Application Of New Metal-organic Framework Materials In Enzyme Immobilization And Mimic

Metal-organic frameworks(MOFs)are a class of porous materials formed by metal nodes and organic ligands through coordination bonds.Due to its high specific surface area,easy to adjust pore size,easy modification of metal nodes and ligands and mild synthesis conditions,MOFs materials are considered to be ideal materials for enzyme immobilization and mimic.Trimellitic acid is an important polycarboxylic acid ligand and a good building unit for the construction of porous coordination polymers.In this paper,trimesic acid was used as an organic ligand to form metal organic framework materials with nickel ions and iron ions,respectively,and their applications were also studied.The main results are as follows:1.Nickel-based metal organic framework materials(Ni-BTC)were synthesized in this paper.Compared with other Ni2+-modified materials,the Ni-BTC materials were easily obtained and required shorter synthesis time.Through characterization experiments,we found that as synthesized Ni-BTC materials generally appeared as a long rod and were formed by the combination of nickel ions and carboxyl groups of trimesic acid.After optimization of the immobilization conditions,Ni-BTC could realize one-step efficient immobilization of histagged carbonic anhydrase(His-hCA ?),and the enzyme activity recovery is about 99%.After immobilization,His-hCA ? had enhanced pH stability and storage stability.The immobilized His-hCA ? exhibited excellent reusability and retains 65%of initial activity after 8 cycles.In the kinetic experiments,the immobilized enzyme and the free enzyme had similar Km and Vmax values.2.In order to improve the recovery of the immobilized enzyme and the separation of the product,magnetic responsive nickel-based metal organic framework materials(Fe3O4/Ni-BTC)were synthesized by a one-step hydrothermal method.The characterization results showed that the Fe3O4/Ni-BTC materials still appeared as long rod-like structures,and magnetic nanoparticles were only attached to the surface of Ni-BTC.The introduction of magnetic nanoparticles makes the Fe3O4/Ni-BTC material have good magnetic responsiveness.Enhanced fluorescent protein with a histidine tag and enhanced fluorescent protein without a histidine tag were prepared to study the binding force between the protein and the carrier.Protein adsorption and desorption experiments demonstrated that the adsorption of protein and carrier is the result of multiple forces.Under high temperature conditions,the Fe3O4/Ni-BTC material could achieve one-step efficient immobilization of the histidine-tagged thermostable S-adenosylmethionine synthetase(SAMS)with an enzyme activity recovery of about 95%.After immobilization,SAMS exhibited enhanced pH stability and thermal stability.The immobilized SAMS showed good reusability and retained 75%of initial activity after 5 cycles.3.In the coordination experiment with various metal ions,only iron ions can form a stable structure with trimesic acid.After a series of conditions optimization,the optimal synthesis conditions for Fe-BTC were 100 mM HEPES(pH 7.4)and Fe/BTC(molar ratio)=5:1.The characterization results showed that the Fe-BTC materials were amorphous structures and formed by the association of iron ions with the carboxylic acid of trimesic acid,and HEPES was also involved in the coordination synthesis.The Fe-BTC material had a simulated peroxidase activity and a good response relationship with hydrogen peroxide in the range of 0-100 ?M.At the same time,Fe-BTC materials exhibited excellent selectivity and reusability.