[en] In a unicellular cyanobacterium, the mobile fraction of phycobilisome (PBS) was found to be maximum at a particular redox value of Q_A (i.e., 0.52). An upward or downward shift in the redox value leads to a decrease in this mobile fraction of PBS. Furthermore, the regulatory effect of the redox state of Q_A on PBS mobility was found to be independent of the effect exerted by the plastoquinone pool. These findings indicate for the first time that PBS mobility is regulated by the Q_A redox state in cyanobacteria. A possible working mechanism underlying this control is discussed.

[en] Present work is devoted to kinetics of reduction of molecular oxidant by metal containing redox. Constructed generalized kinetic model of redox process in the system solid redox - reagent solution allows to perform the general theoretical approach to research and to obtain new results on kinetics and mechanism of interaction of redox with oxidants.

[en] Core@shell nanocrystals (NCs) have been widely explored for oxygen reduction reaction (ORR). In this work, monodisperse PdCu@PtCu NCs with various shell thicknesses and compositions have been synthesized through a two-step protocol. As-synthesized PdCu@PtCu core@shell catalysts show enhanced specific activities (SAs) and mass activities (MAs) towards ORR. When PdCu/PtxCuy (core/shell) atomic ratio and Pt/Cu (x/y) ratio both reach 1/1, the core@shell catalyst exhibits the highest SA and MA (normalized with total mass of Pt and Pd). It is also found that the core@shell catalysts show drastically enhanced stability compared with pure PtCu alloy catalyst. It is proposed that both the activity and stability enhancements can be ascribed to the electronic interaction or charge transfer between Pd atoms (in core) and the shell elements. This work demonstrates a new family of core@shell catalysts that can be potentially used as cathode electro-catalysts in fuel cells.

[en] Highlights: • Protein Disulfide Isomers can interact with α11 integrin in response to adhesion. • Complexes PDI- α11 are linked by disulfide bonds. • Free thiol blockers and PDI inhibitors blocks adhesion and migration mediated by α11 integrin. Integrins belong to a family of transmembrane receptors that mediate cell migration and adhesion to ECM. Extracellular domains of integrin heterodimers contain cysteine-rich regions, which are potential sites of thiol-disulfide exchanges. Rearrangements of extracellular disulfide bonds regulate activation of integrin receptors by promoting transition from an inactive state into a ligand-binding competent state. Modifications of integrin disulfide bonds dependent on oxidation-reduction can be mediated by Protein Disulfide Isomerse (PDI). This paper provides evidences that binding to integrin ligands initiate changes in free thiol pattern on cell surface and that thiol-disulfide exchange mediated by PDI leads to activation of integrin subunit α11. By employing co-immunoprecipitation and confocal microscopy analysis we showed that α11β1 and PDI create complexes bounded by disulfide bonds. Using surface plasmon resonance we provide biochemical evidence that PDI can interact directly with integrin subunit α11.

[en] The reduction mechanism of Th"4"+|Th couple in LiCl-KCl eutectic at inert and cadmium electrodes was studied in the temperature range 698-798 K using electrochemical techniques such as cyclic voltammetry, open circuit chronopotentiometry (OCP) and electrochemical impedance spectroscopy (EIS). While there was only cathodic peak associated with a single-step four electron transfer for the reduction of Th"4"+ at inert electrode, two cathodic peaks were observed at cadmium electrode, associated with under-potential deposition of thorium due to formation of ThCd_1_1 and ThCd_5. Impedance data were measured at different potentials at inert and cadmium electrodes were fitted to equivalent circuits comprising of solution and charge transfer resistance, diffusional component and double layer capacitance elements. The heterogeneous rate constant for the charge transfer process of thorium reduction was also estimated from the impedance data. (author)

[en] Experiments have been performed both on a peraluminous leucogranitic (DK89) and a F-, Li-, P-rich pegmatitic (B2) melt to constrain the stability of micas in evolved crustal silicic magmas and refine mica-melt partition coefficients for F, Li, and Be. The experiments were conducted in parallel in two fO₂ ranges, “oxidizing” (NNO +1 to +3) and “reducing” (NNO –1.6 to –1.4). One two-stage reducing-oxidizing experiment was conducted in a vessel fitted with a H₂-permeable Shaw-type membrane. The approach toward equilibrium was tested by imposing long experimental durations and combining mica crystallization experiments with mica dissolution experiments using mica seeds. Experimental micas and melts were analyzed for major elements by electron microprobe and for light elements by nuclear microprobe. At 3 kbar, 620 °C, and under oxidizing conditions, B2 crystallized only muscovite, the biotite seeds reacting to form a new mica intermediate between phengite and Li-rich phengite. Under reducing conditions, biotite (siderophyllite composition) appeared as the stable mica. The two-stage experiment yielded a composite mica assemblage with siderophyllite cores mantled by muscovite rims. At 3.5–3.8 kbar, 720 °C, and under oxidizing conditions, DK89 crystallized only aluminous biotite and muscovite seeds reacted to form biotite-bearing assemblages; muscovite appeared together with biotite at 700 °C. Under reducing conditions, Al-rich biotite is also the stable mica at 720 °C. Partition coefficients show that F and Li are preferentially incorporated in biotite rather than in muscovite, the opposite as for Be. Biotite fractionation buffers the F and increases the Li and Be contents of the residual melt. Muscovite increases the Li content of the melt and has little influence on F and Be concentrations. Our experiments reproduce mica assemblages and compositions typical of Variscan pegmatites and leucogranites, yet very Li-rich micas (e.g., lepidolites) were not obtained. The results stress the differential influence of fO₂ on mica stability in moderately and highly fractionated crustal melts. Mica crystallization in leucogranites does not appear to be strongly dependent on fO₂. In contrast, a very strong influence of fO₂ on stable mica assemblages is demonstrated for the pegmatitic melt. The reducing experiments emphasize the existence of a stability field for biotite in melts poor in Fe, Mg, and Ti. If fO₂ is reducing, biotite must crystallize in moderately to highly evolved peraluminous crustal melts. In contrast, the crystallization of muscovite as the sole mica in evolved crustal melts constitutes an indicator of oxidizing fO₂. Such an oxidizing evolution that deviates from classical buffered T-logfO₂ trajectories is the consequence of a mechanism of magma “self-oxidation” that is proposed to result from dissociation of H₂O in the melt. (author)

No abstract available

[en] PEDOT:PSS-modified GC (PEDOT:PSS/GC) electrode shows enhanced electrocatalytic activity for Pu(IV)/Pu(III) redox couple in sulphuric acid solution compared to GC, Au and Pt electrodes. (author)

[en] A simple and effective method is presented for producing light-emitting porous silicon (PSi). A thin (d<10 nm) layer of Au, Pt, or Au/Pd is deposited on the (100) Si surface prior to immersion in a solution of HF and H₂O₂. Depending on the type of metal deposited and Si doping type and doping level, PSi with different morphologies and light-emitting properties is produced. PSi production occurs on the time scale of seconds, without electrical current, in the dark, on both p- and n-type Si. Thin metal coatings facilitate the etching in HF and H₂O₂, and of the metals investigated, Pt yields the fastest etch rates and produces PSi with the most intense luminescence. A reaction scheme involving local coupling of redox reactions with the metal is proposed to explain the metal-assisted etching process. The observation that some metal remains on the PSi surface after etching raises the possibility of fabricating in situ PSi contacts

[en] Atomic-scale structures of oxygen reduction reaction (ORR) active sites in non-platinum group metal (non-PGM) catalysts, made from pyrolysis of carbon, nitrogen, and transition-metal (TM) precursors have been the subject of continuing discussion in the fuel cell electrocatalysis research community. Quantum chemical modeling is one path forward for understanding of these materials and how they catalyze the ORR. We here demonstrate through literature examples of how such modeling can be used to better understand non-PGM ORR active site relative stability and activity and how such efforts can also aid in the interpretation of experimental signatures produced by these materials.