Synthesis And Application Of Biomacromolecules-Metal-Organic Frameworks Complex

Metal-Organic-Frameworks(MOFs)are a new class of porous materials with unique properties such as ultra-high porosity,structural adjustability,surface topology and channel structure.The rigid-flexible balance and controllability of the MOFs can provide structural protection for the guest molecules,and some MOF structures are biocompatible,which can be used as a carrier for bio-macromolecules.In this paper,ZIF-8 was selected as the metal organic framework material,and the enzyme/plasmid-metal organic framework complex system was constructed to explore the size effect on enzyme activity of the enzyme-MOF complex and investigate the chemical regulation of cell-free expression system based on plasmid-MOF acidic dissociation.In this paper,an enzyme-metal organic framework complex was prepared by simple and mild aqueous phase in situ synthesis.By changing the molar ratio of precursors,a batch of different sizes of ZIF-8 was prepared for embedding cytochrome c.Various characterization methods were used to characterize the structure of the complex and explore the size effect on the enzyme activity,including X-rays diffraction,thermogravimetric analysis,and infrared spectroscopy.The nitrogen adsorption results showed that the specific surface area increased with the decrease of particle size.The results of Michaelis constant revealed that as the particle size decreased,the Km value decreased,and the increase of substrate affinity led to the improvement of the apparent activity of the enzyme.The Km decreased by a maximum of 260 times,the activity of Cytochrome c increased 10-28 folds at different particle sizes.The phenomenon that the activity of cytochrome c is increased after embedding has been discovered before,but no one has ever explored the conformational change of protein.In this paper,UV-Vis,RR and other characterization methods were used to investigate the changes of the conformation of cytochrome c in metal-organic frameworks.Due to these conformational changes of cytochrome c,the protein partially unfolds,and the originally compact heme center forms a part of "holes",which facilitates the entry of the substrate H2O2,leading to the increase of the apparent activity of the enzyme.Furthermore,a plasmid-metal complex system was constructed.Due to the acidic dissolution property of ZIF-8 structure,hydrochloric acid was added to the cell-free system to lower the pH,and the plasmid-MOF complex was decomposed to release the plasmid,arousing the protein expression in the cell-free system.In the co-embedded plasmid and glucose oxidase system,the add of glucose which was oxided to gluconic acid by glucose oxidase caused the reduction of pH,leading to the release of plasmid and the protein expression in the cell-free system.The expression results showed that the system didn't express protein at first.After adding hydrochloric acid or glucose to the system,one hour later,the system began to express protein and the amount of fluorescence began to increase.The analysis of the mRNA transcription process showed that the mRNA content increased one hour later after the addition of hydrochloric acid or glucose,resulting in higher level of transcription and translation in the cell-free system.