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Updated: Oct 11, 2025
14:44
Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
9.7K
Salicylate coordination in metal-protochelin complexes.
Sarah A Doydora1, Oliver Baars2, James M Harrington3
1Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, 27695, USA.
Summary
Molybdenum (Mo) is vital for bacterial enzymes. Protochelin chelates Mo, aiding its uptake, with a structural shift at low pH impacting availability in soils.
Area of Science:
- Biogeochemistry
- Microbial Ecology
- Environmental Chemistry
Background:
- Molybdenum (Mo) is an essential trace element for bacterial metalloenzymes involved in crucial biogeochemical cycles.
- Mo scarcity and low bioavailability in soils can limit nitrogen fixation in ecosystems.
- Microbes produce siderophores, like protochelin, to chelate and solubilize scarce metals for uptake.
Purpose of the Study:
- To determine the structure and stability of molybdenum-protochelin complexes.
- To investigate the pH-dependent binding modes and coordination shifts of Mo-protochelin.
Main Methods:
- Spectrophotometric titration to determine stability constants and pKa values.
- Mass spectrometry to confirm complex charge.
- K-edge Extended X-ray absorption fine structure (EXAFS) spectroscopy to analyze Mo coordination.
Main Results:
- Protochelin chelates Mo across a wide pH range.
- A coordination shift from catecholate to salicylate binding occurs for Mo-protochelin complexes at pH < 5.
- Mo-protochelin complexes are negatively charged at pH 6, confirmed by mass spectrometry.
Conclusions:
- Protochelin effectively chelates molybdenum, influencing its biological availability.
- The pH-dependent coordination shift of Mo-protochelin complexes impacts Mo retention in acidic environments.
- Understanding Mo-protochelin interactions is crucial for soil biogeochemistry and microbial processes.
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