The requirement for Ca2+ in the Mn(2+)-dependent photoactivation of oxygen evolution was re-evaluated using 17 kDa/24 kDa-less photosystem II (PSII) membranes depleted of (Mn)4-clusters by NH2OH extraction. At optimum conditions (1 mM Mn2+/10 microM 2,6-dichlorphenolindophenol (DCIP)/20 mM Ca2+), the light-induced increase of oxygen-evolution activity, the increase of membrane-bound Mn, and the B-band thermoluminescence emission intensity occurred in parallel. The extent of recovery of the oxygen-evolution activity was equivalent to 88% and 66% of the activity shown by parent NaCl-extracted PSII membranes and by PSII membranes, respectively. Neither photodamage of primary electron transport nor photoligation of nonfunctional Mn > or = 3+ occurred. Analyses of the Ca2+ concentration dependence for the maximum recovery of oxygen evolution activity gave evidence for Ca(2+)-binding site(s) having Km values of approximately 38 and approximately 1300 microM. Illumination of membranes in the strict absence of Ca2+ resulted in large increases (up to 18 Mn/200 chlorophyll) of EDTA nonextractable, EPR silent, nonfunctional membrane-bound Mn > or = 3+ and small increases of oxygen-evolution capability, dependent on pH and concentrations of Mn2+ and DCIP. No photodamage of primary electron transport and only approximately 17% decrease of AT-band thermoluminescence occurred during the photoligation of the Mn > or = 3%. In the strict absence of Ca2+, significant recovery of oxygen-evolution activity was obtained under a limited set of conditions permitting photoligation of a limited abundance of the nonfunctional Mn > or = 3+. Small (NH2-OH, H2O2) as well as bulky external reductants readily reduced and dissociated the Mn > or = 3+ from the membranes. Reillumination of these membranes under optimal conditions for photoactivation (plus Ca2+) gave a high yield of (Mn)4-clusters and oxygen-evolution capability. Similarly, simple addition of Ca2+ to membranes containing nonfunctional Mn > or = 3+ followed by reillumination resulted in the conversion of Mn > or = 3+ to (Mn)4-clusters. It is argued that Ca2+ promotes the conformational change involved in the conversion of the Mn2+ mononuclear intermediate to the Mn(3+)-Mn2+ binuclear intermediate in the photoactivation mechanism, thereby permitting photoassembly of (Mn)4-clusters and preventing photo-inactivation by Mn > or = 3+ ions.

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Graphdiyne (GDY), a new kind of two-dimensional (2D) carbon allotropes, has extraordinary electrical, mechanical, and optical properties, leading to advanced applications in the fields of energy storage, photocatalysis, electrochemical catalysis, and sensors. However, almost all reported methods require metallic copper as a substrate, which severely limits their large-scale application because of the high cost and low specific surface area (SSA) of copper substrate. Here, freestanding three-dimensional GDY (3DGDY) is successfully prepared using naturally abundant and inexpensive diatomite as template. In addition to the intrinsic properties of GDY, the fabricated 3DGDY exhibits a porous structure and high SSA that enable it to be directly used as a lithium-ion battery anode material and a 3D scaffold to create Rh@3DGDY composites, which would hold great potential applications in energy storage and catalysts, respectively.

β-Graphdiyne (β-GDY) is a member of 2D graphyne family with zero band gap, and is a promising material with potential applications in energy storage, organic electronics, etc. However, the synthesis of β-GDY has not been realized yet, and the measurement of its intrinsic properties remains elusive. In this work, β-GDY-containing thin film is successfully synthesized on copper foil using modified Glaser-Hay coupling reaction with tetraethynylethene as precursor. The as-grown carbon film has a smooth surface and is continuous and uniform. Electrical measurements reveal the conductivity of 3.47 × 10 S m and the work function of 5.22 eV. TiO @β-GDY nanocomposite is then prepared and presented with an enhancement of photocatalytic ability compared to pure TiO .

A method for cellular fractionation of Chiamydomonas reinhardii, SAG 11-32/b, and isolation of intact chloroplasts from synchronized cells of the alga is described. The procedure for ceil fractionation comprises essentially four steps: (1) protoplast production with autolysine; (2) lysis of the protoplasts with digitonin; (3) aggregation of broken protoplasts; and (4) separation of organelles by differential centrifugations.Replacing the differential centrifugations (step 4) by Percoll cushion centrifugations yields intact chloroplasts. Starting with 100 milliliters of an algal culture containing 3000 micrograms chlorophyll, intact chloroplasts with 100 to 200 micrograms of chlorophyll can be isolated. Envelope integrity is about 90% (ferricyanide assay). Examination of the chloroplasts by electron microscopy and marker enzyme activities indicated some mitochondrial and cytoplasmic contamination.The biochemistry and physiology of unicellular green algae have been studied intensively because these algae can be maintained easily under laboratory conditions. Cultures can be synchronized (21) and some strains grow heterotrophically as well as autotrophically and mixotrophically. Many similarities with the metabolism of higher plants have been established. The pathway of photosynthetic CO2 reduction was primarily elucidated with unicellular green algae. Enzymes of the glyoxylate cycle and glycolate metabolism, previously found in higher plants, could also be measured in algae, proving the general occurrence of these pathways in plants. Although it was possible to relate these pathways and cycles to cellular organelles in higher plants, very few investigations are reported on the compartmentation of metabolism in unicellular green algae. The first detailed study of localization of enzymes in a unicellular alga of the Chlamydomonas type was made by Kombrink and Wober (16) who were able to demonstrate the activity of starch-metabolizing enzymes in chloroplasts of Dunaliella marina. In their investigation, they used a new method involving DEAE-dextran for cell lysis.One reason for the difficulties in cell fractionation of unicellular

The anaerobic photodissimilation of acetate by Chlamydomonas reinhardii F-60 adapted to a hydrogen metabolism was studied utilizing manometric and isotopic techniques. The rate of photoanaerobic (N2) acetate uptake was approximately 20 moles per milligram chlorophyll per hour or one-half that of the photoaerobic (air) rate. Under N2, cells produced 1.7 moles H2 and 0.8 mole CO2 per mole of acetate consumed. Gas production and acetate uptake were inhibited by monofluoroacetic acid (MFA), 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU) and by H2. Acetate uptake was inhibited about 50% by 5% H2 (95% N2 (3) suggested that acetate increased gas production by consuming ATP which regulated the unspecified sequence of reactions giving rise to CO2 and H2. Healey (18) modifying a mechanism put forward by Jones and Myers (20) to explain the Kok effect in blue-green algae, proposed a flow of electrons from acetate via the citric acid cycle into PSI resulting in the photoevolution of H2 from reduced Fd. The operation of an anaerobic and light-dependent citric acid cycle which affects the stoichiometric conversion of acetate to CO2 and H2 had been documented in the photosynthetic purple bacteria ( 13).The present communication summarizes the results of a detailed investigation of the anaerobic photometabolism of acetate by C. reinhardii F-60, with reference to stoichiometry of gas (CO2 and H2) production, incorporation into cellular components, and sensitivity of the process to a variety of inhibitors. The stoichiometric relationships observed, together with the isotopic distribution following assimilation of ["4C]acetate, constitute strong evidence for the conclusion that anaerobic carbon oxidation occurs in part through the reactions of the glyoxylate and citric acid cycles. MATERIALS AND METHODSAlgal Growth Conditions. Chlamydomonas reinhardii (Dangeard) F-60, a mutant strain with an incomplete photosynthetic carbon reduction cycle but with an intact photosynthetic electron transport chain, was obtained from R. K. Togasaki, Indiana University. Cells were grown in batch cultures on an acetatesupplemented medium (14)

Activation of the Wnt/β-catenin pathway has been observed in at least 1/3 of hepatocellular carcinomas (HCC), and a significant number of these have mutations in the β-catenin gene. Therefore, effective inhibition of this pathway could provide a novel method to treat HCC. The purposed of this study was to determine whether FH535, which was previously shown to block the β-catenin pathway, could inhibit β-catenin activation of target genes and inhibit proliferation of Liver Cancer Stem Cells (LCSC) and HCC cell lines. Using β-catenin responsive reporter genes, our data indicates that FH535 can inhibit target gene activation by endogenous and exogenously expressed β-catenin, including the constitutively active form of β-catenin that contains a Serine37Alanine mutation. Our data also indicate that proliferation of LCSC and HCC lines is inhibited by FH535 in a dose-dependent manner, and that this correlates with a decrease in the percentage of cells in S phase. Finally, we also show that expression of two well-characterized targets of β-catenin, Cyclin D1 and Survivin, is reduced by FH535. Taken together, this data indicates that FH535 has potential therapeutic value in treatment of liver cancer. Importantly, these results suggest that this therapy may be effective at several levels by targeting both HCC and LCSC.

The search for low-cost, highly active, and stable catalysts to replace the Pt-based catalysts for oxygen reduction reaction (ORR) has recently become a topic of interest. Herein, we report a new strategy to design a nitrogen-doped carbon nanomaterial for use as a metal-free ORR catalyst based on facile pyrolysis of protein-rich enoki mushroom (Flammulina velutipes) biomass at 900 °C with carbon nanotubes as a conductive agent and inserting matrix. We found that various forms of nitrogen (nitrile, pyrrolic and graphitic) were incorporated into the carbon molecular skeleton of the product, which exhibited more excellent ORR electrocatalytic activity and better durability in alkaline medium than those in acidic medium. Remarkably, the ORR half-wave potential measured on our material was around 0.81 V in alkaline medium, slightly lower than that on the commercial 20 wt% Pt/C catalyst (0.86 V). Meanwhile, the ORR followed the desired 4-electron transfer mechanism involving the direct reduction pathway. The ORR performance was also markedly better than or at least comparable to the leading results in the literature based on biomass-derived carbon-based catalysts. Besides, we significantly proposed that the graphitic-nitrogen species that is most responsible for the ORR activity can function as the electrocatalytically active center for ORR, and the pyrrolic-nitrogen species can act as an effective promoter for ORR only. The results suggested a promising route based on economical and sustainable fungi biomass towards the large-scale production of valuable carbon nanomaterials as highly active and stable metal-free catalysts for ORR under alkaline conditions.