Document Type
Article
Publication Date
7-2019
Abstract
A disulfide-bridged peptide containing two Ni2+ binding sites based on the nickel superoxide dismutase protein, {Ni2(SODmds)} has been prepared. At physiological pH (7.4), it was found that the metal sites are mononuclear with a square planar NOS2 coordination environment with the two sulfur-based ligands derived from cysteinate residues, the nitrogen ligand derived from the amide backbone, and a water ligand. Furthermore, S K-edge X-ray absorption spectroscopy indicated that the two cysteinate sulfur atoms ligated to nickel are each protonated. Elevation of the pH to 9.6 results in the deprotonation of the cysteinate sulfur atoms, and yields a binuclear, cysteinate bridged Ni22+ center with each nickel contained in a distorted square planar geometry. At both pH = 7.4 and 9.6, the nickel sites are moderately air sensitive, yielding intractable oxidation products. However, at pH = 9.6, {Ni2(SODmds)} reacts with O2 at an ~3.5-fold faster rate than at pH = 7.4. Electronic structure calculations indicate that the reduced reactivity at pH = 7.4 is a result of a reduction in S(3p) character and deactivation of the nucleophilic frontier molecular orbitals upon cysteinate sulfur protonation.
DOI
10.3390/inorganics7070090
Publisher
Multidisciplinary Digital Publishing Institute AG
Repository Citation
Keegan, B. C., Ocampo, D., Shearer, J. (2019). pH dependent reversible formation of a binuclear Ni2 metal-center within a peptide scaffold. Inorganics, 7(7), Article 90. https://doi.org/10.3390/inorganics7070090
Publication Information
Inorganics
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.