors make the case for taking part in the robotic phase of the Asteroid Redirect Mission (ARM). In addition to taking manned spaceflights deeper into space than ever before, the proposed mission would also bring some benefit for planetary science. Further, the mission has potential implications for a field called planetary defence. The next step for human space exploration after the International Space Station is to send astronauts on a Near Earth Asteroid by 2025, as planned by NASA. This constitutes an intermediate step towards future manned missions to Mars. The planned ARM mission has been part of the NASA program since 2013.The robotic spacecraft would cruise in deep space towards a near-Earth asteroid, using a technology called advanced Solar Electric Propulsion. Under the proposed plan, Italy would contribute by enhancing the carrying capacity of that spacecraft.
M. Tantardini and E. Flamini, Synergies between human space exploration and science in the asteroid redirect mission and the potential Italian participation in the asteroid redirect robotic mission phase, Eur. Phys. J. Plus 132, 314 (2017)
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Information stored in quantum states of water fragments (Vol. 48, No. 5-6)
Does water have memory? Well, not in the usual sense. But it is known, that if you tear water molecules apart, the remaining fragments can tell you a story about how it happened. To investigate this phenomenon, a plasma reactor producing miniature lightnings in direct contact with water level was constructed. The electrical discharges are powerful enough to cause dissociation of water molecules in various ways. To facilitate the electrical breakdown, the atmosphere in the reactor was replaced by argon.
The water molecule can be broken by impact of sufficiently fast electron, absorption of deep UV photon or previously excited argon atom. Each of these processes has a different energy balance and the remaining energy is partially conserved in quantum states of the water fragments. By careful analysis of the light emitted by the relaxing OH radicals, we can disentangle the respective contributions to the total spectrum and calculate the portion of water molecules undergoing various dissociation mechanisms.
The water fragments really remember what preceded their creation and they let us know by emitting photons. The time scale for "forgetting" depends on the collisional rate, i.e. the pressure. At atmospheric pressure, the information can be kept for several nanoseconds.
J. Voráč, P. Synek, V. Procházka and T. Hoder, State-by-state emission spectra fitting for non-equilibrium plasmas: OH spectra of surface barrier discharge at argon/water interface, J. Phys. D: Appl. Phys. 50, 294002 (2017)
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