Next Article in Journal
On the Aqueous Solution Behavior of C-Substituted 3,1,2-Ruthenadicarbadodecaboranes
Next Article in Special Issue
Theoretical Studies of Nickel-Dependent Enzymes
Previous Article in Journal / Special Issue
Concise Review of Nickel Human Health Toxicology and Ecotoxicology
Open AccessArticle

pH Dependent Reversible Formation of a Binuclear Ni2 Metal-Center within a Peptide Scaffold

Department of Chemistry, Trinity University, 1 Trinity Place, San Antonio, TX 78212, USA
*
Author to whom correspondence should be addressed.
Inorganics 2019, 7(7), 90; https://doi.org/10.3390/inorganics7070090
Received: 24 May 2019 / Revised: 27 June 2019 / Accepted: 3 July 2019 / Published: 16 July 2019
(This article belongs to the Special Issue Bioinorganic Chemistry of Nickel)
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. View Full-Text
Keywords: biological nickel sites; nickel-thiolates; dinuclear nickel metallopeptides; thiolate oxidative damage biological nickel sites; nickel-thiolates; dinuclear nickel metallopeptides; thiolate oxidative damage
Show Figures

Graphical abstract

MDPI and ACS Style

Keegan, B.C.; Ocampo, D.; Shearer, J. pH Dependent Reversible Formation of a Binuclear Ni2 Metal-Center within a Peptide Scaffold. Inorganics 2019, 7, 90.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop