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FeS-Induced Radical Formation and Its Effect on Plasmid DNA
Authors:D Rickard  B Hatton  D M Murphy  I B Butler  A Oldroyd  A Hann
Institution:1. School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF103YE, UK
2. School of Chemistry, Cardiff University, Cardiff, CF103YE, UK
3. School of Geosciences, University of Edinburgh, Edinburgh, EH9 3JW, UK
4. ECOSSE (Edinburgh Collaborative of Subsurface Science and Engineering), A joint research Institute of the Edinburgh Research Partnership in Engineering and Mathematics, Edinburgh, UK
5. School of Biosciences, Cardiff University, Cardiff, CF103YE, UK
Abstract:Plasmid DNA was incubated at 25°C with aqueous solutions of dissolved Fe(II), S(-II), and nanoparticulate FeS with a mackinawite structure, FeSm. At ??0.1 mM total dissolved Fe(II) and S(-II), an increase in the proportion of the relaxed plasmid DNA occurs, through scission of the DNA backbone. In solutions where FeSm was precipitated, nanoparticulate FeSm binds to the DNA molecules. In solutions with concentrations below the FeSm solubility product, nicking of supercoiled pDNA occurs. Plasmid DNA appears to be a sensitive proxy for radical reactions. The reactant is proposed to be a sulfur-based radical produced from the iron-catalyzed decomposition of bisulfide, in a manner analogous to the Fenton reaction. This is further supported by experiments that suggest that sulfide free radicals are produced during the photolysis of aqueous solutions of polysulfides. Supercoiling of DNA affects nearly all DNA?Cprotein transactions so the observation of relaxation of supercoiled forms through reaction with FeS solutions has direct implications to biochemistry. The results of this experimentation suggest that genotoxicity in FeS-rich systems is a further contributory factor to the limited survival of organisms in sulfidic environments. Mutations resulting from the interactions of organisms and mobile elements, such as plasmids, in sediments will also be affected in sulfide-rich environments.
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