Metallothionein-like multinuclear clusters of mercury(II) and sulfur in peat

Environmental Science & Technology
By: , and 

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Abstract

Strong mercury(II)–sulfur (Hg-SR) bonds in natural organic matter, which influence mercury bioavailability, are difficult to characterize. We report evidence for two new Hg-SR structures using X-ray absorption spectroscopy in peats from the Florida Everglades with added Hg. The first, observed at a mole ratio of organic reduced S to Hg (Sred/Hg) between 220 and 1140, is a Hg4Sx type of cluster with each Hg atom bonded to two S atoms at 2.34 Å and one S at 2.53 Å, and all Hg atoms 4.12 Å apart. This model structure matches those of metal–thiolate clusters in metallothioneins, but not those of HgS minerals. The second, with one S atom at 2.34 Å and about six C atoms at 2.97 to 3.28 Å, occurred at Sred/Hg between 0.80 and 4.3 and suggests Hg binding to a thiolated aromatic unit. The multinuclear Hg cluster indicates a strong binding environment to cysteinyl sulfur that might impede methylation. Along with a linear Hg(SR)2 unit with Hg—S bond lengths of 2.34 Å at Sred/Hg of about 10 to 20, the new structures support a continuum in Hg-SR binding strength in natural organic matter.

Publication type Article
Publication Subtype Journal Article
Title Metallothionein-like multinuclear clusters of mercury(II) and sulfur in peat
Series title Environmental Science & Technology
DOI 10.1021/es201025v
Volume 45
Issue 17
Year Published 2011
Language English
Publisher ACS
Contributing office(s) Mercury Research Laboratory, Toxic Substances Hydrology Program
Description 9 p.
First page 7298
Last page 7306
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