Light-induced Oxygen Evolution Research Articles

Multimodale Analyse lichtinduzierter Wasseroxidation in nanoporösen Blockcopolymer‐Membranen**

AbstractDie heterogene lichtgetriebene Katalyse ist ein Eckpfeiler nachhaltiger Energieumwandlung. Die meisten katalytischen Studien konzentrieren sich auf die Analyse von Wasserstoff und Sauerstoff, wobei in der Regel über die Gesamtantwort gemittelt wird, und somit eine Korrelation von Heterogenitäten der Matrix mit unterschiedlichen molekularen Aktivitäten limitiert ist. Hier berichten wir von Untersuchungen eines heterogenisierten Katalysator‐Photosensibilisator‐Systems, bei dem ein Polyoxometalat‐Katalysator zur Wasseroxidation und ein molekularer Modell‐Photosensibilisator gemeinsam in einer nanoporösen Blockcopolymer‐Membran immobilisiert wurden. Mittels elektrochemischer Rastersondenmikroskopie (SECM) wurde die lichtinduzierte Sauerstoffentwicklung mit Natriumperoxodisulfat (Na2S2O8) als Opferelektronenakzeptor an den modifizierten Blockcopolymer‐Membranen lokal bestimmt. Ex situ elementspezifische Analysen erzielten räumlich Informationen über die lokale Konzentration und Verteilung der molekularen Komponenten. Untersuchungen der modifizierten Membranen mittels abgeschwächter Infrarot‐Totalreflexion (IR‐ATR) zeigten keinen Abbau des Wasseroxidationskatalysators unter den beschriebenen lichtinduzierten Bedingungen.

Multimodal Analysis of Light-Driven Water Oxidation in Nanoporous Block Copolymer Membranes.

Heterogeneous light-driven catalysis is a cornerstone of sustainable energy conversion. Most catalytic studies focus on bulk analyses of the hydrogen and oxygen evolved, which impede the correlation of matrix heterogeneities, molecular features, and bulk reactivity. Here, we report studies of a heterogenized catalyst/photosensitizer system using a polyoxometalate water oxidation catalyst and a model, molecular photosensitizer that were co-immobilized within a nanoporous block copolymer membrane. Via operando scanning electrochemical microscopy (SECM), light-induced oxygen evolution was determined using sodium peroxodisulfate (Na2 S2 O8 ) as sacrificial electron acceptor. Ex situ element analyses provided spatially resolved information on the local concentration and distribution of the molecular components. Infrared attenuated total reflection (IR-ATR) studies of the modified membranes showed no degradation of the water oxidation catalyst under the reported light-driven conditions.

Real-time imaging of photosynthetic oxygen evolution from spinach using LSI-based biosensor

The light-driven splitting of water to oxygen (O2) is catalyzed by a protein-bound tetra-manganese penta-oxygen calcium (Mn4O5Ca) cluster in Photosystem II. In the current study, we used a large-scale integration (LSI)-based amperometric sensor array system, designated Bio-LSI, to perform two-dimensional imaging of light-induced O2 evolution from spinach leaves. The employed Bio-LSI chip consists of 400 sensor electrodes with a pitch of 250 μm for fast electrochemical imaging. Spinach leaves were illuminated to varying intensities of white light (400–700 nm) which induced oxygen evolution and subsequent electrochemical images were collected using the Bio-LSI chip. Bio-LSI images clearly showed the dose-dependent effects of the light-induced oxygen release from spinach leaves which was then significantly suppressed in the presence of urea-type herbicide 3-(3,4-dichlorophenyl)−1,1-dimethylurea (DCMU). Our results clearly suggest that light-induced oxygen evolution can be monitored using the chip and suggesting that the Bio-LSI is a promising tool for real-time imaging. To the best of our knowledge, this report is the first to describe electrochemical imaging of light-induced O2 evolution using LSI-based amperometric sensors in plants.

Effect of sucrose-bound polynuclear iron oxyhydroxide nanoparticles on the efficiency of electron transport in the photosystem II membranes.

Effect of water-soluble and stable sucrose-bound iron oxyhydroxide nanoparticles [Fe[III] sucrose complex (FSC)] on the efficiency of electron transport in the photosystem II membranes was studied. FSC significantly increases (by a factor 1.5) the rate of light-induced oxygen evolution in the presence of alternative electron acceptor 2,6-dichloro-p-benzoquinone (DCBQ). Without DCBQ, FSC only slightly (5%) provides the oxygen evolution. Electron transport supported by pair DCBQ + FSC is inhibited by diuron. Maximum of stimulating effect was recorded at Fe(III) concentration 5µM. In the case of another benzoquinone electron acceptor (2-phenyl-p-benzoquinone and 2,3-dimethyl-p-benzoquinone) and 2,6-dichlorophenolindophenol, stimulating effect of FSC was not observed. Incubation of PSII membranes at different concentrations with FSC is accompanied by binding of Fe(III) by membrane components but only about 50% of iron can be extracted by membranes from Fe(III) solution at pH 6.5. This result implies the heterogeneity of FSC solution in a buffer. The heterogeneity depends on pH and decreases with its rising. At pH around 9.0 Fe(III), sucrose solution is homogeneous. The study of pH effect has shown that stimulation of electron transport is induced only by iron cations which can be bound by membranes. Not extractable iron pool cannot activate electron transfer from oxygen-evolving complex to DCBQ.

Unraveling compositional effects on the light-induced oxygen evolution in Bi(V–Mo–X)O4 material libraries

The influence of elements Mo and W on the PEC response of BiVO4 based thin films is visualized concerning the photocurrent and in situ detection of locally evolved O2 at a photoabsorber.

Solar Water Splitting By Transition Metal Oxide – Silicon Photoanodes Prepared under Cathodic Electrochemical Conditions

Photo-assisted water splitting represents a pivotal strategy for realization of the hydrogen economy of the future. In this approach, the preparation of stable and efficient photoanodes is challenging due to the susceptibility of sensitive semiconductors to photocorrosion. Here, we demonstrate a metalorganic electrochemical approach by which amorphous transition metal oxides are formed on silicon under cathodic electrochemical conditions. This approach makes anti-corrosive interlayers potentially superfluous and realizes an oxide-silicon heterostructure with enhanced activity for the light-induced oxygen evolution reaction in alkaline electrolytes. Exemplifying analysis of electronic and optical properties is provided for a nickel oxide / silicon heterojunction. Interface engineering is demonstrated by formation of nanoscopic Au-Si heterocontacts acting as rectifying nanoemitters for light-induced holes toward the electrocatalytic nickel oxide layer.

Net light-induced oxygen evolution in photosystem I deletion mutants of the cyanobacterium Synechocystis sp. PCC 6803

Oxygenic photosynthesis in cyanobacteria, algae, and plants requires photosystem II (PSII) to extract electrons from H2O and depends on photosystem I (PSI) to reduce NADP+. Here we demonstrate that mixotrophically-grown mutants of the cyanobacterium Synechocystis sp. PCC 6803 that lack PSI (ΔPSI) are capable of net light-induced O2 evolution in vivo. The net light-induced O2 evolution requires glucose and can be sustained for more than 30min. Utilizing electron transport inhibitors and chlorophyll a fluorescence measurements, we show that in these mutants PSII is the source of the light-induced O2 evolution, and that the plastoquinone pool is reduced by PSII and subsequently oxidized by an unidentified electron acceptor that does not involve the plastoquinol oxidase site of the cytochrome b6f complex. Moreover, both O2 evolution and chlorophyll a fluorescence kinetics of the ΔPSI mutants are highly sensitive to KCN, indicating the involvement of a KCN-sensitive enzyme(s). Experiments using 14C-labeled bicarbonate show that the ΔPSI mutants assimilate more CO2 in the light compared to the dark. However, the rate of the light-minus-dark CO2 assimilation accounts for just over half of the net light-induced O2 evolution rate, indicating the involvement of unidentified terminal electron acceptors. Based on these results we suggest that O2 evolution in ΔPSI cells can be sustained by an alternative electron transport pathway that results in CO2 assimilation and that includes PSII, the platoquinone pool, and a KCN-sensitive enzyme.

Electrochemical Behavior of Nanocrystalline Transition Metal Sulfide and Oxide Electrodes for Light-Induced Oxygen Evolution from Water

not Available.

Early effect of sodium pentachlorophenate on photosynthetic activity of the alga Chlorella pyrenoidosa Chick. S-39

Early effects of 0.0001-10 mM sodium pentachlorophenate (PCP-Na) on the green alga Chlorella pyrenoidosa Chick. S-39 involves a rapid (within 1-2 min) decrease in the light-induced oxygen evolution by algal cells. The suppressed relative yield of variable chlorophyll fluorescence in C. pyrenoidosa in the presence of high PCP-Na concentrations and its dynamics provide evidence for rapid inactivation of photosystem 2, which is not observed at low concentrations of the toxicant. An analysis of the induction curve of delayed chlorophyll fluorescence in algal cells suggests that PCP-Na at low concentrations disturbs the coupling of electron transport and phosphorylation, whereas at high concentrations it inhibits electron transport and decreases the energy potential of photosynthetic membranes. The early toxic effect of PCP-Na is responsible for subsequent impairment of C. pyrenoidosa productivity.

Reduction of photosystem I reaction center in DrgA mutant of the cyanobacterium Synechocystis sp. PCC 6803 lacking soluble NAD(P)H:quinone oxidoreductase.

Photoautotrophically grown cells of the cyanobacterium Synechocystis sp. PCC 6803 wild type and the Ins2 mutant carrying an insertion in the drgA gene encoding soluble NAD(P)H:quinone oxidoreductase (NQR) did not differ in the rate of light-induced oxygen evolution and Photosystem I reaction center (P700+) reduction after its oxidation with a white light pulse. In the presence of DCMU, the rate of P700+ reduction was lower in mutant cells than in wild type cells. Depletion of respiratory substrates after 24 h dark-starvation caused more potent decrease in the rate of P700+ reduction in DrgA mutant cells than in wild type cells. The reduction of P700+ by electrons derived from exogenous glucose was slower in photoautotrophically grown DrgA mutant than in wild type cells. The mutation in the drgA gene did not impair the ability of Synechocystis sp. PCC 6803 cells to oxidize glucose under heterotrophic conditions and did not impair the NDH-1-dependent, rotenone-inhibited electron transfer from NADPH to P700+ in thylakoid membranes of the cyanobacterium. Under photoautotrophic growth conditions, NADPH-dehydrogenase activity in DrgA mutant cells was less than 30% from the level observed in wild type cells. The results suggest that NQR, encoded by the drgA gene, might participate in the regulation of cytoplasmic NADPH oxidation, supplying NADP+ for glucose oxidation in the pentose phosphate cycle of cyanobacteria.

Cooperative binding of oxygen to the water-splitting enzyme in the filamentous cyanobacterium Oscillatoria chalybea

In the filamentous cyanobacterium Oscillatoria chalybea photolysis of water does not take place in the complete absence of oxygen. A catalytic oxygen partial pressure of 15×10 −6 Torr has to be present for effective water splitting to occur. By means of mass spectrometry we measured the photosynthetic oxygen evolution in the presence of H 2 18O in dependence on the oxygen partial pressure of the atmosphere and analysed the liberations of 16O 2, 16O 18O and 18O 2 simultaneously. The observed dependences of the light-induced oxygen evolution on bound oxygen yield sigmoidal curves. Hill coefficient values of 3.0, 3.1 and 3.2, respectively, suggest that the binding is cooperative and that four molecules of oxygen have to be bound per chain to the oxygen evolving complex. Oxygen seems to prime the water-splitting reaction by redox steering of the S-state system, putting it in the dark into the condition from which water splitting can start. It appears that in O. chalybea an interaction of oxygen with S 0 and S 1 leads to S 2 and S 3, thus yielding the typical oxygen evolution pattern in which even after extensive dark adaptation substantial amounts of Y 1 and Y 2 are found. The interacting oxygen is apparently reduced to hydrogen peroxide. Mass spectrometry permits to distinguish this highly specific oxygen requirement from the interaction of bulk atmospheric oxygen with the oxygen evolving complex of the cyanobacterium. This interaction leads to the formation H 2O 2 which is decomposed under O 2 evolution in the light. The dependence on oxygen-partial pressure and temperature is analysed. Structural peculiarities of the cyanobacterial reaction centre of photosystem II referring to the extrinsic peptides might play a role.

Ca2+ and Mg2+-binding and a putative calmodulin type Ca2+-binding site in Synechococcus Photosystem II

Thylakoids and Photosystem II particles prepared from the cyanobacterium Synechococcus PCC 7942 washed with a HEPES/glycerol buffer exhibited low rates of light-induced oxygen evolution. Addition of either Ca(2+) or Mg(2+) to both thylakoids and Photosystem II particles increased oxygen evolution independently, maximal rates being obtained by addition of both ions. If either preparation was washed with NaCl, light induced O2 evolution was completely inhibited, but re-activated in the same manner by Ca(2+) and Mg(2+) but to a lower level. In the presence of Mg(2+), the reactivation of O2 evolution by Ca(2+) allowed sigmoid kinetics, implying co-operative binding. The results are interpreted as indicating that not only Ca(2+), but also Mg(2+), is essential for light-induced oxygen evolution in thylakoids and Photosystem II particles from Synechococcus PC 7942. The significance of the reactivation kinetics is discussed. Reactivation by Ca(2+) was inhibited by antibodies to mammalian calmodulin, indicating that the binding site in Photosystem II may be analogous to that of this protein.

Blue Light-Enhanced Photosynthetic Oxygen Evolution from Liposome-Bound Photosystem II Particles; Possible Role of the Xanthophyll Cycle in the Regulation of Cyclic Electron Flow Around Photosystem II?

Abstract Light-driven electron transport in liposome-bound photosystem II (PS-II) particles be­tween water and ferricyanide was monitored by bare platinum electrode oxymetry. The modi­fication of the experimental system with the exogenous quinones α-tocopherol quinone ( α-TQ) or plastoquinone (PQ) resulted in a pronounced effect on photosynthetic oxygen evolution. The presence of α-tocopherolquinone ( α-TQ) in PS-II samples decreased the rate of red light-induced oxygen evolution but increased the rate of green light-induced oxygen evolution. Blue light applied to the assay system in which oxygen evolution was saturated by red light resulted in a further increase of the oxygen signal. These findings are interpreted in terms of a cyclic electron transport around PS-II, regulated by an excitation state of β-carotene in the reaction centre of PS-II. A mechanism is postulated according to which energetic coupling of β-carotene in the reaction centre of PS-II and that of other antenna carotenoid pigments is regulated by the portion of the xanthophyll violaxanthin, which is under control of the xanthophyll cycle.

Proteolytic enzymes stimulate both the ATP synthesis and hydrolysis functions of the chloroplast ATPase complex

The effects of trypsin and chymotrypsin on phosphorylation and ATP hydrolysis by the ATPase in isolated thylakoid membranes of pea have been compared. Tentoxin-sensitive hydrolysis stimulated by both treatments in the light led to reverse proton pumping, seen as a quenching of the light-induced fluorescence of 9-aminoacridine, and which was also reflected as an acceleration of the rate of decay of the flash-induced field-indicating absorption change at 515 nm. Treatments in the dark were essentially ineffective. Trypsin treatment in the light (5 min) led to complete inhibition of phosphorylation but only to partial inhibition of light-induced oxygen evolution. However, at short incubation times in the light with trypsin (1 min) there was stimulation both of phosphorylation and of oxygen evolution, whilst no change was observed in the P O 2 ratio. Similar findings have been reported for dithiothreitol, suggesting that the trypsin-induced stimulation of ATP hydrolysis is not a consequence of uncoupling but results from an alteration in the catalytic state of the ATPase complex. In contrast, chymotrypsin inhibited both O 2 evolution and phosphorylation: no stimulation in either of these parameters was seen under the conditions investigated.

Comparison of the effects of trypsin and chymotrypsin on thylakoid membrane function

The thylakoid membranes are the functional units upon which the photosynthetic energy-tansducing reactions occur. There is a strict relationship between the structure of these membranes and their functional capabilities; this is because the components of the photosynthetic electron-transport chain are bound to proteins in the membrane in a specific manner. Functional changes can be induced by using protediytic enzymes to alter the structure of the proteins. Two enzymes, trypsin (which digests bonds involving arginine and lysine) and chymotrypsin (which digest bonds involving tryptophan, tryosine and phenylalanine) have been used to investigate the functions of the thylakoid membrane. The rationale was that because these enzymes have different specificities for the bonds which they attack they may induce different functional changes in the membrane. The effects of these enzymes are compared. Measurements of light-induced oxygen evolution rates in the presence of exogenous electron acceptors showed that both trypsin and chymotrypsin altered the electron transport reactions in a number of ways. At higher concentrations both trypsin and chymotrypsin treatment of thylakoids caused the rate of electron transport to be dependent on the type of electron acceptor present and rendered electron transport insensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea which inhibits photosystem II. These effects of trypsin have previously been shown to be due to partial digestion of a 32KDa protein on the acceptor side of photosystem II. Thus chymotrypsin may also affect this polypeptide. At lower concentrations trypsin, and to a lesser extent chymotrypsin, stimulated the rate of electron transport. This suggested that both of these enzymes tend to uncouple the thylakoid membranes. Trypsin and chymotrypsin altered the flash-induced field indicating absorption change measured at 520 nm (the electrochromic bandshift) in two ways : 1) the half-time of decay was decreased suggesting increased trans-membrane ion flux and 2) the extent was reduced. The decrease in the half-time of the decay of the electrochromic bandshift was correlated with uncoupling, by trypsin and to a lesser extent by chymotrypsin, of the thylakoid membrane. This proposal was supported by phosphorylation measurements which showed that both trypsin and chymotrypsin can, at least partially, inhibit ATP synthesis. But after brief trypsin incubation in the light a stimulation in the rate of phosphorylation and oxygen evolution (water to methyl viologen) was evident. It is possible that trypsin affects the e sub-unit, believed to be an inhibitor of ATPase function, however, no evidence to support this proposal was seen in polyacrylamide gel electrophoresis analysis of the ATPase. (Abstract shortened by ProQuest.).

Photoelectrolytic reactivity of Ru pairs in semiconducting RuP 3 electrodes

From a theoretical point of view, RuP 3 should be a promising semiconductor electrode for light-induced oxygen evolution from water. Owing to the presence of RuP 6 octahedra in the crystsal lattice and as a result of Ru-Ru bonds, the valence band of RuP 3 (Δ E G ≈ 1.67 eV) is derived from Ru d-states. In addition, the existence of Ru pairs (Ru-Ru = 286.9 and 279.5 pm) indicates the possibility of cooperative oxidation of water molecules on two adjacent reaction sites. Experimental evidence confirms the photoelectrochemical reactivity of RuP 3 with water but equally establishes the generation of oxidation products of Ru (RuO 2, RuO 4) and P (PO 3− 4) which lead to photocorrosion and to a gradual deterioration of the electrode surface. Interestingly, the addition of PO 3− 4 to the electrolyte enhances photoevolution of oxygen strongly. Possibly because of its less electronegative character and owing to its stronger bonds to oxygen, phosphorus is apparently a less favourable chemical ligand than sulphur in a semiconducting system capable of evolving oxygen under illumination (e.g. RuS 2). The investigation shows that the ligand environment of transition metal centres, including the double layer, in photoelectrochemical catalysis can control the reaction pathway. Some general photoelectrochemical properties of RuP 3 are described.

Visible light-induced oxygen evolution in aqueous cadmium sulfide suspensions

Donnees sur le degagement d'oxygene sous l'effet d'une irradiation par de la lumiere visible de suspensions aqueuses de CdS chargees avec des oxydes de metaux nobles, en presence de PtCl 6 2− en tant qu'intercepteur des electrons de la bande de conduction. L'activite catalytique de Rh 2 O 3 est superieure a celle de RuO 2 pour l'oxydation de l'eau dans des conditions alcalines. On note qu'il n'y a pas de generation d'oxygene en l'absence de catalyseur redox

In vitro analogs of photosystem II. Combined flash photolytic and conductometric study of light-induced oxygen evolution from water mediated by colloidal rubidium dioxide/titanium dioxide

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIn vitro analogs of photosystem II. Combined flash photolytic and conductometric study of light-induced oxygen evolution from water mediated by colloidal rubidium dioxide/titanium dioxideRobin Humphry-Baker, Jochen Lilie, and Michael GraetzelCite this: J. Am. Chem. Soc. 1982, 104, 2, 422–425Publication Date (Print):January 1, 1982Publication History Published online1 May 2002Published inissue 1 January 1982https://doi.org/10.1021/ja00366a008RIGHTS & PERMISSIONSArticle Views183Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (510 KB) Get e-Alerts Get e-Alerts

Changes in photosystem 2 activity associated with plant tolerance to lead

Two races of Phalaris arundinacea L. were identified and collected; one tolerant to lead, one intolerant to lead. Addition of lead to isolated leaf segments caused stimulation of light-induced leaf fluorescence and inhibition of oxygen evolution. Higher lead concentrations were required to elicit these effects in the tolerant grass compared with the non-tolerant grass. Estimation of leaf chlorophylls showed there to be a higher ratio of chlorophyll b to chlorophyll a in leaves from the tolerant grass than the non-tolerant one. The light-induced oxygen evolution rates, on a chlorophyll basis, were also higher in the leaves from tolerant grass. Leaf total chlorophyll content was similar from both races of plant. Effects of the inhibitors 3-(3,4-dichlorophenyl)1,1-dimethyl urea (DCMU) and antimycin A on the leaf fluoroescence were such as to suggest that rates of non-cyclic electron transport were greater in leaves from lead tolerant plants. On the basis of these observations, it is suggested that Photosystem 2 activity is greater in P. arundinacea that is tolerant to lead.

Toxicity of soluble copper and other metal ions to Elodea canadensis

A procedure for observing the effects of dissolved copper and other metal ions on the submersed aquatic macrophyte Elodea canadensis has been described. Metal concentrations have been determined which inhibit light-induced oxygen evolution from plant segments after short-term exposure (24h), and which produce phytotoxicity in whole plants over a longer period (28 days). These results are discussed in terms of the phytotoxic effects on Elodea resulting from dissolved metal ions present in polluting concentrations in natural water bodies or from the use of added copper as an aquatic herbicide.