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Title: Molecular Mechanisms of Bacterial Mercury Transformation

Mercury (Hg) is a major global pollutant arising from both natural and anthropogenic sources. Defining the factors that determine the relative affinities of different ligands for the mercuric ion, Hg2+, is critical to understanding its speciation, transformation, and bioaccumulation in the environment. Here, we used quantum chemistry to dissect the relative binding free energies for a series of inorganic anion complexes of Hg2+. The results show that, whereas in the gas phase the binding affinity of two identical anionic ligands (forming HgL2) increases with ligand (Lā€“) hardness, in contrast, in the aqueous phase the affinity increases with ligand softness. This switch in affinity upon hydration is shown to result mostly from interactions with only a small number (e.g. one or two) of water molecules. The results yield a clear, robust periodic trend within the chalcogenide and halide groups and are in agreement with the well-known experimentally observed preference of Hg2+ for soft ligands. By comparing the Hg2+ binding of one with two anions, the gas phase preferences are found to arise from the enhancement of reactivity of the cationic complex (HgL+) with the hardness of Lā€“. The approach establishes a theoretical basis for understanding Hg speciation in the biosphere.
Publication Date:
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Technical Report
Research Org:
University of Tennessee
Sponsoring Org:
USDOE; USDOE Office of Science (SC); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Contributing Orgs:
University of Tennessee
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES mercury, computational science