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Title: Emergence of nucleic acids in an iron-sulphur world
Author: Hatton, Bryan
ISNI:       0000 0004 2750 6714
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2007
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One hypothesis for the origin of life suggests that life emerged in a hydrothermal mineral assemblage containing sulphides and hydroxides. The research reported in this thesis shows that these minerals interact with nucleic acid polymers. This has two consequences. Firstly, metal sulphides, particularly iron sulphides, cause the scission of DNA and thus the survival of DNA in this environment is improbable. On the other hand, the reactions at low concentrations could lead to rapid mutations of DNA-like molecules and thus would have affected its evolution. These reactions also have biochemical consequences. For DNA to retain its function as the hereditary molecule it needs to be separated from concentrations of FeS. This also suggests that the results of the molecular ecology of sulfide-rich environments might be affected by reaction with iron sulphides. The effect that these nanoparticulate sulphides have had on the emergence and survival of nucleic acid polymers has been investigated through plasmid electrophoresis and UV-Vis spectrometry. Metal sulphides interact with DNA in two ways: scission of the DNA backbone and binding with sulphide particles. Treatment of pDNA with FeS, CuS, Fe(II), and Cu(II) breaks the ribo-phosphate backbone of the DNA molecule. This occurs through sulphur-based free radicals produced through redox reactions between S22" and Fe(II) and Cu(I) ions. Migration of oligomeric DNA in electrophoresis is retarded by FeS, CuS and ZnS which is attributed to the binding of nanoparticulate sulphides to the DNA. DNA, RNA, adenine, deoxyadenosine and deoxyadenosine monophosphate bind to FeS, CuS, ZnS and Fe(II)/Fe(III) hydroxides. This occurs through the nucleobase rather than the phosphate. Longer DNA molecules adsorb more readily than oligomers, RNA or monomers. Thus the hypothesis that iron-sulphide minerals could adsorb and concentrate nucleic acid constituents promoting nucleic acid formation and then polymerisation is supported, although the hypothesis that the phosphate group emerged to allow this binding is not necessary In the absence of sulphide, Fe(II) causes similar effects. Scission of the DNA occurs through hydroxyl radicals produced through a reaction with trace amounts of Ot also DNA adsorbed onto precipitated green rusts (Fe(II)/(III) hydroxides). Sulphide, in the absence of metal ions, induced no effect on DNA. In the absence of redox, transition metals oxyhydroxides adsorb to DNA but do not act to break up the molecule. Therefore, non-redox active metal sulphides, such as zinc, could have provided some of the functionality of iron sulphide especially with regards to nucleic acid formation, but without producing free radicals and therefore, simultaneous nucleic acid destruction.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available