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Kinetic study of catalytic CO2 hydration by metal-substituted biomimetic carbonic anhydrase model complexes.

ABSTRACT: The rapid rise of the CO2 level in the atmosphere has spurred the development of CO2 capture methods such as the use of biomimetic complexes that mimic carbonic anhydrase. In this study, model complexes with tris(2-pyridylmethyl)amine (TPA) were synthesized using various transition metals (Zn2+, Cu2+ and Ni2+) to control the intrinsic proton-donating ability. The pKa of the water coordinated to the metal, which indicates its proton-donating ability, was determined by potentiometric pH titration and found to increase in the order [(TPA)Cu(OH2)]2+ < [(TPA)Ni(OH2)]2+ < [(TPA)Zn(OH2)]2+. The effect of pKa on the CO2 hydration rate was investigated by stopped-flow spectrophotometry. Because the water ligand in [(TPA)Zn(OH2)]2+ had the highest pKa, it would be more difficult to deprotonate it than those coordinated to Cu2+ and Ni2+. It was, therefore, expected that the complex would have the slowest rate for the reaction of the deprotonated water with CO2 to form bicarbonate. However, it was confirmed that [(TPA)Zn(OH2)]2+ had the fastest CO2 hydration rate because the substitution of bicarbonate with water (bicarbonate release) occurred easily.

SUBMITTER: Park D

PROVIDER: S-EPMC6731748 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Kinetic study of catalytic CO2 hydration by metal-substituted biomimetic carbonic anhydrase model complexes.

Park DongKook D Lee Man Sig MS

Royal Society open science 20190807 8

The rapid rise of the CO2 level in the atmosphere has spurred the development of CO2 capture methods such as the use of biomimetic complexes that mimic carbonic anhydrase. In this study, model complexes with tris(2-pyridylmethyl)amine (TPA) were synthesized using various transition metals (Zn2+, Cu2+ and Ni2+) to control the intrinsic proton-donating ability. The pKa of the water coordinated to the metal, which indicates its proto ...[more]

PMID: 31598240

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Project description:In this work, maximizing the utilization of CO2 and its precipitation as CaCO3 by using immobilized bovine carbonic anhydrase (BCA) was evaluated. In this way, selection of suitable carriers which have a gas adsorption function would enhance the CO2 sequestration efficiency of the carbonic anhydrase (CA). So a metal-organic framework (MOF), an excellent material for gas adsorption and enzyme immobilization was used. In this manner, BCA was encapsulated into the microporous zeolite imidazolate framework, ZIF-8, for the first time, using a bottle-around-a-ship method. Systematic characterization including powder X-ray diffraction (PXRD), UV-vis, and Fourier transform infrared (FT-IR) spectroscopies, BET, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) confirmed that the entrapment of BCA molecules was successfully achieved during the crystal growth of ZIF-8 with an enzyme loading of ca. 100 ± 1.2 mg g-1 of BCA-ZIF-8. Optimization of the matrix for increasing the stability of the enzyme in an encapsulated form is the main aim of the present study. The de novo approach was proposed because this method provides better enzyme protection from degradation, minimizes enzyme leaching and enables multiple reuse. Then, the influence of different parameters, including pH, temperature, storage and reusability, was evaluated for enzyme@MOF composites versus free enzymes. The prepared biocatalyst exhibited outstanding activity in a wide pH and temperature range and demonstrates high storage stability up to 37 days. This efficient and simple association procedure seems well-adapted to produce an enzymatic bio-catalyst for biocatalytic hydration of CO2. The FT-IR analysis revealed that the structure of BCA was well maintained during the encapsulation process. The thermal stability and reusability of the BCA-ZIF-8 increased noticeably due to the structural rigidity and confinement of the ZIF-8 scaffolds. These two parameters are very important for practical applications.

Dataset Information

Kinetic study of catalytic CO2 hydration by metal-substituted biomimetic carbonic anhydrase model complexes.

Publications

Kinetic study of catalytic CO<sub>2</sub> hydration by metal-substituted biomimetic carbonic anhydrase model complexes.

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