HR: 11:35h
AN: B12A-06    [Abstracts]
TI: A Molecular Approach Towards Understanding the Biogenic Formation of CeO2 and its Interactions with Biomolecules
AU: * Cervini-Silva, J
EM: jcervini@nature.berkeley.edu
AF: University of California, 108 Mulford Hall #3110, Berkeley, CA 94709 United States
AU: Fakra, S
EM: sfakra@lbl.gov
AF: Lawrence Berkeley National Laboratory, Advanced Light Source, Berkeley, CA 94720 United States
AU: Gilbert, B
EM: bgilbert@lbl.gov
AF: Lawrence Berkeley National Laboratory, Advanced Light Source, Berkeley, CA 94720 United States
AU: Banfield, J
EM:
AF: University of California, 108 Mulford Hall #3110, Berkeley, CA 94709 United States
AB: Cerium is the most abundant lanthanide and generally the only one to undergo redox reactions at the Earth's surface. The oxidation state influences the environmental chemistry and toxicology of Ce because it alters the mechanisms of interaction between Ce and biomolecules. For instance, as opposed to Ce(III) or other lanthanide ions, Ce(IV) has shown a remarkable efficiency to hydrolyze DNA. The selectivity of Ce as Ce(IV) relates to the specific coordination of water molecules and their orientation. Ce(IV) may also bind selectivity to biomolecules such as RNA-type substrates, or monocleotides such as AMP, to instigate conformational changes or cleavage of complexes, which affect metabolic pathways pivotal to growth and survival. On the other hand, biogenic ligands can promote the oxidation of Ce(III) to small sized-CeO2 and are subsequently degraded by this product to CO2 and humic material. Here, we study molecular interactions between CeO2 and biomolecules (e.g., catechol) using carbon and cerium, XRD, and IR spectroscopy. Results show a progressive increase in catechol transformation (as % carbon) with decreasing CeO2 particle diameter (13 < d < 84), which substantiates an intimate relation between CeO2 unit cell expansion and reactivity towards organics susceptible to undergo redox transformations. As shown by C and Ce spectroscopy, organic polymers that form because of catechol oxidation are distributed next to the mineral surface and its occurrence is coupled to Ce reduction-oxidation.
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0418 Bioremediation
DE: 0419 Biomineralization
DE: 0444 Evolutionary geobiology
SC: Biogeosciences [B]
MN: Fall Meeting 2005