Artificial photosynthesis device that utilizes sunlight across a wide wavelength range

Abstract

This invention provides an artificial photosynthesis device that reconstitutes photosynthetic proteins, electron transport molecules, and oxidoreductases from purple bacteria and other organisms, and utilizes sunlight across a wide wavelength range, including near-infrared light. [Solution] The working electrode comprises a glass substrate 7, a transparent electrode 6a as a conductive substrate, a first lipid membrane laminated and fixed in a patterned region on the surface of the transparent electrode 6a, a second lipid membrane which is a fluid lipid membrane laminated in a region other than the first region on the surface of the transparent electrode 6a and contains photosynthetic protein 4a, photosynthetic protein 4b, photosynthetic protein 4c, photosynthetic protein 4d, photosynthetic protein 4e, electron transport molecule 3 and oxidoreductase, and an aqueous layer 5 in which at least the second lipid membrane is immersed. In the working electrode, electrons can be generated from light energy 8 in the second lipid membrane and electrical energy 9 can be extracted from the transparent electrode 6a.

Description

Technical Field

[0001] The present invention relates to an artificial photosynthesis device that utilizes sunlight in a wide wavelength range.

Background Art

[0002] In the construction of a sustainable society, the issue of energy resources is one of the most important issues. Near-infrared light accounts for about 40% of the sunlight that shines on the ground. However, since the energy of near-infrared light is lower than that of visible light, it cannot be used in plant photosynthesis, solar power generation, etc., and thus remains an unused energy resource. Purple photosynthetic bacteria (hereinafter also referred to as purple bacteria) are known to have the ability to convert low-energy near-infrared light into useful energy, and there is a possibility of utilizing near-infrared-responsive artificial photosynthesis devices. Purple bacteria perform photosynthesis by converting near-infrared light, which is not utilized by plants or cyanobacteria, into useful energy by means of the light-harvesting 1 reaction center pigment protein complex (LH1-RC) they contain. In the reaction center (RC) of purple bacteria, it is presumed that quinone is converted into quinol by light energy, and this is diffusively transported within the photosynthetic membrane, thereby transporting the reducing power necessary for the carbon fixation reaction (dark reaction) that fixes and reduces CO2. The present inventor, Kimura, has reconstituted the photosynthetic membrane of purple bacteria and monitored the quinone dynamics from quinone reduction to quinol transport by vibrational spectroscopy, and has studied the effects of substitutions of quinone, protein, and lipid.

[0003] On the other hand, thylakoid membranes in the chloroplasts of plants and cyanobacteria convert solar energy into chemical energy for photosynthesis, and their structure and function have been widely studied. However, the heterogeneous and dynamic nature of the membrane structure is still not fully understood. This is because studying natural thylakoid membranes in vivo is difficult due to their small size and limited external access to the interior of chloroplasts. Furthermore, a bottom-up approach based on model systems is difficult due to the complexity of natural membranes. Therefore, the inventor, Morigaki, has reconstructed the entire thylakoid membrane into a patterned substrate-supported planar bilayer (Patent Document 1) and is studying the dynamic properties of the membrane structure (see Non-Patent Documents 1 and 2). Specifically, a mixture of thylakoid membrane purified from spinach leaves (a green plant) and synthetic phospholipids, along with a patterned polymer bilayer scaffold, was used to spontaneously form a planar membrane with lateral diffusion properties and fluid membrane components. This reconstituted the entire thylakoid membrane into a patterned substrate-supported planar bilayer. Due to its lateral diffusion properties, the membrane components diffuse two-dimensionally within the planar membrane, interacting with specific proteins to form complexes and accumulating in specific lipid regions, thereby expressing functions such as signal transduction and energy conversion. Furthermore, a functional substrate with a nanogap structure using a lipid membrane has already been proposed (Patent Document 2), which can be used in biosensors and biochips capable of highly sensitive measurement of biomolecules. This functional substrate is formed by partially laminating adhesive layers of uniform thickness to bond a lipid membrane and a solid phase on a support, and has a nanospace (nanogap structure) with a thickness of 5 to 200 nm between the lipid membrane and the solid phase. Because the nanogap structure is very thin, background noise (background signal) can be suppressed, enabling highly sensitive measurements with an improved signal-to-noise ratio. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-063041 [Patent Document 2] Japanese Patent Publication No. 2016-125946 [Non-patent literature]

[0005] [Non-Patent Document 1] T. Yoneda et al., “Photosynthetic Model Membranes of Natural Plant Thylakoid Embedded in a Patterned Polymeric Lipid Bilayer”, ACS Publications, Langmuir 36, pp.5863-5871 (2020). [Non-Patent Document 2] SAMeredith et al., “Model Lipid Membranes Assembled from Natural Plant Thylakoids into 2D Microarray Patterns as a Platform to Assess the Organization and Photophysics of Light-Harvesting Proteins”, small, 2006608 (2021). [Overview of the project] [Problems that the invention aims to solve]

[0006] As described above, the inventors have studied the photosynthetic molecular mechanism of purple bacteria that perform photosynthesis using near-infrared light, and have also proposed a technology to reconstruct photosynthetic tissues from plants and other organisms on a substrate surface. However, a device like a solar panel that can reconstruct photosynthetic tissue on a substrate surface and stably extract the energy obtained through photosynthesis as electrical or chemical energy has not yet been realized. Furthermore, near-infrared light from sunlight has low energy and is not currently being utilized for plant photosynthesis or solar power generation.

[0007] In view of these circumstances, the present invention aims to provide an artificial photosynthesis apparatus that can utilize sunlight across a wide wavelength range, including near-infrared light, by reconstituting photosynthetic proteins, electron transport molecules, oxidoreductases, etc., of purple bacteria, cyanobacteria, etc. [Means for solving the problem]

[0008] To solve the above problems, an artificial photosynthesis apparatus according to the first aspect of the present invention has a working electrode comprising a conductive substrate, a first lipid membrane laminated and fixed in a patterned region on the surface of the conductive substrate, a second lipid membrane which is a fluid lipid membrane laminated in a region other than the aforementioned region on the surface of the conductive substrate and contains photosynthetic proteins, electron transport molecules and oxidoreductases, and an aqueous layer in which at least the second lipid membrane is immersed. In the working electrode of the artificial photosynthesis apparatus according to the first aspect, electrons can be generated from light energy in the second lipid membrane and extracted from the conductive substrate. By forming a patterned artificial film on the surface of a conductive substrate (such as conductive glass or gold), it becomes possible to generate electrons from light energy through photosynthetic proteins, electron transport molecules, and oxidoreductases, and extract them as electrical energy.

[0009] Furthermore, an artificial photosynthesis apparatus according to a second aspect of the present invention has a structure comprising a substrate, a first lipid membrane laminated and fixed in a patterned region on the surface of the substrate, a second lipid membrane which is a fluid lipid membrane laminated in a region other than the said region on the surface of the substrate and contains photosynthetic proteins, electron transport molecules and oxidoreductases, an adhesive layer laminated on the first lipid membrane, an aqueous layer in which at least the second lipid membrane is immersed, and a substrate laminated via the substrate and the adhesive layer. In the structure of the artificial photosynthesis apparatus according to the second aspect, electrons are generated from light energy in the second lipid membrane, and high-energy molecules can be obtained by a reduction reaction of molecules using the electrons in the aqueous solution space formed on the second lipid membrane. By confining a photosynthetic membrane in a nanospace formed between a patterned artificial membrane and a substrate, it becomes possible to extract light energy as chemical energy by obtaining high-energy molecules through molecular reduction reactions using electrons generated from light energy via photosynthetic proteins, electron transport molecules, and oxidoreductases. Here, the adhesive layer is composed of fine particles with a substantially uniform diameter, surface-modified with functional groups that adhere to the substrate or biocompatible polymers.

[0010] In the artificial photosynthesis apparatus according to the first aspect of the present invention described above, the photosynthetic protein is preferably a light-harvesting reaction center pigment protein complex (LH1-RC). Furthermore, the photosynthetic protein is preferably of the non-oxygen-evolving type. In addition, the photosynthetic protein in the artificial photosynthesis apparatus according to the first aspect of the present invention is preferably a purple photosynthetic bacterium. By using purple photosynthetic bacterium, photosynthesis can be performed in the near-infrared wavelength range, and unused energy resources can be utilized. Specifically, the photosynthetic protein can perform photosynthesis using near-infrared light energy with a wavelength of 800 to 1050 nm. Here, purple photosynthetic bacteria capable of performing photosynthesis using near-infrared light energy with wavelengths of 800-1050 nm can be arbitrarily selected from H. halochloris, B. viridis, B. tepida, H. abdelmalekii, T. frisius, T. tepidum, C. japonicum, R. parvum, A. pfennigii, A. tepidum, A. vinosum, R. sphaeroides, R. bogoriensis, and R. antarcticus. However, since there are no purple photosynthetic bacteria capable of performing photosynthesis across the entire wavelength range of 800-1050 nm, multiple purple photosynthetic bacteria are selected for the photosynthetic proteins. Furthermore, the photosynthetic proteins in the artificial photosynthesis apparatus according to the second aspect of the present invention are preferably photosystem I (PSI) and photosystem II (PSII). The photosynthetic proteins are also preferably oxygen-evolving. Additionally, the photosynthetic protein 2 in the artificial photosynthesis apparatus according to the second aspect of the present invention is preferably cyanobacteria. By using cyanobacteria, photosynthesis can be performed in the visible light wavelength range, making it possible to produce NADPH, a high-energy molecule.

[0011] Furthermore, in the artificial photosynthesis apparatus according to the first aspect of the present invention, it is preferable that the surface of the conductive substrate is hydrophilic and that a hydration layer exists between it and the lipid membrane. An artificial photosynthesis apparatus according to the first aspect of the present invention can be used as a solar cell because it generates electrons from solar energy and extracts electrical energy. Furthermore, an artificial photosynthesis apparatus according to the second aspect of the present invention can be used as a chemical reaction reactor because it generates electrons from light energy and extracts chemical energy. [Effects of the Invention]

[0012] The artificial photosynthesis apparatus of the present invention has the advantage of being relatively simple in structure and function, and having excellent durability. Furthermore, the artificial photosynthesis apparatus of the present invention has the advantage of being able to extract electrical energy from near-infrared light and chemical energy from visible light. Since photosynthesis is performed using near-infrared light, it has the advantage of being able to utilize unused energy resources. [Brief explanation of the drawing]

[0013] [Figure 1] Schematic diagram of the artificial photosynthesis apparatus (Example 1) from the first perspective. [Figure 2] Schematic diagram of an artificial photosynthesis membrane [Figure 3] Schematic diagram illustrating the flow of artificial photosynthesis membrane fabrication. [Figure 4] Diagram illustrating how to extract light energy as electrical energy. [Figure 5]Schematic diagram of the configuration of the artificial photosynthesis device from the second perspective (Example 2) [Figure 6] Schematic diagram for explaining the production flow of the nano space [Figure 7] Explanatory diagram for extracting light energy as chemical energy [Figure 8] Graph of near-infrared light absorption characteristics of the light-harvesting 1 reaction center complex contained in purple photosynthetic bacteria

Embodiments for Carrying Out the Invention

[0014] The schematic diagram of the configuration of the artificial photosynthesis device from the first perspective of the present invention is shown in FIG. 1. The artificial photosynthesis device (first perspective) has a working electrode having the following configurations 1a) to 1d). 1a) Conductive substrate. 1b) The first lipid membrane laminated and immobilized on the patterned region on the surface of the conductive substrate. 1c) A fluid lipid membrane laminated on the region other than the above-mentioned region on the surface of the conductive substrate, which is the second lipid membrane containing photosynthetic proteins, electron transfer molecules and redox enzymes. 1d) An aqueous layer that immerses at least the second lipid membrane. In this specification, in electrochemical energy conversion, an electrode where the main electrochemical process occurs is called a "working electrode", and an electrode that creates an electron flow corresponding to the working electrode is called a "counter electrode". Also, an electrode for controlling the potential is called a "reference electrode". In the artificial photosynthesis device of the present invention, there is an aqueous layer in the space between the working electrode and the counter electrode, an electron flow occurs between the working electrode and the counter electrode, and electricity can be obtained.

[0015] Hereinafter, each configuration of the working electrode, which is a feature of the artificial photosynthesis device (first perspective), will be described in detail. The above-mentioned "conductive substrate" in 1a) may be a substrate having conductivity itself (such as a metal substrate of Au, Ag, Pt, etc.), or an electrode formed with a conductive layer on a substrate such as glass or resin (such as conductive glass). The conductive substrate may be transparent, translucent, or opaque, but a transparent conductive substrate is preferred. A transparent conductive substrate is one on which electrodes are formed using conductive metal oxides such as tin-doped indium oxide (ITO), tin oxide (SnO2), or fluorinated tin oxide (FTO), on a transparent substrate such as glass (quartz glass), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), or polyethersulfone (PES). The thickness of the conductive substrate is not particularly limited, but can be arbitrarily selected according to the required strength, capacitance, light transmittance, etc., when used as a conductive substrate.

[0016] The "immobilized first lipid film" in 1b) above refers to a lipid film immobilized on the conductive substrate by physical interaction or chemical bonding, and specifically, a stable polymerized film. Furthermore, "laminated in a patterned region on the surface of the conductive substrate" means, for example, that after laminating monomer lipids on the surface of the conductive substrate to form a monomer layer, the areas other than those to be photopolymerized are masked and light is irradiated to laminate a patterned polymer lipid film onto the conductive substrate. When laminating a polymer lipid film onto a substrate by photopolymerization, monomer lipids having photopolymerizable groups are used. Examples of photopolymerizable groups include double bonds, triple bonds, epoxy salts, and α,β-unsaturated carbonyl groups. Each lipid molecule contains 1 to 10 photopolymerizable groups. After photopolymerization, the monomer lipid film is removed with a surfactant to form a patterned polymer lipid film.

[0017] The "fluid lipid membrane" in 1c) above refers to a lipid membrane that has a membrane structure equivalent to that of a biological membrane and is fluid like a cell membrane. Fluidity is a property of the membrane, specifically the property of lipid molecules constituting the membrane to diffuse within the membrane. In particular, the movement of lipid molecules to change their positions and to move laterally within the same monolayer is called lateral diffusion. In this invention, the fluid lipid membrane includes photosynthetic proteins, electron transport molecules, and oxidoreductases.

[0018] In this invention, the photosynthetic protein is a protein responsible for the reaction that converts light energy from sunlight into electrical energy through photosynthesis, and specifically, it is a membrane protein called the light-harvesting 1 reaction center (LH1-RC). The light energy collected by the LH1 protein complex is transferred to the special pair (SP) of the reaction center RC by uphill energy transfer, and is converted from light energy to electrochemical energy (photoelectric conversion). The resulting electrons are then transferred to quinone, an electron transport molecule.

[0019] Furthermore, electron transport molecules refer to quinone molecules. Quinone molecules bound to the inside of RC accept electrons generated by the photoelectric conversion of SP and are reduced to quinol. This quinol is released from LH1-RC by diffusion transport and reoxidized by the oxidoreductase Cyt b / c1 complex via the quinone pool present in the lipid bilayer, regenerating quinone. The quinone is then transported again by diffusion and binds to the inside of RC.

[0020] Furthermore, oxidoreductases are a general term for enzymes that catalyze redox reactions, and can be classified into oxidases, reductases, dehydrogenases, etc., depending on their mechanism of action and reaction products. In this invention, nicotinamide adenine dinucleotide (NAD)-dependent oxidoreductases are preferably used. NAD-dependent enzymes are those that use NAD as a coenzyme. In their natural state, NAD is required for the expression of enzyme activity. Examples of NAD-dependent oxidoreductases include formate dehydrogenase (FDH), aldehyde dehydrogenase (AldDH), alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), and glutamate dehydrogenase. The reaction conditions can be the general temperature and pH conditions for the enzyme used, but for example, 20-40°C and pH 6-8 can be used as reaction conditions.

[0021] The phrase "laminated on the surface of the conductive substrate in areas other than the aforementioned region" in 1c) above means that the first lipid film described in 1b) above is fixed to a patterned region (referred to here as region A) on the surface of the conductive substrate, and a fluid second lipid film is laminated in the area other than region A (referred to here as region B). The second lipid film is formed in a state in which it can flow into region B.

[0022] The "aqueous layer immersing at least the second lipid membrane" in 1d) above refers to the layer of water in which the second lipid membrane, which is formed in region B above in a state equivalent to that of a natural biological membrane and capable of flowing, is immersed. The aqueous layer may be enclosed with a sealing material to create a closed system structure, or it may be an open system structure without enclosing the aqueous layer. The aqueous layer between the second lipid membrane and the conductive substrate only needs to be several nanometers or thicker to allow the second lipid membrane to form a membrane that can flow as well as a natural biological membrane. The aqueous layer on the opposite side of the conductive substrate has no thickness limit and only needs to protect the second lipid membrane from contact with air.

[0023] Next, Figure 5 shows a schematic diagram of the configuration of an artificial photosynthesis apparatus according to a second aspect of the present invention. The artificial photosynthesis apparatus (second aspect) has a structure comprising the following 2a) to 2f). 2a) Substrate. 2b) A first lipid film that is laminated and immobilized on a patterned region on the surface of the substrate. 2c) A second lipid film, which is a fluid lipid film laminated on the surface of a substrate in a region other than the aforementioned region, and which contains photosynthetic proteins, electron transport molecules, and oxidoreductases. 2d) An adhesive layer laminated on top of the first lipid film. 2e) A water layer in which at least the second lipid membrane is immersed. 2f) Substrate laminated with the substrate and the adhesive layer

[0024] In the first aspect of artificial photosynthesis, electrons are generated from light energy in the second lipid membrane and extracted from a conductive substrate. In contrast, in the second aspect of artificial photosynthesis, electrons are generated from light energy in the second lipid membrane, and high-energy molecules are obtained through a molecular reduction reaction using these electrons in an aqueous solution space formed on the second lipid membrane.

[0025] The explanations for 2a) to 2c) above are the same as those for 1a) to 1c) above. However, the "substrate" in 2a) to 2c) does not need to be conductive, as electrons are transferred from photosynthetic proteins and electron transfer molecules to molecules in the membrane and aqueous solution; insulating materials and semiconductors can also be used. In other words, in the artificial photosynthesis apparatus (second perspective), the substrate to which the second lipid membrane is adsorbed may or may not be an electrode.

[0026] Furthermore, the "adhesive layer" in 2d) above refers to a layer that adheres the lipid film to the substrate and controls the thickness of the void structure. Polymer-coated silica nanoparticles can be suitably used as the adhesive layer. The material constituting the adhesive layer is not particularly limited as long as the particle size is constant, and nanoparticles such as silicon, metal, diamond, and quantum dots can be used.

[0027] Furthermore, the "substrate" in 2f) above is laminated on the side opposite to the substrate via an adhesive layer. The material of the substrate can be polymer elastomer, glass, quartz, metal, etc., and can be selected as appropriate. Polymer elastomer is a general term for industrial materials that have rubber-like elasticity, and specifically refers to styrene-based, olefin-based, PVC-based, urethane-based, amide-based elastomers, etc. For example, a silicon elastomer such as polydimethylsiloxane (PDMS) can be used.

[0028] Furthermore, in the artificial photosynthesis apparatus (second aspect), the "aqueous solution space" is a nanogap space provided between the lipid membrane and the substrate, and is filled with an aqueous solution. Its thickness is controlled by an adhesive layer. Its thickness is, for example, 5 to 200 nm, preferably 10 to 100 nm, and more preferably 10 to 50 nm. If the thickness is less than 5 nm, it may be difficult to introduce molecules due to steric hindrance, while if the thickness is 200 nm or more, water-soluble molecules are diluted in the aqueous layer, reducing electron transfer efficiency. By using an adhesive layer of uniform thickness to bond the first lipid membrane, which is laminated and immobilized on a patterned region of the lipid membrane, to the substrate, a nanogap structure with a controlled thickness can be fabricated.

[0029] The "conductive substrate" in 1a) and the "substrate" in 2a) above are preferably hydrophilic substrates because they come into contact with a fluid second lipid film. On hydrophilic substrates, a hydration layer several nanometers thick spontaneously forms between the adsorbed lipid film and the substrate through physical interaction. As a result, lipid molecules formed on the hydrophilic substrate can diffuse laterally, similar to biological membranes. Furthermore, because the substrate is smooth, the first and second lipid films formed on the substrate surface can be formed as continuous, defect-free films.

[0030] We will reconstruct photosynthetic proteins, electron transport molecules, and oxidoreductases from purple photosynthetic bacteria and other organisms that perform photosynthesis using near-infrared light energy, and create artificial films that can utilize sunlight across a wide wavelength range, including near-infrared light. In particular, by forming films on the surface of conductive substrates (conductive glass, gold, etc.), electrons will be generated from light energy through photosynthetic proteins (LH1-RC, etc.), electron transport molecules (quinone, etc.), and oxidoreductases (Cyt b / c1, etc.), and extracted as electrical energy. Furthermore, by confining a photosynthetic membrane in a nanospace formed between a patterned artificial membrane and a substrate such as polydimethylsiloxane (PDMS), it becomes possible to carry out molecular reduction reactions using electrons generated through photosynthetic proteins (photosystem I, photosystem II, cytochrome b6f complex (Cyt b6 / f)), electron transport molecules, and oxidoreductases of higher plants or cyanobacteria that perform photosynthesis using visible light energy (e.g., NADP). + →NADPH). This allows light energy to be extracted as chemical energy.

[0031] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. It should be noted that the scope of the present invention is not limited to the following embodiments or illustrated examples, and numerous modifications and variations are possible. [Examples]

[0032] Figure 1 shows a schematic diagram of one embodiment of an artificial photosynthesis apparatus from a first perspective. As shown in Figure 1, a transparent electrode (ITO) 6a is laminated on a glass substrate 7 as a conductive substrate, and a water layer 5 and a sealing material 11 such as an elastomer are sequentially laminated on the ITO. The artificial photosynthesis membrane 1 is immersed in the water layer 5. Figure 2 shows a schematic diagram of an artificial photosynthetic membrane. As shown in Figure 2, the artificial photosynthetic membrane 1 is composed of a lipid membrane 2, electron transport molecules 3, and photosynthetic proteins (4a-4e). A portion of the lipid membrane 2 is laminated and immobilized as the first lipid membrane in a patterned region on the surface of the transparent electrode (ITO) 6a. Furthermore, the fluid lipid membrane 2 laminated in regions other than those immobilized as the first lipid membrane on the surface of the transparent electrode (ITO) 6a functions as the second lipid membrane and contains photosynthetic proteins (4a-4e), electron transport molecules 3, and oxidoreductases (not shown). The aqueous layer 5 immerses at least the second lipid membrane; in this embodiment, the entire artificial photosynthetic membrane 1, i.e., the first and second lipid membranes, is immersed in the aqueous layer 5. The working electrode is composed of an artificial photosynthetic membrane 1, a water layer 5, and a transparent electrode (ITO) 6a. Light energy 8 is received from below via the glass substrate 7 and the transparent electrode (ITO) 6a. Then, electrons are generated from the light energy 8 in the second lipid membrane within the artificial photosynthetic membrane 1, and these electrons are extracted from the transparent electrode (ITO) 6a to form electrical energy 9.

[0033] Here, we will explain the method for fabricating artificial photosynthesis membrane 1. Photosynthetic membranes were fabricated by immobilizing a polymer lipid membrane (first lipid membrane) and a fluid lipid membrane (second lipid membrane) on the surface of a conductive substrate using the LB / LS (Langmuir-Blodgett / Langmuir-Schaefer) membrane preparation method or the vesicle fusion method. Specifically, as shown in Figure 3, monomer lipid membranes were layered on the surface of a conductive substrate using photopolymerizable lipids (DiynePC), and patterned artificial membranes were fabricated by photolithography polymerization. After photolithography polymerization, the monomer lipid membranes were removed with a surfactant, and a natural fluid lipid membrane containing photosynthetic proteins, electron transport molecules, and oxidoreductases was introduced. The stable polymer lipid membrane (first lipid membrane 21) and the bio-lipid membrane (second lipid membrane 22) with properties equivalent to those of a biological membrane were then integrated in a predetermined pattern.

[0034] (Reconstruction of the photosynthetic membrane) When introducing a biological lipid membrane into an artificial membrane assembled in a predetermined pattern (hereinafter sometimes referred to as a patterned artificial membrane), a photosynthetic membrane and phospholipid vesicles (e.g., DOPC) are mixed and introduced together. This creates a planar lipid membrane in the compartment surrounded by the polymer lipid membrane, where the photosynthetic membrane and phospholipid membrane are mixed. The planar lipid membrane contains photosynthetic proteins derived from the photosynthetic membrane. For example, photosystem I incorporated into the polymer lipid membrane and ferredoxin and ferredoxin-NADP added to an aqueous solution. + By combining reductases, electrons generated by light energy are transferred to NADP + NADPH can be produced from it.

[0035] (Reconstructing the photosynthetic membrane on the electrode surface) By forming a patterned artificial film on the surface of a conductive substrate (conductive glass, gold, etc.), electrons can be generated from light energy through photosynthetic proteins (such as LH1-RC), electron transport molecules (such as quinones), and oxidoreductases (such as Cyt b / c1), and extracted as electrical energy. Figure 4 is an explanatory diagram of how light energy is extracted as electrical energy. Photosynthetic proteins (4a,4b) convert light energy 8 into electrical energy, and the resulting electrons are transferred to electron transport molecule 3. The electrons transferred to electron transport molecule 3 are taken up by the electrode via oxidoreductase 14 and extracted as electrical energy 9. [Examples]

[0036] Figure 5 shows a schematic diagram of one embodiment of an artificial photosynthesis apparatus from a second perspective. As shown in Figure 5, an Au substrate 6b is provided as the substrate. An aqueous layer 5 and a transparent sealing material 11 are provided in order on the Au substrate 6b, and the artificial photosynthesis membrane 1 is immersed in the aqueous layer 5. As shown in Figure 5, a portion of the lipid membrane 2 is laminated and immobilized as the first lipid membrane in a patterned region on the surface of the Au substrate 6b. Furthermore, the fluid lipid membrane 2 laminated in regions other than those immobilized as the first lipid membrane on the surface of the Au substrate 6b is the second lipid membrane and contains photosynthetic proteins (4a-4e), electron transport molecules 3, and oxidoreductase (not shown). The aqueous layer 5 immerses the second lipid membrane in an aqueous solution space (hereinafter sometimes referred to as a nanospace) formed between the Au substrate 6b and the sealing material 11 (substrate) laminated via an adhesive layer laminated on the first lipid membrane. The second lipid membrane generates electrons from light energy 8, and in the aqueous solution space of the aqueous layer 5 formed on the second lipid membrane, the electrons generated in the second lipid membrane are used in a molecular reduction reaction to obtain high-energy molecules 13 (such as NADPH) with chemical energy 10.

[0037] (Creation of nanospaces) By bonding uniformly sized silica microparticles with adhesive properties to the polymer lipid membrane portion of a pre-formed patterned artificial membrane, and then further bonding polydimethylsiloxane (PDMS), a minute nanospace is formed in the region where the biological lipid membrane exists, with the thickness determined by the silica microparticles.

[0038] (Reconstructing photosynthetic membranes in nanoscale spaces) By confining a photosynthetic membrane in a nanospace formed between a patterned artificial membrane and PDMS, electrons generated from light energy through photosynthetic proteins (PSI, PSII, etc.), electron transport molecules (quinones, etc.), and oxidoreductases (Cyt b6 / f, etc.) are used to carry out molecular reduction reactions, thereby obtaining high-energy molecules (e.g., NADP). + →NADPH), which extracts light energy as chemical energy. Figure 7 is an explanatory diagram illustrating the extraction of light energy as chemical energy. Photosynthetic proteins (4a, 4b) convert light energy 8 into electrical energy, and the resulting electrons are transferred to electron transport molecules 3. The electrons transferred to electron transport molecules 3 undergo a molecular reduction reaction in aqueous solution 5 via oxidoreductase 14, yielding high-energy molecules 13 (such as NADH and NADPH). If the high-energy molecules 13 are water-soluble, the high-energy molecules 13 can be recovered using a microfluidic channel, and the recovered high-energy molecules 13 can be used in biomolecular reactions (e.g., enzyme-mediated sugar synthesis) to extract chemical energy 10 from the high-energy molecules 13. Since high-energy molecules are used in various biological reactions, it is desirable to combine them with systems that produce molecules useful to living organisms. [Examples]

[0039] In the above-described Example 1 (artificial photosynthesis apparatus according to the first aspect), purple photosynthetic bacteria that absorb light in the near-infrared region can be used as photosynthetic proteins. Purple photosynthetic bacteria are described below, and the procedure for isolating and purifying the light-harvesting reaction center (LH1-RC) of these bacteria to high purity is explained. (purple photosynthetic bacteria) Figure 8 is a graph showing the near-infrared light absorption characteristics of each light-harvesting reaction center complex (LH1-RC) contained in 14 species of purple photosynthetic bacteria. For four representative species (B. tepida, T. frisius, A. pfennigii, R. antarcticus), one example of a combination designed to comprehensively absorb light in the 800-1050 nm range is shown. As shown in Figure 8, in addition to the four species mentioned above, there are purple photosynthetic bacteria that absorb light in various near-infrared regions. By combining these, it is possible to construct an artificial photosynthesis apparatus that can effectively utilize near-infrared light in the 800-1050 nm range. It is also possible to change the combination depending on the usage conditions, such as from the perspective of heat resistance. Note that among the 14 species of purple photosynthetic bacteria, the species on the longer wavelength side are limited. Here, the purification of LH1-RC was carried out using the following procedure.

[0040] (Purification of photosynthetic membrane vesicles) The live bacterial suspension was collected, and unwanted senescent cells, waste products, and water-soluble proteins were removed by sonication, centrifugation, and ultracentrifugation to prepare photosynthetic membrane vesicles. Specifically, first, the viable bacterial suspension was centrifuged using a high-speed refrigerated centrifuge (Hitachi Koki Co., Ltd., CR22GII) and an angle rotor (RPR12-2) at a rotation speed of 8000 rpm and a temperature of 4°C for 5 minutes. The precipitate was suspended in 20 mM Tris-HCl buffer (pH 7.5). It was sonicated on ice (Amp. 13%, 1 minute ON / 1 minute OFF x 15), and then centrifuged using a high-speed refrigerated centrifuge and an angle rotor (R20A2) at a rotation speed of 15000 rpm and a temperature of 4°C for 5 minutes, and the supernatant was collected. Subsequently, ultracentrifugation was performed using an ultracentrifuge (Beckman Coulter, Ltd., Beckman L60) and an angle rotor (60Ti) at a rotation speed of 40000 rpm and a temperature of 4°C for 60 minutes, and the precipitate (ICM) was collected and stored on ice.

[0041] (Solubilization of membrane proteins) The type and concentration of surfactant were optimized from photosynthetic membrane vesicles, and the LH1-RC crude fraction was extracted. One example of the procedure is as follows: First, the precipitate was suspended in 20 mM Tris-HCl buffer (pH 7.5) so that the OD at approximately 850 nm was 20. Dodecyl-β-D-maltoside and a small amount of ascorbic acid were added to a final concentration of 1%, and the mixture was stirred using a shaker (EYLA Shaker, Tokyo Rikakikai Co., Ltd.) at 127 rpm for 60 minutes at room temperature. Then, ultracentrifugation was performed using an ultracentrifuge (Beckman L60) with an angle rotor (60Ti) at a rotation speed of 40,000 rpm and a temperature of 4°C for 60 minutes. The supernatant was then collected and stored on ice.

[0042] (Purification of high-purity LH1-RC) To increase the purity of the LH1-RC fraction obtained by solubilizing membrane proteins, separation was performed by anion exchange column chromatography using the surfactant Dodecyl-β-D-maltoside (DDM). Using A-buffer (20 mM Tris-HCl buffer, pH 8.0, 0.1% DDM) and B-buffer (A-buffer + 40-200 mM NaCl), a high-purity LH1-RC fraction was isolated by utilizing the NaCl concentration gradient.

[0043] The procedure was as follows: First, 40 mL of DEAE column preparation was set on the column and equilibrated with MilliQ water (flow rate 1.0 mL / min, 30 min), then equilibrated with A-buffer (flow rate 1.0 mL / min, 30 min). The LH1-RC fraction obtained by solubilization was loaded and equilibrated with A-buffer (flow rate 1.0 mL / min, 30 min). B-buffer was loaded (40, 60, 80, 100, 120, 140, 160, 180, 200 mM NaCl, flow rate 1.0 mL / min, 15 min each). Then, the colored eluted fractions were collected, and those satisfying ODQy / OD280 ≥ 2 were collected as the LH1-RC fraction. Using an ultrafiltration filter (Millipore, AMICON ULTRA, molecular weight cutoff: 100K), a high-speed refrigerated centrifuge (Kubota Manufacturing Co., Ltd., KUBOTA6000), and an angle rotor (A508), the concentrated LH1-RC sample was centrifuged at 5000 rpm and 4°C for 5 minutes, and the concentrated LH1-RC sample was stored on ice. [Industrial applicability]

[0044] This invention can be used as a solar cell that generates electrons from solar energy and extracts electrical energy. It can also be used as a chemical reaction reactor that generates electrons from light energy and extracts chemical energy. [Explanation of Symbols]

[0045] 1 Artificial photosynthetic membrane 2 Lipid membrane 3 Electron transfer molecules 4a-4e Photosynthetic proteins 5 water layer 6a Transparent electrode (ITO) 6b Au substrate 7 Glass substrate 8. Light energy 9 Electrical energy 10 Chemical Energy 11. Sealing material 12 Adhesive layer 13 High-energy molecules 14 Oxidoreductase 21 First lipid membrane 22 Second lipid membrane

Claims

1. A conductive substrate and A first lipid film is laminated and fixed in a patterned region on the surface of the conductive substrate, A fluid lipid film laminated on the surface of the conductive substrate in a region other than the aforementioned region, comprising a second lipid film containing photosynthetic proteins, electron transport molecules, and oxidoreductases, At least a aqueous layer immersing the second lipid membrane, An artificial photosynthesis apparatus having a working electrode equipped with a second lipid membrane, which generates electrons from light energy and extracts electrons from the conductive substrate.

2. circuit board and A first lipid film is laminated and immobilized on a patterned region on the surface of the substrate, A fluid lipid film laminated on the surface of the substrate in a region other than the aforementioned region, comprising a second lipid film containing photosynthetic proteins, electron transport molecules, and oxidoreductases, An adhesive layer laminated on the first lipid film, At least a aqueous layer in which the second lipid membrane is immersed, A substrate laminated with the aforementioned substrate and the aforementioned adhesive layer, An artificial photosynthesis device having a structure comprising a second lipid membrane, which generates electrons from light energy, and which uses these electrons to obtain high-energy molecules through a molecular reduction reaction in an aqueous solution space formed on the second lipid membrane.

3. The artificial photosynthesis apparatus according to claim 1, wherein the photosynthetic protein is a light-harvesting reaction center pigment protein complex (LH1-RC).

4. The artificial photosynthesis apparatus according to claim 3, wherein the photosynthetic protein is of the non-oxygen-evolving type.

5. The artificial photosynthesis apparatus according to claim 4, wherein the photosynthetic protein is a purple photosynthetic bacterium.

6. The artificial photosynthesis apparatus according to claim 5, wherein the photosynthetic protein performs photosynthesis using near-infrared light energy with a wavelength of 800 to 1050 nm.

7. The artificial photosynthesis apparatus of claim 6, wherein the photosynthetic protein comprises a plurality of purple photosynthetic bacteria selected from the group consisting of H. halochloris, B. viridis, B. tepida, H. abdelmalekii, T. frisius, T. tepidum, C. japonicum, R. parvum, A. pfennigii, A. tepidum, A. vinosum, R. sphaeroides, R. bogoriensis, and R. antarcticus.

8. The artificial photosynthesis apparatus according to claim 1, wherein the surface of the conductive substrate is hydrophilic and a hydration layer exists between it and the lipid film.

9. The artificial photosynthesis apparatus according to claim 2, wherein the adhesive layer is composed of fine particles of substantially uniform diameter, surface-modified with functional groups that adhere to the substrate or biocompatible polymers.

10. A solar cell comprising an artificial photosynthesis apparatus according to claim 1 or 2.

11. A chemical reaction reactor comprising an artificial photosynthesis apparatus according to claim 1 or 2.

Images