Ligand Field Stabilization Control of Metal Ion Binding
Final rept. 15 Mar 1990-14 Mar 1993
JOHNS HOPKINS UNIV BALTIMORE MD SCHOOL OF MEDICINE
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Specific metal ions bind to particular sites within proteins. The factors that might influence the thermodynamics of metal ion binding to proteins include metal ion radius, hard-soft acid-base effects, and ligand field stabilization energy changes. We have probed the contributions of these effects through the use of a series of peptides based on naturally occuring zinc finger domains. The metal ion binding sites studied include Cys2His2, Cys3His, Cys4, and Cys2HisX where X OH2, Cl-, N- methylimidazole, and - SCH2Ch2OH. Metal ions tested included ZnII, CoII, CdII, FeII, NiII, and MnII. We found that ligand field stabilization energy changes quantitatively account for preferences for ZnII over CoII. For CdII, hard- soft acid-base effects are dominant with a greater than 100-fold increase in affinity for CdII over ZnII for each Cys for His replacement. For other metal ions, multiple factors clearly contribute. These studies provide components for a rational basis for the design of specific metal binding sites for biosensors and other applications.
- Inorganic Chemistry
- Organic Chemistry
- Atomic and Molecular Physics and Spectroscopy