From Natural To Artificial:Photosynthesis-Based Molecular Biomimetic Systems

The photosynthesis provides the crucial substances and energy for all of the lives in the world.It converts the solar energy into bio-energy,electrical energy,and chemical energy,converts the inorganic compounds into organic compounds,and maintains the carbon-oxygen equilibrium.From natural to artificial,from biology to biomimetic,from reading the nature to simulation,then to practicing it in human society,it is of great significance that investigating the process of photosynthesis and the biomimetic chemistry.Inspired by the nature,more and more scientists focus on the photosynthesisbased biomimetic chemistry research in vitro by molecular assembly.On the one hand,it promoted a deeper understanding of the mechanism of the photosynthesis.On the other hand,it also provided a new idea on the research of energy conversion based on the mechanism of photosynthesis.In addition,it has broad application prospects.In the paper,from the basic process of photosynthesis reaction in green plants,some functional units were isolated,and their activity identification and molecular assembly were carried out.A series of bionic systems in vitro were designed and produced,and the ability of the biomimetic system involved was evaluated.The light energy is successfully converted to bioenergy or electrical energy,respectively.The specific contents are summarized as follows:(1)We extracted thylakoid membrane from spinach chloroplasts,isolated,purified,and identified photosystem II pigment protein complexes and ATP synthase by modified multiple protein extraction method.In addition,ATP synthase and the liposome were reconstituted to form the "ATPase-liposome" structure,and the activity and stability were characterized.The raw materials with high activity and stable properties are provided for the follow-up experiment.(2)We integrated PSII and ATPase-liposome into one system by molecular assembly.PSII complexes were assembled on the cellulose acetate honeycomb substrate via layer-by-layer.Then,the ATPase-liposome was deposited onto the outmost layer to simulate the natural stacking structure of the thylakoid membrane.Thus,under light illumination,protons were generated and accumulated in the caves of the honeycomb to form the proton gradient,which is crucial to drive ATPase for ATP production.The system is responsible for light “on/ off” switch,PSII inhibitor,or ATPase inhibitor,and the effect of different numbers of PSII multilayers were discussed.The energy conversion from light energy to bio-energy(ATP)were realized.(3)Chlorophyll derivatives were synthesized for bionic photoelectric devices.In this system,we take both of the role of "pigment antenna" capturing the light energy and the role of "active molecular" generating of electrons.By comparing the molecular structure and photoelectric properties of chlorophyll derivatives with two different derivatives,we discussed the effect of different structures on the capture of light harvesting and the separation ability of electron separation for chlorophyll derivatives.The advantage structure is established,and the conversion of light energy to electric energy is realized in vitro,and the photoelectric conversion efficiency is 0.11%.(4)Four chlorophyll derivatives with molecular self-assembly ability were designed and synthesized.The J-aggregates could be assembled via simple spin-coating method to simulate the role of electron transport substances in natural photosynthesis.By comparing the structure and properties of four chlorophyll derivatives employed as hole-transporters,we discussed the influence of different structures on the formation of J-aggregates and transport capacity of molecules.The dominant molecular structure was established,and the optimum conditions were improved and the photoelectric conversion efficiency was further improved to 0.86%.