TY - JOUR A1 - Meyer, Susann A1 - Schroeter, M. -A. A1 - Hahn, Marc B. A1 - Solomun, T. A1 - Sturm, Heinz A1 - Kunte, H. J. T1 - Ectoine can enhance structural changes in DNA in vitro JF - Scientific reports N2 - Strand breaks and conformational changes of DNA have consequences for the physiological role of DNA. The natural protecting molecule ectoine is beneficial to entire bacterial cells and biomolecules such as proteins by mitigating detrimental effects of environmental stresses. It was postulated that ectoine-like molecules bind to negatively charged spheres that mimic DNA surfaces. We investigated the effect of ectoine on DNA and whether ectoine is able to protect DNA from damages caused by ultraviolet radiation (UV-A). In order to determine different isoforms of DNA, agarose gel electrophoresis and atomic force microscopy experiments were carried out with plasmid pUC19 DNA. Our quantitative results revealed that a prolonged incubation of DNA with ectoine leads to an increase in transitions from supercoiled (undamaged) to open circular (single-strand break) conformation at pH 6.6. The effect is pH dependent and no significant changes were observed at physiological pH of 7.5. After UV-A irradiation in ectoine solution, changes in DNA conformation were even more pronounced and this effect was pH dependent. We hypothesize that ectoine is attracted to the negatively charge surface of DNA at lower pH and therefore fails to act as a stabilizing agent for DNA in our in vitro experiments. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-07441-z SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Hahn, Marc Benjamin A1 - Meyer, Susann A1 - Schröter, Maria-Astrid A1 - Seitz, Harald A1 - Kunte, Hans-Jörg A1 - Solomun, Tihomir A1 - Sturm, Heinz T1 - Direct electron irradiation of DNA in a fully aqueous environment BT - Damage determination in combination with Monte Carlo simulations JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies N2 - We report on a study in which plasmid DNA in water was irradiated with 30 keV electrons generated by a scanning electron microscope and passed through a 100 nm thick Si3N4 membrane. The corresponding Monte Carlo simulations suggest that the kinetic energy spectrum of the electrons throughout the water is dominated by low energy electrons (<100 eV). The DNA radiation damage, single-strand breaks (SSBs) and double-strand breaks (DSBs), was determined by gel electrophoresis. The median lethal dose of D-1/2 = 1.7 +/- 0.3 Gy was found to be much smaller as compared to partially or fully hydrated DNA irradiated under vacuum conditions. The ratio of the DSBs to SSBs was found to be 1 : 12 as compared to 1 : 88 found for hydrated DNA. Our method enables quantitative measurements of radiation damage to biomolecules (DNA, proteins) in solutions under varying conditions (pH, salinity, co-solutes) for an electron energy range which is difficult to probe by standard methods. Y1 - 2016 U6 - https://doi.org/10.1039/c6cp07707b SN - 1463-9076 SN - 1463-9084 VL - 19 IS - 3 SP - 1798 EP - 1805 PB - RSC Publ. CY - Cambridge ER - TY - JOUR A1 - Oprzeska-Zingrebe, Ewa Anna A1 - Meyer, Susann A1 - Roloff, Alexander A1 - Kunte, Hans-Jörg A1 - Smiatek, Jens T1 - Influence of compatible solute ectoine on distinct DNA structures BT - thermodynamic insights into molecular binding mechanisms and destabilization effects JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - In nature, the cellular environment of DNA includes not only water and ions, but also other components and co-solutes, which can exert both stabilizing and destabilizing effects on particular oligonucleotide conformations. Among them, ectoine, known as an important osmoprotectant organic co-solute in a broad range of pharmaceutical products, turns out to be of particular relevance. In this article, we study the influence of ectoine on a short single-stranded DNA fragment and on double-stranded helical B-DNA in aqueous solution by means of atomistic molecular dynamics (MD) simulations in combination with molecular theories of solution. Our results demonstrate a conformation-dependent binding behavior of ectoine, which favors the unfolded state of DNA by a combination of electrostatic and dispersion interactions. In conjunction with the Kirkwood-Buff theory, we introduce a simple framework to compute the influence of ectoine on the DNA melting temperature. Our findings reveal a significant linear decrease of the melting temperature with increasing ectoine concentration, which is found to be in qualitative agreement with results from denaturation experiments. The outcomes of our computer simulations provide a detailed mechanistic rationale for the surprising destabilizing influence of ectoine on distinct DNA structures. Y1 - 2018 U6 - https://doi.org/10.1039/c8cp03543a SN - 1463-9076 SN - 1463-9084 VL - 20 IS - 40 SP - 25861 EP - 25874 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Hahn, Marc Benjamin A1 - Solomun, Tihomir A1 - Wellhausen, Robert A1 - Hermann, Sabrina A1 - Seitz, Harald A1 - Meyer, Susann A1 - Kunte, Hans-Jörg A1 - Zeman, Johannes A1 - Uhlig, Frank A1 - Smiatek, Jens A1 - Sturm, Heinz T1 - Influence of the Compatible Solute Ectoine on the Local Water Structure: Implications for the Binding of the Protein G5P to DNA JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - Microorganisms accumulate molar concentrations of compatible solutes like ectoine to prevent proteins from denaturation. Direct structural or spectroscopic information on the mechanism and about the hydration shell around ectoine are scarce. We combined surface plasmon resonance (SPR), confocal Raman spectroscopy, molecular dynamics simulations, and density functional theory (DFT) calculations to study the local hydration shell around ectoine and its influence on the binding of a gene-S-protein (G5P) to a single-stranded DNA (dT(25)). Due to the very high hygroscopicity of ectoine, it was possible to analyze the highly stable hydration shell by confocal Raman spectroscopy. Corresponding molecular dynamics simulation results revealed a significant change of the water dielectric constant in the presence of a high molar ectoine concentration as compared to pure water. The SPR data showed that the amount of protein bound to DNA decreases in the presence of ectoine, and hence, the protein-DNA dissociation constant increases in a concentration-dependent manner. Concomitantly, the Raman spectra in terms of the amide I region revealed large changes in the protein secondary structure. Our results indicate that ectoine strongly affects the molecular recognition between the protein and the oligonudeotide, which has important consequences for osmotic regulation mechanisms. Y1 - 2015 U6 - https://doi.org/10.1021/acs.jpcb.5b09506 SN - 1520-6106 VL - 119 IS - 49 SP - 15212 EP - 15220 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hahn, Marc Benjamin A1 - Meyer, Susann A1 - Kunte, Hans-Jorg A1 - Solomun, Tihomir A1 - Sturm, Heinz T1 - Measurements and simulations of microscopic damage to DNA in water by 30 keV electrons: A general approach applicable to other radiation sources and biological targets JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - The determination of the microscopic dose-damage relationship for DNA in an aqueous environment is of a fundamental interest for dosimetry and applications in radiation therapy and protection. We combine GEANT4 particle-scattering simulations in water with calculations concerning the movement of biomolecules to obtain the energy deposit in the biologically relevant nanoscopic volume. We juxtaposition these results to the experimentally determined damage to obtain the dose-damage relationship at a molecular level. This approach is tested for an experimentally challenging system concerning the direct irradiation of plasmid DNA (pUC19) in water with electrons as primary particles. Here a microscopic target model for the plasmid DNA based on the relation of lineal energy and radiation quality is used to calculate the effective target volume. It was found that on average fewer than two ionizations within a 7.5-nm radius around the sugar-phosphate backbone are sufficient to cause a single strand break, with a corresponding median lethal energy deposit being E-1/2 = 6 +/- 4 eV. The presented method is applicable for ionizing radiation (e.g.,.gamma rays, x rays, and electrons) and a variety of targets, such as DNA, proteins, or cells. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevE.95.052419 SN - 2470-0045 SN - 2470-0053 VL - 95 PB - American Physical Society CY - College Park ER -