Carbonic Anhydrase‐Mimetic Bolaamphiphile Self‐Assembly for CO₂ Hydration and Sequestration

Abstract

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-α-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 Zn(2+) ions. Spectroscopic analysis demonstrated the coordination of the Zn(2+) 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 Ca(2+) 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.

Effects of transition metal ions on the catalytic activity of carbonic anhydrase mimics

“…To compare the catalytic performance of the various catalysts prepared, the kinetics parameters of turnover numbers (k cat ) and Michaelis constants (K M ) were determined based on p-NPA deacetylation experiments, and then the catalytic efficiencies (k cat /K M ) were calculated. The kinetic parameters of Zn-catalyst were taken from a previous report [10]. Turnover numbers of the metal-catalysts decreased in the following order: Zn > Co > Cd ≈ Ni (Fig.…”

“…For the creation of a CA-mimetic catalyst, histidyl bolaamphiphile molecules were synthesized according to a reported procedure [10,12]. Briefly, the histidyl bolaamphiphile was synthesized by conjugating histidine benzylester p-toluenesulfonate with azelaic acid (98%).…”

“…The effects of transition metal ions on the catalytic activity of transition metal ion-ligand complexes should be evaluated further to guide the design principles of biomimetic catalysts. Recently, we reported a CA-mimetic catalyst formed by means of histidyl bolaamphiphile self-assembly with a zinc ion cofactor [10]. By means of the self-assembly, nanoscale CA analogues with densely packed surface-exposed histidine imidazoles were created in an aqueous solution, and then zinc ions were http://dx.doi.org/10.1016/j.molcata.2015.07.006 1381-1169/© 2015 Elsevier B.V. All rights reserved.…”

Metal organic frameworks mimicking natural enzymes: a structural and functional analogy

“…29a). 284 Under basic medium this bolaamphiphilic molecule aggregates to a non-uniform spherical material possessing a peripheral area crafted with an imidazole group which can effectively bind Zn(II) ion but collapses in acidic media. This catalyst pursued excellent CO 2 hydration at pH 9.5 with k cat 134 AE 8 s À1 and a catalytic efficiency [k cat /K m = (3.8 AE 0.5) Â 10 4 M À1 s À1 ] compared to 9.2 Â 10 7 M À1 s À1 for the actual CAII enzyme.…”

Copper‐Coordinated Histidyl Bolaamphiphile Assembly as an Oxidative Catalyst: Coordination Structure and Catalytic Activity in Cyclohexane Oxidation

“…[9,[23][24][25] In addition to the surface-exposed functional groups, the assembled structure characterized by dense, particulate aggregation of histidyl bolaamphiphiles displays considerable resistance to vacuum and dry environments, which is distinct from the properties of other supramolecular structures comprised of surfactants. Due to the amphiphilicity of the molecule, histidyl bolaamphiphiles self-assemble to form colloidal particles in aqueous solution, exposing the hydrophilic imidazole and carboxyl groups of histidine on the surface.…”