Protonation of the Hydroxide Ligand in a Synthetic Analogue of Carbonic Anhydrase, [TpBut,Me]ZnOH:  Inhibition of Reactivity Towards CO2

Bergquist, Catherine; Parkin, Gerard

doi:10.1021/ja991134j

Cited by 68 publications

(47 citation statements)

References 20 publications

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“…348 The deprotonated form Tp-Zn II -OH, as expected, was in equilibrium with the bicarbonate as Tp-Zn II -OCOOH, while its conjugate acid Tp-Zn II -OH 2 + showed no reactivity toward CO 2 . 347,348 Sprigings and Hall reported a simple water-soluble tripodal complex of 1,1,1-tris (aminomethyl)ethane with Zn II (Figure 8B), with water of pK a = 8.0 as the fourth ligand. 349 This complex exhibited enzyme-like Michaelis-Menten saturation kinetics during the hydrolysis of p-nitrophenyl acetate, but its second-order rate constant for the hydrolysis was 2 orders of magnitude lower than that of the native enzyme.…”

Section: Physical-organic Models Of the Active Site Of Casupporting

confidence: 65%

Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

et al. 2008

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I. Introduction to Carbonic Anhydrase (CA) and to the Review 948 1. Introduction: Overview of CA as a Model 948 1.1. Value of Models 950 1.2. Objectives and Scope of the Review 950 2. Overview of Enzymatic Activity 950 3. Medical Relevance 951 II. Structure and Structure−Function Relationships of CA 953 4. Global and Active-Site Structure 953 4.1. Structure of Isoforms 953 4.2. Isolation and Purification 954 4.3. Crystallization 954 4.4. Structures Determined by X-ray Crystallography and NMR 955 4.4.1. Structures Determined by X-ray Crystallography 955 4.4.2. Structure Determined by NMR 955 4.5. Global Structural Features 963 4.6. Structure of the Binding Cavity 964 4.7. Zn II -Bound Water 965 5. Metalloenzyme Variants 966 6. Structure−Function Relationships in the Catalytic Active Site of CA 968 6.1. Effects of Ligands Directly Bound to Zn II 968 6.2. Effects of Indirect Ligands 969 7. Physical-Organic Models of the Active Site of CA 969 III. Using CA as a Model to Study Protein−Ligand Binding 970 8. Assays for Measuring Thermodynamic and Kinetic Parameters for Binding of Substrates and Inhibitors 970 8.1. Overview 970 8.

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Section: Physical-organic Models Of the Active Site Of Casupporting

confidence: 65%

Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

et al. 2008

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“…The geometry at the zinc ion in 1 is distorted tetrahedral with Zn–O 1.900(2) Å and Zn–N average = 2.052(2) Å. The chelating Ttz ligand leads to large N–Zn–O angles and smaller N–Zn–N angles ( τ 4 = 0.78; τ 4 is a geometry index where 1 is tetrahedral and 0 is square planar), as is typically seen with such chelates , . The structure of 1 is similar to (Tp t Bu,Me )ZnOH with Zn–O 1.850(8) Å and Zn–N avg 2.052(5) Å .…”

Section: Resultsmentioning

confidence: 88%

“…In the tris(pyrazolyl)borate (Tp) literature, (Tp)ZnOH complexes are made by two routes: 1) treatment of Zn(ClO 4 ) 2 · 6H 2 O with KTp to form the proposed water bound complex which is in situ treated with base, and 2) treatment of TpZnLG (LG = leaving group = OAc, NO 3 , Cl, or Br) with hydroxide (Scheme ). In our experience with bulky Ttz ligands, these routes have not produced (Ttz)ZnOH complexes.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Biomimetic Zinc Complexes for CO2 Activation and the Influence of Steric Changes in the Ttz Ligands [Ttz = Tris(triazolyl)borate]

et al. 2015

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Carbon dioxide fixation with zinc complexes of the anionic tris(triazolyl)borate (Ttz) ligand offers biomimetic structures in a hydrophilic environment. However, the synthetic result depends greatly on the steric bulk of the Ttz ligand. Synthetic routes adapted from the synthesis of (Tp)ZnOH have been applied to bulky Ttz ligands, but side products often result because Ttz frequently forms complexes with +1 metals or cations used in the synthesis. Nonetheless, (Ttz tBu,Me )-ZnOH (1) has been successfully synthesized and crystallographically characterized, but only via the hydrolysis of the zinc (hex-(1) [a] 2495 Scheme 2. The application of synthetic routes that are known in the literature to form TpZnOH leads to different results when applied to the formation of biomimetic Ttz zinc complexes. However, zinc hydroxide complexes of Ttz can be achieved in some cases. In this Scheme M = Na, K, NMe 4 and L = Tp or Ttz of varied steric bulk (this work focuses on L = Ttz tBu,Me , Ttz iPr2 , Ttz Ph,Me ). 2496Scheme 3. Successful route to (Ttz tBu,Me )ZnOH (1) via Zn amide (6). Zn amide structure is tentatively assigned as κ 3 or κ 2 .Scheme 4. Synthesis of the zinc hydroxide (2a) and zinc carbonate (2b) complexes. Two equivalents of 2a react with CO 2 to eliminate water and form one equivalent of 2b.

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“…In addition to the structural analogy of pyrazole to imidazole, 72 the Tp chelates offer easy access to a number of structural homologs. Combined with the high-symmetry of these systems, this allows for a more detailed analysis than is usually possible.…”

Section: Introductionmentioning

confidence: 99%

Integrated Paramagnetic Resonance of High-Spin Co(II) in Axial Symmetry: Chemical Separation of Dipolar and Contact Electron−Nuclear Couplings

2008

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Integrated paramagnetic resonance, utilizing EPR, NMR and ENDOR, of a series of cobalt bis-trispyrazolylborates, Co(Tpx)2, are reported. Systematic substitutions at the ring carbons and on the apical boron provide a unique opportunity to separate through-bond and through-space contributions to the NMR hyperfine shifts for the parent, unsubstituted Tp complex. A simple relationship between the chemical shift difference (δH − δMe) and the contact shift of the proton in that position is developed. This approach allows independent extraction of the isotropic hyperfine coupling, Aiso, for each proton in the molecule. The Co··H contact coupling energies derived from the NMR, together with the known metrics of the compounds, were used to predict the ENDOR couplings at gζ. Proton ENDOR data is presented that shows good agreement with the NMR-derived model. ENDOR signals from all other magnetic nuclei in the complex (14N, coordinating and non-coordinating, 11B and 13C) are also reported.

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Protonation of the Hydroxide Ligand in a Synthetic Analogue of Carbonic Anhydrase, [Tp^Bu^{^t}^,Me]ZnOH: Inhibition of Reactivity Towards CO₂

Cited by 68 publications

References 20 publications

Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

Synthesis of Biomimetic Zinc Complexes for CO2 Activation and the Influence of Steric Changes in the Ttz Ligands [Ttz = Tris(triazolyl)borate]

Integrated Paramagnetic Resonance of High-Spin Co(II) in Axial Symmetry: Chemical Separation of Dipolar and Contact Electron−Nuclear Couplings

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