Details

Autor(en) / Beteiligte

• Gourier, Didier
• Delpoux, Olivier
• Bonduelle, Audrey
• Binet, Laurent
• Ciofini, Ilaria
• Vezin, Hervé

Titel

EPR, ENDOR, and HYSCORE Study of the Structure and the Stability of Vanadyl−Porphyrin Complexes Encapsulated in Silica: Potential Paramagnetic Biomarkers for the Origin of Life

Ist Teil von

• The journal of physical chemistry. B, 2010-03, Vol.114 (10), p.3714-3725

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2010

Quelle

MEDLINE

Beschreibungen/Notizen

• The possibility of using vanadyl ions as paramagnetic biomarkers for the identification of traces of primitive life fossilized in silica rocks is studied by cw-EPR, ENDOR, HYSCORE, and DFT calculations. It is well-known that porphyrins, which are common to all living organisms, form vanadyl−porphyrin complexes in sediments deposited in oceans. However, the stability of these complexes over a very long time (more than 3 billion years) is not known. By encapsulating vanadyl−porphyrin complexes in silica synthesized by a sol−gel method to mimic SiO2 sediments, we studied the structure and stability of these complexes upon step heating treatments by monitoring the evolution of the g factor and of the hyperfine interactions with 51V, 1H, 14N, 13C, and 29Si nuclei. It is found that vanadyl−porphyrin complexes are progressively transformed into oxygenated vanadyl complexes by transfer of the VO2+ ion from the porphyrin ring to the mineral matrix. The organic component is transformed into carbonaceous matter which contains paramagnetic centers (IOM• centers). To test the validity of this approach, we studied by EPR a 3490 million years old chert (polycrystalline SiO2 rock) containing some of the oldest putative traces of life. This rock contains oxygenated vanadyl complexes and IOM• centers very similar to those found in the synthetic analogues.