TY - CONF A1 - Schröter, Maria-Astrid A1 - Meyer, Susann A1 - Hahn, Marc Benjamin A1 - Solomun, Tihomir A1 - Kunte, Hans-Jörg A1 - Sturm, Heinz T1 - Structural changes in plasmid DNA caused by radiation and its protection by Ectoine: an AFM analysis N2 - Most ionizing radiation in water ends in an avalanche of low energy electrons which play a dominant role together with OH-radicals in damaging DNA. In the present study we irradiated plasmid DNA with electrons (primary energy 30keV) under physiological conditions, performed with as well as without Ectoine. Ectoine is a compatible solute, synthesized and accumulated in molar concentration within bacteria to withstand osmotic stress or different other stressors. Plasmid DNA (pUC19, 2686 bp) was studied due to its supercoiled isoform which is highly sensitive to radiation damage. In biochemistry gel electrophoresis is applied for structural analysis of DNA. Although it is a standard technique, a reliable discrimination of short fragments caused by radiation is often difficult. AFM is also commonly used for imaging susceptible biomolecules and, since it is based on a single molecule observation, for analysis of contour lengths of linear DNA as well. Therefore, in our study the structural changes in plasmid DNA after irradiation with different doses were quantitatively analyzed by means of intermittent contact AFM. The figure shows representative AFM images of electron irradiated pUC19 DNA (bar=200nm). For AFM imaging the DNA was chemically fixed on ultra-smooth mica. As can be clearly seen, with increasing radiation dose the number of undamaged DNA declines and fragmented DNA arises (A, B). In aqueous Ectoine solution (1M) the effect of radiation on DNA is dramatically depressed. Ectoine apparently confers protection even against high radiation: the plasmids remain predominantly in the supercoiled isoform (D). Therefore, we strongly believe that Ectoine is a potent protective substance of DNA against ionizing radiation. T2 - AFM BioMed CY - Krakau, Poland DA - 04.09.2017 KW - AFM KW - Plasmid DNA KW - Ectoine KW - Electron radiation PY - 2017 AN - OPUS4-42027 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hahn, Marc Benjamin A1 - Solomun, Tihomir A1 - Meyer, Susann A1 - Kunte, Hans-Jörg A1 - Schröter, Maria-Astrid A1 - Sturm, Heinz T1 - Development of a standard procedure for the irradiation of biomolecules N2 - In dosimetry the determination of the effectiveness of the damaging processes is standardized and accounted for by the radiation and tissue weighting factor. For the underlying constituents of the tissue, that is the various biomolecules, such a systematic approach doesn't exist. This makes it difficult to compare results obtained under different experimental conditions. In the following work, we will describe a method to obtain comparable values for the radiation-biomolecule interaction, measured under different conditions. This approach can lead to standardization of dosedamage relationship at the molecular level. Such approach is necessary for a better understanding of the relations between the damage of the single constituents of biological tissue and the whole – finally gaining a more complete picture of irradiation damage. T2 - 14th International Congress of the International Raditation Protection Association (IRPA) CY - Cape Town, South Africa DA - 09.05.2016 KW - Dosimetry PY - 2017 VL - 14 SP - 1 EP - 5 AN - OPUS4-41164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Meyer, Susann A1 - Hahn, Marc Benjamin A1 - Solomun, Tihomir A1 - Kunte, Hans-Jörg A1 - Sturm, Heinz T1 - Structural changes in plasmid DNA verified by gel electrophoresis and AFM: Sample AFM preparation and imaging (II) N2 - Tapping mode AFM (TM-AFM) is a standard technique to image biomolecules and cells avoiding damage to susceptible samples. For preparing AFM samples we fixed (untreated and radiated) plasmids chemically on ultra-smooth mica silanized with APTES. The recorded AFM images were examined concerning the contour length, the conformation and the writhing number of the plasmids. We found that the measured contour length is in accordance with the number of base pairs. Apart from that, we indicate different structures of plasmids from our AFM images, which were assigned to our plasmid data from agarose gel-electrophoresis. T2 - AFM BioMed Conference CY - Porto, Portugal DA - 11.04.2016 KW - Plasmid DNA KW - Sample AFM preparation PY - 2016 AN - OPUS4-35884 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Weimann, Christiane A1 - Sturm, Heinz A1 - Holschneider, M. T1 - Bridging the scales: Direct SEM imaging of nanometer vibrations for the analysis of stick-slip behaviour at microscales T2 - EGU 2012 CY - Vienna, Austria DA - 2012-04-22 PY - 2012 AN - OPUS4-34330 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Sturm, Heinz A1 - Ritter, Martin A1 - Holschneider, M. T1 - How to image vibrating spatial MEMS structures? T2 - Microscopy Conference 2015 CY - Göttingen, Germany DA - 2015-09-06 PY - 2015 AN - OPUS4-34317 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Holschneider, M. A1 - Ritter, M. A1 - Weimann, Christiane A1 - Sturm, Heinz T1 - Theoretical analysis of vibrating microstructuresusing Dynamic Scanning Electron Microscopy (DySEM) T2 - Deutsche Physikalische Gesellschaft (DPG) 2015 CY - Berlin, Germany DA - 2015-03-15 PY - 2015 AN - OPUS4-32863 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Ritter, Martin A1 - Holzschneider, M. A1 - Sturm, Heinz T1 - Analysis of vibrating microstructures using Dynamic Scanning Electron Microscopy (DySEM) T2 - Deutsche Physikalische Gesellschaft (DPG) 2015 CY - Berlin, Germany DA - 2015-03-15 PY - 2015 AN - OPUS4-32862 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Holschneider, M. A1 - Weimann, Christiane A1 - Sturm, Heinz T1 - Analysis of amplitude and phase patterns of vibrating cantilevers using Dynamic Scanning Electron Microscopy (DySEM) T2 - NanoMeasure 2013 CY - Warsaw, Poland DA - 2013-06-25 PY - 2013 AN - OPUS4-28747 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Holschneider, M. A1 - Weimann, Christiane A1 - Ritter, M. A1 - Sturm, Heinz T1 - Dynamic SEM image analysis of vibrating cantilevers (II) T2 - Deutsche Physikalische Gesellschaft (DPG) 2013 CY - Regensburg, Germany DA - 2013-03-10 PY - 2013 AN - OPUS4-27867 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Holzschneider, M. A1 - Weimann, Christiane A1 - Ritter, M. A1 - Sturm, Heinz T1 - Dynamic SEM image analysis of vibrating cantilevers (I) T2 - Deutsche Physikalische Gesellschaft (DPG) 2013 CY - Regensburg, Germany DA - 2013-03-10 PY - 2013 AN - OPUS4-27866 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Weimann, Christiane A1 - Sturm, Heinz A1 - Holzschneider, M. T1 - Analytical solutions for SE/LIA imaging experiments with vibrating microcantilevers T2 - International Conference on Micro- and Nano-Engineering (MNE) CY - Toulouse, France DA - 2012-09-16 PY - 2012 AN - OPUS4-27341 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Weimann, Christiane A1 - Sturm, Heinz A1 - Holzschneider, M. T1 - Towards a deeper understanding of the dynamic properties of cantilever probes T2 - DPG 2012 CY - Berlin, Germany DA - 2012-03-25 PY - 2012 AN - OPUS4-26491 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Weimann, Christiane A1 - Sturm, Heinz A1 - Holschneider, M. T1 - Towards a deeper understanding of the dynamic properties of cantilever probes T2 - 37. Int. Conf. Micro and Nano Engineering CY - Berlin, Germany DA - 2011-09-19 PY - 2011 AN - OPUS4-23866 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröter, Maria-Astrid A1 - Weimann, Christiane A1 - Sturm, Heinz A1 - Holschneider, M. T1 - Towards a simplified mechanical model of insect wings T2 - Microscopy Conference CY - Kiel, Germany DA - 2011-08-28 PY - 2011 AN - OPUS4-23581 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Schröter, Maria-Astrid T1 - Untersuchung schwingender Mikrostrukturen mittels dynamischer Rasterelektronenmikroskopie: Experiment und Theorie N2 - Die vorgelegte Arbeit zeigt die Ausarbeitung und die Überprüfung einer Theorie, mit welcher die Ergebnisse aus einem neu entwickelten Mess-Verfahren (DySEM-Technik) beschrieben werden können. Mit dem Begriff “DySEM“ (Dynamic Scanning Electron Microscopy) wird ein experimentelles Verfahren bezeichnet, bei dem ein Elektronenstrahl als Mess-Sonde über einem mikroskaligen Schwinger verfahren wird, wobei die Schwingung durch eingesetzte Lock-In Technik frequenzaufgelöst dargestellt werden kann. Neben dem klassischen Sekundärelektronen-Signal wird zur Bildgebung auch der Anteil aus dem Signal genutzt, der sich anregungssynchron ändert. Die DySEM-Technik ermöglicht eine direkte Visualisierung der Schwingungsdynamik der oszillierenden Struktur, da zwischen unterschiedlichen Eigenmoden (flexural, torsional) als auch den jeweiligen höheren Harmonischen optisch eindeutig unterschieden werden kann. Damit bietet sich dieses Verfahren als ein Werkzeug der Modal-Analyse mikroskaliger Schwinger an, welche in mikro- bzw. nanoelektromechanischen Systemen (MEMS bzw. NEMS) häufig Verwendung finden und bei denen eine Optimierung der Designparameter oft erst durch die Bildgebung der Schwingung zu erreichen ist. Zusätzlich zeigen die DySEM-Bilder charakteristische Amplituden-abhängige Bildmerkmale, die theoretisch verstanden werden müssen. Prinzipiell ist die DySEM-Technik nicht an den Elektronenstrahl als Mess-Sonde gekoppelt. Allerdings erweist sich gerade im Zuge fortschreitender Miniaturisierung mit immer kleinskaligeren Schwingern eine elektronenoptische Orts-Auflösung als günstig. Bei der theoretischen Analyse des Abbildungsmechanismus liegt der Fokus auf der Untersuchung der raum-zeitlichen Dynamik der Wechselwirkung zwischen Elektronenstrahl und der periodisch darunter hinweg schwingenden Mikrostruktur, für die erstmals ein umfängliches Modell abgeleitet werden konnte, wodurch die detaillierte Interpretation der experimentellen Ergebnisse möglich wurde. Zusätzlich spielen lokale Eigenschaften (Materialeigenschaften) des Schwingers eine Rolle. Ebenso müssen die Beiträge von Energieverlustmechanismen zur Bildgebung berücksichtigt werden. Um die bildgebenden Gleichungen explizit ableiten zu können, beschränkt sich die mathematische Analyse in dieser Arbeit auf die Annahme eines frei oszillierenden, einseitig geklemmten Schwingers ohne Wechselwirkung mit Materie, wie es im DySEM-Experiment durch die Bildgebung im Hochvakuum angenähert wird. Die aufgrund dieses Modells simulierten DySEM-Bilder stimmen mit den experimentell gewonnenen Ergebnissen qualitativ und quantitativ gut überein. N2 - The thesis presented shows the development and verification of a theory, with which the results of a newly developed measuring method (DySEM technique) can be described. The term ”DySEM” (Dynamic Scanning Electron Microscopy) denotes an experimental procedure for measuring the vibrational dynamics of a microscale oscillator using a scanning electron beam. In addition to the classical secondary electron (SE) signal, the dynamic part of the signal can be obtained using a lock-in amplifier synchronized to the excitation frequency. The DySEM technique enables the direct observation of freely vibrating structures, including several modes in the normal and torsional direction as well as their higher harmonics. Thus, this method is a tool of modal analysis of microscale structure in oscillation, which is frequently used in micro- and nanoelectromechanical systems (MEMS and NEMS) and where an optimization of the design parameters often only can be achieved by imaging the vibration. Additionally, the DySEM images contain characteristic amplitude-dependent image features that need to be understood theoretically. Thanks to the precise local definition of electron beam and to lock-in technique the vibration images exhibit high spatial resolution. Thus, in the framework of progressing miniaturization of vibrating structures an electron-optical resolution is proved to be advantageously. In this framework a new quantitative theoretical model is proposed for the interpretation of the characteristic properties of the obtained measurements. The model of imaging generating mechanism relates the experimental images to the spatio-temporal interaction between electron beam and periodically vibrating microstructure. So, for the first time the detailed interpretation of the experimental results was possible. In addition, local properties (material properties) of the micro-oscillator are important. Similarly, the contributions of energy loss mechanisms must be considered for imaging. To explicitly derive the imaging equations, the mathematical analysis is limited in this work to the adoption of a free oscillating unilaterally clamped oscillator without interaction with matter, as it is approximated in DySEM experiment by imaging in high vacuum. Simulated images show very good qualitatively and quantitatively correspondence to the experimental data. First the theoretical model of the imaging process makes it possible to use the DySEM-technique as a quantitative analysis tool. Without such an understanding of the relationship between image contrast and interaction geometry, a quantitative interpretation of the DySEM images is hardly possible. The advantage of DySEM technique is the ability to distinguish between artefacts based on the imaging process and features which carry relevant VII information (i.e. nonlinear mechanical behavior of the micro-oscillator). The analysis of the imaging of oscillating microstructures by means of scanning electron microscopy is thereby achieved in this work presented as a combination of experiment, theory and simulation. T3 - BAM Dissertationsreihe - 124 KW - Dynamische Rasterelektronenmikroskopie (DySEM) KW - Bildgebung schwingender Mikrostrukturen KW - Modalanalyse KW - Federbalken KW - Theoretisches Modell der Bildentstehung PY - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-4644 SN - 978-3-9816668-3-0 VL - 124 SP - 1 EP - 134 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-464 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -