Construction Of Artificial Enzymes Via Amino Acids Or Amino Acid Derivatives Based Metal Organic Frameworks

Natural enzymes usually have many limitations in practical use such as lack of sources,low stability,easy inactivation and poor reusability.Many natural enzymes fail to meet the actual requirement of reactions,which prompts people to design and develop synthetic materials to mimic the catalytic function of natural enzymes.Metal organic frameworks(MOFs)are a kind of porous materials formed via coordinating organic ligands with metal ions,which have the advantages of diverse composition and functions,strong stability,easy separation and recovery.Therefore,MOFs have become ideal materials for the construction of artificial enzymes.Amino acids are the basic components of proteins.The carboxyl,amino and some side chain groups of amino acids are easy to coordinate with various metal ions,which are expected to form catalytic active centers that similar to natural enzymes.Based on this,we presented the construction of two kinds of MOFs with natural enzymatic activity via the coordination of amino acid or amino acid derivative as organic ligands with specific metal ions.The catalytic performances and stability of the MOFs-based enzyme mimics were investigated.The main conclusions are as follows:(1)A defective MOF(DE-MIP-202)with alkaline phosphatase-like activity was created via the coordination of L-aspartic acid with Zr ions,and adding the acid modulator acetic acid during the synthesis.The results showed that the introduction of defects did not change the structure of MIP-202,but enhanced its alkaline phosphatase catalytic hydrolysis activity.Compared with natural alkaline phosphatase,DE-MIP-202 exhibited superior stability during the long-time incubation in extreme pH or temperature environments,and also showed good reusability.DE-MIP-202showed specificity toward phosphate substrate,but no hydrolysis ability toward carboxylate substrate.(2)A MOF(Cu-Cys)with laccase-like activity was created via the coordination of L-cystine with Cu ions.Structural analysis showed that Cu-Cys possesses a Cu~?-Cu~? electron transfer system similar to natural laccase.Reaction kinetic studies demonstrated that Cu-Cys follows the typical Michaelis-Menten model.Compared with natural laccase,Cu-Cys exhibited superior stability during the long-time incubation in extreme pH,temperature or high salt conditions,as well as the good reusability.Finally,based on the laccase-like activity of Cu-Cys,a colorimetric method for epinephrine detection was developed,which achieved a wider linear range(9?455?M)and a lower detection limit(2.7?M).Cu-Cys displayed excellent accuracy and sensitivity toward epinephrine in the practical detection of urine samples.