Cellular metabolism comprises energy transduction machineries that operate by a series of redox-active components to store energies from nutrients, which are transduced into high-energy intermediates for cellular works such as chemical synthesis, transport, and movement. Biological energy transduction mechanism hints at the construction of a man-made energy storage system. Herein, we present a bio-inspired strategy to design high-performance energy devices based on the analogy between energy storage phenomena of mitochondria and lithium rechargeable batteries. Flavins, a key redox element in respiration and photosynthesis, facilitate either one- or two-electron-transfer redox processes accompanying proton transfer at nitrogen atoms of diazabutadiene motif during cellular metabolism. We have successfully demonstrated flavins as a molecularly tunable cathode material that exhibits reversible reactivity with two lithium ions and electrons per formula unit. Analysis of both the ex situ characterizations and density-functional theory (DFT)-based calculations revealed that the redox reaction occurs via two successive single-electron transfer steps, which is analogous to the proton-coupled electron transfer mechanism of flavoenzymes. Tailored flavin analogues obtained via chemical substitution on the isoalloxazine ring showed fine tunability of electrochemical properties, exhibiting a gravimetric capacity of 174 mAh/g and an average redox potential of 2.65 V, and its expected energy density is comparable to that of LiFePO4.
This study successfully demonstrates that hydrogen-terminated silicon nanowires (H-SiNWs) are an ideal artificial photosynthetic material, which possesses suitable photocatalytic properties to regenerate reducing power (i.e., NADH) and synthesize chemicals by photoenzymatic reaction. H-SiNWs, fabricated by a metal-assisted chemical etching process, possessed an enlarged band gap from the effect of quantum confinement and enabled a cascading electron transfer from electron donor to NAD via an Rh-based electron mediator. Approximately 80% of NADH was photo-regenerated from NAD by H-SiNWs within 2 hrs of light irradiation (wavelength > 420 nm), which was successfully coupled with the photoenzymatic synthesis of L-glutamate. Our work suggests that H-SiNWs are an ideal artificial photosynthetic material, which possesses suitable photocatalytic properties to regenerate NADH and synthesize chemicals by photoenzymatic reaction.
We report on the capability of polydopamine (PDA), a mimic of mussel adhesion proteins, as an electron gate as well as a versatileadhesive for mimicking natural photosynthesis. This work demonstrates that PDA accelerates the rate of photoinduced electron transferfrom light-harvesting molecules through two-electron and two-proton redox-coupling mechanism. The introduction of PDA as a chargeseparator significantly increased the efficiency of photochemical water oxidation. Furthermore, simple incorporation of PDA ad-layer onthe surface of conducting materials (such as carbon nanotubes) facilitated fast charge separation and oxygen evolution through the synergistic effect of PDA-mediated, proton-coupled electron transfer and substrate materials high conductivity. Our work shows thatPDA is an excellent electron acceptor as well as a versatile adhesive; thus, it opens a new electron gate for harvesting photoinduced electrons and designing artificial photosynthetic systems.
Cellulose, a main component of green plants, is the most abundant organic chemical on Earth, produced 1011 tons per year in the biosphere. The polysaccharide consists of D-glucose units linked by beta-1,4-glycosidic bonds and has been widely utilized in diverse engineering fields because of its biocompatibility, abundance, and high chemical stability. In this work, we have demonstrated the utility of carboxymethyl cellulose (CMC) fibers as a sacrificial template to produce binary and tertiary metal oxides fibers. The electrostatic interaction between metal ions and the carboxyl groups in CMC fibers induced a hierarchical structure of metal oxides. The morphologies of synthesized metal oxides (e.g., CeO2, ZnO, and CaMn2O4) could be controlled according to synthetic conditions, such as metal precursor concentration, calcination temperature, and the amount of CMC fibers. Thus-synthesized CMC-templated metal oxide fibers exhibited enhanced performances for photocatalytic, photochemical, and electrocatalytic reactions. The CeO2 fibers showed much higher photocatalytic activity than CeO2 nanoparticles due to superior ability to generate reactive oxygen species which can degrade organic pollutants. We also demonstrated that hierarchical ZnO fibers hybridized with g-C3N4 could provide directional charge transfer pathway and showed their utility for biocatalyzed artificial photosynthesis through visible light-driven chemical NADH regeneration coupled with redox enzymatic reaction. The electrochemical properties of CaMn2O4 fibers enabled bi-functional reactions of oxygen reduction and evolution reactions. We expect that the economical and environmentally friend approach could be extended to green synthesis of hierarchically structured materials of other metal oxides.
In the past 50 years, cytochrome P450 monooxygenases (P450s) have been given significant attention for the synthesis of natural products (e.g., vitamins, steroids, lipids) and pharmaceuticals. Despite their potential, however, costly nicotinamide cofactors such as NAD(P)H are required as reducing equivalents; thus, in situ regeneration of NAD(P)H is essential to sustaining P450-catalyzed reactions. Furthermore, poor stability of P450s has been considered as a hurdle, hampering industrial implementations of P450-catalyzed reactions. Herein we describe the development of an economic and robust process of P450-catalyzed reactions by the combination of P450 immobilization and solar-induced NADPH regeneration. The P450 monooxygenase could be efficiently immobilized on a P(3HB) biopolymer, which enabled simple purification from the E. coli host. We clearly demonstrated that the P450-P(3HB) complex exhibited much higher enzymatic yield and stability than free P450 did against changes of pH, temperature, and concentrations of urea and ions. Using the robust P450-P(3HB) complex and solar-tracking module, we successfully conducted P450-catalyzed artificial photosynthesis under the irradiation of natural sunlight in a preparative scale (500 mL) for multiple days. To the best of our knowledge, this is the largest reactor volume in P450-catalyzed reactions reported so far. We believe that our robust platform using simple immobilization and abundant solar energy promises a significant breakthrough for the broad applications of cytochrome P450 monooxygenases.
Self-assembled light-harvesting peptide nanotubes are synthesized for artificial photosynthesis. Light-harvesting by natural photosynthesis occurs by means of two large protein complexes called photosystem I and II, which are composed of light-harvesting antenna (i.e., chlorophyll a and b) and catalytic metal clusters embedded within proteins. We have succeeded in the development of light-harvesting peptide nanotubes that integrate photosynthetic units, thus mimicking natural photosynthesis. Light-harvesting peptide nanotubes were synthesized by the self-assembly of diphenylalanine (Phe-Phe, FF) and porphyrin. We found that the J-aggregation of porphyrin occurs during the self-assembly of the FF nanotubes via electrostatic attraction and hydrogen bonding. The light-harvesting peptide nanotubes were suitable for mimicking photosynthesis because of their structure and electrochemical properties similar to natural photosystem. We demonstrated that the integrated photocatalytic system is effective for visible light-driven NADH regeneration coupled with redox enzymatic synthesis of fine chemicals such as L-glutamate.
Students will need to write a procedural plan for using WOW data to demonstrate that photosynthesis and respiration occur in a lake. The plan should be detailed enough for others to follow.
This collaborative activity allows students to work in groups to demonstrate their prior knowledge on plants and photosynthesis. Students will work in groups of 3-4 to make a concept map using Post-It notes or note cards on chart paper. Students will begin this activity by brainstorming words or concepts about plants. Students will write each word or concept on each Post-It note. Students are encouraged to draw a picture on the Post-It note to represent each word. Students will then arrange the Post-It notes on chart paper and draw lines to show the relationship between all of the words. Students may also include connecting words along the linking lines to clarify the connection. Connecting words may include words like requires, produces, absorbs, reflects, etc. When the groups have completed their concept maps, they will place them around the perimeter of the classroom in preparation for the gallery walk.
Students are challenged to demonstrate that photosynthesis and respiration occur in lakes. They begin by attempting to demonstrate that photosynthesis and respiration can be measured in lab microcosms. Students need to choose a water quality measure(s) to analyze in laboratory microcosms. They should begin by researching the effects that respiration can have on water temperature, pH, CO2, and DO, using the "Understanding" portion of the WOW website. They should choose a measure(s) that they feel correlates strongly to photosynthesis and . Students should write a procedural plan for testing their hypothesis.
The student inquiry lesson asks students to demonstrate the effects of photosynthesis and respiration. Students decide which variables to analyze in a microcosm study related to photosynthesis and respiration. They produce a written paper, oral presentation, poster, or multi-media presentation instead of a worksheet. The teacher specifies the format. It is helpful if students can refer to printed directions.
Students demonstrate their knowledge of photosynthesis by creating a new verse for the song “You are my Sunshine.” Students will work as a team of 4 students, but each student must create their own verse. Students must include correct information about photosynthesis and incorporate as many key words as possible. It is recommended that students have a time limit, approximately 25 minutes to develop their verse independently. Students will then gather as a group and share their verse with the other students. The groups will need approximately 20 minutes to fit the verses together to form a completed song. The song can then be performed in front of the other groups for an enjoyable musical learning activity about photosynthesis.