Carbonic anhydrase-mimetic bolaamphiphile self-assembly for CO₂ hydration and sequestration

A biomimetic catalyst was prepared through the self-assembly of a bolaamphiphilic molecule with histidine moieties for the sequestration of carbon dioxide. The histidyl bolaamphiphilic molecule bis(N-a-amidohistidine)-1,7-heptane dicarboxylate has been synthesized and self-assembled to produce analogues of the active sites of carbonic anhydrase (CA) after association with Zn2+ ions. Spectroscopic analysis demonstrated the coordination of the Zn2+ ions with histidine imidazole moieties, which is the core conformation of CA active sites. The Zn-associated self-assembly worked as a CA-mimetic catalyst that shows catalytic activity for CO₂ hydration. Evaluation of the kinetics of using para-nitrophenylacetate revealed that the kinetic parameters of the CA-mimetic catalyst were maximized at the optimal Zn concentration and that excess Zn ions resulted in deteriorated catalytic activity. The performance of the CA-mimetic catalyst was enhanced by changing the pH value and temperature of the reaction, which implies that the hydrolysis of the substrate is the rate-determining step. The catalyst-assisted sequestration of CO₂ was demonstrated by CaCO₃ precipitation upon the addition of Ca2+ ions. This study offers an easy way to prepare enzyme analogues for CO₂ sequestration through the self-assembly of bolaamphiphile molecules with designer biochemical moieties.