Structure and stability of metal-siderophore complexes

GEOC 59

Owen W Duckworth, owend@nature.berkeley.edu, Division of Ecosystem Sciences, UC Bekeley, 140 Mulford Hall, Bekeley, CA 94502-3114, John R. Bargar, bargar@slac.stanford.edu, Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road, MS 69, Menlo Park, CA 94025, Andrzej Jarzecki, jarzecki@brooklyn.cuny.edu, Chemistry Department, Brooklyn College and the Graduate School of the City University of New York, Brooklyn, NY 11210, Thomas G. Spiro, spiro@princeton.edu, Department of Chemistry, Princeton University, Princeton, NJ 08540, and Garrison Sposito, gsposito@nature.berkeley.edu, Division of Ecosystem Sciences, University of California, 137 Mulford Hall #3114, Berkeley, CA 94720-3114.
Siderophores are biogenic chelating agents exuded to solublize ferric iron. These chelating agents also form stable complexes with a wide range of nutrient and contaminant metals, affecting their fate, transport, and biogeochemical cycling. To understand better the factors that control the stability and reactivity of siderophore complexes, we employ in situ techniques to probe the structure of complexes formed between the trihydroxamate siderophore desferrioxamine B (DFOB) and Co, Cu, Cr, Fe, Ga, Mn, Ni, and Zn in solution. We find that all metal studied are in octahedral coordination, with significant Jahn-Teller distortion of Mn(III)HDFOB+ and Cu(II)HDFOB0. Additionally, complex stability constants correlate not only with the metal-oxygen bond lengths but also the overall size of the chelating center. The derived structure-activity relationship not only quantitatively relates the measured physical architecture of aqueous complexes to their observed stability but also allows for the prediction of siderophore-metal stability constants.
 

Frontiers in Geochemistry: Commemorating the 25th Anniversary of the ACS-Geochemistry Division
9:00 AM-12:00 PM, Monday, 11 September 2006 Moscone Center -- Room 262, Oral

Sci-Mix
8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Geochemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006