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Preparation and Characterization of Carbonic Anhydrase-Conjugated Liposomes for Catalytic Synthesis of Calcium Carbonate Particles

Preparation and Characterization of Carbonic Anhydrase-Conjugated Liposomes for Catalytic Synthesis of Calcium Carbonate Particles

Keisuke Maeshima, Makoto Yoshimoto

Enzyme Microb Technol. 2017 Oct;105:9-17.

PMID: 28756864

Abstract:

The biomimetic approach using immobilized enzymes is useful for the synthesis of structurally defined inorganic materials. In this work, carbonic anhydrase (CA) from bovine erythrocytes was covalently conjugated at 25°C to the liposomes composed of 15mol% 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine-N-(glutaryl) (NG-POPE), and the zwitterionic and anionic phospholipids with the same acyl chains as NG-POPE. For the conjugation, the carboxyl groups of liposomal NG-POPE were activated with 11mM 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and 4.6mM N-hydroxysulfosuccinimide (sulfo-NHS). The carbonic anhydrase-conjugated liposomes (CALs) with the mean hydrodynamic diameter of 149nm showed the esterase activity corresponding to on average 5.5×102 free CA molecules per liposome. On the other hand, the intrinsic fluorescence and absorbance measurements consistently revealed that on average 1.4×103 CA molecules were conjugated to a liposome, suggesting that the molecular orientation of enzyme affected its activity. The formation of calcium carbonate particles was significantly accelerated by the CALs ([lipid]=50μ M) in the 0.3M Tris solution at 10-40°C with dissolved CO2 (≈17mM) and CaCl2 (46mM). The anionic CALs were adsorbed with calcium as revealed with the ζ-potential measurements. The CAL system offered the calcium-rich colloidal interface where the bicarbonate ions were catalytically produced by the liposome-conjugated CA molecules. The CALs also functioned in the external loop airlift bubble column operated with a model flue gas (10vol/vo% CO2), yielding partly agglomerated calcium carbonate particles as observed with the scanning electron microscopy (SEM).

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP9001030	Carbonic Anhydrase from bovine erythrocytes		9001-03-0	Price

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