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Natural Organic Photosynthetic Solar Energy Transduction
Published in Sun Sam-Shajing, Sariciftci Niyazi Serdar, Organic Photovoltaics, 2017
The electrons extracted from water are donated to Photosystem II, and after a second light-driven electron transfer step by Photosystem I [8], eventually reduce an intermediate electron acceptor, the oxidized form of nicotinamide adenine dinucleotide phosphate (NADP+). Protons are also transported across the membrane and into the thylakoid lumen during the process of the noncyclic electron transfer, creating a pH difference, which contributes to the proton motive force. The energy in this proton motive force is used to make ATP. The NADPH and ATP that are formed in the light-driven steps of photosynthesis are used to fix CO2 to form sugars and other organic products that give energy for metablolism and growth of the organism. Excess stored energy is available to us in the form of food, fiber, and biomass.
Hybrid Scanning Electrochemical Techniques
Published in Allen J. Bard, Michael V. Mirkin, Scanning Electrochemical Microscopy, 2022
Christine Kranz, Christophe Demaille
SPECM has also recently been extensively employed to study biophotocathodes, comprising natural photosystems I and II. Photosystem I (PSI) is a photosynthetic membrane protein complex that, in nature, utilizes light to generate electrons needed for producing the energy carrier NADPH, while simultaneously oxidizing plastocyanine. These reduction and oxidation reactions occur at distinct sites of PSI, labeled FB− and P700, respectively. Zhao et al. integrated PSI into a redox hydrogel deposited on an electrode surface in such a way that the oxidizing P700 site was efficiently wired to the electrode via electron hoping between the gel-bound redox sites (Figure 17.31) [231].
Production of Clean Energy from Cyanobacterial Biochemical Products
Published in Stephen A. Roosa, International Solutions to Sustainable Energy, Policies and Applications, 2020
Figure 4-1 shows the oxygenic “light reactions” of photosynthesis driven by the solar energy captured by the light-harvesting complexes of PSI and PSII. Electrons extracted from H2O by the oxygen-evolving complex of PSII are passed along to the photosynthetic electron transport chain via plastoquinone (PQ), the cytochrome b6f complex (Cyt b6f), plastocyanin (PC), photosystem I (PSI), and ferredoxin (Fd), then by ferredox- in-NADP+ oxidoreductase to NADP+ ultimately producing NADPH. H+ are released into the thylakoid lumen by the PSII and PQ/PQH2 cycles and used for adenosine triphosphate (ATP) production via ATP synthase.
Vibrational spectroscopy of free di-manganese oxide cluster complexes with di-hydrogen
Published in Molecular Physics, 2023
Sandra M. Lang, Thorsten M. Bernhardt, Joost M. Bakker, Bokwon Yoon, Uzi Landman
In the natural photosystem, protons and electrons are sequentially transferred away from PS II to photosystem I where they are used for the reduction of CO2 to carbohydrates [21]. In an electrochemical environment protons migrate through the electrolyte to finally undergo reaction (2) at the cathode [22]. Both processes are of course not feasible under gas phase conditions. Thus, due to this lack of proton/electron transfer channels and the high intrinsic endothermicity of the water oxidation reaction, H2O2 formation does not proceed in a full catalytic reaction cycle under the thermal room temperature conditions of an ion trap. Instead hydrogenated manganese oxide clusters and H2O2 are formed [13,18–20], but the HER step that would complete the catalytic reaction cycle is inhibited. Consequently, aiming at gaining insight into this important reaction step, we focus on the reverse reaction, the H2 dissociation, and investigate the interaction of the di-manganese oxide clusters with hydrogen.
Sinapis alba as a useful plant in bioremediation – studies of defense mechanisms and accumulation of As, Tl and PGEs
Published in International Journal of Phytoremediation, 2022
Beata Krasnodębska-Ostręga, Monika Sadowska, Ewa Biaduń, Radosław Mazur, Joanna Kowalska
Plants grown in soil with the addition of sediments exhibited a delay in leaf development. In control plants, 10–11 fully developed leaves were observed, while in plants grown on sediments only 4–5 (Figure 1). The addition of MnO2 did not change the number of leaves. Total chlorophyll concentration in leaf tissue was comparable in all experimental conditions (Figure 2(A)), while the ratio of chlorophyll a to chlorophyll b content was lower in plants grown on sediments and sediments with MnO2 (Figure 2(B)). This observation suggests different organization of photosynthetic chlorophyll–protein complexes and in consequence changes in photosynthesis yield. Growth on polluted soil influences plants’ photochemical efficiency (Figure 2(C–E)). The maximal (Fv/Fm) and effective (Y(II)) quantum yields of photosystem II were lower compared to control conditions (Figure 2(C,D)). However, these results are not statistically significant, implying a diverse response of individual plants to stress conditions. In contrast, there is clear evidence of a decrease of photochemical efficiency of photosystem I (Y(I)) in plants grown on sediments (Figure 2(E)). The addition of MnO2 to sediments did not affect photochemical efficiency (Figure 2(C–E)). The decrease of chlorophyll a to chlorophyll b ratio observed in this study was not detected in S. alba plants grown hydroponically in the presence of Tl (Mazur et al.2016) suggesting different action of Tl alone and in a mixture of various metals from sediments.
Suitability of pre-digested dairy effluent for mixotrophic cultivation of the hydrogen-producing microalgae Tetraselmis subcordiformis
Published in Environmental Technology, 2022
Marcin Dębowski, Magda Dudek, Anna Nowicka, Piera Quattrocelli, Joanna Kazimierowicz, Marcin Zieliński
One interesting and very promising species of microalgae is the halophilous Tetraselmis subcordiformis. When grown under the right conditions, its biomass is rich in protein and carbohydrates for the food industry, and lipid substances for the bio-energy industry [11]. However, the most encouraging avenue of leveraging T. subcordiformis biomass is using it for hydrogen production through direct biophotolysis [12]. This mechanism is mainly mediated by hydrogenase activity, which catalyses reversible H2 oxidation and generates gaseous hydrogen by reducing protons [13]. Two transmembrane peptide complexes, the so-called photosystem I (PSI) and photosystem II (PSII) are responsible for the photolysis of water molecules. PSII produces O2, while PSI anaerobically transfers electrons through ferredoxin to the hydrogenase which initiates the production of hydrogen. Anaerobic conditions are required to induce hydrogen production and hydrogenase activity. It has been shown that environments with oxygen levels below 0.1% provide the best conditions for cell systems for hydrogen production [14]. Removal of sulfur from the medium causes the reversible inactivation of PSII, leading to the inhibition of oxygen evolution by photosynthesis. The oxygen level drops below the level consumed by the respiratory metabolism. However, the PSI photosystem remains active by activating the production of hydrogen [15].