Decomposition of RNA in the presence of synthetic Nipyrites

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Decomposition of RNA in the presence of synthetic
Ni-pyrites

• Maria T. Minjares1,2, Martin A Schoonen2, Corey
  A. Cohn2, and F. Marc Michel2.
• Our Lady of the Lake University, San Antonio,
  TX,
• Department of Geosciences Center for
  Environmental Molecular Science, Stony Brook
  University,Stony Brook, NY

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Outline

• Motivation of study
• Synthesis of Ni-pyrites
• Batch Experiments
• Results
• Conclusion

NiS2
FeS2
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Background

• Ni compounds, such as Ni-OH phases, Ni-oxides,
  and Ni3S2, are known carcinogens
• Many of these Ni compounds are known to degrade
  nucleic acids.
• NiS2 is iso-structural to FeS2 and the two phases
  form a solid solution.
• Pyrite, FeS2, has recently been shown to degrade
  RNA (Cohn et al. EPSL 04).

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Pyrite-RNA interaction
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Motivation Fe-Ni-S2 as a model system

• Research QuestionHow does the addition of Ni to
  pyrite affect its reactivity toward RNA?
• Strategy
• synthesize Ni-Fe-S2 compounds with different
  Ni/Fe ratio as well as endmembers
• conduct a series of batch kinetic experiments to
  determine the rate of RNA degradation.

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Hydrothermal Synthesis

• Reagents Fe(NH4)2(SO4).6H20, NiCl2, Na2S.9H2O,
  S(0).
• Starting reagents dissolved in N2-purged DI
  H2O,loaded in 316 SS hydrothermal vessel lined
  with teflon insert at room tempature
• Heated to 200C for 5 to 7 days. Shaken during
  aging.
• Samples recovered in anaerobic glovebox,
  characterized with XRD and SEM

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Synthesis Setup
Oven and shaker
TEFLON insert
135 mL vessel
 
 
Anaerobic glovebox
 
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CharacterizationNi-Doped Pyrite Solid State
Solution

• Shift in vaesite peaks
• Small traces of pyrite
• Indicates solid solution

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CharacterizationMixed Phases

• Slight shift in vaesite peaks

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Scanning Electron Microscopy (SEM)
FeS2 120hrs _at_ 198oC 26.96 KX
Fe0.25Ni0.75S2 85hrs _at_198oC 67.14 KX
Fe0.5Ni0.5S2 115hrs _at_ 192oC 52.37 KX
Fe0.75Ni0.25S2 93 hrs _at_ oC 16.85 KX
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RNA Exposure to Ni-pyrites

• Batch experiments conducted in anaerobic
  glovebox
• RNA concentration analyzed using Ribogreen
• Ribogreen is a molecular probe that intercalates
  in winding of RNA helix and then becomes
  flourescent. Intercalation is inhibited if RNA
  is degraded in small fragments. Strength
  fluorescence signal proportional to concentration
  of in tact RNA.
• Also collected UV-Vis spectra for filtered
  solutions.

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Data
Note that RNA is rapidly decomposed in presence
of Ni-rich phases
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Rate first order in RNA
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Effect of Ni on Rate
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Fate of RNA
A260 due to base
A260 lost as base reacts with OH radical
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CONCLUSIONS

• Ni promotes the decomposition of RNA
• Mechanism likely to involve OH radicals
• First time that Ni-Fe-S2 phases have been studied
• Ni-pyrites may be more harmful than pure pyrite
• Thanks NSF-Chemistry for support.

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2004 CEMS Summer Scholars