Recruitment kinetics of DNA repair proteins Mdc1 and Rad52 but not 53BP1 depend on damage complexity.

The recruitment kinetics of double-strand break (DSB) signaling and repair proteins Mdc1, 53BP1 and Rad52 into radiation-induced foci was studied by live-cell fluorescence microscopy after ion microirradiation. To investigate the influence of damage density and complexity on recruitment kinetics, which cannot be done by UV laser irradiation used in former studies, we utilized 43 MeV carbon ions with high linear energy transfer per ion (LET = 370 keV/µm) to create a large fraction of clustered DSBs, thus forming complex DNA damage, and 20 MeV protons with low LET (LET = 2.6 keV/µm) to create mainly isolated DSBs. Kinetics for all three proteins was characterized by a time lag period T(0) after irradiation, during which no foci are formed. Subsequently, the proteins accumulate into foci with characteristic mean recruitment times τ(1). Mdc1 accumulates faster (T(0) = 17 ± 2 s, τ(1) = 98 ± 11 s) than 53BP1 (T(0) = 77 ± 7 s, τ(1) = 310 ± 60 s) after high LET irradiation. However, recruitment of Mdc1 slows down (T(0) = 73 ± 16 s, τ(1) = 1050 ± 270 s) after low LET irradiation. The recruitment kinetics of Rad52 is slower than that of Mdc1, but exhibits the same dependence on LET. In contrast, the mean recruitment time τ(1) of 53BP1 remains almost constant when varying LET. Comparison to literature data on Mdc1 recruitment after UV laser irradiation shows that this rather resembles recruitment after high than low LET ionizing radiation. So this work shows that damage quality has a large influence on repair processes and has to be considered when comparing different studies

Survival of tumor cells after proton irradiation with ultra-high dose rates

<p>Abstract</p> <p>Background</p> <p>Laser acceleration of protons and heavy ions may in the future be used in radiation therapy. Laser-driven particle beams are pulsed and ultra high dose rates of >10⁹Gy s^-1may be achieved. Here we compare the radiobiological effects of pulsed and continuous proton beams.</p> <p>Methods</p> <p>The ion microbeam SNAKE at the Munich tandem accelerator was used to directly compare a pulsed and a continuous 20 MeV proton beam, which delivered a dose of 3 Gy to a HeLa cell monolayer within < 1 ns or 100 ms, respectively. Investigated endpoints were G2 phase cell cycle arrest, apoptosis, and colony formation.</p> <p>Results</p> <p>At 10 h after pulsed irradiation, the fraction of G2 cells was significantly lower than after irradiation with the continuous beam, while all other endpoints including colony formation were not significantly different. We determined the relative biological effectiveness (RBE) for pulsed and continuous proton beams relative to x-irradiation as 0.91 ± 0.26 and 0.86 ± 0.33 (mean and SD), respectively.</p> <p>Conclusions</p> <p>At the dose rates investigated here, which are expected to correspond to those in radiation therapy using laser-driven particles, the RBE of the pulsed and the (conventional) continuous irradiation mode do not differ significantly.</p

Whole-Day Schools - Management and Education

Ganztagsschulen haben durch ihr Mehr an Zeit einen größeren Spielraum, die Schulgestaltung an den Bedürfnissen der Beteiligten zu orientieren. In einer Auseinandersetzung mit anderen Perspektiven kann es gelingen, die Ausrichtung der eigenen Schule zu diskutieren, zu festigen und zu schärfen. Pädagogische Fortbildungsveranstaltungen bieten dazu eine Möglichkeit. Der zweite bayerische Ganztagsschulkongress Ganztagsschule gestalten – ganztags Unterricht organisieren am 3. und 4. März 2010 in Forchheim bot den Teilnehmerinnen und Teilnehmern anhand vielfältiger Vorträge und Workshops ein Forum zur Diskussion mit Perspektiven aus Wissenschaft, Schulpraxis und Bildungspolitik. Die Dokumentation der Veranstaltung liegt hiermit vor.All-day schools stand out against other types of schools due to the extended availability of time and therewith a wider range of possibilities to adjust the orientation of the school to the needs of the persons involved. Schools can evolve and strengthen their orientation by a discursive examination and discussion of different approaches. A good opportunity for advancing this discussion are events in pedagogical further education. During the second Bavarian all-day school congress "Modelling All-Day School - Organizing All-Day Tuition", held on the 3rd and 4th of March 2010 in Forchheim/Germany, participants had the opportunity to attend numerous workshops and presentations as well as a panel discussion featuring experts from the fields of educational science, educational policy and teaching. The documentation of the congress is now available

Qualitätsentwicklung an Ganztagsschulen

Durch die Verlagerung bzw. Stärkung von Entscheidungskompetenzen auf die bzw. der Ebene der Einzelschule wird es ermöglicht, Lösungs-/Gestaltungsansätze zu entwickeln, die auf die jeweiligen Bedürfnisse und Gegebenheiten vor Ort zugeschnitten werden können. Die kritische Auseinandersetzung mit den Erfahrungen anderer, die auf entsprechenden Fortbildungsveranstaltungen kommuniziert werden können, lässt Good-practice-Beispiele entstehen, aus denen sich Anregungen zur Realisierung eigener Vorhaben im Zuge der Ganztagsschulentwicklung ableiten lassen. Der dritte bayerische Ganztagsschulkongress "Qualitätsentwicklung an Ganztagsschulen" am 1. und 2. März 2012 in Forchheim bot den Teilnehmerinnen und Teilnehmern anhand diverser Vorträge, Workshops und Schulbesuchen die Möglichkeit zu Diskussion und Austausch. Der vorliegende Band dokumentiert die Veranstaltung

Precise nitrogen depth profiling by high-resolution RBS in combination with angle-resolved XPS

Nitrogen depth profiling in a high-k gate stack structure, SiON/HfO2/SiON/Si(0 0 1) was performed by high-resolution Rutherford backscattering spectroscopy (HRBS) in combination with angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The nitrogen depth profile is determined so that both the HRBS spectrum and the angular dependence of the XPS yield are reproduced. The obtained nitrogen profile is compared with the result of high-resolution elastic recoil detection (ERD) which is the most reliable technique for depth profiling of light elements. The agreement between the result of the present combination analysis and that of high-resolution ERD is fairly good, showing that the present combination analysis is a promising method for the analysis of light elements

Live cell imaging at the Munich ion microbeam SNAKE - a status report

Ion microbeams are important tools in radiobiological research. Still, the worldwide number of ion microbeam facilities where biological experiments can be performed is limited. Even fewer facilities combine ion microirradiation with live-cell imaging to allow microscopic observation of cellular response reactions starting very fast after irradiation and continuing for many hours. At SNAKE, the ion microbeam facility at the Munich 14 MV tandem accelerator, a large variety of biological experiments are performed on a regular basis. Here, recent developments and ongoing research projects at the ion microbeam SNAKE are presented with specific emphasis on live-cell imaging experiments. An overview of the technical details of the setup is given, including examples of suitable biological samples. By ion beam focusing to submicrometer beam spot size and single ion detection it is possible to target subcellular structures with defined numbers of ions. Focusing of high numbers of ions to single spots allows studying the influence of high local damage density on recruitment of damage response proteins