Date of Thesis
Heterobimetallic cofactors are commonly found in proteins and allow them to perform unique chemical processes that would otherwise not be possible. The interactions between these metals allow the protein to accomplish difficult chemical transformations. Previously, the thermodynamic stability of a FeII /MnII cluster in the dinucleating ligand F-HXTA (5-fluoro-2-hydroxy-1,3-xylene-α,α′-diamine-N,N,N′,N′-tetraacetic acid) has been investigated in our lab as a model of cluster assembly in the proteins ribonucleotide reductase (RNR) and R2-like ligand binding oxidases (R2lox). By measuring equilibrium concentrations of F-HXTA complexes via 19F-NMR, it was found that the equilibrium for metal exchange between the homobimetallic FeII /FeII and MnII /MnII complexes favored the hetereobimetallic FeII /MnII product (K = 2.2) This work has been extended to see if the enhanced heterobimetallic stability is a general phenomenon or if it is specific to FeII and MnII. We investigated three new pairs of divalent metal ions: FeII /MgII, ZnII /FeII, and ZnII /MgII using the same methodology. Crystals of the complexes [Mg(H2O)6][Mg2(F-HXTA)(H2O)4]2•14H2O and [Zn(H2O)6][Zn2(F-HXTA)(H2O)3] 2•10H2O were grown and characterized via x-ray crystallography 1H-NMR and 19F-NMR confirming the proposed structures of each complex in solution. It was found that each new metal ion pair exhibited enhanced stability for their respective heterobimetallic complexes. The metal exchange equilibria for FeII /MgII, ZnII /FeII, and ZnII /MgII complexes had equilibrium constants favoring the hetereobimetallic products with KFeMg = 4.15(0.07), KZnFe = 4.4(0.3), and KZnMg = 5.59(0.09).
metalloclusters, heterobimetallic, protein model systems, thermodynamic exchange, HXTA
Master of Science
Hartnett, Sean, "Stability of Bimetallic Clusters in Protein Model Systems" (2018). Master’s Theses. 214.