Artificial Design Of Carbon Dioxide Reductase Based On Copper Protein

The increase of CO₂ concentration in atmosphere is considered to have an important impact on global climate change.To reverse this effect,we need not only to curb our dependence on fossil fuels,but also to develop effective strategies to capture and utilize carbon dioxide in the atmosphere.The reduction of CO₂ by visible light has attracted much attention.The visible light-driven redox system consists of electron donors,photosensitizers,electronic intermediates and catalysts.It is a promising research hotspot to study the CO₂reductase designed artificially and then imitate the natural photosynthesis system to absorb light energy to achieve the function of catalyzing CO₂ reduction.The copper protein Cue O was purified by cloning expression and quantified by UV-visible absorption spectroscopy.After the expression and purification of Cue O,the copper content of the protein was identified by the method of coordination.Based on the fact that Cue O is a homogeneous enzyme with multiple copper ions and high expression efficiency,this paper uses this enzyme as catalyst,[Ru（bpy）₃]²⁺as photosensitizer,and sodium ascorbate as sacrificial reductant in the anaerobic system under light,it can reduce CO₂ to CO.The advantage of this reaction system is that photocatalytic activity can be produced without a chemical molecular catalyst and an organic solvent.In order to further understand the reaction mechanism,the combination of copper and carbonyl was identified by UV-visible spectroscopy and infrared absorption spectroscopy.sf YFP can be transformed into photosynthetic protein similar to natural photosynthesis.By using gene codon expansion technique,sf YFP can specifically insert 4-formyl-l-phenylalanine unnatural amino acids（Bpa）.The unnatural amino acids replace the tyrosine of the chromophore.Using X-ray crystallography,the diffraction data of sf YFPDE95C with 1.8（?）resolution were collected.Compared with the wild-type fluorescent protein,66 sites of the photosensitive protein sf YFPDE95C were successfully inserted with the unnatural amino acid Bpa.The photosensitizers used in photocatalytic reduction of CO₂ are usually small molecular complexes.There are many problems in the synthesis of small molecular complexes.With the research of photosensitizers,more and more fluorescent proteins have been widely recognized.In order to develop the whole enzyme catalytic system of light driven CO₂ reduction,the photosensitive protein super folded YFP can be designed as a kind of biological photosensitive protein by using the luminescent characteristics of fluorescent protein.In the previous work,according to the characteristics of fluorescent protein,fluorescent protein was designed as a photosensitive protein,which realized the visible light-driven reduction of carbon dioxide.In order to further develop the whole enzyme catalytic system that can drive protein to reduce carbon dioxide,a series of cysteine mutations of photosensitive proteins were carried out.The structure of one of the mutant photosensitive proteins,sf YFPDE95C,was analyzed by X-ray crystal diffraction method,and the diffraction data were collected at 1.8（?）resolution.