gas contaminants capturing by gamma-carbonic anhydrase catalyst: a quantum chemical approach

in this paper, we used quantum chemical approach to shed light on the catalytic mechanism of γ-carbonic anhydrase (γ-ca) to convert carbon dioxide to bicarbonate ion. density functional theory (dft) using b3lyp and ub3lyp functional and three split-valance including 6-31g*, 6-311g** and 6-311++g** basis sets were used to calculate the details of electronic structure and electronic energy of active and inactive forms of γ-ca enzyme active center, and complex between γ-ca and carbon dioxide. the catalytic mechanism involved the nucleophilic attack of cobalt bound hydroxide ion to co2. in the following, the five coordinate cobalt complex as a transition state is formed and then the produced bicarbonate is displaced by a water molecule and give cobalt bound hydroxide for the next turn of catalysis. the activation energy barrier for this mechanism is about 7.9 kcal/mol.