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Sample records for psii reaction centers

  1. In vivo assessment of effect of phytotoxin tenuazonic acid on PSII reaction centers.

    Science.gov (United States)

    Chen, Shiguo; Strasser, Reto Jörg; Qiang, Sheng

    2014-11-01

    Tenuazonic acid (TeA), a phytotoxin produced by the fungus Alternaria alternata isolated from diseased croftonweed (Ageratina adenophora), exhibits a strong inhibition in photosystem II (PSII) activity. In vivo chlorophyll fluorescence transients of the host plant croftonweed, show that the dominant effect of TeA is not on the primary photochemical reaction but on the biochemical reaction after QA. The most important action site of TeA is the QB site on the PSII electron-acceptor side, blocking electron transport beyond QA(-) by occupying the QB site in the D1 protein. However, TeA does not affect the antenna pigments, the energy transfer from antenna pigment molecules to reaction centers (RCs), and the oxygen-evolving complex (OEC) at the donor side of PSII. TeA severely inactivated PSII RCs. The fraction of non-QA reducing centers and non-QB reducing centers show a time- and concentration-dependent linear increase. Conversely, the amount of active QA or QB reducing centers declined sharply in a linear way. The fraction of non-QB reducing centers calculated from data of fluorescence transients is close to the number of PSII RCs with their QB site filled by TeA. An increase of the step-J level (VJ) in the OJIP fluorescence transients attributed to QA(-) accumulation due to TeA bound to the QB site is a typical characteristic response of the plants leaf with respect to TeA penetration. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  2. Spectroscopic properties of photosystem II reaction center revisited

    Science.gov (United States)

    Gelzinis, Andrius; Abramavicius, Darius; Ogilvie, Jennifer P.; Valkunas, Leonas

    2017-09-01

    Photosystem II (PSII) is the only biological system capable of splitting water to molecular oxygen. Its reaction center (RC) is responsible for the primary charge separation that drives the water oxidation reaction. In this work, we revisit the spectroscopic properties of the PSII RC using the complex time-dependent Redfield (ctR) theory for optical lineshapes [A. Gelzinis et al., J. Chem. Phys. 142, 154107 (2015)]. We obtain the PSII RC model parameters (site energies, disorder, and reorganization energies) from the fits of several spectra and then further validate the model by calculating additional independent spectra. We obtain good to excellent agreement between theory and calculations. We find that overall our model is similar to some of the previous asymmetric exciton models of the PSII RC. On the other hand, our model displays differences from previous work based on the modified Redfield theory. We extend the ctR theory to describe the Stark spectrum and use its fit to obtain the parameters of a single charge transfer state included in our model. Our results suggest that C h lD1 +P h e oD1 - is most likely the primary charge transfer state, but that the Stark spectrum of the PSII RC is probably also influenced by other states.

  3. Photosystem II reaction center damage and repair cycle: chloroplast acclimation strategy to irradiance stress.

    Science.gov (United States)

    Vasilikiotis, C; Melis, A

    1994-07-19

    A daily occurrence in the life of a plant is the function of a photosystem II (PSII) damage and repair cycle in chloroplasts. This unique phenomenon involves the frequent turnover of D1, the 32-kDa reaction-center protein of PSII (chloroplast psbA gene product). In the model organism Dunaliella salina (a green alga), growth under low light (100 mol of photons per m2 per sec) entails damage, degradation, and replacement of D1 every 7 hr. Growth under irradiance stress (2200 micromol of photons per m2 per sec) entails damage to D1 every 20 min. The rate of de novo D1 biosynthesis under conditions of both low light and irradiance stress was found to be fairly constant on a per chloroplast or cell basis. The response of D. salina to the enhanced rate of damage entails an accumulation of photodamaged centers (80% of all PSII) and the formation of thylakoid membranes containing a smaller quantity of photosystem I (PSI) centers (about 10% of that in cells grown under low light). These changes contribute to a shift in the PSII/PSI ratio from 1.4:1 under low-light conditions to 15:1 under irradiance stress. The accumulation of photodamaged PSII under irradiance stress reflects a chloroplast inability to match the rate of D1 degradation or turnover with the rate of damage for individual PSII complexes. The altered thylakoid membrane organization ensures that a small fraction of PSII centers remains functional under irradiance stress and sustains electron flow from H2O to ferredoxin with rates sufficient for chloroplast photosynthesis and cell growth.

  4. Photosystem II reaction center damage and repair cycle: chloroplast acclimation strategy to irradiance stress.

    OpenAIRE

    Vasilikiotis, C; Melis, A

    1994-01-01

    A daily occurrence in the life of a plant is the function of a photosystem II (PSII) damage and repair cycle in chloroplasts. This unique phenomenon involves the frequent turnover of D1, the 32-kDa reaction-center protein of PSII (chloroplast psbA gene product). In the model organism Dunaliella salina (a green alga), growth under low light (100 mol of photons per m2 per sec) entails damage, degradation, and replacement of D1 every 7 hr. Growth under irradiance stress (2200 micromol of photons...

  5. Formation of photosystem II reaction centers that work as energy sinks in lichen symbiotic Trebouxiophyceae microalgae.

    Science.gov (United States)

    Guéra, Alfredo; Gasulla, Francisco; Barreno, Eva

    2016-04-01

    Lichens are poikilohydric symbiotic organisms that can survive in the absence of water. Photosynthesis must be highly regulated in these organisms, which live under continuous desiccation-rehydration cycles, to avoid photooxidative damage. Analysis of chlorophyll a fluorescence induction curves in the lichen microalgae of the Trebouxiophyceae Asterochloris erici and in Trebouxia jamesii (TR1) and Trebouxia sp. (TR9) phycobionts, isolated from the lichen Ramalina farinacea, shows differences with higher plants. In the presence of the photosynthetic electron transport inhibitor DCMU, the kinetics of Q(A) reduction is related to variable fluorescence by a sigmoidal function that approaches a horizontal asymptote. An excellent fit to these curves was obtained by applying a model based on the following assumptions: (1) after closure, the reaction centers (RCs) can be converted into "energy sink" centers (sRCs); (2) the probability of energy leaving the sRCs is very low or zero and (3) energy is not transferred from the antenna of PSII units with sRCs to other PSII units. The formation of sRCs units is also induced by repetitive light saturating pulses or at the transition from dark to light and probably requires the accumulation of reduced Q(A), as well as structural changes in the reaction centers of PSII. This type of energy sink would provide a very efficient way to protect symbiotic microalgae against abrupt changes in light intensity.

  6. Solar UV-B effects on PSII performance in Betula nana are influenced by PAR level and reduced by EDU

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Mikkelsen, Teis Nørgaard; Ro-Poulsen, Helge

    2012-01-01

    The long-term and diurnal responses of photosystem II (PSII) performance to near-ambient UV-B radiation were investigated in High Arctic Betula nana. We conducted an UV exclusion experiment with five replicated blocks consisting of open control (no filter), photosynthetic active radiation and UV...... the effects of UV-B. Chlorophyll-a fluorescence induction curves were used for analysis of OJIP test parameters. Near-ambient UV-B radiation reduced across season maximum quantum yield (TRo /ABS = Fv /Fm ), approximated number of active PSII reaction center (RC/ABS) and the performance index (PIABS ), despite...... in reduced UV-B compared to near-ambient UV-B. This demonstrates current solar UV-B to reduce the PSII performance both on a daily as well as a seasonal basis in this High Arctic species....

  7. Origin and evolution of photosynthetic reaction centers

    Science.gov (United States)

    Olson, John M.; Pierson, Beverly K.

    1987-09-01

    The prototype reaction center may have used protoporphyrin-IX associated with small peptides to transfer electrons or protons across the primitive cell membrane. The precursor of all contemporary reaction centers contained chlorophylla molecules as both primary electron donor and initial electron acceptor and an Fe-S center as secondary acceptor (RC-1 type). The biosynthetic pathway for chlorophylla evolved along with the evolution of a better organized reaction center associated with cytochromes and quinones in a primitive cyclic electron transport system. This reaction center probably functioned initially in photoassimilation, but was easily adapted to CO2 fixation using H2 and H2S as reductants. During this phase bacteriochlorophyllg may have evolved from chlorophylla in response to competition for light, and thereby initiated the gram-positive line of eubacteria. A second reaction center (RC-2) evolved from RC-1 between 3.5 and 2.5 Ga ago in response to the competition for reductants for CO2 fixation. The new organism containing RC-2 in series with RC-1 would have been able to use poor reducing agents such as the abundant aqueous ferrous ion in place of H2 and H2S. This new organism is proposed to be the common ancestor of all phototrophic eubacteria except those related to the gram-positive bacteria. All organisms containing bacteriochlorophylla lost either RC-1 or RC-2, while those organisms containing chlorophylla (ancestors of cyanobacteria) added a water-splitting enzyme to RC-2 between 3.0 and 2.5 Ga ago in order to use H2O in place of hydrated ferrous ion as electron donor for autotrophic photosynthesis.

  8. Stoichiometric relationship between the (Mn){sub 4}-cluster and PSII Ca{sup 2+} necessary for O{sub 2}-evolution. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-01

    This report focuses on the following research accomplishments: Stoichiometric relationship between the (Mn){sub 4}-cluster and PSII Ca{sup 2+} necessary for O{sub 2}-evolution; Photodamage of Mn-depleted PSII membranes: Sites and mechanisms of photoinactivation of primary reactions; The photoassembly of the PSII (Mn){sub 4}cluster is modulated by Ca{sup 2+} and DCIP; The natural product sorgoleone inhibits electron transfer at the Q{sub A}/Q{sub B} site of PSII; and Photodamages of Ca{sup 2+}-depleted PSII membranes: Sites and mechanisms of inactivation of donor side reactions.

  9. Automatic determination of reaction mappings and reaction center information. 2. Validation on a biochemical reaction database.

    Science.gov (United States)

    Apostolakis, Joannis; Sacher, Oliver; Körner, Robert; Gasteiger, Johann

    2008-06-01

    The correct identification of the reacting bonds and atoms is a prerequisite for the analysis of the reaction mechanism. We have recently developed a method based on the Imaginary Transition State Energy Minimization approach for automatically determining the reaction center information and the atom-atom mapping numbers. We test here the accuracy of this ITSE approach by comparing the predictions of the method against more than 1500 manually annotated reactions from BioPath, a comprehensive database of biochemical reactions. The results show high agreement between manually annotated mappings and computational predictions (98.4%), with significant discrepancies in only 24 cases out of 1542 (1.6%). This result validates both the computational prediction and the database, at the same time, as the results of the former agree with expert knowledge and the latter appears largely self-consistent, and consistent with a simple principle. In 10 of the discrepant cases, simple chemical arguments or independent literature studies support the predicted reaction center. In five reaction instances the differences in the automatically and manually annotated mappings are described in detail. Finally, in approximately 200 cases the algorithm finds alternate reaction centers, which need to be studied on a case by case basis, as the exact choice of the alternative may depend on the enzyme catalyzing the reaction.

  10. Observation of Coherence in the Photosystem II Reaction Center

    CERN Document Server

    Fuller, Franklin D; Senlik, S Seckin; Wilcox, Daniel E; Ogilvie, Jennifer P

    2013-01-01

    Photosynthesis powers life on our planet. The basic photosynthetic architecture comprises antenna complexes to harvest solar energy and reaction centers to convert the energy into a stable charge separated state. In oxygenic photosynthesis, the initial charge separation event occurs in the photosystem II reaction center; the only known natural enzyme that uses solar energy to split water. Energy transfer and charge separation in photosynthesis are rapid and have high quantum efficiencies. Recently, nonlinear spectroscopic experiments have suggested that electronic coherence may play a role in energy transfer efficiency in antenna complexes. Here we report the observation of coherence in the photosystem II reaction center by two dimensional electronic spectroscopy. The frequencies of the observed coherences match exciton difference frequencies and/or known vibrational modes of the photosystem II reaction center. These observations raise questions about the possible role of electronic and/or vibrational coheren...

  11. Photosystem II: the reaction center of oxygenic photosynthesis.

    Science.gov (United States)

    Vinyard, David J; Ananyev, Gennady M; Dismukes, G Charles

    2013-01-01

    Photosystem II (PSII) uses light energy to split water into chemical products that power the planet. The stripped protons contribute to a membrane electrochemical potential before combining with the stripped electrons to make chemical bonds and releasing O2 for powering respiratory metabolisms. In this review, we provide an overview of the kinetics and thermodynamics of water oxidation that highlights the conserved performance of PSIIs across species. We discuss recent advances in our understanding of the site of water oxidation based upon the improved (1.9-Å resolution) atomic structure of the Mn4CaO5 water-oxidizing complex (WOC) within cyanobacterial PSII. We combine these insights with recent knowledge gained from studies of the biogenesis and assembly of the WOC (called photoassembly) to arrive at a proposed chemical mechanism for water oxidation.

  12. Site Energies of Active and Inactive Pheophytins in the Reaction Center of Photosystem II from Chlamydomonas Reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Acharya, K.; Neupane, B.; Zazubovich, V.; Sayre, R. T.; Picorel, R.; Seibert, M.; Jankowiak, R.

    2012-03-29

    It is widely accepted that the primary electron acceptor in various Photosystem II (PSII) reaction center (RC) preparations is pheophytin {alpha} (Pheo {alpha}) within the D1 protein (Pheo{sub D1}), while Pheo{sub D2} (within the D2 protein) is photochemically inactive. The Pheo site energies, however, have remained elusive, due to inherent spectral congestion. While most researchers over the past two decades placed the Q{sub y}-states of Pheo{sub D1} and Pheo{sub D2} bands near 678-684 and 668-672 nm, respectively, recent modeling [Raszewski et al. Biophys. J. 2005, 88, 986-998; Cox et al. J. Phys. Chem. B 2009, 113, 12364-12374] of the electronic structure of the PSII RC reversed the assignment of the active and inactive Pheos, suggesting that the mean site energy of Pheo{sub D1} is near 672 nm, whereas Pheo{sub D2} ({approx}677.5 nm) and Chl{sub D1} ({approx}680 nm) have the lowest energies (i.e., the Pheo{sub D2}-dominated exciton is the lowest excited state). In contrast, chemical pigment exchange experiments on isolated RCs suggested that both pheophytins have their Q{sub y} absorption maxima at 676-680 nm [Germano et al. Biochemistry 2001, 40, 11472-11482; Germano et al. Biophys. J. 2004, 86, 1664-1672]. To provide more insight into the site energies of both Pheo{sub D1} and Pheo{sub D2} (including the corresponding Q{sub x} transitions, which are often claimed to be degenerate at 543 nm) and to attest that the above two assignments are most likely incorrect, we studied a large number of isolated RC preparations from spinach and wild-type Chlamydomonas reinhardtii (at different levels of intactness) as well as the Chlamydomonas reinhardtii mutant (D2-L209H), in which the active branch Pheo{sub D1} is genetically replaced with chlorophyll {alpha} (Chl {alpha}). We show that the Q{sub x}-/Q{sub y}-region site energies of Pheo{sub D1} and Pheo{sub D2} are {approx}545/680 nm and {approx}541.5/670 nm, respectively, in good agreement with our previous assignment

  13. Mathematical Model of Synthesis Catalyst with Local Reaction Centers

    Directory of Open Access Journals (Sweden)

    I. V. Derevich

    2017-01-01

    Full Text Available The article considers a catalyst granule with a porous ceramic passive substrate and point active centers on which an exothermic synthesis reaction occurs. A rate of the chemical reaction depends on the temperature according to the Arrhenius law. Heat is removed from the pellet surface in products of synthesis due to heat transfer. In our work we first proposed a model for calculating the steady-state temperature of a catalyst pellet with local reaction centers. Calculation of active centers temperature is based on the idea of self-consistent field (mean-field theory. At first, it is considered that powers of the reaction heat release at the centers are known. On the basis of the found analytical solution, which describes temperature distribution inside the granule, the average temperature of the reaction centers is calculated, which then is inserted in the formula for heat release. The resulting system of transcendental algebraic equations is transformed into a system of ordinary differential equations of relaxation type and solved numerically to achieve a steady-state value. As a practical application, the article considers a Fischer-Tropsch synthesis catalyst granule with active cobalt metallic micro-particles. Cobalt micro-particles are the centers of the exothermic reaction of hydrocarbons macromolecular synthesis. Synthesis occurs as a result of absorption of the components of the synthesis gas on metallic cobalt. The temperature distribution inside the granule for a single local center and reaction centers located on the same granule diameter is found. It was found that there is a critical temperature of reactor exceeding of which leads to significant local overheating of the centers - thermal explosion. The temperature distribution with the local reaction centers is qualitatively different from the granule temperature, calculated in the homogeneous approximation. It is shown that, in contrast to the homogeneous approximation, the

  14. Stochastic discrete event simulation of germinal center reactions

    Science.gov (United States)

    Figge, Marc Thilo

    2005-05-01

    We introduce a generic reaction-diffusion model for germinal center reactions and perform numerical simulations within a stochastic discrete event approach. In contrast to the frequently used deterministic continuum approach, each single reaction event is monitored in space and time in order to simulate the correct time evolution of this complex biological system. Germinal centers play an important role in the immune system by performing a reaction that aims at improving the affinity between antibodies and antigens. Our model captures experimentally observed features of this reaction, such as the development of the remarkable germinal center morphology and the maturation of antibody-antigen affinity in the course of time. We model affinity maturation within a simple affinity class picture and study it as a function of the distance between the initial antibody-antigen affinity and the highest possible affinity. The model reveals that this mutation distance may be responsible for the experimentally observed all-or-none behavior of germinal centers; i.e., they generate either mainly output cells of high affinity or no high-affinity output cells at all. Furthermore, the exact simulation of the system dynamics allows us to study the hypothesis of cell recycling in germinal centers as a mechanism for affinity optimization. A comparison of three possible recycling pathways indicates that affinity maturation is optimized by a recycling pathway that has previously not been taken into account in deterministic continuum models.

  15. The three-dimensional structures of bacterial reaction centers.

    Science.gov (United States)

    Olson, T L; Williams, J C; Allen, J P

    2014-05-01

    This review presents a broad overview of the research that enabled the structure determination of the bacterial reaction centers from Blastochloris viridis and Rhodobacter sphaeroides, with a focus on the contributions from Duysens, Clayton, and Feher. Early experiments performed in the laboratory of Duysens and others demonstrated the utility of spectroscopic techniques and the presence of photosynthetic complexes in both oxygenic and anoxygenic photosynthesis. The laboratories of Clayton and Feher led efforts to isolate and characterize the bacterial reaction centers. The availability of well-characterized preparations of pure and stable reaction centers allowed the crystallization and subsequent determination of the structures using X-ray diffraction. The three-dimensional structures of reaction centers revealed an overall arrangement of two symmetrical branches of cofactors surrounded by transmembrane helices from the L and M subunits, which also are related by the same twofold symmetry axis. The structure has served as a framework to address several issues concerning bacterial photosynthesis, including the directionality of electron transfer, the properties of the reaction center-cytochrome c 2 complex, and the coupling of proton and electron transfer. Together, these research efforts laid the foundation for ongoing efforts to address an outstanding question in oxygenic photosynthesis, namely the molecular mechanism of water oxidation.

  16. Bio-Photoelectrochemical Solar Cells Incorporating Reaction Center and Reaction Center Plus Light Harvesting Complexes

    Science.gov (United States)

    Yaghoubi, Houman

    Harvesting solar energy can potentially be a promising solution to the energy crisis now and in the future. However, material and processing costs continue to be the most important limitations for the commercial devices. A key solution to these problems might lie within the development of bio-hybrid solar cells that seeks to mimic photosynthesis to harvest solar energy and to take advantage of the low material costs, negative carbon footprint, and material abundance. The bio-photoelectrochemical cell technologies exploit biomimetic means of energy conversion by utilizing plant-derived photosystems which can be inexpensive and ultimately the most sustainable alternative. Plants and photosynthetic bacteria harvest light, through special proteins called reaction centers (RCs), with high efficiency and convert it into electrochemical energy. In theory, photosynthetic RCs can be used in a device to harvest solar energy and generate 1.1 V open circuit voltage and ~1 mA cm-2 short circuit photocurrent. Considering the nearly perfect quantum yield of photo-induced charge separation, efficiency of a protein-based solar cell might exceed 20%. In practice, the efficiency of fabricated devices has been limited mainly due to the challenges in the electron transfer between the protein complex and the device electrodes as well as limited light absorption. The overarching goal of this work is to increase the power conversion efficiency in protein-based solar cells by addressing those issues (i.e. electron transfer and light absorption). This work presents several approaches to increase the charge transfer rate between the photosynthetic RC and underlying electrode as well as increasing the light absorption to eventually enhance the external quantum efficiency (EQE) of bio-hybrid solar cells. The first approach is to decrease the electron transfer distance between one of the redox active sites in the RC and the underlying electrode by direct attachment of the of protein complex

  17. Conformational regulation of charge recombination reactions in a photosynthetic bacterial reaction center

    DEFF Research Database (Denmark)

    Katona, Gergely; Snijder, Arjan; Gourdon, Pontus

    2005-01-01

    In bright light the photosynthetic reaction center (RC) of Rhodobacter sphaeroides stabilizes the P(+)(870).Q(-)(A) charge-separated state and thereby minimizes the potentially harmful effects of light saturation. Using X-ray diffraction we report a conformational change that occurs within the cy...... the cytoplasmic domain of this RC in response to prolonged illumination with bright light. Our observations suggest a novel structural mechanism for the regulation of electron transfer reactions in photosynthesis....

  18. Photophysical processes in models of reaction centers of photosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Solov`yov, K.N.; Losev, A.P.; Kuz`mitskii, V.A. [Academy of Sciences of Belarus (Russian Federation)] [and others

    1995-11-01

    Simulation modeling of photosynthesis remains an urgent problem for two reasons. First, the cognitive value of this approach has not been exhausted yet. Second, this should lead to practical use of solar energy with the yield of oxygen, organic products, and nitrogen compounds. At present it has been found that photochemical stages of photosynthesis occur in reaction centers. A greater part of chlorophyll or bacteriochlorophyll molecules function as a light-harvesting antenna. The energy of an absorbed quantum migrates over the antenna and reaches the reaction centers, where the charge is separated and a chemical potential is generated. These are followed by dark stages of photosynthesis. The authors have investigated the photophysical properties of chlorophyll-like molecules and have approached the problem of intramolecular photoinduced electron transfer (PET) in studies of nitroporphyrins.

  19. The Type 1 Homodimeric Reaction Center in Heliobacterium modesticaldum

    Energy Technology Data Exchange (ETDEWEB)

    Golbeck, John [Pennsylvania State Univ., University Park, PA (United States)

    2018-01-15

    In this funding period, we (i) found that strong illumination of Heliobacterium modesticaldum cells results in saturation of the electron acceptor pool, leading to reduction of the acceptor side and the creation of a back-reacting state that gives rise to delayed fluorescence; (ii) noted that when the FX cluster is reduced in purified reaction centers, no electron transfer occurs beyond A0, even though a quinone is present; (iii) observed by photochemically induced dynamic nuclear polarization (photo-CIDNP) studies of whole cells of Heliobacterium mobilis that primary charge separation is retained even after conversion of the majority of BChl g to Chl aF. ; and (iv) purified a homogeneous preparation of reaction center cores, which led to promising crystallization trials to obtain a three-dimensional structure.

  20. Dynamic response of a plane-symmetrical exothermic reaction center.

    Science.gov (United States)

    Meyer, J. W.; Oppenheim, A. K.

    1972-01-01

    ?sger,An analysis of the dynamic behavior of an idealized, plane-symmetrical exothermic reaction center is presented. The conservation equations for the reaction center are combined and yield a single integral equation expressing a nonlinear transfer function of the system for which the input is provided by a given time profile of the heat released per unit mass while the output gives the pressure pulse it generates under the restriction of plane-symmetrical motion. The solution is governed by a Daumk]hler number. For a given form of the exothermic power pulse profile, the dynamic behavior of the system is completely specified in terms of only this Daumk]hler number and the heat of reaction per unit mass of the combustible medium. Specific solutions are worked out for a set of typical elementary power pulse profiles, and the practical significance of the results is illustrated by their application to the problem of transition to detonation in an explosive gas.

  1. A multi-pathway model for Photosynthetic reaction center

    CERN Document Server

    Qin, M; Yi, X X

    2015-01-01

    Charge separation in light-harvesting complexes occurs in a pair of tightly coupled chlorophylls at the heart of photosynthetic reaction centers of both plants and bacteria. Recently it has been shown that quantum coherence can, in principle, enhance the efficiency of a solar cell, working like a quantum heat engine (QHE). Here, we propose a biological quantum heat engine (BQHE) motivated by Photosystem {\\rm II} reaction center (PS{\\rm II} RC) to describe the charge separation. Our model mainly considers two charge-separation pathways more than that in the published literature. The two pathways can interfere via cross-couplings and work together to enhance the charge-separation yields. We explore how these cross-couplings increase the current and voltage of the charge separation and discuss the advantages of multiple pathways in terms of current and power. The robustness of the BQHE against the charge recombination in natural PS{\\rm II} RC and dephasing induced by environments is also explored, and extension ...

  2. Photosynthetic reaction center as a quantum heat engine.

    Science.gov (United States)

    Dorfman, Konstantin E; Voronine, Dmitri V; Mukamel, Shaul; Scully, Marlan O

    2013-02-19

    Two seemingly unrelated effects attributed to quantum coherence have been reported recently in natural and artificial light-harvesting systems. First, an enhanced solar cell efficiency was predicted and second, population oscillations were measured in photosynthetic antennae excited by sequences of coherent ultrashort laser pulses. Because both systems operate as quantum heat engines (QHEs) that convert the solar photon energy to useful work (electric currents or chemical energy, respectively), the question arises whether coherence could also enhance the photosynthetic yield. Here, we show that both effects arise from the same population-coherence coupling term which is induced by noise, does not require coherent light, and will therefore work for incoherent excitation under natural conditions of solar excitation. Charge separation in light-harvesting complexes occurs in a pair of tightly coupled chlorophylls (the special pair) at the heart of photosynthetic reaction centers of both plants and bacteria. We show the analogy between the energy level schemes of the special pair and of the laser/photocell QHEs, and that both population oscillations and enhanced yield have a common origin and are expected to coexist for typical parameters. We predict an enhanced yield of 27% in a QHE motivated by the reaction center. This suggests nature-mimicking architectures for artificial solar energy devices.

  3. Trolox, a water-soluble analogue of α-tocopherol, photoprotects the surface-exposed regions of the photosystem II reaction center in vitro. Is this physiologically relevant?

    Science.gov (United States)

    Arellano, Juan B; Li, Heng; González-Pérez, Sergio; Gutiérrez, Jorge; Melø, Thor Bernt; Vacha, Frantisek; Naqvi, K Razi

    2011-10-04

    Can Trolox, a water-soluble analogue of α-tocopherol and a scavenger of singlet oxygen ((1)O(2)), provide photoprotection, under high irradiance, to the isolated photosystem II (PSII) reaction center (RC)? To answer the question, we studied the endogenous production of (1)O(2) in preparations of the five-chlorophyll PSII RC (RC5) containing only one β-carotene molecule. The temporal profile of (1)O(2) emission at 1270 nm photogenerated by RC5 in D(2)O followed the expected biexponential behavior, with a rise time, unaffected by Trolox, of 13 ± 1 μs and decay times of 54 ± 2 μs (without Trolox) and 38 ± 2 μs (in the presence of 25 μM Trolox). The ratio between the total (k(t)) and chemical (k(r)) bimolecular rate constants for the scavenging of (1)O(2) by Trolox in aqueous buffer was calculated to be ~1.3, with a k(t) of (2.4 ± 0.2) × 10(8) M(-1) s(-1) and a k(r) of (1.8 ± 0.2) × 10(8) M(-1) s(-1), indicating that most of the (1)O(2) photosensitized by methylene blue chemically reacts with Trolox in the assay buffer. The photoinduced oxygen consumption in the oxygen electrode, when RC5 and Trolox were mixed, revealed that Trolox was a better (1)O(2) scavenger than histidine and furfuryl alcohol at low concentrations (i.e., Trolox was able to photoprotect the surface-exposed regions of the D1-D2 heterodimer, but not the RC5 pigments, which were oxidized, together with the membrane region of the protein matrix of the PSII RC, by (1)O(2). These results are discussed and compared with those of studies dealing with the physiological role of tocopherol molecules as a (1)O(2) scavenger in thylakoid membranes of photosynthetic organisms.

  4. Isolated photochemical reaction centers from bacteriochlorophyll b - containing organisms

    Energy Technology Data Exchange (ETDEWEB)

    Thornber, J.P.; Dutton, P.L.; Fajer, J.; Parson, W.W.; Prince, R.C.; Tiede, D.M.; Windsor, M.W.

    1977-01-01

    Optical, ESR and pulsed laser spectroscopic examination of isolated bacteriochlorophyll (BChl) b-containing reaction centers (RCs) demonstrates that their composition (1 P960 : 2 bacteriopheophytin (BPh) b : 2 cyt c 558 : 2 cyt c 553 : BChl/BPh = 2) and their mechanism for charge separation are very similar to those in BChl a-containing RCs; however, P960/sup +/, the oxidized form of the primary electron donor, is apparently not a symmetrical dimer of BChl b. The ''primary'' electron acceptor (X) is a quinone-iron complex, and I, the intermediary electron carrier between P960 and X, is BPh which interact(s) strongly with one or more of the other components in the RC. Comparison of the optical spectra of isolated RCs of the BChl b-containing bacteria, Rhodopseudomonas viridis and Thiocapsa pfennigii, with those of their intact cells shows that the BPh in the RC is not generated during the isolation procedure.

  5. Quantum Redirection of Antenna Absorption to Photosynthetic Reaction Centers.

    Science.gov (United States)

    Caycedo-Soler, Felipe; Schroeder, Christopher A; Autenrieth, Caroline; Pick, Arne; Ghosh, Robin; Huelga, Susana F; Plenio, Martin B

    2017-12-04

    The early steps of photosynthesis involve the photoexcitation of reaction centers (RCs) and light-harvesting (LH) units. Here, we show that the historically overlooked excitonic delocalization across RC and LH pigments results in a redistribution of absorption amplitudes that benefits the absorption cross section of the optical bands associated with the RC of several species. While we prove that this redistribution is robust to the microscopic details of the dephasing between these units in the purple bacterium Rhodospirillum rubrum, we are able to show that the redistribution witnesses a more fragile, but persistent, coherent population dynamics which directs excitations from the LH toward the RC units under incoherent illumination and physiological conditions. Even though the redirection does not seem to affect importantly the overall efficiency in photosynthesis, stochastic optimization allows us to delineate clear guidelines and develop simple analytic expressions in order to amplify the coherent redirection in artificial nanostructures.

  6. Quantum delocalization directs antenna absorption to photosynthetic reaction centers

    CERN Document Server

    Caycedo-Soler, Felipe; Autenrieth, Caroline; Ghosh, Robin; Huelga, Susana F; Plenio, Martin B

    2015-01-01

    Photosynthesis -- the conversion of sunlight to chemical energy -- is fundamental for supporting life on our planet. Despite its importance, the physical principles that underpin the primary steps of photosynthesis, from photon absorption to electronic charge separation, remain to be understood in full. Previously, electronic coherence within tightly-packed light-harvesting (LH) units or within individual reaction centers (RCs) has been recognized as an important ingredient for a complete understanding of the excitation energy transfer dynamics. However, the electronic coherence across RC and LH units has been consistently neglected as it does not play a significant role during these relatively slow transfer processes. Here, we turn our attention to the absorption process, which occurs on much shorter timescales. We demonstrate that the - often overlooked - spatially extended but short-lived excitonic delocalization across RC and LH units plays a relevant role in general photosynthetic systems, as it causes a...

  7. Regulation of Germinal Center Reactions by B and T Cells

    Directory of Open Access Journals (Sweden)

    Yeonseok Chung

    2013-10-01

    Full Text Available Break of B cell tolerance to self-antigens results in the development of autoantibodies and, thus, leads to autoimmunity. How B cell tolerance is maintained during active germinal center (GC reactions is yet to be fully understood. Recent advances revealed several subsets of T cells and B cells that can positively or negatively regulate GC B cell responses in vivo. IL-21-producing CXCR5+ CD4+ T cells comprise a distinct lineage of helper T cells—termed follicular helper T cells (TFH—that can provide help for the development of GC reactions where somatic hypermutation and affinity maturation take place. Although the function of TFH cells is beneficial in generating high affinity antibodies against infectious agents, aberrant activation of TFH cell or B cell to self-antigens results in autoimmunity. At least three subsets of immune cells have been proposed as regulatory cells that can limit such antibody-mediated autoimmunity, including follicular regulatory T cells (TFR, Qa-1 restricted CD8+ regulatory T cells (CD8+TREG, and regulatory B cells (BREG. In this review, we will discuss our current understanding of GC B cell regulation with specific emphasis on the newly identified immune cell subsets involved in this process.

  8. Rice Photosynthetic Productivity and PSII Photochemistry under Nonflooded Irrigation

    Directory of Open Access Journals (Sweden)

    Haibing He

    2014-01-01

    Full Text Available Nonflooded irrigation is an important water-saving rice cultivation technology, but little is known on its photosynthetic mechanism. The aims of this work were to investigate photosynthetic characteristics of rice during grain filling stage under three nonflooded irrigation treatments: furrow irrigation with plastic mulching (FIM, furrow irrigation with nonmulching (FIN, and drip irrigation with plastic mulching (DI. Compared with the conventional flooding (CF treatment, those grown in the nonflooded irrigation treatments showed lower net photosynthetic rate (PN, lower maximum quantum yield (Fv/Fm, and lower effective quantum yield of PSII photochemistry (ΦPSII. And the poor photosynthetic characteristics in the nonflooded irrigation treatments were mainly attributed to the low total nitrogen content (TNC. Under non-flooded irrigation, the PN, Fv/Fm, and ΦPSII significantly decreased with a reduction in the soil water potential, but these parameters were rapidly recovered in the DI and FIM treatments when supplementary irrigation was applied. Moreover, The DI treatment always had higher photosynthetic productivity than the FIM and FIN treatments. Grain yield, matter translocation, and dry matter post-anthesis (DMPA were the highest in the CF treatment, followed by the DI, FIM, and FIN treatments in turn. In conclusion, increasing nitrogen content in leaf of rice plants could be a key factor to improve photosynthetic capacity in nonflooded irrigation.

  9. Bullet Cantilever Embedded MOSFET Characteristics for Detection of Photosystem I Reaction Centers

    Directory of Open Access Journals (Sweden)

    Sazia A. Eliza

    2008-04-01

    Full Text Available This paper presents a micro sensor for detection and characterization of biomolecular photodiodes - Photosystem I (PS I reaction centers. In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers, Photosystems I and II (PS I and PS II. Photon capture triggers rapid charge separation and the conversion of light energy into an electric voltage across the nanometer-scale (~6 nm reaction centers. In this work, MOSFET embedded micro cantilevers have been used to detect the energy harvesting biomolecules. The bending of cantilevers due to immobilization of reaction centers induces stress on MOSFET gate and hence modulates the MOSFET current voltage characteristics. Again, the optoelectrical property of PS I alter the electrostatic properties of the MOS gate, which reflects in the transport characteristics of the transistor.

  10. Protein structure, electron transfer and evolution of prokaryotic photosynthetic reaction centers

    Science.gov (United States)

    Blankenship, R. E.

    1994-01-01

    Photosynthetic reaction centers from a variety of organisms have been isolated and characterized. The groups of prokaryotic photosynthetic organisms include the purple bacteria, the filamentous green bacteria, the green sulfur bacteria and the heliobacteria as anoxygenic representatives as well as the cyanobacteria and prochlorophytes as oxygenic representatives. This review focuses on structural and functional comparisons of the various groups of photosynthetic reaction centers and considers possible evolutionary scenarios to explain the diversity of existing photosynthetic organisms.

  11. High throughput engineering to revitalize a vestigial electron transfer pathway in bacterial photosynthetic reaction centers.

    Science.gov (United States)

    Faries, Kaitlyn M; Kressel, Lucas L; Wander, Marc J; Holten, Dewey; Laible, Philip D; Kirmaier, Christine; Hanson, Deborah K

    2012-03-09

    Photosynthetic reaction centers convert light energy into chemical energy in a series of transmembrane electron transfer reactions, each with near 100% yield. The structures of reaction centers reveal two symmetry-related branches of cofactors (denoted A and B) that are functionally asymmetric; purple bacterial reaction centers use the A pathway exclusively. Previously, site-specific mutagenesis has yielded reaction centers capable of transmembrane charge separation solely via the B branch cofactors, but the best overall electron transfer yields are still low. In an attempt to better realize the architectural and energetic factors that underlie the directionality and yields of electron transfer, sites within the protein-cofactor complex were targeted in a directed molecular evolution strategy that implements streamlined mutagenesis and high throughput spectroscopic screening. The polycistronic approach enables efficient construction and expression of a large number of variants of a heteroligomeric complex that has two intimately regulated subunits with high sequence similarity, common features of many prokaryotic and eukaryotic transmembrane protein assemblies. The strategy has succeeded in the discovery of several mutant reaction centers with increased efficiency of the B pathway; they carry multiple substitutions that have not been explored or linked using traditional approaches. This work expands our understanding of the structure-function relationships that dictate the efficiency of biological energy-conversion reactions, concepts that will aid the design of bio-inspired assemblies capable of both efficient charge separation and charge stabilization.

  12. Reactions to Rituximab in an Outpatient Infusion Center: A 5-Year Review.

    Science.gov (United States)

    Levin, Amy S; Otani, Iris M; Lax, Timothy; Hochberg, Ephraim; Banerji, Aleena

    Reactions to rituximab occur frequently, with up to 77% of patients developing a reaction during initial exposure. The safety of rechallenging patients after a reaction is not clear and standard guidelines are lacking. To better understand clinical decision making surrounding rituximab reactions and subsequent rechallenge. We performed a 5-year retrospective review of all rituximab reactions at a large academic outpatient infusion center. Patients' demographic characteristics, clinical symptoms, and management of reactions were reviewed. Reaction severity was classified using standard criteria. Between June 2006 and January 2011, 67 patients (mean age, 58 ± 13 years, 54% men) with at least 1 rituximab reaction were identified. Most reactions occurred during the first exposure to rituximab (63%). Most reactions (n = 59 [88%]) were grade 1 or 2. Fifty-one patients (n = 51 [88%]) were rechallenged with rituximab on the same day as the initial reaction. Most patients with a grade 1 reaction tolerated rechallenge. Conversely, all 4 patients with a grade 3 reaction had a reaction during rechallenge. The outcome of same-day rechallenge after an initial grade 2 reaction was varied; most patients (26 of 31 [84%]) tolerated same-day challenge, but 5 patients had a reaction (all grade 1-2 severity). Consistent with previous data, our observations suggest that patients who experience grade 1 reactions to rituximab can be safely rechallenged the same day. A grade 3 or 4 reaction should prompt referral to an allergy specialist for risk assessment before additional rituximab administration. Further research is needed to understand the optimal management of patients with grade 2 reactions. Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

  13. Photosynthetic antennas and reaction centers: Current understanding and prospects for improvement

    Energy Technology Data Exchange (ETDEWEB)

    Blankenship, R.E. [Arizona State Univ., Tempe, AZ (United States)

    1996-09-01

    A brief introduction to the principles, structures and kinetic processes that take place in natural photosynthetic reaction center complexes is presented. Energy is first collected by an antenna system, and is transferred to a reaction center complex where primary electron transfer takes place. Secondary reactions lead to oxidation of water and reduction of CO{sub 2} in some classes of organisms. Antenna systems are highly regulated to maximize energy collection efficiency while avoiding photodamage. Some areas that are presently not well understood are listed.

  14. Photochemistry of a photosynthetic reaction center immobilized in lipidic cubic phases

    Energy Technology Data Exchange (ETDEWEB)

    Hochkoeppler, A.; Venturoli, G.; Zannoni, D. [Univ. of Bologna (Italy). Dept. of Biology; Landau, E.M.; Luisi, P.L. [ETH Zentrum, Zuerich (Switzerland). Inst. fuer Polymere; Feick, R. [Max-Planck Inst. fuer Biochemie, Martinsried (Germany)

    1995-04-20

    Photosynthetic reaction centers, isolated and purified from the facultative phototrophic bacterium Chloroflexus aurantiacus, were immobilized in optically transparent lipidic cubic phases composed of 42% (w/w) 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine and 58% (w/w) water. The immobilized photosynthetic protein retains its native properties, as indicated by visible and circular dichroic spectra. The ground state visible spectrum of the immobilized reaction centers is very similar to the corresponding spectrum in aqueous solution, indicating that the protein pigments are not extracted into the lipidic regions of the cubic phase. The secondary structure of the protein is maintained in the immobilized state, as determined by far-UV circular dichroism spectroscopy in the 200- to 250-nm range. Moreover, immobilized reaction centers retain their photochemical activity: a reversible photo-oxidation of the primary electron donor (P) is seen upon continuous illumination. Furthermore, the entrapment of reaction centers does not affect the kinetics of charge recombination between the photo-oxidized primary donor (P{sup +}) and the photoreduced primary quinone acceptor, generated by a short flash of light. Reaction centers devoided of the secondary quinone acceptor can be easily reconstituted in cubic phases by means of their coimmobilization with 1,4-naphthoquinone.

  15. In vitro biosynthesis and membrane association of photosynthetic reaction center subunits for Rhodopseudomonas sphaeroides

    Energy Technology Data Exchange (ETDEWEB)

    Hoger, J.H.; Chory, J.; Kaplan, S.

    1986-03-01

    The reaction center of Rhodopseudomonas sphaeroides is an integral membrane protein complex responsible for primary photochemical charge separation in photosynthesis. The authors report the synthesis of two of the three subunits of the photosynthetic reaction center using a DNA-directed in vitro transcription-translation system prepared from R. sphaeroides. The in vitro-synthesized polypeptides, as resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, had apparent M/sub r/s of 24,000 and 21,000 and were shown to be synthesized in equimolar amounts. This corresponds precisely to the in vivo reaction center subunits M and L, respectively. The invitro-synthesized polypeptides were immunoprecipitated with antibody prepared against whole native reaction centers. In addition, the identity of the in vitro-synthesized polypeptides as L and M was verified by comparing the protease digestion products of in vivo- with in vitro-synthesized reaction center subunits. Both of the in vitro-synthesized polypeptides were also found to partition with the particulate material in the transcription-translation system and to associate with added membranes.

  16. Vasovagal reactions in whole blood donors at 3 REDS-II blood centers in Brazil

    Science.gov (United States)

    Goncalez, T. T.; Sabino, E. C.; Schlumpf, K.S.; Wright, D.J.; Leao, S.; Sampaio, D.; Takecian, P. L.; Carneiro-Proietti, AB; Murphy, E.; Busch, M.; Custer, B.

    2013-01-01

    Background In Brazil little is known about adverse reactions during donation and the donor characteristics that may be associated with such events. Donors are offered snacks and fluids prior to donating and are required to consume a light meal after donation. For these reasons the frequency of reactions may be different than those observed in other countries. Methods A cross-sectional study was conducted of eligible whole blood donors at three large blood centers located in Brazil between July 2007 and December 2009. Vasovagal reactions (VVRs) along with donor demographic and biometric data were collected. Reactions were defined as any presyncopal or syncopal event during the donation process. Multivariable logistic regression was performed to identify predictors of VVRs. Results Of 724,861 donor presentations, 16,129 (2.2%) VVRs were recorded. Rates varied substantially between the three centers: 53, 290 and 381 per 10,000 donations in Recife, São Paulo and Belo Horizonte, respectively. Although the reaction rates varied, the donor characteristics associated with VVRs were similar [younger age (18–29), replacement donors, first time donors, low estimated blood volume (EBV)]. In multivariable analysis controlling for differences between the donor populations in each city younger age, first-time donor status and lower EBV were the factors most associated with reactions. Conclusion Factors associated with VVRs in other locations are also evident in Brazil. The difference in VVR rates between the three centers might be due to different procedures for identifying and reporting the reactions. Potential interventions to reduce the risk of reactions in Brazil should be considered. PMID:22073941

  17. Vasovagal reactions in whole blood donors at three REDS-II blood centers in Brazil.

    Science.gov (United States)

    Gonçalez, Thelma T; Sabino, Ester C; Schlumpf, Karen S; Wright, David J; Leao, Silvana; Sampaio, Divaldo; Takecian, Pedro L; Proietti, Anna B; Proitetti, Anna B; Murphy, Edward; Busch, Michael; Custer, Brian

    2012-05-01

    In Brazil little is known about adverse reactions during donation and the donor characteristics that may be associated with such events. Donors are offered snacks and fluids before donating and are required to consume a light meal after donation. For these reasons the frequency of reactions may be different than those observed in other countries. A cross-sectional study was conducted of eligible whole blood donors at three large blood centers located in Brazil between July 2007 and December 2009. Vasovagal reactions (VVRs) along with donor demographic and biometric data were collected. Reactions were defined as any presyncopal or syncopal event during the donation process. Multivariable logistic regression was performed to identify predictors of VVRs. Of 724,861 donor presentations, 16,129 (2.2%) VVRs were recorded. Rates varied substantially between the three centers: 53, 290, and 381 per 10,000 donations in Recife, São Paulo, and Belo Horizonte, respectively. Although the reaction rates varied, the donor characteristics associated with VVRs were similar (younger age [18-29 years], replacement donors, first-time donors, low estimated blood volume [EBV]). In multivariable analysis controlling for differences between the donor populations in each city younger age, first-time donor status, and lower EBV were the factors most associated with reactions. Factors associated with VVRs in other locations are also evident in Brazil. The difference in VVR rates between the three centers might be due to different procedures for identifying and reporting the reactions. Potential interventions to reduce the risk of reactions in Brazil should be considered. © 2011 American Association of Blood Banks.

  18. Application of thermostable reaction centers from Chloroflexus aurantiacus as a protonmotive force generating system

    NARCIS (Netherlands)

    SPEELMANS, G; HILLENGA, D; POOLMAN, B; KONINGS, WN

    1993-01-01

    Reaction centers (RCs) were purified from the thermophilic phototrophic bacterium Chloroflexus aurantiacus and reconstituted into liposomes. The dependence of cyclic electron transfer via horse-heart cytochrome c, UQ0 and purified or reconstituted RCs on pH, temperature and ionic strength was

  19. Reactions of carbon radicals generated by 1,5-transposition of reactive centers

    Directory of Open Access Journals (Sweden)

    ZIVORAD CEKOVIC

    2005-03-01

    Full Text Available Radical intermediates can undergo specific reactions, such as intramolecular rearrangements, i.e., the transpositions of radical centers, which are not known in classical ionic organic reactions. 1,5-Transposition of a radical center to a non-activated carbon atom are of great synthetic importance. It can be successfully applied for the introduction of different functional groups (oxygen, nitrogen, sulfur, halogens onto a carbon atom remote from the present functional group. In addition to functionalization of a remote non-activated carbon atom, the formation of new C-C bonds on the d-carbon atom have also been achieved. 1,5-Transposition of the radical centers takes place from alkoxyl, aminyl and carbon radicals to a remote carbon atom. Relocation of the radical centers preferentially involves 1,5-transfer of a hydrogen atom, although migrations of some other groups are known. The reactions of the carbon radical generated by 1,5-relocation of the radical center are presented and their synthetic applications are reviewed.

  20. Lead induced changes in phosphorylation of PSII proteins in low light grown pea plants.

    Science.gov (United States)

    Wioleta, Wasilewska; Anna, Drożak; Ilona, Bacławska; Kamila, Kąkol; Elżbieta, Romanowska

    2015-02-01

    Light-intensity and redox-state induced thylakoid proteins phosphorylation involved in structural changes and in regulation of protein turnover. The presence of heavy metal ions triggers a wide range of cellular responses including changes in plant growth and photosynthesis. Plants have evolved a number of mechanisms to protect photosynthetic apparatus. We have characterized the effect of lead on PSII protein phosphorylation in pea (Pisum sativum L.) plants grown in low light conditions. Pb ions affected only slightly photochemical efficiency of PSII and had no effect on organization of thylakoid complexes. Lead activated strongly phosphorylation of PSII core D1 protein and dephosphorylation of this protein did not proceed in far red light. D1 protein was also not degraded in this conditions. However, phosphorylation of LHCII proteins was not affected by lead. These results indicate that Pb(2+) stimulate the phosphorylation of PSII core proteins and by disturbing the disassembly of supercomplexes play a role in PSII repair mechanism. LHCII phosphorylation could control the distribution of energy between the photosystems in low light conditions. This demonstrates that plants may respond to heavy metals by induction different pathways responsible for protein protection under stress conditions.

  1. Chloroplast movement provides photoprotection to plants by redistributing PSII damage within leaves.

    Science.gov (United States)

    Davis, Phillip A; Hangarter, Roger P

    2012-09-01

    Plants use light to fix carbon through the process of photosynthesis but light also causes photoinhibition, by damaging photosystem II (PSII). Plants can usually adjust their rate of PSII repair to equal the rate of damage, but under stress conditions or supersaturating light-intensities damage may exceed the rate of repair. Light-induced chloroplast movements are one of the many mechanisms plants have evolved to minimize photoinhibition. We found that chloroplast movements achieve a measure of photoprotection to PSII by altering the distribution of photoinhibition through depth in leaves. When chloroplasts are in the low-light accumulation arrangement a greater proportion of PSII damage occurs near the illuminated surface than for leaves where the chloroplasts are in the high-light avoidance arrangement. According to our findings chloroplast movements can increase the overall efficiency of leaf photosynthesis in at least two ways. The movements alter light profiles within leaves to maximize photosynthetic output and at the same time redistribute PSII damage throughout the leaf to reduce the amount of inhibition received by individual chloroplasts and prevent a decrease in photosynthetic potential.

  2. Geometric phase and quantum interference in photosynthetic reaction center: Regulation of electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yuming, E-mail: ymsun@ytu.edu.cn; Su, Yuehua; Dai, Zhenhong; Wang, WeiTian

    2016-10-20

    Photosynthesis is driven by electron transfer in reaction centers in which the functional unit is composed of several simple molecules C{sub 2}-symmetrically arranged into two branches. In view of quantum mechanism, both branches are possible pathways traversed by the transferred electron. Due to different evolution of spin state along two pathways in transmembrane electric potential (TEP), quantum state of the transferred electron at the bridged site acquires a geometric phase difference dependent on TEP, the most efficient electron transport takes place in a specific range of TEP beyond which electron transfer is dramatically suppressed. What’s more, reaction center acts like elaborately designed quantum device preparing polarized spin dependent on TEP for the transferred electron to regulate the reduction potential at bridged site. In brief, electron transfer generates the TEP, reversely, TEP modulates the efficiency of electron transfer. This may be an important approach to maintaining an appreciable pH environment in photosynthesis.

  3. Geometric phase and quantum interference in photosynthetic reaction center: Regulation of electron transfer

    Science.gov (United States)

    Sun, Yuming; Su, Yuehua; Dai, Zhenhong; Wang, WeiTian

    2016-10-01

    Photosynthesis is driven by electron transfer in reaction centers in which the functional unit is composed of several simple molecules C2-symmetrically arranged into two branches. In view of quantum mechanism, both branches are possible pathways traversed by the transferred electron. Due to different evolution of spin state along two pathways in transmembrane electric potential (TEP), quantum state of the transferred electron at the bridged site acquires a geometric phase difference dependent on TEP, the most efficient electron transport takes place in a specific range of TEP beyond which electron transfer is dramatically suppressed. What's more, reaction center acts like elaborately designed quantum device preparing polarized spin dependent on TEP for the transferred electron to regulate the reduction potential at bridged site. In brief, electron transfer generates the TEP, reversely, TEP modulates the efficiency of electron transfer. This may be an important approach to maintaining an appreciable pH environment in photosynthesis.

  4. A single residue controls electron transfer gating in photosynthetic reaction centers

    Czech Academy of Sciences Publication Activity Database

    Shlyk, O.; Samish, I.; Matěnová, M.; Dulebo, A.; Poláková, H.; Kaftan, David; Scherz, A.

    2017-01-01

    Roč. 7, MAR 16 (2017), s. 1-13, č. článku 44580. ISSN 2045-2322 R&D Projects: GA ČR GA15-00703S; GA MŠk(CZ) LO1416 Institutional support: RVO:61388971 Keywords : BACTERIA L REACTION CENTERS * INDUCED STRUCTURAL-CHANGES * ATOMIC-FORCE MICROSCOPE Subject RIV: EE - Microbiology, Virology Impact factor: 4.259, year: 2016

  5. Light dependence of quantum yields for PSII charge separation and oxygen evolution in eucaryotic algae

    NARCIS (Netherlands)

    Flameling, I.A.; Kromkamp, J.C.

    1998-01-01

    Quantum yields of photosystem II (PSII) charge separation (Phi(P)) and oxygen production (Phi(O2)) were determined by simultaneous measurements of oxygen production and variable fluorescence in four different aquatic microalgae representing three different taxonomic groups: the freshwater alga

  6. Oxyradicals and PSII activity in maize leaves in the absence of UV ...

    Indian Academy of Sciences (India)

    ... oxyradicals invoked higher activity of antioxidant enzymes like superoxide dismutase and peroxidase under ambient UV, they also imposed limitation on the photosynthetic efficiency of PSII. Exclusion of UV components (UV-B 280–315 nm; UV-A 315–400 nm) translated to enhanced photosynthesis, growth and biomass.

  7. Phenomenological description of a three-center insertion reaction: an information-theoretic study.

    Science.gov (United States)

    Esquivel, Rodolfo O; Flores-Gallegos, Nelson; Dehesa, Jesús S; Angulo, Juan Carlos; Antolín, Juan; López-Rosa, Sheila; Sen, K D

    2010-02-04

    Information-theoretic measures are employed to describe the course of a three-center chemical reaction in terms of detecting the transition state and the stationary points unfolding the bond-forming and bond-breaking regions which are not revealed in the energy profile. The information entropy profiles for the selected reactions are generated by following the intrinsic-reaction-coordinate (IRC) path calculated at the MP2 level of theory from which Shannon entropies in position and momentum spaces at the QCISD(T)/6-311++G(3df,2p) level are determined. Several complementary reactivity descriptors are also determined, such as the dipole moment, the molecular electrostatic potential (MEP) obtained through a multipole expansion (DMA), the atomic charges and electric potentials fitted to the MEP, the hardness and softness DFT descriptors, and several geometrical parameters which support the information-theoretic analysis. New density-based structures related to the bond-forming and bond-breaking regions are proposed. Our results support the concept of a continuum of transient of Zewail and Polanyi for the transition state rather than a single state, which is also in agreement with reaction-force analyses.

  8. On the mechanism of ubiquinone mediated photocurrent generation by a reaction center based photocathode.

    Science.gov (United States)

    Friebe, Vincent M; Swainsbury, David J K; Fyfe, Paul K; van der Heijden, Wessel; Jones, Michael R; Frese, Raoul N

    2016-12-01

    Upon photoexcitation, the reaction center (RC) pigment-proteins that facilitate natural photosynthesis achieve a metastable separation of electrical charge among the embedded cofactors. Because of the high quantum efficiency of this process, there is a growing interest in their incorporation into biohybrid materials for solar energy conversion, bioelectronics and biosensing. Multiple bioelectrochemical studies have shown that reaction centers from various photosynthetic organisms can be interfaced with diverse electrode materials for the generation of photocurrents, but many mechanistic aspects of native protein functionality in a non-native environment is unknown. In vivo, RC's catalyse ubiquinone-10 reduction, protonation and exchange with other lipid phase ubiquinone-10s via protein-controlled spatial orientation and protein rearrangement. In contrast, the mechanism of ubiquinone-0 reduction, used to facilitate fast RC turnover in an aqueous photoelectrochemical cell (PEC), may not proceed via the same pathway as the native cofactor. In this report we show truncation of the native isoprene tail results in larger RC turnover rates in a PEC despite the removal of the tail's purported role of ubiquinone headgroup orientation and binding. Through the use of reaction centers with single or double mutations, we also show the extent to which two-electron/two-proton ubiquinone chemistry that operates in vivo also underpins the ubiquinone-0 reduction by surface-adsorbed RCs in a PEC. This reveals that only the ubiquinone headgroup is critical to the fast turnover of the RC in a PEC and provides insight into design principles for the development of new biophotovoltaic cells and biosensors. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Quantum non-equilibrium approach for fast electron transport in open systems: photosynthetic reaction centers

    CERN Document Server

    Pudlak, M; Nazmitdinov, R G; Pincak, R

    2011-01-01

    Creation of electron or exciton by external fields in a system with initially statistically independent unrelaxed vibrational modes leads to an initial condition term. The contribution of this term in the time convolution generalized master equation approach is studied in second order of the perturbation theory for electron-phonon coupling in the parth integral formalism. The developed approach, applied for analysis of dynamics in the photosynthetic reaction center, exhibits the key role of the initial condition term at the primary stage of electron transfer.

  10. Overexpressed Superoxide Dismutase and Catalase Act Synergistically to Protect the Repair of PSII during Photoinhibition in Synechococcus elongatus PCC 7942.

    Science.gov (United States)

    Sae-Tang, Penporn; Hihara, Yukako; Yumoto, Isao; Orikasa, Yoshitake; Okuyama, Hidetoshi; Nishiyama, Yoshitaka

    2016-09-01

    The repair of PSII under strong light is particularly sensitive to reactive oxygen species (ROS), such as the superoxide radical and hydrogen peroxide, and these ROS are efficiently scavenged by superoxide dismutase (SOD) and catalase. In the present study, we generated transformants of the cyanobacterium Synechococcus elongatus PCC 7942 that overexpressed an iron superoxide dismutase (Fe-SOD) from Synechocystis sp. PCC 6803; a highly active catalase (VktA) from Vibrio rumoiensis; and both enzymes together. Then we examined the sensitivity of PSII to photoinhibition in the three strains. In cells that overexpressed either Fe-SOD or VktA, PSII was more tolerant to strong light than it was in wild-type cells. Moreover, in cells that overexpressed both Fe-SOD and VktA, PSII was even more tolerant to strong light. However, the rate of photodamage to PSII, as monitored in the presence of chloramphenicol, was similar in all three transformant strains and in wild-type cells, suggesting that the overexpression of these ROS-scavenging enzymes might not protect PSII from photodamage but might protect the repair of PSII. Under strong light, intracellular levels of ROS fell significantly, and the synthesis de novo of proteins that are required for the repair of PSII, such as the D1 protein, was enhanced. Our observations suggest that overexpressed Fe-SOD and VktA might act synergistically to alleviate the photoinhibition of PSII by reducing intracellular levels of ROS, with resultant protection of the repair of PSII from oxidative inhibition. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  11. Mutations to R. sphaeroides Reaction Center Perturb Energy Levels and Vibronic Coupling but Not Observed Energy Transfer Rates.

    Science.gov (United States)

    Flanagan, Moira L; Long, Phillip D; Dahlberg, Peter D; Rolczynski, Brian S; Massey, Sara C; Engel, Gregory S

    2016-03-10

    The bacterial reaction center is capable of both efficiently collecting and quickly transferring energy within the complex; therefore, the reaction center serves as a convenient model for both energy transfer and charge separation. To spectroscopically probe the interactions between the electronic excited states on the chromophores and their intricate relationship with vibrational motions in their environment, we examine coherences between the excited states. Here, we investigate this question by introducing a series of point mutations within 12 Å of the special pair of bacteriochlorophylls in the Rhodobacter sphaeroides reaction center. Using two-dimensional spectroscopy, we find that the time scales of energy transfer dynamics remain unperturbed by these mutations. However, within these spectra, we detect changes in the mixed vibrational-electronic coherences in these reaction centers. Our results indicate that resonance between bacteriochlorophyll vibrational modes and excitonic energy gaps promote electronic coherences and support current vibronic models of photosynthetic energy transfer.

  12. Comparing the temperature dependence of photosynthetic electron transfer in Chloroflexus aurantiacus and Rhodobactor sphaeroides reaction centers.

    Science.gov (United States)

    Guo, Zhi; Lin, Su; Xin, Yueyong; Wang, Haiyu; Blankenship, Robert E; Woodbury, Neal W

    2011-09-29

    The process of electron transfer from the special pair, P, to the primary electron donor, H(A), in quinone-depleted reaction centers (RCs) of Chloroflexus (Cf.) aurantiacus has been investigated over the temperature range from 10 to 295 K using time-resolved pump-probe spectroscopic techniques. The kinetics of the electron transfer reaction, P* → P(+)H(A)(-), was found to be nonexponential, and the degree of nonexponentiality increased strongly as temperature decreased. The temperature-dependent behavior of electron transfer in Cf. aurantiacus RCs was compared with that of the purple bacterium Rhodobacter (Rb.) sphaeroides . Distinct transitions were found in the temperature-dependent kinetics of both Cf. aurantiacus and Rb. sphaeroides RCs, at around 220 and 160 K, respectively. Structural differences between these two RCs, which may be associated with those differences, are discussed. It is suggested that weaker protein-cofactor hydrogen bonding, stronger electrostatic interactions at the protein surface, and larger solvent interactions likely contribute to the higher transition temperature in Cf. aurantiacus RCs temperature-dependent kinetics compared with that of Rb. sphaeroides RCs. The reaction-diffusion model provides an accurate description for the room-temperature electron transfer kinetics in Cf. aurantiacus RCs with no free parameters, using coupling and reorganization energy values previously determined for Rb. sphaeroides , along with an experimental measure of protein conformational diffusion dynamics and an experimental literature value of the free energy gap between P* and P(+)H(A)(-). © 2011 American Chemical Society

  13. Assessing the additive risks of PSII herbicide exposure to the Great Barrier Reef.

    Science.gov (United States)

    Lewis, Stephen E; Schaffelke, Britta; Shaw, Melanie; Bainbridge, Zoë T; Rohde, Ken W; Kennedy, Karen; Davis, Aaron M; Masters, Bronwyn L; Devlin, Michelle J; Mueller, Jochen F; Brodie, Jon E

    2012-01-01

    Herbicide residues have been measured in the Great Barrier Reef lagoon at concentrations which have the potential to harm marine plant communities. Monitoring on the Great Barrier Reef lagoon following wet season discharge show that 80% of the time when herbicides are detected, more than one are present. These herbicides have been shown to act in an additive manner with regards to photosystem-II inhibition. In this study, the area of the Great Barrier Reef considered to be at risk from herbicides is compared when exposures are considered for each herbicide individually and also for herbicide mixtures. Two normalisation indices for herbicide mixtures were calculated based on current guidelines and PSII inhibition thresholds. The results show that the area of risk for most regions is greatly increased under the proposed additive PSII inhibition threshold and that the resilience of this important ecosystem could be reduced by exposure to these herbicides. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Deletion of CGLD1 Impairs PSII and Increases Singlet Oxygen Tolerance of Green Alga Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Jiale Xing

    2017-12-01

    Full Text Available The green alga Chlamydomonas reinhardtii is a key model organism for studying photosynthesis and oxidative stress in unicellular eukaryotes. Using a forward genetics approach, we have identified and characterized a mutant x32, which lacks a predicted protein named CGLD1 (Conserved in Green Lineage and Diatom 1 in GreenCut2, under normal and stress conditions. We show that loss of CGLD1 resulted in minimal photoautotrophic growth and PSII activity in the organism. We observed reduced amount of PSII complex and core subunits in the x32 mutant based on blue-native (BN/PAGE and immunoblot analysis. Moreover, x32 exhibited increased sensitivity to high-light stress and altered tolerance to different reactive oxygenic species (ROS stress treatments, i.e., decreased resistance to H2O2/or tert-Butyl hydroperoxide (t-BOOH and increased tolerance to neutral red (NR and rose bengal (RB that induce the formation of singlet oxygen, respectively. Further analysis via quantitative real-time PCR (qRT-PCR indicated that the increased singlet-oxygen tolerance of x32 was largely correlated with up-regulated gene expression of glutathione-S-transferases (GST. The phenotypical and physiological implications revealed from our experiments highlight the important roles of CGLD1 in maintaining structure and function of PSII as well as in protection of Chlamydomonas under photo-oxidative stress conditions.

  15. Follicular regulatory T (Tfr) cells with dual Foxp3 and Bcl6 expression suppress germinal center reactions

    Science.gov (United States)

    Chung, Yeonseok; Tanaka, Shinya; Chu, Fuliang; Nurieva, Roza; Martinez, Gustavo J.; Rawal, Seema; Wang, Yi-Hong; Lim, Ho Yong; Reynolds, Joseph M.; Zhou, Xiao-hui; Fan, Hui-min; Liu, Zhong-ming; Neelapu, Sattva S.; Dong, Chen

    2011-01-01

    Foxp3+ regulatory T (Treg) cells suppress different types of immune responses to help maintain homeostasis in the body. How Treg cells regulate humoral immunity, including germinal center reactions, is unclear. Here we identify a subset of Treg cells expressing CXCR5 and Bcl6, and localized in the germinal centers in mouse as well as human. The expression of CXCR5 on Treg cells depends on Bcl6. These CXCR5+Bcl6+ Treg cells are absent in thymus but can be de novo generated from CXCR5-Foxp3+ natural Treg precursors. Lack of CXCR5+ Treg cells leads to greater germinal center reactions. These results unveil a Bcl6-CXCR5 axis in Treg cells that undermines the development of follicular regulatory T (Tfr) cells that function to inhibit the germinal center reaction. PMID:21785430

  16. Chemical proprieties of the iron-quinone complex in mutated reaction centers of Rb. sphaeroides

    Science.gov (United States)

    Hałas, Agnieszka; Derrien, Valerie; Sebban, Pierre; Matlak, Krzysztof; Korecki, Józef; Kruk, Jerzy; Burda, Kvĕtoslava

    2012-03-01

    We investigated type II bacterial photosynthetic reaction centers, which contain a quinone - iron complex (QA-Fe-QB) on their acceptor side. Under physiological conditions it was observed mainly in a reduced high spin state but its low spin ferrous states were also observed. Therefore, it was suggested that it might regulate the dynamical properties of the iron-quinone complex and the protonation and deprotonation events in its neighbourhood. In order to get insight into the molecular mechanism of the NHFe low spin state formation, we preformed Mössbauer studies of a wild type of Rb. sphaeroides and its two mutated forms. Our Mössbauer measurements show that the hydrophobicity of the QA binding site can be crucial for stabilization of the high spin ferrous state of NHFe.

  17. Chemical proprieties of the iron-quinone complex in mutated reaction centers of Rb. sphaeroides

    Energy Technology Data Exchange (ETDEWEB)

    Halas, Agnieszka [AGH University, Faculty of Physics and Computer Science, Department of Medical Physics and Biophysics (Poland); Derrien, Valerie; Sebban, Pierre [University of Paris XI, Laboratoire de Chimie Physique (France); Matlak, Krzysztof; Korecki, Jozef [AGH University, Faculty of Physics and Computer Science, Department of Solid State Physics (Poland); Kruk, Jerzy [Jagiellonian University, Faculty of Biochemistry, Biophysics and Biotechnology (Poland); Burda, Kvetoslava, E-mail: kvetoslava.burda@fis.agh.edu.pl [AGH University, Faculty of Physics and Computer Science, Department of Medical Physics and Biophysics (Poland)

    2012-03-15

    We investigated type II bacterial photosynthetic reaction centers, which contain a quinone - iron complex (Q{sub A}-Fe-Q{sub B}) on their acceptor side. Under physiological conditions it was observed mainly in a reduced high spin state but its low spin ferrous states were also observed. Therefore, it was suggested that it might regulate the dynamical properties of the iron-quinone complex and the protonation and deprotonation events in its neighbourhood. In order to get insight into the molecular mechanism of the NHFe low spin state formation, we preformed Moessbauer studies of a wild type of Rb. sphaeroides and its two mutated forms. Our Moessbauer measurements show that the hydrophobicity of the Q{sub A} binding site can be crucial for stabilization of the high spin ferrous state of NHFe.

  18. Electronic pathway in reaction centers from Rhodobacter sphaeroides and Chloroflexus aurantiacus.

    Science.gov (United States)

    Pudlak, Michal; Pincak, Richard

    2010-06-01

    The reaction centers (RC) of Chloroflexus aurantiacus and Rhodobacter sphaeroidesH(M182)L mutant were investigated. Prediction for electron transfer (ET) at very low temperatures was also performed. To describe the kinetics of the C. aurantiacus RCs, the incoherent model of electron transfer was used. It was shown that the asymmetry in electronic coupling parameters must be included to explain the experiments. For the description of R. sphaeroidesH(M182)L mutant RCs, the coherent and incoherent models of electron transfer were used. These two models are discussed with regard to the observed electron transfer kinetics. It seems likely that the electron transfer asymmetry in R. sphaeroides RCs is caused mainly by the asymmetry in the free energy levels of L- and M-side cofactors. In the case of C. aurantiacus RCs, the unidirectionality of the charge separation can be caused mainly by the difference in the electronic coupling parameters in two branches.

  19. Kinetics of several oxygenated carbon-centered free radical reactions with NO2.

    Science.gov (United States)

    Rissanen, Matti P; Arppe, Suula L; Timonen, Raimo S

    2013-05-16

    Five oxygenated carbon-centered free radical reactions with nitrogen dioxide (NO2) have been studied in direct time-resolved measurements. Experiments were conducted in a temperature-controlled flow tube reactor coupled to a 193 nm exciplex laser photolysis and a resonance gas lamp photoionization mass spectrometer. Reactions were investigated under pseudofirst-order conditions, with the NO2 concentrations of the experiments in great excess over the initial radical concentrations ([R]0 reactions with NO2 and, hence, includes the three smallest hydroxyalkyl radical species (CH2OH, CH2CH2OH, and CH3CHOH). The obtained rate coefficients are high with the temperature-dependent rate coefficients given by a formula k(T) = k300K × (T/300 K)(-n) as (in units of cm(3) molecule(-1) s(-1)): k(CH2OH + NO2) = (8.95 ± 2.70) × 10(-11) × (T/300 K)(-0.54±0.27) (T = 298-363 K), k(CH2CH2OH + NO2) = (5.99 ± 1.80) × 10(-11) × (T/300 K)(-1.49±0.45)(T = 241-363 K), k(CH3CHOH + NO2) = (7.48 ± 2.24) × 10(-11) × (T/300 K)(-1.36±0.41) (T = 266-363 K), k(CH3OCH2 + NO2) = (7.85 ± 2.36) × 10(-11) × (T/300 K)(-0.93±0.28) (T = 243-363 K), and k(CH3CO + NO2) = (2.87 ± 0.57) × 10(-11) × (T/300 K)(-2.45±0.49) (T = 241-363 K), where the uncertainties refer to the estimated overall uncertainties of the values obtained. The determined rate coefficients show negative temperature dependence with no apparent bath gas pressure dependence under the current experimental conditions (241-363 K and about 1-3 Torr helium). This behavior is typical for a radical-radical addition mechanism with no potential energy barrier above the energy of the separated reactants in the entrance channel of the reaction. Unfortunately the absence of detected product signals prevented gaining deeper insight into the reaction mechanism.

  20. [Adverse drug reactions in pediatrics: Experience of a regional pharmacovigilance center].

    Science.gov (United States)

    Saint-Martin, Caroline; Kanagaratnam, Lukshe; de Boissieu, Paul; Azzouz, Brahim; Abou Taam, Malak; Trenque, Thierry

    2016-10-01

    To describe the adverse drug reactions (ADR) and the drugs involved in pediatrics. An observational study on all ADR notifications recorded in the French pharmacovigilance database by the Regional Pharmacovigilance Center of Champagne-Ardenne between 1 January 1985 and 31 December 2014 involving children from 0 to 17 years inclusive was performed. For all notifications, we studied the patient and the ADR characteristics. During the study period, 632 notifications were collected. The most frequently reported ATC (anatomical, therapeutic and chemical) classes were vaccines (15.9%), antineoplastics (12%) and antibiotics (11.1%). Forty-six percent of the notifications were serious. For serious ADRs, the most involved drugs were paracetamol, asparaginase and ibuprofen. Skin reactions were the most often reported ADRs. The most common lowest level terms (LLT) were urticaria (4.9%), hypersensitivity (4.1%), fever (2.9%) and vomiting (2.8%). ADR reporting to the pharmacovigilance system, in particular pediatric ADRs, should be encouraged. Information on the use of medicinal products, especially on self-medication use, need to be improve. Copyright © 2016 Société française de pharmacologie et de thérapeutique. Published by Elsevier Masson SAS. All rights reserved.

  1. Competitive effects between stationary chemical reaction centres: A theory based on off-center monopoles

    Science.gov (United States)

    Biello, Joseph A.; Samson, René

    2015-03-01

    The subject of this paper is competitive effects between multiple reaction sinks. A theory based on off-center monopoles is developed for the steady-state diffusion equation and for the convection-diffusion equation with a constant flow field. The dipolar approximation for the diffusion equation with two equal reaction centres is compared with the exact solution. The former turns out to be remarkably accurate, even for two touching spheres. Numerical evidence is presented to show that the same holds for larger clusters (with more than two spheres). The theory is extended to the convection-diffusion equation with a constant flow field. As one increases the convective velocity, the competitive effects between the reactive centres gradually become less significant. This is demonstrated for a number of cluster configurations. At high flow velocities, the current methodology breaks down. Fixing this problem will be the subject of future research. The current method is useful as an easy-to-use tool for the calibration of other more complicated models in mass and/or heat transfer.

  2. Ex vivo engineered immune organoids for controlled germinal center reactions.

    Science.gov (United States)

    Purwada, Alberto; Jaiswal, Manish K; Ahn, Haelee; Nojima, Takuya; Kitamura, Daisuke; Gaharwar, Akhilesh K; Cerchietti, Leandro; Singh, Ankur

    2015-09-01

    Ex vivo engineered three-dimensional organotypic cultures have enabled the real-time study and control of biological functioning of mammalian tissues. Organs of broad interest where its architectural, cellular, and molecular complexity has prevented progress in ex vivo engineering are the secondary immune organs. Ex vivo immune organs can enable mechanistic understanding of the immune system and more importantly, accelerate the translation of immunotherapies as well as a deeper understanding of the mechanisms that lead to their malignant transformation into a variety of B and T cell malignancies. However, till date, no modular ex vivo immune organ has been developed with an ability to control the rate of immune reaction through tunable design parameter. Here we describe a B cell follicle organoid made of nanocomposite biomaterials, which recapitulates the anatomical microenvironment of a lymphoid tissue that provides the basis to induce an accelerated germinal center (GC) reaction by continuously providing extracellular matrix (ECM) and cell-cell signals to naïve B cells. Compared to existing co-cultures, immune organoids provide a control over primary B cell proliferation with ∼100-fold higher and rapid differentiation to the GC phenotype with robust antibody class switching. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Interplay between excitation kinetics and reaction-center dynamics in purple bacteria

    Science.gov (United States)

    Caycedo-Soler, Felipe; Rodríguez, Ferney J.; Quiroga, Luis; Johnson, Neil F.

    2010-09-01

    Photosynthesis is arguably the fundamental process of life, since it enables energy from the Sun to enter the food chain on the Earth. It is a remarkable non-equilibrium process in which photons are converted to many-body excitations, which traverse a complex biomolecular membrane, where they are captured and fuel chemical reactions within a reaction center (RC) in order to produce nutrients. The precise nature of these dynamical processes—which lie at the interface between quantum and classical behavior and involve both noise and coordination—is still being explored. Here, we focus on a striking recent empirical finding concerning an illumination-driven transition in the biomolecular membrane architecture of the purple bacteria Rsp. photometricum. Using stochastic realizations to describe a hopping rate model for excitation transfer, we show numerically and analytically that this surprising shift in preferred architectures can be traced to the interplay between the excitation kinetics and the RC dynamics. The net effect is that the bacteria profit from efficient metabolism at low illumination intensities while using dissipation to avoid an oversupply of energy at high illumination intensities.

  4. Immobilization and nanoscale film structure of bacterial reaction centers on gold

    Science.gov (United States)

    Bhalla, Vijayender; Zazubovich, Valter

    2012-08-01

    Photosynthetic bacterial reaction centers (BRC) have shown great potential for bioengineering applications. In the present work we demonstrate their preferentially oriented immobilization on top of a mercaptopropionic acid (MPA) self assembled monolayer (SAM) formed on gold screen printed electrodes (Au-SPE). The AFM of the self assembled biofilm reveals formation of nanohole features with the depths of 2.2-2.5 nm, consistent with the thickness of the BRC (~ 3 nm). Thus, BRCs organize into a sub-monolayer film on top of the MPA SAM layer. The square-wave voltammogram of the BRC films exhibits features due to the redox reactions for the bacteriochlorophyll dimer (the strongest), bacteriopheophytin, and the quinones (weak), indicating that the BRCs are more likely immobilized with the dimer side towards the electrode surface. Non-saturating illumination of the BRC film at open circuit conditions leads to a sharp spike of negative current which could be due to the electron acceptance by the oxidized dimer.

  5. Kinetics and energetics of electron transfer in reaction centers of the photosynthetic bacterium Roseiflexus castenholzii.

    Science.gov (United States)

    Collins, Aaron M; Kirmaier, Christine; Holten, Dewey; Blankenship, Robert E

    2011-03-01

    The kinetics and thermodynamics of the photochemical reactions of the purified reaction center (RC)-cytochrome (Cyt) complex from the chlorosome-lacking, filamentous anoxygenic phototroph, Roseiflexus castenholzii are presented. The RC consists of L- and M-polypeptides containing three bacteriochlorophyll (BChl), three bacteriopheophytin (BPh) and two quinones (Q(A) and Q(B)), and the Cyt is a tetraheme subunit. Two of the BChls form a dimer P that is the primary electron donor. At 285K, the lifetimes of the excited singlet state, P*, and the charge-separated state P(+)H(A)(-) (where H(A) is the photoactive BPh) were found to be 3.2±0.3 ps and 200±20 ps, respectively. Overall charge separation P*→→ P(+)Q(A)(-) occurred with ≥90% yield at 285K. At 77K, the P* lifetime was somewhat shorter and the P(+)H(A)(-) lifetime was essentially unchanged. Poteniometric titrations gave a P(865)/P(865)(+) midpoint potential of +390mV vs. SHE. For the tetraheme Cyt two distinct midpoint potentials of +85 and +265mV were measured, likely reflecting a pair of low-potential hemes and a pair of high-potential hemes, respectively. The time course of electron transfer from reduced Cyt to P(+) suggests an arrangement where the highest potential heme is not located immediately adjacent to P. Comparisons of these and other properties of isolated Roseiflexus castenholzii RCs to those from its close relative Chloroflexus aurantiacus and to RCs from the purple bacteria are made. Copyright © 2010 Elsevier B.V. All rights reserved.

  6. Structure and protein binding interactions of the primary donor of the Chloroflexus aurantiacus reaction center.

    Science.gov (United States)

    Ivancich, A; Feick, R; Ertlmaier, A; Mattioli, T A

    1996-05-14

    Soret resonance, QX resonance, and QY near-infrared Fourier transform (FT) (pre)resonance Raman spectroscopies were used to determine pigment-protein interactions of specific bacteriochlorin molecules in the reaction center from Chloroflexus aurantiacus. FT Raman spectroscopy, using 1064 nm excitation, was used to selectively obtain preresonance and resonance vibrational Raman spectra of the primary donor (P) of reaction centers (RCs) from Chloroflexus aurantiacus in the Po and P.+ states, respectively. The FT Raman spectrum of RCs in their neutral P (Po) state exhibits bands at 1605, 1632, 1648, and 1696 cm-1 which are attributable to P in its resting neutral state. Specifically, the latter three Raman bands can be assigned to the conjugated C2 acetyl and C9 keto carbonyl groups of the bacteriochlorophyll (BChl) molecules constituting P. The observation of at least three such bands is indicative of a non-monomeric nature of P, consistent with the proposal that it is a dimer of BChl molecules. The 1632 cm-1 band is consistent only with a hydrogen bonded BChl acetyl carbonyl, while the 1648 cm-1 band is assigned to a non-hydrogen bonded acetyl carbonyl. The 1696 cm-1 band is consistent only with a non-hydrogen bonded keto carbonyl group; from the unusually high intensity of this latter band compared to the others, we propose that the 1696 cm-1 band contains contributions from two keto carbonyl groups, both free of hydrogen bonds. From published protein sequence alignments of the L and M subunits of Rhodobacter (Rb.) sphaeroides and Chloroflexus aurantiacus we assign the 1632 cm-1 band as arising from the C2 acetyl carbonyl of the analogous PM constituent of P, which is hydrogen bonded to tyrosine M187 in the Chloroflexus RC, and propose a pigment-protein structural model for the primary donor of Chloroflexus aurantiacus. The FT Raman spectrum of RCs in the P degrees+ state indicates that one component of the 1696 cm-1 band has upshifted 21 cm-1 to 1717 cm-1

  7. Excited state dynamics in photosynthetic reaction center and light harvesting complex 1

    Science.gov (United States)

    Strümpfer, Johan; Schulten, Klaus

    2012-08-01

    Key to efficient harvesting of sunlight in photosynthesis is the first energy conversion process in which electronic excitation establishes a trans-membrane charge gradient. This conversion is accomplished by the photosynthetic reaction center (RC) that is, in case of the purple photosynthetic bacterium Rhodobacter sphaeroides studied here, surrounded by light harvesting complex 1 (LH1). The RC employs six pigment molecules to initiate the conversion: four bacteriochlorophylls and two bacteriopheophytins. The excited states of these pigments interact very strongly and are simultaneously influenced by the surrounding thermal protein environment. Likewise, LH1 employs 32 bacteriochlorophylls influenced in their excited state dynamics by strong interaction between the pigments and by interaction with the protein environment. Modeling the excited state dynamics in the RC as well as in LH1 requires theoretical methods, which account for both pigment-pigment interaction and pigment-environment interaction. In the present study we describe the excitation dynamics within a RC and excitation transfer between light harvesting complex 1 (LH1) and RC, employing the hierarchical equation of motion method. For this purpose a set of model parameters that reproduce RC as well as LH1 spectra and observed oscillatory excitation dynamics in the RC is suggested. We find that the environment has a significant effect on LH1-RC excitation transfer and that excitation transfers incoherently between LH1 and RC.

  8. An overview on chlorophylls and quinones in the photosystem I-type reaction centers.

    Science.gov (United States)

    Ohashi, Shunsuke; Iemura, Tatsuya; Okada, Naoki; Itoh, Shingo; Furukawa, Hayato; Okuda, Masaaki; Ohnishi-Kameyama, Mayumi; Ogawa, Takuro; Miyashita, Hideaki; Watanabe, Tadashi; Itoh, Shigeru; Oh-oka, Hirozo; Inoue, Kazuhito; Kobayashi, Masami

    2010-06-01

    Minor but key chlorophylls (Chls) and quinones in photosystem (PS) I-type reaction centers (RCs) are overviewed in regard to their molecular structures. In the PS I-type RCs, the prime-type chlorophylls, namely, bacteriochlorophyll (BChl) a' in green sulfur bacteria, BChl g' in heliobacteria, Chl a' in Chl a-type PS I, and Chl d' in Chl d-type PS I, function as the special pairs, either as homodimers, (BChl a')(2) and (BChl g')(2) in anoxygenic organisms, or heterodimers, Chl a/a' and Chl d/d' in oxygenic photosynthesis. Conversions of BChl g to Chl a and Chl a to Chl d take place spontaneously under mild condition in vitro. The primary electron acceptors, A (0), are Chl a-derivatives even in anoxygenic PS I-type RCs. The secondary electron acceptors are naphthoquinones, whereas the side chains may have been modified after the birth of cyanobacteria, leading to succession from menaquinone to phylloquinone in oxygenic PS I.

  9. Femtosecond phase of charge separation in reaction centers of Chloroflexus aurantiacus.

    Science.gov (United States)

    Yakovlev, A G; Shkuropatova, T A; Vasilieva, L G; Shkuropatov, A Ya; Shuvalov, V A

    2009-08-01

    Difference absorption spectroscopy with temporal resolution of approximately 20 fsec was used to study the primary phase of charge separation in isolated reaction centers (RCs) of Chloroflexus aurantiacus at 90 K. An ensemble of difference (light-minus-dark) absorption spectra in the 730-795 nm region measured at -0.1 to 4 psec delays relative to the excitation pulse was analyzed. Comparison with analogous data for RCs of HM182L mutant of Rhodobacter sphaeroides having the same pigment composition identified the 785 nm absorption band as the band of bacteriopheophytin Phi(B) in the B-branch. By study the bleaching of this absorption band due to formation of Phi(B)(-), it was found that a coherent electron transfer from P* to the B-branch occurs with a very small delay of 10-20 fsec after excitation of dimer bacteriochlorophyll P. Only at 120 fsec delay electron transfer from P* to the A-branch occurs with the formation of bacteriochlorophyll anion B(A)(-) absorption band at 1028 nm and the appearance of P* stimulated emission at 940 nm, as also occurs in native RCs of Rb. sphaeroides. It is concluded that a nuclear wave packet motion on the potential energy surface of P* after a 20-fsec light pulse excitation leads to the coherent formation of the P(+)Phi(B)(-) and P(+)B(A)(-) states.

  10. Assembly of photosynthetic reaction center with ABA tri-block polymersomes: highlights on the protein localization.

    KAUST Repository

    Tangorra, Roberto Rocco

    2015-07-07

    The reconstitution of the integral membrane protein photosynthetic reaction center (RC) in polymersomes, i. e. artificial closed vesicles, was achieved by the micelle-to-vesicle transition technique, a very mild protocol based on size exclusion chromatography often used to drive the incorporation of proteins contemporarily to liposomes formation. An optimized protocol was used to successfully reconstitute the protein in a fully active state in polymersomes formed by the tri-block copolymers PMOXA22-PDMS61-PMOXA22. The RC is very sensitive to its solubilizing environment and was used to probe the positioning of the protein in the vesicles. According to charge-recombination experiments and to the enzymatic activity assay, the RC is found to accommodate in the PMOXA22 region of the polymersome, facing the water bulk solution, rather than in the PDMS61 transmembrane-like region. Furthermore, polymersomes were found to preserve protein integrity efficiently as the biomimetic lipid bilayers but show a much longer temporal stability than lipid based vesicles.

  11. Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides.

    Science.gov (United States)

    Vermaas, Josh V; Taguchi, Alexander T; Dikanov, Sergei A; Wraight, Colin A; Tajkhorshid, Emad

    2015-03-31

    Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis across a vast number of organisms. Prior experimental results have shown that the photosynthetic reaction center (RC) from Rhodobacter sphaeroides is only fully functional with a limited set of methoxy-bearing quinones, suggesting that specific interactions with this substituent are required to drive electron transport and the formation of quinol. The nature of these interactions has yet to be determined. Through parameterization of a CHARMM-compatible quinone force field and subsequent molecular dynamics simulations of the quinone-bound RC, we have investigated and characterized the interactions of the protein with the quinones in the Q(A) and Q(B) sites using both equilibrium simulation and thermodynamic integration. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the Q(B) site and the amide nitrogen of GlyL225 that we implicate in locking the orientation of the 2-methoxy group, thereby tuning the redox potential difference between the quinones occupying the Q(A) and Q(B) sites. Disruption of this interaction leads to weaker binding in a ubiquinone analogue that lacks a 2-methoxy group, a finding supported by reverse electron transfer electron paramagnetic resonance experiments of the Q(A)⁻Q(B)⁻ biradical and competitive binding assays.

  12. Isolation of novel PSII-LHCII megacomplexes from pea plants characterized by a combination of proteomics and electron microscopy.

    Science.gov (United States)

    Albanese, Pascal; Nield, Jon; Tabares, Jose Alejandro Muñoz; Chiodoni, Angelica; Manfredi, Marcello; Gosetti, Fabio; Marengo, Emilio; Saracco, Guido; Barber, James; Pagliano, Cristina

    2016-12-01

    In higher plants, photosystem II (PSII) is a multi-subunit pigment-protein complex embedded in the thylakoid membranes of chloroplasts, where it is present mostly in dimeric form within the grana. Its light-harvesting antenna system, LHCII, is composed of trimeric and monomeric complexes, which can associate in variable number with the dimeric PSII core complex in order to form different types of PSII-LHCII supercomplexes. Moreover, PSII-LHCII supercomplexes can laterally associate within the thylakoid membrane plane, thus forming higher molecular mass complexes, termed PSII-LHCII megacomplexes (Boekema et al. 1999a, in Biochemistry 38:2233-2239; Boekema et al. 1999b, in Eur J Biochem 266:444-452). In this study, pure PSII-LHCII megacomplexes were directly isolated from stacked pea thylakoid membranes by a rapid single-step solubilization, using the detergent n-dodecyl-α-D-maltoside, followed by sucrose gradient ultracentrifugation. The megacomplexes were subjected to biochemical and structural analyses. Transmission electron microscopy on negatively stained samples, followed by single-particle analyses, revealed a novel form of PSII-LHCII megacomplexes, as compared to previous studies (Boekema et al.1999a, in Biochemistry 38:2233-2239; Boekema et al. 1999b, in Eur J Biochem 266:444-452), consisting of two PSII-LHCII supercomplexes sitting side-by-side in the membrane plane, sandwiched together with a second copy. This second copy of the megacomplex is most likely derived from the opposite membrane of a granal stack. Two predominant forms of intact sandwiched megacomplexes were observed and termed, according to (Dekker and Boekema 2005 Biochim Biophys Acta 1706:12-39), as (C2S2)4 and (C2S2 + C2S2M2)2 megacomplexes. By applying a gel-based proteomic approach, the protein composition of the isolated megacomplexes was fully characterized. In summary, the new structural forms of isolated megacomplexes and the related modeling performed provide novel insights into

  13. Optimizing multi-step B-side charge separation in photosynthetic reaction centers from Rhodobacter capsulatus

    Energy Technology Data Exchange (ETDEWEB)

    Faries, Kaitlyn M. [Washington Univ., St. Louis, MO (United States); Kressel, Lucas L. [Argonne National Lab. (ANL), Argonne, IL (United States); Dylla, Nicholas P. [Argonne National Lab. (ANL), Argonne, IL (United States); Wander, Marc J. [Argonne National Lab. (ANL), Argonne, IL (United States); Hanson, Deborah K. [Argonne National Lab. (ANL), Argonne, IL (United States); Holten, Dewey [Washington Univ., St. Louis, MO (United States); Laible, Philip D. [Argonne National Lab. (ANL), Argonne, IL (United States); Kirmaier, Christine [Washington Univ., St. Louis, MO (United States)

    2016-02-01

    Using high-throughput methods for mutagenesis, protein isolation and charge-separation functionality, we have assayed 40 Rhodobacter capsulatus reaction center (RC) mutants for their P+ QB- yield (P is a dimer of bacteriochlorophylls and Q is a ubiquinone) as produced using the normally inactive B-side cofactors BB and HB (where B is a bacteriochlorophyll and H is a bacteriopheophytin). Two sets of mutants explore all possible residues at M131 (M polypeptide, native residue Val near HB) in tandem with either a fixed His or a fixed Asn at L181 (L polypeptide, native residue Phe near BB). A third set of mutants explores all possible residues at L181 with a fixed Glu at M131 that can form a hydrogen bond to HB. For each set of mutants, the results of a rapid millisecond screening assay that probes the yield of P+ QB- are compared among that set and to the other mutants reported here or previously. For a subset of eight mutants, the rate constants and yields of the individual B-side electron transfer processes are determined via transient absorption measurements spanning 100 fs to 50 μs. The resulting ranking of mutants for their yield of P+ QB- from ultrafast experiments is in good agreement with that obtained from the millisecond screening assay, further validating the efficient, high-throughput screen for B-side transmembrane charge separation. Results from mutants that individually show progress toward optimization of P+ HB- → P+ QB- electron transfer or initial P* → P+ HB- conversion highlight unmet challenges of optimizing both processes simultaneously.

  14. FTIR spectroscopy of the reaction center of Chloroflexus aurantiacus: photoreduction of the bacteriopheophytin electron acceptor.

    Science.gov (United States)

    Zabelin, Alexej A; Shkuropatova, Valentina A; Shuvalov, Vladimir A; Shkuropatov, Anatoly Ya

    2011-09-01

    Mid-infrared spectral changes associated with the photoreduction of the bacteriopheophytin electron acceptor H(A) in reaction centers (RCs) of the filamentous anoxygenic phototrophic bacterium Chloroflexus (Cfl.) aurantiacus are examined by light-induced Fourier transform infrared (FTIR) spectroscopy. The light-induced H(A)(-)/H(A) FTIR (1800-1200cm(-1)) difference spectrum of Cfl. aurantiacus RCs is compared to that of the previously well characterized purple bacterium Rhodobacter (Rba.) sphaeroides RCs. The most notable feature is that the large negative IR band at 1674cm(-1) in Rba. sphaeroides R-26, attributable to the loss of the absorption of the 13(1)-keto carbonyl of H(A) upon the radical anion H(A)(-) formation, exhibits only a very minor upshift to 1675cm(-1) in Cfl. aurantiacus. In contrast, the absorption band of the 13¹-keto C=O of H(A)(-) is strongly upshifted in the spectrum of Cfl. aurantiacus compared to that of Rba. sphaeroides (from 1588 to 1623cm(-1)). The data are discussed in terms of: (i) replacing the glutamic acid at L104 in Rba. sphaeroides R-26 RCs by a weaker hydrogen bond donor, a glutamine, at the equivalent position L143 in Cfl. aurantiacus RCs; (ii) a strengthening of the hydrogen-bonding interaction of the 13¹-keto C=O of H(A) with Glu L104 and Gln L143 upon H(A)(-) formation and (iii) a possible influence of the protein dielectric environment on the 13¹-keto C=O stretching frequency of neutral H(A). A conformational heterogeneity of the 13³-ester C=O group of H(A) is detected for Cfl. aurantiacus RCs similar to what has been previously described for purple bacterial RCs. 2011 Elsevier B.V. All rights reserved.

  15. Comparison of Ground Reaction Forces, Center of Pressure and Body Center of Mass Changes in the Voluntary, Semi-Voluntary and Involuntary Gait Termination in Healthy Young Men

    Directory of Open Access Journals (Sweden)

    behrooz teymourian

    2016-03-01

    Full Text Available Objective: The aim of this study was comparing the ground reaction forces, center of pressure and body center of mass changes in voluntary, semi-voluntary and involuntary gait termination in healthy young men. Methods: In this study, 12 young men performed termination of gait in three different patterns. The variable of peak antero-posterior and vertical forces in two directions at both limbs, the time to reach peak and average forces in every limb in both directions, the center of pressure displacement of medio-lateral and antero-posterior direction for each limb and the net center of pressure and the displacement of the center of mass motion in all three motion plates were recorded using motion analysis system and force plate.The repeated measurements test was used to compare three patterns of gait termination at significance level of p&le0.5. Results: The results showed a significant difference in variables of peak antero-posterior force, the time to reach peak antero-posterior force and mean antero-posterior forces of the leading limb, the peak antero-posterior force of the trialing limbs, the depth force of leading limbs, medio-lateral cop of leading limbs displacement and vertical displacement of the center of mass, among different patterns of gait termination. Conclusion: While walking, the probability of a fall or collision damage, when a sudden or unexpected stop is required, increases. Therefore, more coordination between neuromuscular systems is required.

  16. Antagonism between elevated CO2, nighttime warming, and summer drought reduces the robustness of PSII performance to freezing events

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Boesgaard, Kristine Stove; Ro-Poulsen, Helge

    2013-01-01

    out in the CLIMAITE multifactor experiment, which includes the combined impact of elevated CO2 (free air carbon enrichment; CO2), warming (passive nighttime warming; T) and summer drought (rain-excluding curtains; D) in a temperate heath ecosystem. PSII performance was probed by the effective quantum...... in the wavy hair-grass, Deschampsia flexuosa, and in the evergreen dwarf shrub common heather, Calluna vulgaris, and following freezing events the PItotal and Fv′/Fm′ were reduced even more. Contrary to expected, indirect effects of the previous summer drought reduced PSII performance before freezing events......, particularly in Calluna. In combinations with elevated CO2 interactive effects with drought, D×CO2 and warming, T×D×CO2, were negatively skewed and caused the reduction of PSII performance in both species after occurrence of freezing events. Neither passive nighttime warming nor elevated CO2 as single factors...

  17. Variations in morphology and PSII photosynthetic capabilities during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi) Papenfuss (Gracilariales, Rhodophyta).

    Science.gov (United States)

    Xie, Xiujun; Wang, Guangce; Pan, Guanghua; Gao, Shan; Xu, Pu; Zhu, Jianyi

    2010-04-28

    Red algae are primitive photosynthetic eukaryotes, whose spores are ideal subjects for studies of photosynthesis and development. Although the development of red alga spores has received considerable research attention, few studies have focused on the detailed morphological and photosynthetic changes that occur during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi) Papenfuss (Gracilariales, Rhodophyta). Herein, we documented these changes in this species of red algae. In the tetraspores, we observed two types of division, cruciate and zonate, and both could develop into multicellular bodies (disks). During the first 84 hours, tetraspores divided several times, but the diameter of the disks changed very little; thereafter, the diameter increased significantly. Scanning electron microscopy observations and analysis of histological sections revealed that the natural shape of the disk remains tapered over time, and the erect frond grows from the central protrusion of the disk. Cultivation of tissue from excised disks demonstrated that the central protrusion of the disk is essential for initiation of the erect frond. Photosynthetic (i.e., PSII) activities were measured using chlorophyll fluorescence analysis. The results indicated that freshly released tetraspores retained limited PSII photosynthetic capabilities; when the tetraspores attached to a substrate, those capabilities increased significantly. In the disk, the PSII activity of both marginal and central cells was similar, although some degree of morphological polarity was present; the PSII photosynthetic capabilities in young germling exhibited an apico-basal gradient. Attachment of tetraspores to a substrate significantly enhanced their PSII photosynthetic capabilities, and triggered further development. The central protrusion of the disk is the growth point, may have transfer of nutritive material with the marginal cells. Within the young germling, the hetero-distribution of PSII

  18. Variations in morphology and PSII photosynthetic capabilities during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi Papenfuss (Gracilariales, Rhodophyta

    Directory of Open Access Journals (Sweden)

    Gao Shan

    2010-04-01

    Full Text Available Abstract Background Red algae are primitive photosynthetic eukaryotes, whose spores are ideal subjects for studies of photosynthesis and development. Although the development of red alga spores has received considerable research attention, few studies have focused on the detailed morphological and photosynthetic changes that occur during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi Papenfuss (Gracilariales, Rhodophyta. Herein, we documented these changes in this species of red algae. Results In the tetraspores, we observed two types of division, cruciate and zonate, and both could develop into multicellular bodies (disks. During the first 84 hours, tetraspores divided several times, but the diameter of the disks changed very little; thereafter, the diameter increased significantly. Scanning electron microscopy observations and analysis of histological sections revealed that the natural shape of the disk remains tapered over time, and the erect frond grows from the central protrusion of the disk. Cultivation of tissue from excised disks demonstrated that the central protrusion of the disk is essential for initiation of the erect frond. Photosynthetic (i.e., PSII activities were measured using chlorophyll fluorescence analysis. The results indicated that freshly released tetraspores retained limited PSII photosynthetic capabilities; when the tetraspores attached to a substrate, those capabilities increased significantly. In the disk, the PSII activity of both marginal and central cells was similar, although some degree of morphological polarity was present; the PSII photosynthetic capabilities in young germling exhibited an apico-basal gradient. Conclusions Attachment of tetraspores to a substrate significantly enhanced their PSII photosynthetic capabilities, and triggered further development. The central protrusion of the disk is the growth point, may have transfer of nutritive material with the marginal cells. Within

  19. Femtosecond charge separation in dry films of reaction centers of Rhodobacter sphaeroides and Chloroflexus aurantiacus.

    Science.gov (United States)

    Yakovlev, A G; Khmelnitsky, A Yu; Shuvalov, V A

    2012-05-01

    In this work, the influence of the crystallographic water on electron transfer between primary donor P and acceptor B(A) was studied in reaction centers (RCs) of the purple bacterium Rhodobacter sphaeroides and the green bacterium Chloroflexus aurantiacus. For this purpose, time constants and oscillations of charge separation kinetics are compared between dry film RCs and RCs in glycerol-water buffer at 90 K. A common result of the drying of Rba. sphaeroides and Cfx. aurantiacus RCs is slowing of the charge separation process, decrease in amplitude of the oscillatory components of the kinetics, and the depletion of its spectrum. Thus, the major time constant of stimulated emission decay of P* bacteriochlorophyll dimer at 940 nm is increased from 1.1 psec for water-containing Rba. sphaeroides RCs to 1.9 psec for dry films of Rba. sphaeroides RCs. An analogous increase from 3.5 to 4.2 psec takes place in Cfx. aurantiacus RCs. In dry films of Rba. sphaeroides RCs, the amplitude of coherent oscillations of the absorption band of monomeric bacteriochlorophyll B(A)(-) at 1020 nm is 1.8 times less for the 130-cm(-1) component and 2.3 times less for the 32-cm(-1) component than the analogous amplitudes for water-containing RCs. Measurements in the analogous band of Cfx. aurantiacus RCs show that strong decrease (~5-10 times) of the B(A)(-) absorption band and strong slowing (from ~0.8 to ~3 psec) of B(A)(-) accumulation together with ~3-fold decrease in oscillation amplitude occurs on drying of these RCs. The overtones of the 32-cm(-1) component disappeared from the oscillations of the kinetics at 940 and 1020-1028 nm after drying of the Rba. sphaeroides and Cfx. aurantiacus RCs. The results are in agreement with the results for GM203L mutant of Rba. sphaeroides, in which the HOH55 water molecule is sterically removed, and with the results for dry films of pheophytin-modified RCs of Rba. sphaeroides R-26 and for YM210W and YM210L Rba. sphaeroides mutant RCs. The data are

  20. Wave packet motions coupled to electron transfer in reaction centers of Chloroflexus aurantiacus.

    Science.gov (United States)

    Yakovlev, Andrei G; Shkuropatova, Tatiana A; Vasilieva, Lyudmila G; Shkuropatov, Anatoli Ya; Shuvalov, Vladimir A

    2008-08-01

    Transient absorption difference spectroscopy with approximately 20 femtosecond (fs) resolution was applied to study the time and spectral evolution of low-temperature (90 K) absorbance changes in isolated reaction centers (RCs) of Chloroflexus (C.) aurantiacus. In RCs, the composition of the B-branch chromophores is different with respect to that of purple bacterial RCs by occupying the B(B) binding site of accessory bacteriochlorophyll by bacteriopheophytin molecule (Phi(B)). It was found that the nuclear wave packet motion induced on the potential energy surface of the excited state of the primary electron donor P* by approximately 20 fs excitation leads to a coherent formation of the states P+Phi(B)(-) and P+B(A)(-) (B(A) is a bacteriochlorophyll monomer in the A-branch of cofactors). The processes were studied by measuring coherent oscillations in kinetics of the absorbance changes at 900 nm and 940 nm (P* stimulated emission), at 750 nm and 785 nm (Phi(B) absorption bands), and at 1,020-1028 nm (B(A)(-) absorption band). In RCs, the immediate bleaching of the P band at 880 nm and the appearance of the stimulated wave packet emission at 900 nm were accompanied (with a small delay of 10-20 fs) by electron transfer from P* to the B-branch with bleaching of the Phi(B) absorption band at 785 nm due to Phi(B)(-) formation. These data are consistent with recent measurements for the mutant HM182L Rb. sphaeroides RCs (Yakovlev et al., Biochim Biophys Acta 1757:369-379, 2006). Only at a delay of 120 fs was the electron transfer from P* to the A-branch observed with a development of the B(A)(-) absorption band at 1028 nm. This development was in phase with the appearance of the P* stimulated emission at 940 nm. The data on the A-branch electron transfer in C. aurantiacus RCs are consistent with those observed in native RCs of Rb. sphaeroides. The mechanism of charge separation in RCs with the modified B-branch pigment composition is discussed in terms of coupling between

  1. FTIR spectroscopy of the reaction center of Chloroflexus aurantiacus: photooxidation of the primary electron donor.

    Science.gov (United States)

    Zabelin, A A; Shkuropatova, V A; Shuvalov, V A; Shkuropatov, A Ya

    2012-02-01

    Photochemical oxidation of the primary electron donor P in reaction centers (RCs) of the filamentous anoxygenic phototrophic bacterium Chloroflexus (C.) aurantiacus was examined by light-induced Fourier transform infrared (FTIR) difference spectroscopy at 95 K in the spectral range of 4000-1200 cm(-1). The light-induced P(+)Q(A)(-)/PQ(A) IR spectrum of C. aurantiacus RCs is compared to the well-characterized FTIR difference spectrum of P photooxidation in the purple bacterium Rhodobacter (R.) sphaeroides R-26 RCs. The presence in the P(+)Q(A)(-)/PQ(A) FTIR spectrum of C. aurantiacus RCs of specific low-energy electronic transitions at ~2650 and ~2200 cm(-1), as well as of associated vibrational (phase-phonon) bands at 1567, 1481, and 1294-1285 cm(-1), indicates that the radical cation P(+) in these RCs has dimeric structure, with the positive charge distributed between the two coupled bacteriochlorophyll a molecules. The intensity of the P(+) absorbance band at ~1250 nm (upon chemical oxidation of P at room temperature) in C. aurantiacus RCs is approximately 1.5 times lower than that in R. sphaeroides R-26 RCs. This fact, together with the decreased intensity of the absorbance band at ~2650 cm(-1), is interpreted in terms of the weaker coupling of bacteriochlorophylls in the P(+) dimer in C. aurantiacus compared to R. sphaeroides R-26. In accordance with the previous (pre)resonance Raman data, FTIR measurements in the carbonyl stretching region show that in C. aurantiacus RCs (i) the 13(1)-keto C=O groups of P(A) and P(B-) molecules constituting the P dimer are not involved in hydrogen bonding in either neutral or photooxidized state of P and (ii) the 3(1)-acetyl C=O group of P(B) forms a hydrogen bond (probably with tyrosine M187) absorbing at 1635 cm(-1). Differential signals at 1757(+)/1749(-) and 1741(+)/1733(-) cm(-1) in the FTIR spectrum of C. aurantiacus RCs are attributed to the 13(3)-ester C=O groups of P in different environments.

  2. Structure of PSI, PSII and antennae complexes from yellow-green alga Xanthonema debile.

    Science.gov (United States)

    Gardian, Zdenko; Tichý, Josef; Vácha, František

    2011-05-01

    Photosynthetic carbon fixation by Chromophytes is one of the significant components of a carbon cycle on the Earth. Their photosynthetic apparatus is different in pigment composition from that of green plants and algae. In this work we report structural maps of photosystem I, photosystem II and light harvesting antenna complexes isolated from a soil chromophytic alga Xanthonema debile (class Xanthophyceae). Electron microscopy of negatively stained preparations followed by single particle analysis revealed that the overall structure of Xanthophytes' PSI and PSII complexes is similar to that known from higher plants or algae. Averaged top-view projections of Xanthophytes' light harvesting antenna complexes (XLH) showed two groups of particles. Smaller ones that correspond to a trimeric form of XLH, bigger particles resemble higher oligomeric form of XLH.

  3. Ambient UV-B radiation reduces PSII performance and net photosynthesis in high Arctic Salix arctica

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Mikkelsen, Teis Nørgaard; Ro-Poulsen, H.

    2011-01-01

    Ambient ultraviolet-B (UV-B) radiation potentially impacts the photosynthetic performance of high Arctic plants. We conducted an UV-B exclusion experiment in a dwarf shrub heath in NE Greenland (74°N), with open control, filter control, UV-B filtering and UV-AB filtering, all in combination...... was characterized by simultaneous gas exchange and chlorophyll fluorescence measurements and the PSII performance through the growing season was investigated with fluorescence measurements. Leaf harvest towards the end of the growing season was done to determine the specific leaf area and the content of carbon......, nitrogen and UV-B absorbing compounds. Compared to a 60% reduced UV-B irradiance, the ambient solar UV-B reduced net photosynthesis in Salix arctica leaves fixed in the 45° position which exposed leaves to maximum natural irradiance. Also a reduced Calvin Cycle capacity was found, i.e. the maximum rate...

  4. Activation Strain Analysis of SN2 Reactions at C, N, O, and F Centers

    NARCIS (Netherlands)

    Kubelka, Jan; Bickelhaupt, F. Matthias

    2017-01-01

    Fundamental principles that determine chemical reactivity and reaction mechanisms are the very foundation of chemistry and many related fields of science. Bimolecular nucleophilic substitutions (SN2) are among the most common and therefore most important reaction types. In this report, we examine

  5. Effect of leaf dehydration duration and dehydration degree on PSII photochemical activity of papaya leaves.

    Science.gov (United States)

    Liu, Meijun; Zhang, Zishan; Gao, Huiyuan; Yang, Cheng; Fan, Xingli; Cheng, Dandan

    2014-09-01

    Although the effect of dehydration on photosynthetic apparatus has been widely studied, the respective effect of dehydration duration and dehydration degree was neglected. This study showed that, when leaves dehydrated in air, the PSII activities of leaves decreased with the decline of leaf relative water content (RWC). Unexpectedly, when leaves dehydrated to same RWC, the decreases in Fv/Fm, Ψo and RC/CSm were lower in leaves dehydrating at 43 °C than those at 25 °C. However, to reach the same RWC, leaves dehydrating at 43 °C experienced 1/6 of the dehydration duration for leaves dehydrating at 25 °C. To distinguish the respective effect of dehydration degree and dehydration duration on photosynthetic apparatus, we studied the PSII activities of leaves treated with different concentration of PEG solutions. Increasing dehydration degree aggravated the decline of Fv/Fm, Ψo and RC/CSm in leaves with the same dehydration duration, while prolonging the dehydration duration also exacerbated the decline of Fv/Fm, Ψo and RC/CSm in leaves with identical dehydration degree. With the same dehydration degree and duration, high temperature enhanced the decrease of Fv/Fm, Ψo and RC/CSm in the leaves. When leaves dehydrated in air, the effect of high temperature was underestimated due to reduction of dehydration duration. The results demonstrated that, dehydration degree and duration both play important roles in damage to photosynthetic apparatus. We suggest that, under combined stresses, the effects of dehydration degree and duration on plants should be considered comprehensively, otherwise, partial or incorrect results may be obtained. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  6. Axially assembled photosynthetic reaction center mimics composed of tetrathiafulvalene, aluminum(iii) porphyrin and fullerene entities

    Science.gov (United States)

    Poddutoori, Prashanth K.; Lim, Gary N.; Sandanayaka, Atula S. D.; Karr, Paul A.; Ito, Osamu; D'Souza, Francis; Pilkington, Melanie; van der Est, Art

    2015-07-01

    The distance dependence of sequential electron transfer has been studied in six, vertical, linear supramolecular triads, (TTF-Phn-py --> AlPor-Phm-C60, n = 0, 1 and m = 1, 2, 3), constructed using tetrathiafulvalene (TTF), aluminum(iii) porphyrin (AlPor) and fullerene (C60) entities. The C60 and TTF units are bound to the Al center on opposite faces of the porphyrin; the C60 through a covalent axial bond using a benzoate spacer, and the TTF through a coordination bond via an appended pyridine. Time-resolved optical and EPR spectroscopic methods and computational studies are used to demonstrate that excitation of the porphyrin leads to step-wise, sequential electron transfer (ET) between TTF and C60, and to study the electron transfer rates and exchange coupling between the components of the triads as a function of the bridge lengths. Femtosecond transient absorption studies show that the rates of charge separation, kCS are in the range of 109-1011 s-1, depending on the length of the bridges. The lifetimes of the charge-separated state TTF&z.rad;+-C&z.rad;-60 obtained from transient absorbance experiments and the singlet lifetimes of the radical pairs obtained by time-resolved EPR are in good agreement with each other and range from 60-130 ns in the triads. The time-resolved EPR data also show that population of the triplet sublevels of the charge-separated state in the presence of a magnetic field leads to much longer lifetimes of >1 μs. The data show that a modest stabilization of the charge separation lifetime occurs in the triads. The attenuation factor β = 0.36 Å-1 obtained from the exchange coupling values between TTF&z.rad;+ and C&z.rad;-60 is consistent with values reported in the literature for oligophenylene bridged TTF-C60 conjugates. The singlet charge recombination lifetime shows a much weaker dependence on the distance between the donor and acceptor, suggesting that a simple superexchange model is not sufficient to describe the back reaction

  7. Charge separation kinetics in isolated photosynthetic reaction centers of Chloroflexus aurantiacus (with Q A reduced) at low temperatures

    Science.gov (United States)

    Schweitzer, Gerd; Hucke, Mathias; Griebenow, Kai; Müller, Marc G.; Holzwarth, Alfred R.

    1992-02-01

    The picosecond fluorescence kinetics of closed (quinone acceptor Q A reduced) reaction centers isolated from the phototrophic bacterium Chloroflexus aurantiacus shows time constants of ≈ 20 and ≈ 300 ps (amplitude ratio ≈ 1:1), which are nearly independent of temperature (7 to 80 K). Assuming a three-state kinetic model, we tested various assignments of the kinetics to the electron transfer processes. Only two of these assignments seem to be physically reasonable. One of these includes a fast reversible electron transfer between P* and H M, the pheophytin(s) in the M branch of the reaction center which up to now has been considered virtually inactive in electron transfer. The other possible model involves the formation of a monomeric bacteriochlorophyll anion.

  8. Electrostatic calculations of amino acid titration and electron transfer, Q-AQB-->QAQ-B, in the reaction center.

    OpenAIRE

    Beroza, P; Fredkin, D R; Okamura, M Y; Feher, G

    1995-01-01

    The titration of amino acids and the energetics of electron transfer from the primary electron acceptor (QA) to the secondary electron acceptor (QB) in the photosynthetic reaction center of Rhodobacter sphaeroides are calculated using a continuum electrostatic model. Strong electrostatic interactions between titrating sites give rise to complex titration curves. Glu L212 is calculated to have an anomalously broad titration curve, which explains the seemingly contradictory experimental results...

  9. Genetic probes of structure/function relationships in the Q{sub B} binding site of the photosynthetic reaction center

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, D.K.; Tiede, D.M.; Nance, S.L.; Chang, Chong-Hwan; Schiffer, M.

    1991-06-25

    In photosynthetic reaction centers, a quinone molecule, Q{sub B}, is the terminal acceptor in light-induced electron transfer. The crystal structure of the reaction center implicates the protonatable amiho acid residues L212Glu and L213Asp in the binding of Q{sub B} to the reaction center and in proton transfer to the anionic forms of Q{sub B} generated by electron transfer from Q{sub A}. Here we report the construction of the double mutant L212Ala-L213Ala by site-specific mutagenesis, and the isolation and preliminary biophysical characterization of revertant and suppressor strains that have regained the ability to grow under photosynthetic conditions. Our results show that neither L212Glu nor L213Asp is essential for efficient light-induced electron or proton transfer in Rhodobacter capsulatus and that second-site mutations, located within the QB binding pocket or at a more distant site, can compensate for mutations at L212 and L213. Acquisition of a single negatively charged residue (at position L213, or on the other side of the binding pocket at position L225) or loss of a positively charged residue (at position M231) is sufficient to restore activity to the complex.

  10. The binding of quinone to the photosynthetic reaction centers: kinetics and thermodynamics of reactions occurring at the QB-site in zwitterionic and anionic liposomes.

    Science.gov (United States)

    Mavelli, Fabio; Trotta, Massimo; Ciriaco, Fulvio; Agostiano, Angela; Giotta, Livia; Italiano, Francesca; Milano, Francesco

    2014-07-01

    Liposomes represent a versatile biomimetic environment for studying the interaction between integral membrane proteins and hydrophobic ligands. In this paper, the quinone binding to the QB-site of the photosynthetic reaction centers (RC) from Rhodobacter sphaeroides has been investigated in liposomes prepared with either the zwitterionic phosphatidylcholine (PC) or the negatively charged phosphatidylglycerol (PG) to highlight the role of the different phospholipid polar heads. Quinone binding (K Q) and interquinone electron transfer (L AB) equilibrium constants in the two type of liposomes were obtained by charge recombination reaction of QB-depleted RC in the presence of increasing amounts of ubiquinone-10 over the temperature interval 6-35 °C. The kinetic of the charge recombination reactions has been fitted by numerically solving the ordinary differential equations set associated with a detailed kinetic scheme involving electron transfer reactions coupled with quinone release and uptake. The entire set of traces at each temperature was accurately fitted using the sole quinone release constants (both in a neutral and a charge separated state) as adjustable parameters. The temperature dependence of the quinone exchange rate at the QB-site was, hence, obtained. It was found that the quinone exchange regime was always fast for PC while it switched from slow to fast in PG as the temperature rose above 20 °C. A new method was introduced in this paper for the evaluation of constant K Q using the area underneath the charge recombination traces as the indicator of the amount of quinone bound to the QB-site.

  11. Phytoplankton growth and PSII efficiency sensitivity to a glyphosate-based herbicide (Factor 540®).

    Science.gov (United States)

    Smedbol, Élise; Lucotte, Marc; Labrecque, Michel; Lepage, Laurent; Juneau, Philippe

    2017-11-01

    The use of glyphosate-based herbicides in agriculture has increased steadily since the mid 90's and there is now evidence of glyphosate leaching and contamination of aquatic ecosystems. The aim of this study was to evaluate the effects of a glyphosate-based herbicide (Factor 540 ® ) on growth and photosynthetic capacity of algae and cyanobacteria. Six algal and three cyanobacterial species/strains, of three different taxonomic groups, were exposed to five glyphosate concentrations (10, 50, 100, 500 and 1000μgl -1 ) during 48h. All species have significant growth inhibition at concentrations varying between 50 and 500μgl -1 . The photosynthetic response, after glyphosate exposure, varied among species, but a general pattern has emerged. There was an increase in the amount of photons absorbed (ABS/RC), in dissipated (DI O /RC) and trapped (TR O /RC) energy in the photosystem II reaction centers, along with a decreased of the maximum photosystem II quantum yield (F V /F M ) and electron transport per reaction center (ET O /RC). The EC 50 and LOEC values for growth and photosynthesis were calculated and established that growth was the most affected parameter by glyphosate-based herbicide, while parameter TR O /RC was the least affected. All species showed reduced growth at glyphosate concentrations lower than the Canadian standard for the protection of aquatic life, set at 800μgl -1 or the American aquatic life benchmark for acute toxicity in non vascular plants of 12 100μgl -1 questioning the validity of these thresholds in assessing the risks related to the presence of glyphosate and glyphosate-based herbicides in aquatic systems. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

  12. Principal component analysis in ground reaction forces and center of pressure gait waveforms of people with transfemoral amputation.

    Science.gov (United States)

    Soares, Denise Paschoal; de Castro, Marcelo Peduzzi; Mendes, Emilia Assunção; Machado, Leandro

    2016-12-01

    The alterations in gait pattern of people with transfemoral amputation leave them more susceptible to musculoskeletal injury. Principal component analysis is a method that reduces the amount of gait data and allows analyzing the entire waveform. To use the principal component analysis to compare the ground reaction force and center of pressure displacement waveforms obtained during gait between able-bodied subjects and both limbs of individuals with transfemoral amputation. This is a transversal study with a convenience sample. We used a force plate and pressure plate to record the anterior-posterior, medial-lateral and vertical ground reaction force, and anterior-posterior and medial-lateral center of pressure positions of 12 participants with transfemoral amputation and 20 able-bodied subjects during gait. The principal component analysis was performed to compare the gait waveforms between the participants with transfemoral amputation and the able-bodied individuals. The principal component analysis model explained between 74% and 93% of the data variance. In all ground reaction force and center of pressure waveforms relevant portions were identified; and always at least one principal component presented scores statistically different (p analysis was able to discriminate many portions of the stance phase between both lower limbs of people with transfemoral amputation compared to the able-bodied participants. Principal component analysis reduced the amount of data, allowed analyzing the whole waveform, and identified specific sub-phases of gait that were different between the groups. Therefore, this approach seems to be a powerful tool to be used in gait evaluation and following the rehabilitation status of people with transfemoral amputation. © The International Society for Prosthetics and Orthotics 2015.

  13. Proteomic characterization and three-dimensional electron microscopy study of PSII-LHCII supercomplexes from higher plants.

    Science.gov (United States)

    Pagliano, Cristina; Nield, Jon; Marsano, Francesco; Pape, Tillmann; Barera, Simone; Saracco, Guido; Barber, James

    2014-09-01

    In higher plants a variable number of peripheral LHCII trimers can strongly (S), moderately (M) or loosely (L) associate with the dimeric PSII core (C2) complex via monomeric Lhcb proteins to form PSII-LHCII supercomplexes with different structural organizations. By solubilizing isolated stacked pea thylakoid membranes either with the α or β isomeric forms of the detergent n-dodecyl-D-maltoside, followed by sucrose density ultracentrifugation, we previously showed that PSII-LHCII supercomplexes of types C2S2M2 and C2S2, respectively, can be isolated [S. Barera et al., Phil. Trans. R Soc. B 67 (2012) 3389-3399]. Here we analysed their protein composition by applying extensive bottom-up and top-down mass spectrometry on the two forms of the isolated supercomplexes. In this way, we revealed the presence of the antenna proteins Lhcb3 and Lhcb6 and of the extrinsic polypeptides PsbP, PsbQ and PsbR exclusively in the C2S2M2 supercomplex. Other proteins of the PSII core complex, common to the C2S2M2 and C2S2 supercomplexes, including the low molecular mass subunits, were also detected and characterized. To complement the proteomic study with structural information, we performed negative stain transmission electron microscopy and single particle analysis on the PSII-LHCII supercomplexes isolated from pea thylakoid membranes solubilized with n-dodecyl-α-D-maltoside. We observed the C2S2M2 supercomplex in its intact form as the largest PSII complex in our preparations. Its dataset was further analysed in silico, together with that of the second largest identified sub-population, corresponding to its C2S2 subcomplex. In this way, we calculated 3D electron density maps for the C2S2M2 and C2S2 supercomplexes, approaching respectively 30 and 28Å resolution, extended by molecular modelling towards the atomic level. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy. Copyright © 2013. Published by

  14. Energetics of protein fluctuations: Ligand binding to myoglobin and electron transfer in reaction center

    Science.gov (United States)

    McMahon, Benjamin Hamilton

    We have measured the temperature dependent kinetics of two different protein reactions: Psp+Qsbsp{A}{-}-> PQsb{A} electron transfer (ET) in the photosynthetic reaction (RC), and recombination of carbonmonoxide (CO) to myoglobin (Mb) after flash photolysis. The ET reaction allows determination of the temperature dependence of energy dissipation as RC adapts to charge transfer on the 100 ms, 10sp3 and 10sp4 s time scales at temperatures from 5 to 300 K. The adaptation, or conformational relaxation, of RC is observed in four distinct tiers of conformational substrates, with average apparent Arrhenius activation enthalpies of 17, 50, 78, and 110 kJ/mol and pre-exponential factors of 10sp{13},\\ 10sp{15},\\ 10sp{21}, and 10sp{25}\\ ssp{-1}, respectively. This parameterization provides a prediction of the time course of relaxations at all temperatures. At 300 K, relaxations are expected to occur from 1 ps to 1 ms; at lower temperatures the distribution of relaxation times broaden. We extend this study to samples of different pH, viscosity, and salt composition. We observe kinetics of CO recombination to horse heart myoglobin between 10 ns and 100 s at temperatures from 80 to 320 K. Essentially all recombination is visible in this time window, allowing the effect of relaxations to be observed on the nanosecond time scale at high temperatures, as well as microsecond to second time scales at lower temperatures. Variation of the solvent pH from 5.1 to 8.0 changes the average low temperature enthalpy barrier to recombination from 6 to 13 kJ/mol, shifting the time scale probed by the recombination reaction by an order of magnitude. Addition of 500 mM KCl, KSCN, or (NHsb4)sb2SOsb4 significantly changes the probability of geminate recombination without affecting either the enthalpy barrier to recombination or the energetics of CO entry to and exit from the heme pocket of the protein. We present a model of recombination which emphasizes the role of protein fluctuations in

  15. Mimicking the germinal center reaction in hybridoma cells to isolate temperature-selective anti-PEG antibodies.

    Science.gov (United States)

    Su, Yu-Cheng; Al-Qaisi, Talal S; Tung, Hsin-Yi; Cheng, Tian-Lu; Chuang, Kuo-Hsiang; Chen, Bing-Mae; Roffler, Steve R

    2014-01-01

    Modification of antibody class and binding properties typically requires cloning of antibody genes, antibody library construction, phage or yeast display and recombinant antibody expression. Here, we describe an alternative "cloning-free" approach to generate antibodies with altered antigen-binding and heavy chain isotype by mimicking the germinal center reaction in antibody-secreting hybridoma cells. This was accomplished by lentiviral transduction and controllable expression of activation-induced cytidine deaminase (AID) to generate somatic hypermutation and class switch recombination in antibody genes coupled with high-throughput fluorescence-activated cell sorting (FACS) of hybridoma cells to detect altered antibody binding properties. Starting from a single established hybridoma clone, we isolated mutated antibodies that bind to a low-temperature structure of polyethylene glycol (PEG), a polymer widely used in nanotechnology, biotechnology and pharmaceuticals. FACS of AID-infected hybridoma cells also facilitated rapid identification of class switched variants of monoclonal IgM to monoclonal IgG. Mimicking the germinal center reaction in hybridoma cells may offer a general method to identify and isolate antibodies with altered binding properties and class-switched heavy chains without the need to carry out DNA library construction, antibody engineering and recombinant protein expression.

  16. Density functional theoretical study on the C-F and C-O oxidative addition reaction at an AI center

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Seong [Dept. of Science Education, Kyungnam University, Masan (Korea, Republic of); Cho, Hyun; Hwang, Sungu [Dept. of Nanomechatronics Engineering, Pusan National University, Miryang (Korea, Republic of)

    2017-02-15

    In this study, B3LYP/LACVP** level calculations were chosen because the level of theory was applied successfully to calculations of the thermodynamic and kinetic features of the oxidative addition reactions of alkyl and aryl halides to pincer-type complexes. This study examined the effects of the substituents on the phenyl rings of the Al(I) center. Isopropyl side chains in the phenyl rings attached to N atoms of the pincer ligand were replaced with a methyl (Me) (2) or tertiary butyl ( t Bu) group. The oxidative addition of C[BOND]F and C[BOND]O bonds to an Al (I) center was investigated computationally by DFT calculations. The geometries, thermodynamic, and kinetic features were in good agreement with the experimental data, as in previous studies on the transition metal complexes. The computational results showed that the DFT calculations could provide qualitative insight into the reactivity and thermodynamics of the oxidative addition reactions of C[BOND]F bonds.

  17. Spin densities from subsystem density-functional theory: Assessment and application to a photosynthetic reaction center complex model

    Science.gov (United States)

    Solovyeva, Alisa; Pavanello, Michele; Neugebauer, Johannes

    2012-05-01

    Subsystem density-functional theory (DFT) is a powerful and efficient alternative to Kohn-Sham DFT for large systems composed of several weakly interacting subunits. Here, we provide a systematic investigation of the spin-density distributions obtained in subsystem DFT calculations for radicals in explicit environments. This includes a small radical in a solvent shell, a π-stacked guanine-thymine radical cation, and a benchmark application to a model for the special pair radical cation, which is a dimer of bacteriochlorophyll pigments, from the photosynthetic reaction center of purple bacteria. We investigate the differences in the spin densities resulting from subsystem DFT and Kohn-Sham DFT calculations. In these comparisons, we focus on the problem of overdelocalization of spin densities due to the self-interaction error in DFT. It is demonstrated that subsystem DFT can reduce this problem, while it still allows to describe spin-polarization effects crossing the boundaries of the subsystems. In practical calculations of spin densities for radicals in a given environment, it may thus be a pragmatic alternative to Kohn-Sham DFT calculations. In our calculation on the special pair radical cation, we show that the coordinating histidine residues reduce the spin-density asymmetry between the two halves of this system, while inclusion of a larger binding pocket model increases this asymmetry. The unidirectional energy transfer in photosynthetic reaction centers is related to the asymmetry introduced by the protein environment.

  18. Spin densities from subsystem density-functional theory: Assessment and application to a photosynthetic reaction center complex model

    Energy Technology Data Exchange (ETDEWEB)

    Solovyeva, Alisa [Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Technical University Braunschweig, Institute for Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig (Germany); Pavanello, Michele [Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Neugebauer, Johannes [Technical University Braunschweig, Institute for Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig (Germany)

    2012-05-21

    Subsystem density-functional theory (DFT) is a powerful and efficient alternative to Kohn-Sham DFT for large systems composed of several weakly interacting subunits. Here, we provide a systematic investigation of the spin-density distributions obtained in subsystem DFT calculations for radicals in explicit environments. This includes a small radical in a solvent shell, a {pi}-stacked guanine-thymine radical cation, and a benchmark application to a model for the special pair radical cation, which is a dimer of bacteriochlorophyll pigments, from the photosynthetic reaction center of purple bacteria. We investigate the differences in the spin densities resulting from subsystem DFT and Kohn-Sham DFT calculations. In these comparisons, we focus on the problem of overdelocalization of spin densities due to the self-interaction error in DFT. It is demonstrated that subsystem DFT can reduce this problem, while it still allows to describe spin-polarization effects crossing the boundaries of the subsystems. In practical calculations of spin densities for radicals in a given environment, it may thus be a pragmatic alternative to Kohn-Sham DFT calculations. In our calculation on the special pair radical cation, we show that the coordinating histidine residues reduce the spin-density asymmetry between the two halves of this system, while inclusion of a larger binding pocket model increases this asymmetry. The unidirectional energy transfer in photosynthetic reaction centers is related to the asymmetry introduced by the protein environment.

  19. Blockade of STAT3 in T Cells Inhibits Germinal Center Reactions against Intranasal Allergens

    Science.gov (United States)

    Choi, Garam; Chung, Yeonseok

    2016-01-01

    Understanding the developmental mechanisms of humoral immunity against intranasal antigens is essential for the development of therapeutic approaches against air-borne pathogens as well as allergen-induced pulmonary inflammation. Follicular helper T (Tfh) cells expressing CXCR5 are required for humoral immunity by providing IL-21 and ICOS costimulation to activated B cells. However, the regulation of Tfh cell responses against intranasal antigens remains unclear. Here, we found that the generation of Tfh cells and germinal center B cells in the bronchial lymph node against intranasal proteinase antigens was independent of TGF-β. In contrast, administration of STAT3 inhibitor STA-21 suppressed the generation of Tfh cells and germinal center B cells. Compared with wild-type OT-II T cells, STAT3-deficient OT-II T cells transferred into recipients lacking T cells not only showed significantly reduced frequency Tfh cells, but also induced diminished IgG as well as IgE specific for the intranasal antigens. Co-transfer study of wild-type OT-II and STAT3-deficient OT-II T cells revealed that the latter failed to differentiate into Tfh cells. These findings demonstrate that T cell-intrinsic STAT3 is required for the generation of Tfh cells to intranasal antigens and that targeting STAT3 might be an effective approach to ameliorate antibody-mediated pathology in the lung. PMID:27133258

  20. An ONIOM study of the spin density distribution of the QA site plastosemiquinone in the photosystem II reaction center.

    Science.gov (United States)

    Lin, Tzu-Jen; O'Malley, Patrick J

    2011-04-14

    ONIOM (QM/MM) calculations are used to calculate the spin density distribution for the plastosemiquinone anion radical in the Q(A) binding site of photosystem II. A number of models are examined that explore the effect of iron depletion on the Q(A) site semiquinone spin density distribution and resultant hyperfine couplings. For a model system with a divalent metal ion in the nonheme site the calculated spin density in the Q(A) site model suggests that differential hydrogen-bonding strength to the O1 and O4 oxygen atoms of the radical results in an asymmetric spin density distribution in the semiquinone anion free radical form. The hydrogen bond to the proximal O1 atom is significantly stronger. This is similar to the situation shown to exist previously in the bacterial reaction center of Rba sphaeroides. Various models of depleted nonheme site metal show the profound effect that the presence of a divalent ion in this site has on the spin density distribution of the Q(A) site semiquinone. The variation in calculated spin density distribution of the Q(A) site plastosemiquinone as a function of the occupancy of the nonheme site needs to be taken into account in the interpretation of experimental paramagnetic resonance data. For Type II reaction centers a major role for Fe(2+) in the nonheme site may be the raising of the redox potential of the Q(A)/Q(A)(-) couple to ensure that electron transfer from the (bacterio)pheophytin anion free radical occurs at a sufficient rate to compete with wasteful back-reactions.

  1. Temperature-sensitive PSII: a novel approach for sustained photosynthetic hydrogen production.

    Science.gov (United States)

    Bayro-Kaiser, Vinzenz; Nelson, Nathan

    2016-12-01

    The need for energy and the associated burden are ever growing. It is crucial to develop new technologies for generating clean and efficient energy for society to avoid upcoming energetic and environmental crises. Sunlight is the most abundant source of energy on the planet. Consequently, it has captured our interest. Certain microalgae possess the ability to capture solar energy and transfer it to the energy carrier, H2. H2 is a valuable fuel, because its combustion produces only one by-product: water. However, the establishment of an efficient biophotolytic H2 production system is hindered by three main obstacles: (1) the hydrogen-evolving enzyme, [FeFe]-hydrogenase, is highly sensitive to oxygen; (2) energy conversion efficiencies are not economically viable; and (3) hydrogen-producing organisms are sensitive to stressful conditions in large-scale production systems. This study aimed to circumvent the oxygen sensitivity of this process with a cyclic hydrogen production system. This approach required a mutant that responded to high temperatures by reducing oxygen evolution. To that end, we randomly mutagenized the green microalgae, Chlamydomonas reinhardtii, to generate mutants that exhibited temperature-sensitive photoautotrophic growth. The selected mutants were further characterized by their ability to evolve oxygen and hydrogen at 25 and 37 °C. We identified four candidate mutants for this project. We characterized these mutants with PSII fluorescence, P700 absorbance, and immunoblotting analyses. Finally, we demonstrated that these mutants could function in a prototype hydrogen-producing bioreactor. These mutant microalgae represent a novel approach for sustained hydrogen production.

  2. Stereoselective synthesis of organosulfur compounds incorporating N-aromatic heterocyclic motifs and quaternary carbon centers via a sulfa-Michael triggered tandem reaction.

    Science.gov (United States)

    Qin, Tianyou; Cheng, Lu; Zhang, Sean Xiao-An; Liao, Weiwei

    2015-06-14

    A novel sulfa-Michael addition (SMA)-triggered tandem reaction was developed by combining a SMA reaction with a simultaneous rearomatization process utilizing a less reactive carbonyl group as an intramolecular electrophile partner, which provided a unique synthetic route to access various organosulfur compounds incorporating an N-aromatic heterocyclic motif and quaternary carbon centers.

  3. Ruthenium polypyridine complexes. On the route to biomimetic assemblies as models for the photosynthetic reaction center.

    Science.gov (United States)

    Dürr, H; Bossmann, S

    2001-11-01

    We describe in this Account the preparation of RuL(3) complexes and their significance as biomimetic models for the photosynthetic reation center. Their preparation from simple or more complicated bypyridine ligands L and their photophysical data, especially their stability, are reported. Biomimetic models involving three concepts of the interaction of RuL(3) with acceptors in coordinatively, mechanically, or covalently linked supramolecular assemblies are also presented. The electron transfer (ET) of the noncovalently linked assemblies of RuL(3) complexes carrying polyether chains with one or two anisyl binding sites (4 or 5) with the cyclic bisviologen was studied. Molecular modeling and NMR titration clearly show the formation of supramolecular assemblies. Time-resolved spectroscopy demonstrated that ET and charge separation in the RuL(3) complexes with two binding sites are more efficient. The more constrained RuL(3)-bisviologen-catenane (6) possesses two conformations which exhibit different efficiency in ET, creating a charge-separated state in the microsecond domain. The covalently linked Ru(bpy)(3)(2+)-viologen assemblies having one (7, diad) or two bisviologen arms (8, diad) result in efficient ET. Addition of linear polyethers, cyclic polyethers, or crowns generates new triads and tetrads of the pseudorotaxane type. Molecular modeling and NMR titration clearly indicate the formation of supramolecular assemblies. The analysis of time-resolved studies proves fast ET and especially long-lived charge-separated states in these pseudorotaxanes. These data, compared with the findings for the photosynthetic reation center, show conclusive results. The lifetimes of the charge-separated states increase clearly in the sequence for noncovalently < mechanically < and covalently linked assemblies.

  4. Comparison of reaction centers from Rhodobacter sphaeroides and rhodopseudomonas viridis: Overall archistecture and protein-pigment interactions

    Energy Technology Data Exchange (ETDEWEB)

    Elkabbani, Ossama; Chang, Chonghwan; Tiede, D.; Norris, J.; Schiffer, M. (Argonne National Lab., IL (United States))

    1991-06-04

    Photosynthetic reaction centers (RCs) from the photosynthetic bacteria Rhodobacter sphaeroides and Rhodopseudomonas viridis are protein complexes closely related in both structure and function. The structure of the Rps. viridis RC was used to determine the structure of the RC from Rb. sphaeroides. Small but meaningful differences between the positions of the helices and the cofactors in the two complexes were identified. The distances between helices A{sub L} adn A{sub M}, between B{sub L} and B{sub M}, and between bacteriopheophytins BP{sub L} and BP{sub M} are significantly shorter in Rps. viridis than they are in Rb. sphaeroides RCs. There are a number of differences in the amino acid residues that surround the cofactors; some of these residues form hydrogen bonds with the cofactors. Differences in chemical properties of the two RCs.

  5. [Adverse drug reactions in elderly people : First data from the Leipzig Research Center for Civilization Diseases (LIFE)].

    Science.gov (United States)

    Treudler, R; Walther, F; Ahnert, P; Simon, J-C

    2017-01-01

    Few data exist on adverse drug reactions (ADR) in elderly people. In this group, pharmacotherapy represents a challenge with regard to comorbidities, drug interactions and compliance. The aim of this article is to highlight the characteristics of ADR in elderly patients. In addition to a literature review we present the first data from the Leipzig Research Center for Civilization Diseases (LIFE). Between 2011 and 2015 a total of 9537 subjects aged 40-79 years were randomly included in this population-based, age and sex standardized investigation in the inhabitants of Leipzig, Germany and special emphasis was placed on allergies including questions with regard to ADR. Of the 9537 subjects, data on allergies were available from 8979 subjects. Female gender, comorbidities and the use of multiple drugs were significantly associated with an increased risk of ADR. Women also reported ADR significantly more frequently than men. Of the subjects 22% reported suffering from some form of ADR as a result of medications, while in 2.3% this reaction had occurred within the previous 12 months. Less than 15% of LIFE patients with ADR were in possession of a document giving details of the ADR. The occurrence of ADR significantly contributes to morbidity in elderly patients. For prevention of ADR knowledge of patient-related factors, underlying diseases, drug characteristics and drug interactions are necessary.

  6. Regulation of Autoimmune Germinal Center Reactions in Lupus-Prone BXD2 Mice by Follicular Helper T Cells

    Science.gov (United States)

    Kim, Young Uk; Lim, Hoyong; Jung, Ha Eun; Wetsel, Rick A.; Chung, Yeonseok

    2015-01-01

    BXD2 mice spontaneously develop autoantibodies and subsequent glomerulonephritis, offering a useful animal model to study autoimmune lupus. Although initial studies showed a critical contribution of IL-17 and Th17 cells in mediating autoimmune B cell responses in BXD2 mice, the role of follicular helper T (Tfh) cells remains incompletely understood. We found that both the frequency of Th17 cells and the levels of IL-17 in circulation in BXD2 mice were comparable to those of wild-type. By contrast, the frequency of PD-1+CXCR5+ Tfh cells was significantly increased in BXD2 mice compared with wild-type mice, while the frequency of PD-1+CXCR5+Foxp3+ follicular regulatory T (Tfr) cells was reduced in the former group. The frequency of Tfh cells rather than that of Th17 cells was positively correlated with the frequency of germinal center B cells as well as the levels of autoantibodies to dsDNA. More importantly, CXCR5+ CD4+ T cells isolated from BXD2 mice induced the production of IgG from naïve B cells in an IL-21-dependent manner, while CCR6+ CD4+ T cells failed to do so. These results together demonstrate that Tfh cells rather than Th17 cells contribute to the autoimmune germinal center reactions in BXD2 mice. PMID:25768299

  7. Tumor Suppressor Interferon-Regulatory Factor 1 Counteracts the Germinal Center Reaction Driven by a Cancer-Associated Gammaherpesvirus.

    Science.gov (United States)

    Mboko, Wadzanai P; Olteanu, Horatiu; Ray, Avijit; Xin, Gang; Darrah, Eric J; Kumar, Suresh N; Kulinski, Joseph M; Cui, Weiguo; Dittel, Bonnie N; Gauld, Stephen B; Tarakanova, Vera L

    2015-12-30

    Gammaherpesviruses are ubiquitous pathogens that are associated with the development of B cell lymphomas. Gammaherpesviruses employ multiple mechanisms to transiently stimulate a broad, polyclonal germinal center reaction, an inherently mutagenic stage of B cell differentiation that is thought to be the primary target of malignant transformation in virus-driven lymphomagenesis. We found that this gammaherpesvirus-driven germinal center expansion was exaggerated and lost its transient nature in the absence of interferon-regulatory factor 1 (IRF-1), a transcription factor with antiviral and tumor suppressor functions. Uncontrolled and persistent expansion of germinal center B cells led to pathological changes in the spleens of chronically infected IRF-1-deficient animals. Additionally, we found decreased IRF-1 expression in cases of human posttransplant lymphoproliferative disorder, a malignant condition associated with gammaherpesvirus infection. The results of our study define an unappreciated role for IRF-1 in B cell biology and provide insight into the potential mechanism of gammaherpesvirus-driven lymphomagenesis. Gammaherpesviruses establish lifelong infection in most adults and are associated with B cell lymphomas. While the infection is asymptomatic in many hosts, it is critical to identify individuals who may be at an increased risk of virus-induced cancer. Such identification is currently impossible, as the host risk factors that predispose individuals toward viral lymphomagenesis are poorly understood. The current study identifies interferon-regulatory factor 1 (IRF-1) to be one of such candidate host factors. Specifically, we found that IRF-1 enforces long-term suppression of an inherently mutagenic stage of B cell differentiation that gammaherpesviruses are thought to target for transformation. Correspondingly, in the absence of IRF-1, chronic gammaherpesvirus infection induced pathological changes in the spleens of infected animals. Further, we found

  8. Menaquinone-7 in the reaction center complex of the green sulfur bacterium Chlorobium vibrioforme functions as the electron acceptor A1

    DEFF Research Database (Denmark)

    Kjaer, B; Frigaard, N-U; Yang, F

    1998-01-01

    Photosynthetically active reaction center complexes were prepared from the green sulfur bacterium Chlorobium vibrioforme NCIMB 8327, and the content of quinones was determined by extraction and high-performance liquid chromatography. The analysis showed a stoichiometry of 1.7 molecules of menaqui......Photosynthetically active reaction center complexes were prepared from the green sulfur bacterium Chlorobium vibrioforme NCIMB 8327, and the content of quinones was determined by extraction and high-performance liquid chromatography. The analysis showed a stoichiometry of 1.7 molecules...... of menaquinone-7/reaction center. No other quinones were detected in the isolated reaction centers, whereas membrane preparations also contained chlorobiumquinone. The possible involvement of quinones in electron transport was investigated by electron paramagnetic resonance (EPR) spectroscopy. A highly.......7 mT, consistent with its identification as a quinone. This spectrum is highly similar in terms of g values and line widths to photoaccumulated A1- in photosystem I of Synechococcus sp. PCC 7002. The results indicate that menaquinone-7 in the green sulfur bacterial reaction center is analogous...

  9. Coupling of collective motions of the protein matrix to vibrations of the non-heme iron in bacterial photosynthetic reaction centers.

    Science.gov (United States)

    Orzechowska, A; Lipińska, M; Fiedor, J; Chumakov, A; Zajac, M; Slezak, T; Matlak, K; Strzałka, K; Korecki, J; Fiedor, L; Burda, K

    2010-10-01

    Non-heme iron is a conservative component of type II photosynthetic reaction centers of unknown function. We found that in the reaction center from Rba. sphaeroides it exists in two forms, high and low spin ferrous states, whereas in Rsp. rubrum mostly in a low spin state, in line with our earlier finding of its low spin state in the algal photosystem II reaction center (Burda et al., 2003). The temperature dependence of the non-heme iron displacement studied by Mössbauer spectroscopy shows that the surrounding of the high spin iron is more flexible (Debye temperature ~165K) than that of the low spin atom (~207K). Nuclear inelastic scattering measurements of the collective motions in the Rba. sphaeroides reaction center show that the density of vibrational states, originating from non-heme iron, has well-separated modes between lower (4-17meV) and higher (17-25meV) energies while in the one from Rsp. rubrum its distribution is more uniform with only little contribution of low energy (~6meV) vibrations. It is the first experimental evidence that the fluctuations of the protein matrix in type II reaction center are correlated to the spin state of non-heme iron. We propose a simple mechanism in which the spin state of non-heme iron directly determines the strength of coupling between the two quinone acceptors (Q(A) and Q(B)) and fast collective motions of protein matrix that play a crucial role in activation and regulation of the electron and proton transfer between these two quinones. We suggest that hydrogen bond network on the acceptor side of reaction center is responsible for stabilization of non-heme iron in different spin states. Copyright © 2010 Elsevier B.V. All rights reserved.

  10. Altered gene expression by sedaxane increases PSII efficiency, photosynthesis and growth and improves tolerance to drought in wheat seedlings.

    Science.gov (United States)

    Ajigboye, Olubukola O; Lu, Chungui; Murchie, Erik H; Schlatter, Christian; Swart, Gina; Ray, Rumiana V

    2017-04-01

    Succinate dehydrogenase inhibitor (SDHI) fungicides have been shown to increase PSII efficiency and photosynthesis under drought stress in the absence of disease to enhance the biomass and yield of winter wheat. However, the molecular mechanism of improved photosynthetic efficiency observed in SDHI-treated wheat has not been previously elucidated. Here we used a combination of chlorophyll fluorescence, gas exchange and gene expression analysis, to aid our understanding of the basis of the physiological responses of wheat seedlings under drought conditions to sedaxane, a novel SDHI seed treatment. We show that sedaxane increased the efficiency of PSII photochemistry, reduced non-photochemical quenching and improved the photosynthesis and biomass in wheat correlating with systemic changes in the expression of genes involved in defense, chlorophyll synthesis and cell wall modification. We applied a coexpression network-based approach using differentially expressed genes of leaves, roots and pregerminated seeds from our wheat array datasets to identify the most important hub genes, with top ranked correlation (higher gene association value and z-score) involved in cell wall expansion and strengthening, wax and pigment biosynthesis and defense. The results indicate that sedaxane confers tolerant responses of wheat plants grown under drought conditions by redirecting metabolites from defense/stress responses towards growth and adaptive development. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Detection of herbicide effects on pigment composition and PSII photochemistry in Helianthus annuus by Raman spectroscopy and chlorophyll a fluorescence

    Science.gov (United States)

    Vítek, Petr; Novotná, Kateřina; Hodaňová, Petra; Rapantová, Barbora; Klem, Karel

    2017-01-01

    The effects of herbicides from three mode-of-action groups - inhibitors of protoporphyrinogen oxidase (carfentrazone-ethyl), inhibitors of carotenoid biosynthesis (mesotrione, clomazone, and diflufenican), and inhibitors of acetolactate synthase (amidosulfuron) - were studied in sunflower plants (Helianthus annuus). Raman spectroscopy, chlorophyll fluorescence (ChlF) imaging, and UV screening of ChlF were combined to evaluate changes in pigment composition, photosystem II (PSII) photochemistry, and non-photochemical quenching in plant leaves 6 d after herbicide application. The Raman signals of phenolic compounds, carotenoids, and chlorophyll were evaluated and differences in their intensity ratios were observed. Strongly augmented relative content of phenolic compounds was observed in the case of amidosulfuron-treated plants, with a simultaneous decrease in the chlorophyll/carotenoid intensity ratio. The results were confirmed by in vivo measurement of flavonols using UV screening of ChlF. Herbicides from the group of carotenoid biosynthesis inhibitors significantly decreased both the maximum quantum efficiency of PSII and non-photochemical quenching as determined by ChlF. Resonance Raman imaging (mapping) data with high resolution (150,000-200,000 spectra) are presented, showing the distribution of carotenoids in H. annuus leaves treated by two of the herbicides acting as inhibitors of carotenoid biosynthesis (clomazone or diflufenican). Clear signs were observed that the treatment induced carotenoid depletion within sunflower leaves. The depletion spatial pattern registered differed depending on the type of herbicide applied.

  12. Expanding the substrate scope of Ugi five-center, four-component reaction U-5C-4CR): ketones as coupling partners for secondary amino acids.

    Science.gov (United States)

    Dawidowski, Maciej; Sobczak, Sławomir; Wilczek, Marcin; Kulesza, Artur; Turło, Jadwiga

    2014-02-01

    Various symmetrical and unsymmetrical ketones were successfully coupled with secondary amino acids in the course of Ugi five-center, four-component reaction (U-5C-4CR), thus expanding the molecular diversity possible to be achieved by the reaction. The chemical yields depended on the degree of hindrance of the components employed and were satisfactory in view of possible steric interactions in the U-5C-4CR zwitterionic intermediate. The sense of diastereoinduction for reactions employing unsymmetrical ketones was examined by converting the resulting Ugi adducts into the corresponding rigid 2,6-diketopiperazine derivatives.

  13. The 2-methoxy group of ubiquinone is essential for function of the acceptor quinones in reaction centers from Rba. sphaeroides.

    Science.gov (United States)

    Wraight, Colin A; Vakkasoglu, Ahmet S; Poluektov, Yuri; Mattis, Aidas J; Nihan, Danielle; Lipshutz, Bruce H

    2008-01-01

    The orientation of a methoxy substituent is known to substantially influence the electron affinity and vibrational spectroscopy of benzoquinones, and has been suggested to be important in determining the function of ubiquinone as a redox cofactor in bioenergetics. Ubiquinone functions as both the primary (Q(A)) and secondary (Q(B)) quinone in the reaction centers of many purple photosynthetic bacteria, and is almost unique in its ability to establish the necessary redox free energy gap for 1-electron transfer between them. The role of the methoxy substitution in this requirement was examined using monomethoxy analogues of ubiquinone-4 - 2-methoxy-3,5-dimethyl-6-isoprenyl-1,4-benzoquinone (2-MeO-Q) and 3-methoxy-2,5-dimethyl-6-isoprenyl-1,4-benzoquinone (3-MeO-Q). Only 2-MeO-Q was able to simultaneously act as Q(A) and Q(B) and the necessary redox potential tuning was shown to occur in the Q(B) site. In the absence of active Q(B), the IR spectrum of the monomethoxy quinones was examined in vitro and in the Q(A) site, and a novel distinction between the two methoxy groups was tentatively identified, consistent with the unique role of the 2-methoxy group in distinguishing Q(A) and Q(B) functionality.

  14. Identification of protein W, the elusive sixth subunit of the Rhodopseudomonas palustris reaction center-light harvesting 1 core complex.

    Science.gov (United States)

    Jackson, Philip J; Hitchcock, Andrew; Swainsbury, David J K; Qian, Pu; Martin, Elizabeth C; Farmer, David A; Dickman, Mark J; Canniffe, Daniel P; Neil Hunter, C

    2017-11-07

    The X-ray crystal structure of the Rhodopseudomonas (Rps.) palustris reaction center-light harvesting 1 (RC-LH1) core complex revealed the presence of a sixth protein component, variably referred to in the literature as helix W, subunit W or protein W. The position of this protein prevents closure of the LH1 ring, possibly to allow diffusion of ubiquinone/ubiquinol between the RC and the cytochrome bc1 complex in analogous fashion to the well-studied PufX protein from Rhodobacter sphaeroides. The identity and function of helix W have remained unknown for over 13 years; here we use a combination of biochemistry, mass spectrometry, molecular genetics and electron microscopy to identify this protein as RPA4402 in Rps. palustris CGA009. Protein W shares key conserved sequence features with PufX homologs, and although a deletion mutant was able to grow under photosynthetic conditions with no discernible phenotype, we show that a tagged version of protein W pulls down the RC-LH1 complex. Protein W is not encoded in the photosynthesis gene cluster and our data indicate that only approximately 10% of wild-type Rps. palustris core complexes contain this non-essential subunit; functional and evolutionary consequences of this observation are discussed. The ability to purify uniform RC-LH1 and RC-LH1-protein W preparations will also be beneficial for future structural studies of these bacterial core complexes. Copyright © 2017. Published by Elsevier B.V.

  15. Electron transfer in bacterial reaction centers with an energetically raised primary acceptor: ultrafast spectroscopy and ENDOR/TRIPLE studies

    Science.gov (United States)

    Wachtveitl, J.; Huber, H.; Feick, R.; Rautter, J.; Müh, F.; Lubitz, W.

    1998-08-01

    Femtosecond time resolved absorbance changes in the near infrared spectral region were recorded in photosynthetic reaction centers (RCs) of Rhodobacter ( Rb.) sphaeroides and Chloroflexus aurantiacus. For Rb. sphaeroides, wild type and site directed mutant RCs, where the tyrosine at the M210 position was replaced by phenylalanine and leucine, were investigated. In the mutant RCs the decay of the stimulated emission signal was drastically slower and displayed strong multiexponentiality. In the spectral range between 1000 and 1100 nm, the existence of a fast kinetic component with a time constant of 1 ps could be demonstrated. Based on the spectral and dichroic characteristics of the data, we suggest a weakly populated P +B A- state as first electron transfer intermediate in these mutants. The results indicate that primary electron transfer follows a stepwise mechanism, even in the case of an energetically increased primary acceptor. Investigations of the electronic structure of the photooxidized primary donor using ENDOR/TRIPLE spectroscopy demonstrated that changes at the position M210 mainly affect B A and not P.

  16. Manipulating the Energetics and Rates of Electron Transfer in Rhodobacter capsulatus Reaction Centers with Asymmetric Pigment Content.

    Science.gov (United States)

    Faries, Kaitlyn M; Dylla, Nicholas P; Hanson, Deborah K; Holten, Dewey; Laible, Philip D; Kirmaier, Christine

    2017-07-27

    Seemingly redundant parallel pathways for electron transfer (ET), composed of identical sets of cofactors, are a cornerstone feature of photosynthetic reaction centers (RCs) involved in light-energy conversion. In native bacterial RCs, both A and B branches house one bacteriochlorophyll (BChl) and one bacteriopheophytin (BPh), but the A branch is used exclusively. Described herein are the results obtained for two Rhodobacter capsulatus RCs with an unnaturally high degree of cofactor asymmetry, two BPh on the RC's B side and two BChl on the A side. These pigment changes derive, respectively, from the His(M180)Leu mutation [a BPh (Φ B ) replaces the B-side BChl (B B )], and the Leu(M212)His mutation [a BChl (β A ) replaces the A-side BPh (H A )]. Additionally, Tyr(M208)Phe was employed to disfavor ET to the A branch; in one mutant, Val(M131)Glu creates a hydrogen bond to H B to enhance ET to H B . In both Φ B mutants, the decay kinetics of the excited primary ET donor (P*) resolve three populations with lifetimes of ∼9 ps (50-60%), ∼40 ps (10-20%), and ∼200 ps (20-30%), with P + Φ B - formed predominantly from the 9 ps fraction. The 50-60% yield of P + Φ B - is the highest yet observed for a Φ B -containing RC. The results provide insight into factors needed for efficient multistep ET.

  17. A routine method to determine the chlorophyll a, pheophytin a and B-carotene contents of isolated photosystem II reaction center complexes.

    NARCIS (Netherlands)

    Eijckelhoff, C.; Dekker, J.P.

    1997-01-01

    The most simple way in which the stoichiometry of chlorophyll a, pheophytin a and ̄-carotene in isolated Photosystem II reaction center complexes can be determined is by analysis of the spectrum of the extracted pigments in 80% acetone. We present two different calculation methods using the

  18. Mixing of exciton and charge-transfer states in Photosystem II reaction centers: Modeling of stark spectra with modified redfield theory

    NARCIS (Netherlands)

    Novoderezhkin, V.I.; Dekker, J.P.; van Grondelle, R.

    2007-01-01

    We propose an exciton model for the Photosystem II reaction center (RC) based on a quantitative simultaneous fit of the absorption, linear dichroism, circular dichroism, steady-state fluorescence, triplet-minus-singlet, and Stark spectra together with the spectra of pheophytin-modified RCs, and

  19. Cyclic electron flow may provide some protection against PSII photoinhibition in rice (Oryza sativa L.) leaves under heat stress.

    Science.gov (United States)

    Essemine, Jemaa; Xiao, Yi; Qu, Mingnan; Mi, Hualing; Zhu, Xin-Guang

    2017-04-01

    Previously we have shown that a quick down-regulation in PSI activity compares to that of PSII following short-term heat stress for two rice groups including C4023 and Q4149, studied herein. These accessions were identified to have different natural capacities in driving cyclic electron flow (CEF) around PSI; i.e., low CEF (lcef) and high CEF (hcef) for C4023 and Q4149, respectively. The aim of this study was to investigate whether these two lines have different mechanisms of protecting photosystem II from photodamage under heat stress. We observed a stepwise alteration in the shape of Chl a fluorescence induction (OJIP) with increasing temperature treatment. The effect of 44°C treatment on the damping in Chl a fluorescence was more pronounced in C4023 than in Q4149. Likewise, we noted a disruption in the I-step, a decline in the Fv due to a strong damping in the Fm, and a slight increase in the F0. Normalized data demonstrated that the I-step seems more susceptible to 44°C in C4023 than in Q4149. We also measured the redox states of plastocyanin (PC) and P700 by monitoring the transmission changes at 820nm (I820), and observed a disturbance in the oxidation/reduction kinetics of PC and P700. The decline in the amplitude of their oxidation was shown to be about 29% and 13% for C4023 and Q4149, respectively. The electropotential component (Δφ) of ms-DLE appeared more sensitive to temperature stress than the chemical component (ΔpH), and the impact of heat was more evident and drastic in C4023 than in Q4149. Under heat stress, we noticed a concomitant decline in the primary photochemistry of PSII as well as in both the membrane energization process and the lumen protonation for both accessions, and it is evident that heat affects these parameters more in C4023 than in Q4149. All these data suggest that higher CET can confer higher photoprotection to PSII in rice lines, which can be a desirable trait during rice breeding, especially in the context of a "warming

  20. Purple-bacterial photosynthetic reaction centers and quantum-dot hybrid-assemblies in lecithin liposomes and thin films.

    Science.gov (United States)

    Lukashev, Eugeny P; Knox, Petr P; Gorokhov, Vladimir V; Grishanova, Nadezda P; Seifullina, Nuranija Kh; Krikunova, Maria; Lokstein, Heiko; Paschenko, Vladimir Z

    2016-11-01

    Quantum dots (QDs) absorb ultraviolet and long-wavelength visible light energy much more efficiently than natural bacterial light-harvesting proteins and can transfer the excitation energy to photosynthetic reaction centers (RCs). Inclusion of RCs combined with QDs as antennae into liposomes opens new opportunities for using such hybrid systems as a basis for artificial energy-transforming devices that potentially can operate with greater efficiency and stability than devices based only on biological components or inorganic components alone. RCs from Rhodobacter sphaeroides and QDs (CdSe/ZnS with hydrophilic covering) were embedded in lecithin liposomes by extrusion of a solution of multilayer lipid vesicles through a polycarbonate membrane or by dialysis of lipids and proteins dispersed with excess detergent. The efficiency of RC and QD interaction within the liposomes was estimated using fluorescence excitation spectra of the photoactive bacteriochlorophyll of the RCs and by measuring the fluorescence decay kinetics of the QDs. The functional activity of the RCs in hybrid complexes was fully maintained, and their stability was even increased. The efficiency of energy transfer between QDs and RCs and conditions of long-term stability of function of such hybrid complexes in film preparations were investigated as well. It was found that dry films containing RCs and QDs, maintained at atmospheric humidity, are capable of maintaining their functional activity for at least some months as judged by measurements of their spectral characteristics, efficiency of energy transfer from QDs to RCs and RC electron transport activity. Addition of trehalose to the films increases the stability further, especially for films maintained at low humidity. These stable hybrid film structures are promising for further studies towards developing new phototransformation devices for biotechnological applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Affinity and activity of non-native quinones at the QB site of bacterial photosynthetic reaction centers

    Science.gov (United States)

    Zhang, Xinyu; Gunner, M. R.

    2014-01-01

    Purple, photosynthetic reaction centers (RCs) from Rb. sphaeroides bacteria use UQ10 as primary (QA) and secondary (QB) electron acceptors. Many quinones reconstitute QA function, while few will act as QB. Nine quinones were tested for their ability to bind and reconstitute QA and QB function. Only ubiquinone (UQ) reconstitutes both QA and QB function in the same protein. The affinities of the non-native quinones for the QB site were determined by a competitive inhibition assay. The affinities of benzoquinones (BQ), napthoquinone (NQ) and 2-methyl-NQ for the QB site are 7±3 times weaker than for the QA site. However, di-ortho substituted NQs and anthraquinone bind tightly to the QA site (Kd ≤200 nM) and ≥1000 times more weakly to the QB site, perhaps setting a limit on the size of the site. With a low potential electron donor (2-methyl, 3-dimethylamino-1,4-Napthoquinone (Me-diMeAm-NQ)) at QA, QB reduction is 260 meV more favorable than with UQ as QA. Electron transfer from Me-diMeAm-NQ at the QA site to NQ at the QB site can be detected. In the QB site the NQ semiquinone is estimated to be ≈ 60–100 meV higher in energy than the UQ semiquinone, while in the QA site the semiquinone energy level is similar or lower with NQ than with UQ. Thus, the NQ semiquinone is more stable in the QA than QB site. In contrast, the native UQ semiquinone is ≈ 60 meV lower in energy in the QB than the QA site, stabilizing forward electron transfer from QA to QB. PMID:23715773

  2. Air oxidation of hydrazine. 1. Reaction kinetics on natural kaolinites, halloysites, and model substituent layers with varying iron and titanium oxide and O- center contents

    Science.gov (United States)

    Coyne, L.; Mariner, R.; Rice, A.

    1991-01-01

    Air oxidation of hydrazine was studied by using a group of kaolinites, halloysites, and substituent oxides as models for the tetrahedral and octahedral sheets. The rate was found to be linear with oxygen. The stoichiometry showed that oxygen was the primary oxidant and that dinitrogen was the only important nitrogen-containing product. The rates on kaolinites were strongly inhibited by water. Those on three-dimensional silica and gibbsite appeared not to be. That on a supposedly layered silica formed from a natural kaolinite by acid leaching showed transitional behavior--slowed relative to that expected from a second-order reaction relative to that on the gibbsite and silica but faster than those on the kaolinites. The most striking result of the reaction was the marked increase in the rate of reaction of a constant amount of hydrazine as the amount of clay was increased. The increase was apparent (in spite of the water inhibition at high conversions) over a 2 order of magnitude variation of the clay weight. The weight dependence was taken to indicate that the role of the clay is very important, that the number of reactive centers is very small, or that they may be deactivated over the course of the reaction. In contrast to the strong dependence on overall amount of clay, the variation of amounts of putative oxidizing centers, such as structural Fe(III), admixed TiO2 or Fe2O3, or O- centers, did not result in alteration of the rate commensurate with the degree of variation of the entity in question. Surface iron does play some role, however, as samples that were pretreated with a reducing agent were less active as catalysts than the parent material. These results were taken to indicate either that the various centers interact to such a degree that they cannot be considered independently or that the reaction might proceed by way of surface complexation, rather than single electron transfers.

  3. Light-harvesting complex 1 stabilizes P+QB- charge separation in reaction centers of Rhodobacter sphaeroides.

    Science.gov (United States)

    Francia, Francesco; Dezi, Manuela; Rebecchi, Alberto; Mallardi, Antonia; Palazzo, Gerardo; Melandri, Bruno Andrea; Venturoli, Giovanni

    2004-11-09

    The kinetics of charge recombination following photoexcitation by a laser pulse have been analyzed in the reaction center-light harvesting complex 1 (RC-LH1) purified from the photosynthetic bacterium Rhodobacter sphaeroides. In RC-LH1 core complexes isolated from photosynthetically grown cells P(+)Q(B)(-) recombines with an average rate constant, k approximately 0.3 s(-1), more than three times smaller than that measured in RC deprived of the LH1 (k approximately 1 s(-1)). A comparable, slowed recombination kinetics is observed in RC-LH1 complexes purified from a pufX-deleted strain. Slowing of the charge recombination kinetics is even more pronounced in RC-LH1 complexes isolated from wild-type semiaerobically grown cells (k approximately 0.2 s(-1)). Since the kinetics of P(+)Q(A)(-) recombination is unaffected by the presence of the antenna, the P(+)Q(B)(-) state appears to be energetically stabilized in core complexes. Determinations of the ubiquinone-10 (UQ(10)) complement associated with the purified RC-LH1 complexes always yield UQ(10)/RC ratios larger than 10. These quinone molecules are functionally coupled to the RC-LH1 complex, as judged from the extent of exogenous cytochrome c(2) rapidly oxidized under continuous light excitation. Analysis of P(+)Q(B)(-) recombination, based on a kinetic model which considers fast quinone equilibrium at the Q(B) binding site, indicates that the slowing down of charge recombination kinetics observed in RC-LH1 complexes cannot be explained solely by a quinone concentration effect and suggests that stabilization of the light-induced charge separation is predominantly due to interaction of the Q(B) site with the LH1 complex. The high UQ(10) complements detected in RC-LH1 core complexes, but not in purified light-harvesting complex 2 and in RC, are proposed to reflect an in vivo heterogeneity in the distribution of the quinone pool within the chromatophore bilayer.

  4. Structural and preliminary molecular dynamics studies of the Rhodobacter sphaeroides reaction center and its mutant form L(M196)H + H(M202)L

    Science.gov (United States)

    Klyashtorny, V. G.; Fufina, T. Yu.; Vasilieva, L. G.; Shuvalov, V. A.; Gabdulkhakov, A. G.

    2014-07-01

    Pigment-protein interactions are responsible for the high efficiency of the light-energy transfer and conversion in photosynthesis. The reaction center (RC) from the purple bacterium Rhodobacter sphaeroides is the most convenient model for studying the mechanisms of primary processes of photosynthesis. Site-directed mutagenesis can be used to study the effect of the protein environment of electron-transfer cofactors on the optical properties, stability, pigment composition, and functional activity of RC. The preliminary analysis of RC was performed by computer simulation of the amino acid substitutions L(M196)H + H(M202)L at the pigment-protein interface and by estimating the stability of the threedimensional structure of the mutant RC by the molecular dynamics method. The doubly mutated reaction center was overexpressed, purified, and crystallized. The three-dimensional structure of this mutant was determined by X-ray crystallography and compared with the molecular dynamics model.

  5. Development of atom-economical catalytic asymmetric reactions under proton transfer conditions: construction of tetrasubstituted stereogenic centers and their application to therapeutics.

    Science.gov (United States)

    Kumagai, Naoya

    2011-01-01

    The development of atom-economical catalytic asymmetric reactions based on two distinct sets of catalyst, a rare earth metal/amide-based ligand catalyst and a soft Lewis acid/hard Brønsted base catalyst, is reviewed. These catalytic systems exhibit high catalytic activity and stereoselectivity by harnessing a cooperative catalysis through hydrogen bond/metal coordination and soft-soft interactions/hard-hard interactions, respectively. The effectiveness of these cooperative catalysts is clearly delineated by the high stereoselectivity in reactions with highly coordinative substrates, and the specific activation of otherwise low-reactive pronucleophiles under proton transfer conditions. The rare earth metal/amide-based ligand catalyst was successfully applied to catalytic asymmetric aminations, nitroaldol (Henry) reactions, Mannich-type reactions, and conjugate addition reactions, generating stereogenic tetrasubstituted centers. Catalytic asymmetric amination and anti-selective catalytic asymmetric nitroaldol reactions were successfully applied to the efficient enantioselective synthesis of therapeutic candidates, such as AS-3201 and the β(3)-adrenoreceptor agonist, showcasing the practical utility of the present protocols. The soft Lewis acid/hard Brønsted base cooperative catalyst was specifically developed for the chemoselective activation of soft Lewis basic allylic cyanides and thioamides, which are otherwise low-reactive pronucleophiles. The cooperative action of the catalyst allowed for efficient catalytic generation of active carbon nucleophiles in situ, which were integrated into subsequent enantioselective additions to carbonyl-type electrophiles.

  6. Comparison of calculated and experimental isotope edited FTIR difference spectra for purple bacterial photosynthetic reaction centers with different quinones incorporated into the QA binding site.

    Directory of Open Access Journals (Sweden)

    Nan eZhao

    2013-08-01

    Full Text Available Previously we have shown that ONIOM type (QM/MM calculations can be used to simulate isotope edited FTIR difference spectra for neutral ubiquinone in the QA binding site in Rhodobacter sphaeroides photosynthetic reaction centers. Here we considerably extend upon this previous work by calculating isotope edited FTIR difference spectra for reaction centers with a variety of unlabeled and 18O labeled foreign quinones incorporated into the QA binding site. Isotope edited spectra were calculated for reaction centers with 2,3-dimethoxy-5,6-dimethyl-1,4-benzoquinone (MQ0, 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ, and 2,3-dimethyl-l,4-naphthoquinone (DMNQ incorporated, and compared to corresponding experimental spectra. The calculated and experimental spectra agree well, further demonstrating the utility and applicability of our ONIOM approach for calculating the vibrational properties of pigments in protein binding sites.The normal modes that contribute to the bands in the calculated spectra, their composition, frequency and intensity, and how these quantities are modified upon 18O labeling, are presented. This computed information leads to a new and more detailed understanding/interpretation of the experimental FTIR difference spectra. Hydrogen bonding to the carbonyl groups of the incorporated quinones is shown to be relatively weak. It is also shown that there is some asymmetry in hydrogen bonding, accounting for 10-13 cm-1 separation in the frequencies of the carbonyl vibrational modes of the incorporated quinones. The extent of asymmetry H-bonding could only be established by considering the spectra for various types of quinones incorporated into the QA binding site. The quinones listed above are tail-less. Spectra were also calculated for reaction centers with corresponding tail containing quinones incorporated, and it is found that replacement of the quinone methyl group by a phytyl or prenyl chain does not alter ONIOM calculated s

  7. Monitoring of NSAIDs adverse effects based on spontaneous reports from Wrocław regional adverse drug reactions monitoring center.

    Science.gov (United States)

    Jaźwińska-Tarnawska, Ewa; Wiela-Hojeńska, Anna; Wolańczyk-Medrala, Anna; Patkowski, Janusz; Nittner-Marszalska, Marita; Głowacka, Krystyna

    2012-01-01

    The mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs) in majority of cases is responsible for adverse reactions of these therapeutic agents. Obtaining post-registration information on adverse drug reactions (ADRs) by means of the Yellow Card System is a significant element in the process of enhancing the safety of pharmacotherapy. The aim of the study was to analyze ADRs of NSAIDs (anti-inflammatory and analgesic drugs) reported to the Regional Centre for the Monitoring of Adverse Drug Reactions (RCMADR) in Wrocław in the years 2007-2009. The study material included 232 spontaneous reports, which were sent by physicians and pharmacists to the RCMADR in Wrocław, out of which 80 concerned mentioned drugs. Analysis of the obtained data revealed a relationship between the incidence and kind of ADRs and the age, gender of the patients, centre from which the data were supplied, geographical region of administered medication. A significant role of post-registration monitoring of adverse drug reactions during therapy with antiinflammatory and analgesic drugs was confirmed in view of geographically conditioned differences affecting the profile of instituted therapy and the source of information. With an increasing global use of these medications, only thorough monitoring of every adverse reaction, encouraging spontaneous reports, as well as analysis at a global level may increase the knowledge on adverse drug reactions and enable correction of the safety profile of every drug from this group.

  8. Merging Structural Information from X-ray Crystallography, Quantum Chemistry, and EXAFS Spectra: The Oxygen-Evolving Complex in PSII.

    Science.gov (United States)

    Chernev, Petko; Zaharieva, Ivelina; Rossini, Emanuele; Galstyan, Artur; Dau, Holger; Knapp, Ernst-Walter

    2016-10-12

    Structural data of the oxygen-evolving complex (OEC) in photosystem II (PSII) determined by X-ray crystallography, quantum chemistry (QC), and extended X-ray absorption fine structure (EXAFS) analyses are presently inconsistent. Therefore, a detailed study of what information can be gained about the OEC through a comparison of QC and crystallographic structure information combined with the information from range-extended EXAFS spectra was undertaken. An analysis for determining the precision of the atomic coordinates of the OEC by QC is carried out. OEC model structures based on crystallographic data that are obtained by QC from different research groups are compared with one another and with structures obtained by high-resolution crystallography. The theory of EXAFS spectra is summarized, and the application of EXAFS spectra to the experimental determination of the structure of the OEC is detailed. We discriminate three types of parameters entering the formula for the EXAFS spectrum: (1) model-independent, predefined, and fixed; (2) model-dependent that can be computed or adjusted; and (3) model-dependent that must be adjusted. The information content of EXAFS spectra is estimated and is related to the precision of atomic coordinates and resolution power to discriminate different atom-pair distances of the OEC. It is demonstrated how a precise adjustment of atomic coordinates can yield a nearly perfect representation of the experimental OEC EXAFS spectrum, but at the expense of overfitting and losing the knowledge of the initial OEC model structure. Introducing a novel type of penalty function, it is shown that moderate adjustment of atomic coordinates to the EXAFS spectrum limited by constraints avoids overfitting and can be used to validate different OEC model structures. This technique is used to identify the OEC model structures whose computed OEC EXAFS spectra agree best with the measured spectrum. In this way, the most likely S-state and protonation pattern

  9. Functional aspects of the photosynthetic light reactions in heat stressed Arabidopsis deficient in digalactosyl-diacylglycerol.

    Science.gov (United States)

    Essemine, Jemâa; Govindachary, Sridharan; Ammar, Saïda; Bouzid, Sadok; Carpentier, Robert

    2011-09-01

    Plants are often submitted, in their natural environment, to various abiotic stresses such as heat stress. However, elevated temperature has a detrimental impact on overall plant growth and development. We have examined the physiological response of the dgd1-2 and dgd1-3 Arabidopsis mutants lacking 30-40% of digalactosyl-diacylglycerol (DGDG) exposed to heat constraint. These mutants, which grow similarly to wild type under normal conditions, were previously reported to be defective in basal thermotolerance as measured by cotyledon development. However their functional properties were not described. Chlorophyll fluorescence measurements and absorbance changes at 820nm were used to monitor photosystem II (PSII) and PSI activity, respectively. It was observed that both mutants have similar photosystem activities with some differences. The mutants were less able to use near saturation light energy and elicited higher rates of cyclic PSI electron flow compare to wild type. Arabidopsis leaves exposed to short-term (5min) mild (40°C) or strong (44°C) heat treatment have shown a decline in the operating effective quantum yield of PSII and in the proportion of active PSI reaction centers. However, cyclic PSI electron flow was enhanced. The establishment of the energy-dependent non-photochemical quenching of chlorophyll fluorescence was accelerated but its decline under illumination was inhibited. Furthermore, heat stress affected the process implicated in the redistribution of light excitation energy between the photosystems known as the light state transitions. All the effects of heat stress mentioned above were more intense in the mutant leaves with dgd1-3 being even more susceptible. The decreased DGDG content of the thylakoid membranes together with other lipid changes are proposed to influence the thermo-sensitivity of the light reactions of photosynthesis towards heat stress. Copyright © 2011 Elsevier GmbH. All rights reserved.

  10. Probing the Energy Transfer Dynamics of Photosynthetic Reaction Center Complexes Through Hole-Burning and Single-Complex Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Kerry Joseph [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    Photosynthesis is the process by which light energy is used to drive reactions that generate sugars to supply energy for cellular processes. It is one of the most important fundamental biological reactions and occurs in both prokaryotic (e.g. bacteria) and eukaryotic (e.g. plants and algae) organisms. Photosynthesis is also remarkably intricate, requiring the coordination of many different steps and reactions in order to successfully transform absorbed solar energy into a biochemical usable form of energy. However, the net reaction for all photosynthetic organisms can be reduced to the following, deceptively general, equation developed by Van Niel[1] H2 - D + Aimplieshv A - H2 + D where H2-D is the electron donor, e.g. H2O, H2S. A is the electron acceptor, e.g. CO2, and A-H2 is the synthesized sugar. Amazingly, this simple net equation is responsible for creating the oxidizing atmosphere of Earth and the recycling of CO2, both of which are necessary for the sustainment of the global ecosystem.

  11. Microscopic Study and Differentiation of Entamoeba Histolytica from Entamoeba Dispar by Polymerase Chain Reaction in Medical Centers of Zahedan

    Directory of Open Access Journals (Sweden)

    Salimi Khorashad Ali Reza

    2009-09-01

    Full Text Available Background: Entamoeba histolytica, resident in large bowel, is the causative agent of an estimated 40 to 50 million cases of amebic colitis and liver abscess, and is responsible for up to 100000 deaths world wide each year. Based on the results of various studies, it is accepted that Entamoeba histolytica and Entamoeba dispar which are morphologicaly identical, differ in biology and pathogenicity. This study was performed to estimate the prevalence of contamination of stool samples with these species in medical centers of Zahedan city. Materials and Methods: In this descriptive study we used microscopy, Formalin-ether concentration, culture and PCR techniques to differentiate of Entamoeba histolytica from Entamoeba dispar in 1562 stool samples in medical center of Zahedan during July 2004 to January 2006. Data were analyzed with Chi-square, Mann-Whitney and Fisher tests. P value<0.05 considered to be statistically significant.Results: Eight cases (0.51% of all samples were positive for Entamoeba histolytica/ Entamoeba dispar by direct microscopy and Formalin-ether concentration Methods. All isolates were cultured in HSr+s and Robinson Media. Seven samples were examined by 2 set of oligonucleotid primers HSP1,2 and DSP1,2 by PCR technique and six isolates were identified to be Entamoeba dispar.Conclusion: This study by using PCR technique showed that most of the patients referred to medical centers of Zahedan were infected with Entamoeba dispar.

  12. Relationships between PSII-independent hydrogen bioproduction and starch metabolism as evidenced from isolation of starch catabolism mutants in the green alga Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Chochois, Vincent; Constans, Laure; Beyly, Audrey; Soliveres, Melanie; Peltier, Gilles; Cournac, Laurent [CEA, DSV, IBEB, Laboratoire de Bioenergetique et Biotechnologie des Bacteries and Microalgues, Saint Paul Lez Durance, F-13108 (France); CNRS, UMR Biologie Vegetale and Microbiologie Environnementales, Saint Paul lez Durance, F-13108 (France); Aix-Marseille Universite, Saint Paul lez Durance, F-13108 (France); Dauvillee, David; Ball, Steven [Univ Lille Nord de France, F-59000 Lille (France); USTL, UGSF, F-59650 Villeneuve d' Ascq (France); CNRS, UMR 8576, F-59650 Villeneuve d' Ascq (France)

    2010-10-15

    Sulfur deprivation, which is considered as an efficient way to trigger long-term hydrogen photoproduction in unicellular green algae has two major effects: a decrease in PSII which allows anaerobiosis to be reached and carbohydrate (starch) storage. Starch metabolism has been proposed as one of the major factors of hydrogen production, particularly during the PSII-independent (or indirect) pathway. While starch biosynthesis has been characterized in the green alga Chlamydomonas reinhardtii, little remains known concerning starch degradation. In order to gain a better understanding of starch catabolism pathways and identify those steps likely to limit the starch-dependent hydrogen production, we have designed a genetic screening procedure aimed at isolating mutants of the green alga C. reinhardtii affected in starch mobilization. Using two different screening protocols, the first one based on aerobic starch degradation in the dark and the second one on anaerobic starch degradation in the light, eighteen mutants were isolated among a library of 15,000 insertion mutants, eight (std1-8) with the first screen and ten (sda1-10) with the second. Most of the mutant strains isolated in this study showed a reduction or a delay in the PSII-independent hydrogen production. Further characterization of these mutants should allow the identification of molecular determinants of starch-dependent hydrogen production and supply targets for future biotechnological improvements. (author)

  13. The effect of aging on the backward stepping reaction as estimated from the velocity of center of foot pressure and muscular strength.

    Science.gov (United States)

    Takeuchi, Yahiko; Tanaka, Yasuyuki; Shimomura, Yoshihiro; Iwanaga, Koichi; Katsuura, Tetsuo

    2007-03-01

    By estimating the deflection velocity from the center of foot pressure (COP), this study aims to prove that the characteristics of the backward stepping reaction in the elderly are related to the strength of the antigravity muscles. The participants in this study were 10 elderly (average age 75.6+/-7.6 years) and 13 young (average age 22.0+/-2.6 years) subjects. Using force plate analysis, we measured the shift in the deflection velocity (V-RMS) and the maximum deflection velocity (V-MAX) from the beginning of the COP movement to the onset of the stepping reaction. Furthermore, we measured the strength of the antigravity muscles using a hand-held dynamometer. We correlated the V-RMS, V-MAX, and the rate of change of the deflection velocity (MAX/RMS) with muscular strength. When compared with the young subjects, the elderly showed significantly lower values of V-RMS (pmuscles studied (p<0.001). We established a significant correlation between the V-RMS, MAX/RMS, and muscular strength by carrying out a regression analysis (V-RMS: gluteus maximus (r=0.50, p<0.05) and rectus abdominis (r=0.48, p<0.05); MAX/RMS: adductor magnus (r=-0.66, p<0.001) and flexor digitorum longus (r=-0.62, p<0.01)). Differences were observed in the V-RMS and MAX/RMS during the backward stepping reaction; it was proposed that these differences were related to the age and muscular strength of the subjects. Therefore, further investigations should be undertaken in order to understand the effects of aging on the stepping reaction. In other words, the change-in-support strategy, including the preparatory phase of the stepping reaction, and its relationship with muscular strength should be further investigated.

  14. Adverse cutaneous drug reactions: Clinical pattern and causative agents in a tertiary care center in South India

    Directory of Open Access Journals (Sweden)

    Pudukadan David

    2004-01-01

    Full Text Available Background: Adverse cutaneous drug reactions (ACDRs are caused by a wide variety of agents. Aims: Our objective was to ascertain the clinical spectrum of ACDRs and the causative drugs in this part of India and to find any risk factors. Methods: Ninety patients with adverse cutaneous drug reactions were recruited for this study during 2001-2003. Hematological and biochemical investigations were done in all of them. The VDRL and HIV (ELISA tests were performed where the underlying risk factors were present. Patch testing, intradermal testing and oral provocation tests were done wherever feasible. Results: The mean age of the patients with cutaneous drug eruptions was 37.06 years. Most of them (52.2% were in the age group of 20-39 years. The male to female ratio was 0.87: 1. The most common eruptions observed were fixed drug eruption (31.1% and maculopapular rash (12.2%, and the most common causes were co-trimoxazole (22.2% and dapsone (17.7%. Conclusion: The pattern of ACDRs and the drugs causing them is remarkably different in our population. Knowledge of these drug eruptions, the causative drugs and the prognostic indicators is essential for the clinician.

  15. Study of the Mn-binding sites in photosystem II using antibodies raised against lumenal regions of the D1 and D2 reaction center proteins

    Energy Technology Data Exchange (ETDEWEB)

    Dalmasso, E.A.

    1992-04-01

    The experiments discussed in this thesis focus on identifying the protein segments or specific amino acids which provide ligands to the Mn cluster of photosystem II (PS II). This Mn cluster plays a central role in the oxygen-evolving complex (OEC) of PS II. The Mn cluster is thought to be bound by lumenal regions of the PS II reaction center proteins known as D1 and D2. First, several peptides were synthesized which correspond to specific lumenal segments of the D1 and D2 proteins. Next, polyclonal antibodies were successfully elicited using three of these peptides. The peptides recognized by these antibodies correspond to protein segments of the spinach reaction center proteins: Ile-321 to Ala-344 of D1 (D1-a), Asp-319 to Arg-334 of D1 (D1-b), and Val-300 to Asn-319 of D2 (D2-a). These antibodies were then used in assays which were developed to structurally or functionally probe the potential Mn-binding regions of the D1 and D2 proteins.

  16. [Polarization of photosynthetic membranes and reaction centers of Rhodopseudomonas sphaeroides 1760-1 in an external electrical field].

    Science.gov (United States)

    Borisevich, G P; Noks, P P; Kononenko, A A; Rubin, A B; Vozari, E

    1979-01-01

    Electric fields as high as 10(5) V/cm cause polarization of chromatophores and reaction centre films prepared from photosynthesizing bacteria. Photosynthetic pigments, carotenoids in particular, the absorption spectra of which are changed in response to electric fields, may serve as an intrinsic indicator of the development of a polarized state. Polarization occurs due to changes in orientation and spacial position of different charge groups and particles. The field-induced polarized state can be fixed up by exposure to low temperature (-120 degrees C). While heating the system relaxes to the initial state and this can be seen as a current in an electric circuit. The effects of hydration, chemical modification or heat treatment on current indicate the involvement of macromolecule components in the formation of a polarized state, In light-adapted samples the polarization effect is markedly greater and this can indicate that conformational changes occur during the primary photoact. It is supposed that polarization might be implicated in the stabilization of separated charges and in the storage of energy.

  17. New rubrolide analogues as inhibitors of photosynthesis light reactions.

    Science.gov (United States)

    Varejão, Jodieh O S; Barbosa, Luiz C A; Ramos, Gabriela Álvarez; Varejão, Eduardo V V; King-Díaz, Beatriz; Lotina-Hennsen, Blas

    2015-04-01

    Natural products called rubrolides have been investigated as a model for the development of new herbicides that act on the photosynthesis apparatus. This study comprises a comprehensive analysis of the photosynthesis inhibitory ability of 27 new structurally diverse rubrolide analogues. In general, the results revealed that the compounds exhibited efficient inhibition of the photosynthetic process, but in some cases low water solubility may be a limiting factor. To elucidate their mode of action, the effects of the compounds on PSII and PSI, as well as their partial reaction on chloroplasts and the chlorophyll a fluorescence transients were measured. Our results showed that some of the most active rubrolide analogues act as a Hill reaction inhibitors at the QB level by interacting with the D1 protein at the reducing side of PSII. All of the active analogues follow Tice's rule of 5, which indicates that these compounds present physicochemical properties suitable for herbicides. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Photochemical reactions in dehydrated photosynthetic organisms, leaves, chloroplasts and photosystem II particles: reversible reduction of pheophytin and chlorophyll and oxidation of β-carotene

    Science.gov (United States)

    Shuvalov, Vladimir A.; Heber, Ulrich

    2003-11-01

    Photoreactions of dehydrated leaves, isolated broken chloroplasts and PSII membrane fragments of spinach ( Spinacia oleracea) were studied at different air humidities and compared with photoreactions of dry fronds of a fern, Polypodium vulgare, and a dry lichen, Parmelia sulcata, which in contrast to spinach are insensitive to photoinactivation in the dry state. Even in very dry air, P700 in the reaction center of photosystem I of dry leaves was oxidized, and the primary quinone acceptor Q A in the reaction center of photosystem II was photoreduced by low light. These reactions were only very slowly reversed in the dark and saturated under low light intensity. Light-minus-dark difference absorption spectra of the dry leaves, isolated chloroplasts and PSII membrane fragments measured at higher light intensities revealed absorbance changes of β-carotene at 500 nm (light-dependent bleaching) and 980 nm (light-dependent band formation) and bleaching of chlorophyll at 436 and 680 nm with appearance of bands at 450 and 800 nm. Decrease of chlorophyll fluorescence upon strong illumination indicated photoaccumulation of a quencher. All these changes were kinetically related and readily reversible. They are interpreted to show light-induced oxidation of β-carotene (Car) and reduction of chlorophyll-680 (Chl-680) in the reaction center of photosystem II of the dried leaves, chloroplasts and photosystem II particles. The fluorescence quencher was suggested to be Chl-680 - or Car + in close proximity to P680, the primary electron donor. Appreciable photoaccumulation of reduced pheophytin was only observed in dry leaves after Q A reduction had been lost during heat treatment of hydrated leaves prior to dehydration. The observations are interpreted to show light-dependent cyclic electron flow within the reaction center of photosystem II in which Chl-680 (or Pheo) is reduced by P680 * and Car is oxidized by P680 + with consequent recombination of Car + and Chl-680 - (or Pheo

  19. Photochemical reactions in dehydrated photosynthetic organisms, leaves, chloroplasts and photosystem II particles: reversible reduction of pheophytin and chlorophyll and oxidation of {beta}-carotene

    Energy Technology Data Exchange (ETDEWEB)

    Shuvalov, Vladimir A.; Heber, Ulrich

    2003-11-01

    Photoreactions of dehydrated leaves, isolated broken chloroplasts and PSII membrane fragments of spinach (Spinacia oleracea) were studied at different air humidities and compared with photoreactions of dry fronds of a fern, Polypodium vulgare, and a dry lichen, Parmelia sulcata, which in contrast to spinach are insensitive to photoinactivation in the dry state. Even in very dry air, P700 in the reaction center of photosystem I of dry leaves was oxidized, and the primary quinone acceptor Q{sub A} in the reaction center of photosystem II was photoreduced by low light. These reactions were only very slowly reversed in the dark and saturated under low light intensity. Light-minus-dark difference absorption spectra of the dry leaves, isolated chloroplasts and PSII membrane fragments measured at higher light intensities revealed absorbance changes of {beta}-carotene at 500 nm (light-dependent bleaching) and 980 nm (light-dependent band formation) and bleaching of chlorophyll at 436 and 680 nm with appearance of bands at 450 and 800 nm. Decrease of chlorophyll fluorescence upon strong illumination indicated photoaccumulation of a quencher. All these changes were kinetically related and readily reversible. They are interpreted to show light-induced oxidation of {beta}-carotene (Car) and reduction of chlorophyll-680 (Chl-680) in the reaction center of photosystem II of the dried leaves, chloroplasts and photosystem II particles. The fluorescence quencher was suggested to be Chl-680{sup -} or Car{sup +} in close proximity to P680, the primary electron donor. Appreciable photoaccumulation of reduced pheophytin was only observed in dry leaves after Q{sub A} reduction had been lost during heat treatment of hydrated leaves prior to dehydration. The observations are interpreted to show light-dependent cyclic electron flow within the reaction center of photosystem II in which Chl-680 (or Pheo) is reduced by P680* and Car is oxidized by P680{sup +} with consequent recombination of

  20. Core/Shell Face-Centered Tetragonal FePd/Pd Nanoparticles as an Efficient Non-Pt Catalyst for the Oxygen Reduction Reaction.

    Science.gov (United States)

    Jiang, Guangming; Zhu, Huiyuan; Zhang, Xu; Shen, Bo; Wu, Liheng; Zhang, Sen; Lu, Gang; Wu, Zhongbiao; Sun, Shouheng

    2015-11-24

    We report the synthesis of core/shell face-centered tetragonal (fct)-FePd/Pd nanoparticles (NPs) via reductive annealing of core/shell Pd/Fe3O4 NPs followed by temperature-controlled Fe etching in acetic acid. Among three different kinds of core/shell FePd/Pd NPs studied (FePd core at ∼8 nm and Pd shell at 0.27, 0.65, or 0.81 nm), the fct-FePd/Pd-0.65 NPs are the most efficient catalyst for the oxygen reduction reaction (ORR) in 0.1 M HClO4 with Pt-like activity and durability. This enhanced ORR catalysis arises from the desired Pd lattice compression in the 0.65 nm Pd shell induced by the fct-FePd core. Our study offers a general approach to enhance Pd catalysis in acid for ORR.

  1. Photothermal characterization of the light-initiated reaction steps

    OpenAIRE

    Klauß, André

    2012-01-01

    Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on earth. The catalytic site, a manganese-calcium complex and its protein environment in photosystem II (PSII), cycles through four semi-stable states (S0 to S3). Each turnover of the reaction cycle of photosynthetic water oxidation requires the removal of 4 electrons and 4 protons from the Mn-complex. In time-resolved photothermal beam deflection (PBD) experiments, it was p...

  2. Pathway of proton transfer in bacterial reaction centers: replacement of serine-L223 by alanine inhibits electron and proton transfers associated with reduction of quinone to dihydroquinone.

    Science.gov (United States)

    Paddock, M L; McPherson, P H; Feher, G; Okamura, M Y

    1990-01-01

    The pathway of proton transfer in the reaction center (RC) from Rhodobacter sphaeroides was investigated by site-directed mutagenesis. Ser-L223, a putative proton donor that forms a hydrogen bond with the secondary quinone acceptor QB, was replaced with Ala and Thr. RCs with Ala-L223 displayed reduced electron transfer and proton uptake rates in the reaction QA-QB- + 2H+----QAQBH2. The rate constant for this reaction, k(2)AB, was found to be reduced approximately 350-fold to 4.0 +/- 0.2 s-1. Proton uptake measurements using a pH indicator dye showed a rapid uptake of 1 H+ per RC followed by a slower uptake of 1 H+ per RC at a rate of 4.1 +/- 0.1 s-1; native RCs showed a rapid uptake of 2H+ per RC. Evidence is provided that these changes were not due to gross structural changes in the binding site of QB. RCs with Thr-L223 showed little reduction in the rates of electron and proton transfer. These results indicate that proton transfer from the hydroxyl group of Ser-L223 or Thr-L223 is required for fast electron and proton transfer associated with the formation of the dihydroquinone QH2. In contrast, previous work showed that replacing Glu-L212, another putative proton donor to QB, with Gln slowed proton uptake from solution without significantly altering electron transfer. We propose a model that involves two distinct proton transfer steps. The first step occurs prior to transfer of the second electron to QB and involves proton transfer from Ser-L223. The second step occurs after this electron transfer through a pathway involving Glu-L212. PMID:2168561

  3. Measurements of the reaction e/+/e/-/ yielding gamma-gamma at center-of-mass energies in the range 6.2-7.4 GeV

    Science.gov (United States)

    Hilger, E.; Beron, B. L.; Carrington, R. L.; Ford, R. L.; Hill, W. T.; Hofstadter, R.; Hughes, E. B.; Liberman, A. D.; Martin, T. W.; Oneill, L. H.

    1977-01-01

    The cross section for the pair-annihilation reaction e(+)e(-) yields gamma-gamma were measured at center-of-mass energies in the range 6.2-7.4 GeV and at production angles close to 90 deg. The experimental apparatus consisted of two identical spectrometers which were set to view the luminous region at SPEAR-II from opposite directions at an azimuthal angle of 45 deg. In each spectrometer there was a NaI(TI) crystal 20 radiation lengths thick and 30 in. in diameter to measure the gamma-ray energies. Annihilation events were detected by an electronic trigger which required only the observation in coincidence of more than 0.2 GeV in each NaI(TI) crystal within + or - 15 nsec of the crossing beams. The observed rates of pair-annihilation events were found to be in agreement with those expected from quantum electrodynamics (QED) at all the center-of-mass energies used.

  4. An analysis of Staphylococcus aureus infections at a military medical center using the PLEX-ID combined polymerase chain reaction-mass spectrometry system.

    Science.gov (United States)

    Washington, Michael A; Agee, Willie A; Kajiura, Lauren; Staege, Catherine M; Uyehara, Catherine Ft; Barnhill, Jason C

    2014-04-01

    Staphylococcus aureus (S. aureus) is a major cause of morbidity in the military health care setting. Culture-based methods are the most common means of identifying infections caused by this agent. However, culture-based methods lack sensitivity and specificity. The Abbott PLEX-ID instrument uses a combination of the polymerase chain reaction and mass spectrometry for the identification of bacterial isolates. We investigated whether the Abbott PLEX-ID system could identify S. aureus in clinical material and facilitate the epidemiological analysis of individual isolates. The PLEX-ID system positively identified 100% of isolates previously found to be methicillin resistant S. aureus by culture. In addition, analysis using the PLEX-ID software revealed that the majority of S. aureus isolates at Tripler Army Medical Center derive from clonal complex 8 and nearly 100% of these strains express the R-variant of the Panton-Valentine leukocidin virulence factor. These results demonstrate the utility of the PLEX-ID system in identifying clinical isolates and reveal an unexpected level of homogeneity among clinical S. aureus isolates recovered at Tripler Army Medical Center. These results also demonstrate the utility of the PLEX-ID system in identifying the resistance patterns, predicting the virulence properties, and tracking the migration of bacterial pathogens in the clinical setting. Reprint & Copyright © 2014 Association of Military Surgeons of the U.S.

  5. C lostridium difficile surface proteins are anchored to the cell wall using CWB2 motifs that recognise the anionic polymer PSII

    Science.gov (United States)

    Willing, Stephanie E.; Candela, Thomas; Shaw, Helen Alexandra; Seager, Zoe; Mesnage, Stéphane; Fagan, Robert P.

    2015-01-01

    Summary Gram‐positive surface proteins can be covalently or non‐covalently anchored to the cell wall and can impart important properties on the bacterium in respect of cell envelope organisation and interaction with the environment. We describe here a mechanism of protein anchoring involving tandem CWB2 motifs found in a large number of cell wall proteins in the Firmicutes. In the Clostridium difficile cell wall protein family, we show the three tandem repeats of the CWB2 motif are essential for correct anchoring to the cell wall. CWB2 repeats are non‐identical and cannot substitute for each other, as shown by the secretion into the culture supernatant of proteins containing variations in the patterns of repeats. A conserved Ile Leu Leu sequence within the CWB2 repeats is essential for correct anchoring, although a preceding proline residue is dispensable. We propose a likely genetic locus encoding synthesis of the anionic polymer PSII and, using RNA knock‐down of key genes, reveal subtle effects on cell wall composition. We show that the anionic polymer PSII binds two cell wall proteins, SlpA and Cwp2, and these interactions require the CWB2 repeats, defining a new mechanism of protein anchoring in Gram‐positive bacteria. PMID:25649385

  6. Kinetics of H+ ion binding by the P+QA-state of bacterial photosynthetic reaction centers: rate limitation within the protein.

    Science.gov (United States)

    Maróti, P; Wraight, C A

    1997-07-01

    The kinetics of flash-induced H+ ion binding by isolated reaction centers (RCs) of Rhodobacter sphaeroides, strain R-26, were measured, using pH indicators and conductimetry, in the presence of terbutryn to block electron transfer between the primary and secondary quinones (QA and QB), and in the absence of exogenous electron donors to the oxidized primary donor, P+, i.e., the P+QA-state. Under these conditions, proton binding by RCs is to the protein rather than to any of the cofactors. After light activation to form P+QA-, the kinetics of proton binding were monoexponential at all pH values studied. At neutral pH, the apparent bimolecular rate constant was close to the diffusional limit for proton transfer in aqueous solution (approximately 10(11) M-1 s-1), but increased significantly in the alkaline pH range (e.g., 2 x 10(13) M-1 s-1 at pH 10). The average slope of the pH dependence was -0.4 instead of -1.0, as might be expected for a H+ diffusion-controlled process. High activation energy (0.54 eV at pH 8.0) and weak viscosity dependence showed that H+ ion uptake by RCs is not limited by diffusion. The salt dependence of the H+ ion binding rate and the pK values of the protonatable amino acid residues of the reaction center implicated surface charge influences, and Gouy-Chapman theory provided a workable description of the ionic effects as arising from modulation of the pH at the surface of the RC. Incubation in D2O caused small increases in the pKs of the protonatable groups and a small, pH (pD)-dependent slowing of the binding rate. The salt, pH, temperature, viscosity, and D2O dependences of the proton uptake by RCs in the P+QA- state were accounted for by three considerations: 1) parallel pathways of H+ delivery to the RC, contributing to the observed (net) H+ disappearance; 2) rate limitation of the protonation of target groups within the protein by conformational dynamics; and 3) electrostatic influences of charged groups in the protein, via the surface pH.

  7. Multi-modular, tris(triphenylamine) zinc porphyrin-zinc phthalocyanine-fullerene conjugate as a broadband capturing, charge stabilizing, photosynthetic 'antenna-reaction center' mimic.

    Science.gov (United States)

    Kc, Chandra B; Lim, Gary N; D'Souza, Francis

    2015-04-21

    A broadband capturing, charge stabilizing, photosynthetic antenna-reaction center model compound has been newly synthesized and characterized. The model compound is comprised of a zinc porphyrin covalently linked to three units of triphenylamine entities and a zinc phthalocyanine entity. The absorption and fluorescence spectra of zinc porphyrin complemented that of zinc phthalocyanine offering broadband coverage. Stepwise energy transfer from singlet excited triphenylamine to zinc porphyrin, and singlet excited zinc porphyrin to zinc phthalocyanine (kENT ∼ 10(11) s(-1)) was established from spectroscopic and time-resolved transient absorption techniques. Next, an electron acceptor, fullerene was introduced via metal-ligand axial coordination to both zinc porphyrin and zinc phthalocyanine centers, and they were characterized by spectroscopic and electrochemical techniques. An association constant of 4.9 × 10(4) M(-1) for phenylimidazole functionalized fullerene binding to zinc porphyrin, and 5.1 × 10(4) M(-1) for it binding to zinc phthalocyanine was obtained. An energy level diagram for the occurrence of different photochemical events within the multi-modular donor-acceptor conjugate was established from spectral and electrochemical data. Unlike the previous zinc porphyrin-zinc phthalocyanine-fullerene conjugates, the newly assembled donor-acceptor conjugate has been shown to undergo the much anticipated initial charge separation from singlet excited zinc porphyrin to the coordinated fullerene followed by a hole shift process to zinc phthalocyanine resulting in a long-lived charge separated state as revealed by femto- and nanosecond transient absorption spectroscopic techniques. The lifetime of the final charge separated state was about 100 ns.

  8. Pattern of Adverse Drug Reactions in Children Attending the Department of Pediatrics in a Tertiary Care Center: A Prospective Observational Study

    Directory of Open Access Journals (Sweden)

    Kishour Kumar Digra

    2015-01-01

    Full Text Available AIM To study the pattern of various adverse drug reactions (ADRs occurring in children attending the Department of Pediatrics, SMGS Hospital, Jammu over 1 year. Subjects and Methods This was a prospective study, with study population of patients attending Department of Pediatrics over a period of 1 year. A structured format was used to enroll the participants. A pilot study was conducted to test the suitability of the format and feasibility of the study. The study was carried out to review various pattern of ADRs by using the Naranjo probability scale, and severity was assessed by using the Hartwig severity scale. ADRs were classified according to the classification used by the Adverse Drug Reaction Monitoring Center, Central Drugs Standard Control Organization, New Delhi, India. Results In the present study, 104 patients were found to have developed acute drug reactions. Among these, 83.6% were type B, 14.42% type A, and 1.92% were type U. Furthermore, 25.96% ADRs were due to anticonvulsants, followed by antibiotics (22.11%, antipyretics (11.53%, vaccination (8.65%, steroids (6.73%, decongestants (5.67%, snake antivenom and antiemetics (3.84%, and fluids, insulin, and antacids (1.92%. The patients’ dermatological system was involved in 67.30%, followed by the central nervous system (CNS in 11.53% patients. Renal system was involved in 6.73% patients. Cardiac, musculoskeletal, metabolic, and other systems were involved in 4.80%, 3.84%, 2.88%, and 0.96%, respectively. According to the Hartwig severity scale of ADRs, 64.4% patients had moderate ADRs, 29.8% patients had severe ADRs, and 5.76% had mild ADRs. In the present study, 64.4% patients expressed moderate severity, whereas 29.8% expressed high severity and 5.76% expressed mild ADRs. Conclusion ADRs were seen in 71% of the patients between 1 and 5 years of age, 26% in the age group of 5–10 years, and 3% were more than 10 years old. Anticonvulsants (25.96% and antibiotics (22.11% were

  9. Properties of hybrid complexes composed of photosynthetic reaction centers from the purple bacterium Rhodobacter sphaeroides and quantum dots in lecithin liposomes.

    Science.gov (United States)

    Zagidullin, V E; Lukashev, E P; Knox, P P; Seifullina, N Kh; Sokolova, O S; Pechnikova, E V; Lokstein, H; Paschenko, V Z

    2014-11-01

    Quantum dots (QDs) can absorb ultraviolet and long-wavelength light energy much more efficiently than natural light-harvesting proteins and transfer the excitation energy to photosynthetic reaction centers (RCs). Inclusion into liposomes of RC membrane pigment-protein complexes combined with QDs as antennae opens new opportunities for using such hybrid systems as a basis for artificial energy-transforming devices that potentially can operate with greater efficiency and stability than devices based only on biological components. RCs from Rhodobacter sphaeroides and QDs with fluorescence maximum at 530 nm (CdSe/ZnS with hydrophilic covering) were embedded in lecithin liposomes by extrusion of a solution of multilayer lipid vesicles through a polycarbonate membrane or by dialysis of lipids and proteins dispersed with excess detergent. The dimensions of the resulting hybrid systems were evaluated using dynamic light scattering and by transmission cryoelectron microscopy. The efficiency of RC and QD interaction within the liposomes was estimated using fluorescence excitation spectra of the photoactive bacteriochlorophyll of the RCs and by measuring the fluorescence decay kinetics of the QDs. The functional activity of the RCs in hybrid complexes was fully maintained, and their stability was even increased.

  10. The electronic structure of the primary electron donor of reaction centers of purple bacteria at atomic resolution as observed by photo-CIDNP 13C NMR.

    Science.gov (United States)

    Daviso, Eugenio; Prakash, Shipra; Alia, A; Gast, Peter; Neugebauer, Johannes; Jeschke, Gunnar; Matysik, Jörg

    2009-12-29

    Composed of the two bacteriochlorophyll cofactors, P(L) and P(M), the special pair functions as the primary electron donor in bacterial reaction centers of purple bacteria of Rhodobacter sphaeroides. Under light absorption, an electron is transferred to a bacteriopheophytin and a radical pair is produced. The occurrence of the radical pair is linked to the production of enhanced nuclear polarization called photochemically induced dynamic nuclear polarization (photo-CIDNP). This effect can be used to study the electronic structure of the special pair at atomic resolution by detection of the strongly enhanced nuclear polarization with laser-flash photo-CIDNP magic-angle spinning NMR on the carotenoid-less mutant R26. In the electronic ground state, P(L) is strongly disturbed, carrying a slightly negative charge. In the radical cation state, the ratio of total electron spin densities between P(L) and P(M) is 2:1, although it is 2.5:1 for the pyrrole carbons, 2.2:1 for all porphyrinic carbons, and 4:1 for the pyrrole nitrogen. It is shown that the symmetry break between the electronic structures in the electronic ground state and in the radical cation state is an intrinsic property of the special pair supermolecule, which is particularly attributable to a modification of the structure of P(L). The significant difference in electron density distribution between the ground and radical cation states is explained by an electric polarization effect of the nearby histidine.

  11. Electrostatics of the photosynthetic bacterial reaction center. Protonation of Glu L 212 and Asp L 213 - A new method of calculation.

    Science.gov (United States)

    Ptushenko, Vasily V; Cherepanov, Dmitry A; Krishtalik, Lev I

    2015-12-01

    Continuum electrostatic calculation of the transfer energies of anions from water into aprotic solvents gives the figures erroneous by order of magnitude. This is due to the hydrogen bond disruption that suggests the necessity to reconsider the traditional approach of the purely electrostatic calculation of the transfer energy from water into protein. In this paper, the method combining the experimental estimates of the transfer energies from water into aprotic solvent and the electrostatic calculation of the transfer energies from aprotic solvent into protein is proposed. Hydrogen bonds between aprotic solvent and solute are taken into account by introducing an imaginary aprotic medium incapable to form hydrogen bonds with the solute. Besides, a new treatment of the heterogeneous intraprotein dielectric permittivity based on the microscopic protein structure and electrometric measurements is elaborated. The method accounts semi-quantitatively for the electrostatic effect of diverse charged amino acid substitutions in the donor and acceptor parts of the photosynthetic bacterial reaction center from Rhodobacter sphaeroides. Analysis of the volatile secondary acceptor site QB revealed that in the conformation with a minimal distance between quinone QB and Glu L 212 the proton uptake upon the reduction of QB is prompted by Glu L 212 in alkaline and by Asp L 213 in slightly acidic regions. This agrees with the pH dependences of protonation degrees and the proton uptake. The method of pK calculation was applied successfully also for dissociation of Asp 26 in bacterial thioredoxin. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Femtosecond spectroscopy of the primary charge separation in reaction centers of Chloroflexus aurantiacus with selective excitation in the QY and Soret bands.

    Science.gov (United States)

    Xin, Yueyong; Lin, Su; Blankenship, Robert E

    2007-09-27

    The primary charge separation and electron-transfer processes of photosynthesis occur in the reaction center (RC). Isolated RCs of the green filamentous anoxygenic phototrophic bacterium Chloroflexus aurantiacus were studied at room temperature by using femtosecond transient absorption spectroscopy with selective excitation. Upon excitation in the Q(Y) absorbance band of the bacteriochlorophyll (BChl) dimer (P) at 865 nm, a 7.0 +/- 0.5 ps kinetic component was observed in the 538 nm region (Q(X) band of the bacteriopheophytin (BPheo)), 750 nm region (Q(Y) band of the BPheo), and 920 nm region (stimulated emission of the excited-state of P), indicating that this lifetime represents electron transfer from P to BPheo. The same time constant was also observed upon 740 nm or 800 nm excitation. A longer lifetime (300 +/- 30 ps), which was assigned to the time of reduction of the primary quinone, Q(A), was also observed. The transient absorption spectra and kinetics all indicate that only one electron-transfer branch is involved in primary charge separation under these excitation conditions. However, the transient absorption changes upon excitation in the Soret band at 390 nm reveal a more complex set of energy and electron-transfer processes. By comparison to studies on the RCs of the purple bacterium Rhodobacter sphaeroides, we discuss the possible mechanism of electron-transfer pathway dependence on excitation energy and propose a model of the Cf. aurantiacus RC that better explains the observed results.

  13. Influence of temperature on properties of nitrogen plasma source ion implantation (N-PSII) of Ti6A14V alloy

    CERN Document Server

    Geng Man; Zhao Qing

    2001-01-01

    Specimens of Ti6Al4V alloy were implanted with nitrogen plasma source ion implantation (N-PSII) at temperatures between 100 degree C and 600 degree C to a ion dose of 4 x 10 sup 1 sup 7 cm sup - sup 2. Auger Electron Spectroscopy (AES) was used to determine the nitrogen concentration depth profiles. Microhardness measurements and pin-on-disk wear test were performed to evaluate the improvements of the surface modification. Glancing angle X-ray diffraction (XRD) was employed to determine the phases presented in the surface modified layer. The thickness of implanted layer increased by about an order of magnitude when the temperature was elevated from 100 degree C to 600 degree C. Higher surface hardness and wear resistance was also obtained at higher temperature. Scanning electron microscopy (SEM) showed distinct microstructural changes and the presence of titanium nitrides in the implanted surface

  14. Primary electron transfer in reaction centers of YM210L and YM210L/HL168L mutants of Rhodobacter sphaeroides.

    Science.gov (United States)

    Yakovlev, A G; Vasilieva, L G; Khmelnitskaya, T I; Shkuropatova, V A; Shkuropatov, A Ya; Shuvalov, V A

    2010-07-01

    The role of tyrosine M210 in charge separation and stabilization of separated charges was studied by analyzing of the femtosecond oscillations in the kinetics of decay of stimulated emission from P* and of a population of the primary charge separated state P(+)B(A)(-) in YM210L and YM210L/HL168L mutant reaction centers (RCs) of Rhodobacter sphaeroides in comparison with those in native Rba. sphaeroides RCs. In the mutant RCs, TyrM210 was replaced by Leu. The HL168L mutation placed the redox potential of the P(+)/P pair 123 mV below that of native RCs, thus creating a theoretical possibility of P(+)B(A)(-) stabilization. Kinetics of P* decay at 940 nm of both mutants show a significant slowing of the primary charge separation reaction in comparison with native RCs. Distinct damped oscillations in these kinetics with main frequency bands in the range of 90-150 cm(-1) reflect mostly nuclear motions inside the dimer P. Formation of a very small absorption band of B(A)(-) at 1020 nm is registered in RCs of both mutants. The formation of the B(A)(-) band is accompanied by damped oscillations with main frequencies from ~10 to ~150 cm(-1). Only a partial stabilization of the P(+)B(A)(-) state is seen in the YM210L/HL168L mutant in the form of a small non-oscillating background of the 1020-nm kinetics. A similar charge stabilization is absent in the YM210L mutant. A model of oscillatory reorientation of the OH-group of TyrM210 in the electric fields of P(+) and B(A)(-) is proposed to explain rapid stabilization of the P(+)B(A)(-) state in native RCs. Small oscillatory components at ~330-380 cm(-1) in the 1020-nm kinetics of native RCs are assumed to reflect this reorientation. We conclude that the absence of TyrM210 probably cannot be compensated by lowering of the P(+)B(A)(-) free energy that is expected for the double YM210L/HL168L mutant. An oscillatory motion of the HOH55 water molecule under the influence of P(+) and B(A)(-) is assumed to be another potential

  15. Estimating chlorophyll content and photochemical yield of photosystem II (ΦPSII) using solar-induced chlorophyll fluorescence measurements at different growing stages of attached leaves.

    Science.gov (United States)

    Tubuxin, Bayaer; Rahimzadeh-Bajgiran, Parinaz; Ginnan, Yusaku; Hosoi, Fumiki; Omasa, Kenji

    2015-09-01

    This paper illustrates the possibility of measuring chlorophyll (Chl) content and Chl fluorescence parameters by the solar-induced Chl fluorescence (SIF) method using the Fraunhofer line depth (FLD) principle, and compares the results with the standard measurement methods. A high-spectral resolution HR2000+ and an ordinary USB4000 spectrometer were used to measure leaf reflectance under solar and artificial light, respectively, to estimate Chl fluorescence. Using leaves of Capsicum annuum cv. 'Sven' (paprika), the relationships between the Chl content and the steady-state Chl fluorescence near oxygen absorption bands of O2B (686nm) and O2A (760nm), measured under artificial and solar light at different growing stages of leaves, were evaluated. The Chl fluorescence yields of ΦF 686nm/ΦF 760nm ratios obtained from both methods correlated well with the Chl content (steady-state solar light: R(2) = 0.73; artificial light: R(2) = 0.94). The SIF method was less accurate for Chl content estimation when Chl content was high. The steady-state solar-induced Chl fluorescence yield ratio correlated very well with the artificial-light-induced one (R(2) = 0.84). A new methodology is then presented to estimate photochemical yield of photosystem II (ΦPSII) from the SIF measurements, which was verified against the standard Chl fluorescence measurement method (pulse-amplitude modulated method). The high coefficient of determination (R(2) = 0.74) between the ΦPSII of the two methods shows that photosynthesis process parameters can be successfully estimated using the presented methodology. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  16. Second-site mutation at M43 (Asn[r arrow]Asp) compensates for the loss of two acidic residues in the Q[sub B] site of the reaction center

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, D.K.; Nance, S.L.; Schiffer, M. (Argonne National Lab., IL (United States). Biological and Medical Research Division)

    1992-01-01

    Two acidic residues, L212Glu and L213Asp, in the Q[sub B] binding sites of the photosynthetic reaction centers of Rhodobacter capsulatus and Rhodobacter sphaeroides are thought to play central roles in the transfer of protons to the quinone anion(s) generated by photoinduced electron transfer. The authors constructed the site-specific double mutant L212Ala-L213Ala in R. capsulatus, that is incapable of growth under photosynthetic conditions. A photocompetent derivative of that strain has been isolated that carries the original L212Ala-L213Ala double mutation and a second-site suppressor mutation at residue M43 (Asn [r arrow] Asp), outside of the Q, binding site, that is solely responsible for restoring the photosynthetic phenotype. The Asp, Asn combination of residues at the L213 and M43 positions is conserved in the five species of photosynthetic bacteria whose reaction center sequences are known. In R. capsulatus and R. sphaeroides, the pair is L213Asp-M43Asn. But, the reaction centers of Rhodopseudomonas viridis, Rhodospirillum rubrum and Chloroflexus aurantiacus reverse the combination to L213Asn-M43Asp. In this respect, the Q, site of the suppressor strain resembles that of the latter three species in that it couples an uncharged residue at L213 with an acidic residue at M43. These reaction centers, in which L213 is an amide, must employ an alternative proton transfer pathway. The observation that the M43Asn Asp mutation in R. capsulatus compensates for the loss of both acidic residues at L212 and L213 suggests that M43Asp is involved in a new proton transfer route in this species that resembles the one normally used in reaction centers of Rps. viridis, Rsp. rubrum and C. aurantiacus.

  17. The rate of second electron transfer to QB(-) in bacterial reaction center of impaired proton delivery shows hydrogen-isotope effect.

    Science.gov (United States)

    Maróti, Ágnes; Wraight, Colin A; Maróti, Péter

    2015-02-01

    The 2nd electron transfer in reaction center of photosynthetic bacterium Rhodobacter sphaeroides is a two step process in which protonation of QB(-) precedes interquinone electron transfer. The thermal activation and pH dependence of the overall rate constants of different RC variants were measured and compared in solvents of water (H2O) and heavy water (D2O). The electron transfer variants where the electron transfer is rate limiting (wild type and M17DN, L210DN and H173EQ mutants) do not show solvent isotope effect and the significant decrease of the rate constant of the second electron transfer in these mutants is due to lowering the operational pKa of QB(-)/QBH: 4.5 (native), 3.9 (L210DN), 3.7 (M17DN) and 3.1 (H173EQ) at pH7. On the other hand, the proton transfer variants where the proton transfer is rate limiting demonstrate solvent isotope effect of pH-independent moderate magnitude (2.11±0.26 (WT+Ni(2+)), 2.16±0.35 (WT+Cd(2+)) and 2.34±0.44 (L210DN/M17DN)) or pH-dependent large magnitude (5.7 at pH4 (L213DN)). Upon deuteration, the free energy and the enthalpy of activation increase in all proton transfer variants by about 1 kcal/mol and the entropy of activation becomes negligible in L210DN/M17DN mutant. The results are interpreted as manifestation of equilibrium and kinetic solvent isotope effects and the structural, energetic and kinetic possibility of alternate proton delivery pathways are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. The C-terminus of PufX plays a key role in dimerisation and assembly of the reaction center light-harvesting 1 complex from Rhodobacter sphaeroides.

    Science.gov (United States)

    Qian, Pu; Martin, Elizabeth C; Ng, Irene W; Hunter, C Neil

    2017-09-01

    In bacterial photosynthesis reaction center-light-harvesting 1 (RC-LH1) complexes trap absorbed solar energy by generating a charge separated state. Subsequent electron and proton transfers form a quinol, destined to diffuse to the cytochrome bc1 complex. In bacteria such as Rhodobacter (Rba.) sphaeroides and Rba. capsulatus the PufX polypeptide creates a channel for quinone/quinol traffic across the LH1 complex that surrounds the RC, and it is therefore essential for photosynthetic growth. PufX also plays a key role in dimerization of the RC-LH1-PufX core complex, and the structure of the Rba. sphaeroides complex shows that the PufX C-terminus, particularly the region from X49-X53, likely mediates association of core monomers. To investigate this putative interaction we analysed mutations PufX R49L, PufX R53L, PufX R49/53L and PufX G52L by measuring photosynthetic growth, fractionation of detergent-solubilised membranes, formation of 2-D crystals and electron microscopy. We show that these mutations do not affect assembly of PufX within the core or photosynthetic growth but they do prevent dimerization, consistent with predictions from the RC-LH1-PufX structure. We obtained low resolution structures of monomeric core complexes with and without PufX, using electron microscopy of negatively stained single particles and 3D reconstruction; the monomeric complex with PufX corresponds to one half of the dimer structure whereas LH1 completely encloses the RC if the gene encoding PufX is deleted. On the basis of the insights gained from these mutagenesis and structural analyses we propose a sequence for assembly of the dimeric RC-LH1-PufX complex. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

  19. Manipulating the Energetics and Rates of Electron Transfer in Rhodobacter capsulatus Reaction Centers with Asymmetric Pigment Content

    Energy Technology Data Exchange (ETDEWEB)

    Faries, Kaitlyn M. [Department; Dylla, Nicholas P. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Hanson, Deborah K. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Holten, Dewey [Department; Laible, Philip D. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Kirmaier, Christine [Department

    2017-07-17

    Seemingly redundant parallel pathways for electron transfer (ET), composed of identical sets of cofactors, are a cornerstone feature of photosynthetic reaction centers (RCs) involved in light-energy conversion. In native bacterial RCs, both A and B branches house one bacteriochlorophyll (BChl) and one bacteriopheophytin (BPh), but the A branch is used exclusively. Described herein are the results-obtained for two Rhodobacter capsulatus RCs with an unnaturally high degree of cofactor asymmetry, two BPh on the RC's B side and two BChl on the A side. These pigment changes derive, respectively, from the His(M180)Leu mutation [a BPh ((Phi(B)) replaces the B-side BChl (BB)], and the Leu(M212)His mutation [a BChl (beta(A))) replaces the A-side BPh (H-A)]. Additionally, Tyr(M208)Phe was employed to disfavor ET to the A branch; in one mutant, Val(M131)Glu creates a hydrogen bond to H-B to enhance ET to H-B. In both Phi(B) mutants, the decay kinetics of the excited primary ET donor (P*) resolve three populations with lifetimes of similar to 9 ps (50-60%), similar to 40 ps (10-20%), and similar to 200 ps (20-30%), with P+Phi(-)(B) formed predominantly from the 9 ps fraction. The 50-60% yield of P+Phi(B)- is the highest yet observed for a Phi(B)-containing RC. The results provide insight into factors needed for efficient multistep ET.

  20. Investigation of the redox interaction between Mn-bicarbonate complexes and reaction centers from Rhodobacter sphaeroides R-26, Chromatium minutissimum, and Chloroflexus aurantiacus.

    Science.gov (United States)

    Terentyev, V V; Shkuropatov, A Ya; Shkuropatova, V A; Shuvalov, V A; Klimov, V V

    2011-12-01

    The change in the dark reduction rate of photooxidized reaction centers (RC) of type II from three anoxygenic bacteria (Rhodobacter sphaeroides R-26, Chromatium minutissimum, and Chloroflexus aurantiacus) having different redox potentials of the P(+)/P pair and availability of RC for exogenous electron donors was investigated upon the addition of Mn(2+) and HCO(3)(-). It was found that the dark reduction of P(870)(+) from Rb. sphaeroides R-26 is considerably accelerated upon the combined addition of 0.5 mM MnCl(2) and 30-75 mM NaHCO(3) (as a result of formation of "low-potential" complexes [Mn(HCO(3))(2)]), while MnCl(2) and NaHCO(3) added separately had no such effect. The effect is not observed either in RC from Cf. aurantiacus (probably due to the low oxidation potential of the primary electron donor, P(865), which results in thermodynamic difficulties of the redox interaction between P(865)(+) and Mn(2+)) or in RC from Ch. minutissimum (apparently due to the presence of the RC-bound cytochrome preventing the direct interaction between P(870)(+) and Mn(2+)). The absence of acceleration of the dark reduction of P(870)(+) in the RC of Rb. sphaeroides R-26 when Mn(2+) and HCO(3)(-) were replaced by Mg(2+) or Ca(2+) and by formate, oxalate, or acetate, respectively, reveals the specificity of the Mn2+-bicarbonate complexes for the redox interaction with P(+). The results of this work might be considered as experimental evidence for the hypothesis of the participation of Mn(2+) complexes in the evolutionary origin of the inorganic core of the water oxidizing complex of photosystem II. © Pleiades Publishing, Ltd., 2011.

  1. Effect of detergent concentration on the thermal stability of a membrane protein: The case study of bacterial reaction center solubilized by N,N-dimethyldodecylamine-N-oxide.

    Science.gov (United States)

    Palazzo, Gerardo; Lopez, Francesco; Mallardi, Antonia

    2010-01-01

    We report on the response of reaction center (RC) from Rhodobacter sphaeroides (an archetype of membrane proteins) to the exposure at high temperature. The RCs have been solubilized in aqueous solution of the detergent N,N-dimethyldodecylamine-N-oxide (LDAO). Changes in the protein conformation have been probed by monitoring the variation in the absorbance of the bacteriochlorine cofactors and modification in the efficiency of energy transfer from tryptophans to cofactors and among the cofactors (through fluorescence measurements). The RC aggregation taking place at high temperature has been investigated by means of dynamic light scattering. Two experimental protocols have been used: (i) isothermal kinetics, in which the time evolution of RC after a sudden increase of the temperature is probed, and (ii) T-scans, in which the RCs are heated at constant rate. The analysis of the results coming from both the experiments indicates that the minimal kinetic scheme requires an equilibrium step and an irreversible process. The irreversible step is characterized by a activation energy of 205+/-14 kJ/mol and is independent from the detergent concentration. Since the temperature dependence of the aggregation rate was found to obey to the same law, the aggregation process is unfolding-limited. On the other hand, the equilibrium process between the native and a partially unfolded conformations was found to be strongly dependent on the detergent concentration. Increasing the LDAO content from 0.025 to 0.5 wt.% decreases the melting temperature from 49 to 42 degrees C. This corresponds to a sizeable (22 kJ/mol at 25 degrees C) destabilization of the native conformation induced by the detergent. The nature of the aggregates formed by the denatured RCs depends on the temperature. For temperature below 60 degrees C compact aggregates are formed while at 60 degrees C the clusters are less dense with a scaling relation between mass and size close to that expected for diffusion

  2. Retardation of Protein Dynamics by Trehalose in Dehydrated Systems of Photosynthetic Reaction Centers. Insights from Electron Transfer and Thermal Denaturation Kinetics.

    Science.gov (United States)

    Malferrari, Marco; Francia, Francesco; Venturoli, Giovanni

    2015-10-29

    Conformational protein dynamics is known to be hampered in amorphous matrixes upon dehydration, both in the absence and in the presence of glass forming disaccharides, like trehalose, resulting in enhanced protein thermal stability. To shed light on such matrix effects, we have compared the retardation of protein dynamics in photosynthetic bacterial reaction centers (RC) dehydrated at controlled relative humidity in the absence (RC films) or in the presence of trehalose (RC-trehalose glasses). Small scale RC dynamics, associated with the relaxation from the dark-adapted to the light-adapted conformation, have been probed up to the second time scale by analyzing the kinetics of electron transfer from the photoreduced quinone acceptor (QA(-)) to the photoxidized primary donor (P(+)) as a function of the duration of photoexcitation from 7 ns (laser pulse) to 20 s. A more severe inhibition of dynamics is found in RC-trehalose glasses than in RC films: only in the latter system does a complete relaxation to the light-adapted conformation occur even at extreme dehydration, although strongly retarded. To gain insight into the large scale RC dynamics up to the time scale of days, the kinetics of thermal denaturation have been studied at 44 °C by spectral analysis of the Qx and Qy bands of the RC bacteriochlorin cofactors, as a function of the sugar/protein molar ratio, m, varied between 0 and 10(4). Upon increasing m, denaturation is slowed progressively, and above m ∼ 500 the RC is stable at least for several days. The stronger retardation of RC relaxation and dynamics induced by trehalose is discussed in the light of a recent molecular dynamics simulation study performed in matrixes of the model protein lysozyme with and without trehalose. We suggest that the efficiency of trehalose in retarding RC dynamics and preventing thermal denaturation stems mainly from its propensity to form and stabilize extended networks of hydrogen bonds involving sugar, residual water, and

  3. Novel insights into the origin and diversification of photosynthesis based on analyses of conserved indels in the core reaction center proteins.

    Science.gov (United States)

    Khadka, Bijendra; Adeolu, Mobolaji; Blankenship, Robert E; Gupta, Radhey S

    2017-02-01

    The evolution and diversification of different types of photosynthetic reaction centers (RCs) remains an important unresolved problem. We report here novel sequence features of the core proteins from Type I RCs (RC-I) and Type II RCs (RC-II) whose analyses provide important insights into the evolution of the RCs. The sequence alignments of the RC-I core proteins contain two conserved inserts or deletions (indels), a 3 amino acid (aa) indel that is uniquely found in all RC-I homologs from Cyanobacteria (both PsaA and PsaB) and a 1 aa indel that is specifically shared by the Chlorobi and Acidobacteria homologs. Ancestral sequence reconstruction provides evidence that the RC-I core protein from Heliobacteriaceae (PshA), lacking these indels, is most closely related to the ancestral RC-I protein. Thus, the identified 3 aa and 1 aa indels in the RC-I protein sequences must have been deletions, which occurred, respectively, in an ancestor of the modern Cyanobacteria containing a homodimeric form of RC-I and in a common ancestor of the RC-I core protein from Chlorobi and Acidobacteria. We also report a conserved 1 aa indel in the RC-II protein sequences that is commonly shared by all homologs from Cyanobacteria but not found in the homologs from Chloroflexi, Proteobacteria and Gemmatimonadetes. Ancestral sequence reconstruction provides evidence that the RC-II subunits lacking this indel are more similar to the ancestral RC-II protein. The results of flexible structural alignments of the indel-containing region of the RC-II protein with the homologous region in the RC-I core protein, which shares structural similarity with the RC-II homologs, support the view that the 1 aa indel present in the RC-II homologs from Cyanobacteria is a deletion, which was not present in the ancestral form of the RC-II protein. Our analyses of the conserved indels found in the RC-I and RC-II proteins, thus, support the view that the earliest photosynthetic lineages with living descendants

  4. Arabidopsis plants lacking PsbQ and PsbR subunits of the oxygen-evolving complex show altered PSII super-complex organization and short-term adaptive mechanisms.

    Science.gov (United States)

    Allahverdiyeva, Yagut; Suorsa, Marjaana; Rossi, Fabio; Pavesi, Andrea; Kater, Martin M; Antonacci, Alessia; Tadini, Luca; Pribil, Mathias; Schneider, Anja; Wanner, Gerhard; Leister, Dario; Aro, Eva-Mari; Barbato, Roberto; Pesaresi, Paolo

    2013-08-01

    The oxygen-evolving complex of eukaryotic photosystem II (PSII) consists of four extrinsic subunits, PsbO (33 kDa), PsbP (23 kDa), PsbQ (17 kDa) and PsbR (10 kDa), encoded by seven nuclear genes, PsbO1 (At5g66570), PsbO2 (At3g50820), PsbP1 (At1g06680), PsbP2 (At2g30790), PsbQ1 (At4g21280), PsbQ2 (At4g05180) and PsbR (At1g79040). Using Arabidopsis insertion mutant lines, we show that PsbP1, but not PsbP2, is essential for photoautotrophic growth, whereas plants lacking both forms of PsbQ and/or PsbR show normal growth rates. Complete elimination of PsbQ has a minor effect on PSII function, but plants lacking PsbR or both PsbR and PsbQ are characterized by more pronounced defects in PSII activity. Gene expression and immunoblot analyses indicate that accumulation of each of these proteins is highly dependent on the presence of the others, and is controlled at the post-transcriptional level, whereas PsbO stability appears to be less sensitive to depletion of other subunits of the oxygen-evolving complex. In addition, comparison of levels of the PSII super-complex in wild-type and mutant leaves reveals the importance of the individual subunits of the oxygen-evolving complex for the supramolecular organization of PSII and their influence on the rate of state transitions. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

  5. Selected phytotoxins and organic extracts from endophytic fungus Edenia gomezpompae as light reaction of photosynthesis inhibitors.

    Science.gov (United States)

    Macías-Rubalcava, Martha Lydia; Ruiz-Velasco Sobrino, María Emma; Meléndez-González, Claudio; King-Díaz, Beatriz; Lotina-Hennsen, Blas

    2014-09-05

    In a search for natural herbicides, we investigated the action mechanism of the naphthoquinone spiroketals, isolated from the endophytic fungus Edenia gomezpompae: preussomerins EG1 (1) and EG4 (2), and palmarumycins CP17 (3), and CP2 (4) on the photosynthesis light reactions. The naphthoquinone spiroketals 1-4 inhibited the ATP synthesis in freshly lysed spinach thylakoids from water to MV, and they also inhibited the non-cyclic electron transport in the basal, phosphorylating and uncoupled conditions from water to MV. Therefore, they act as Hill reaction inhibitors. The results suggested that naphthoquinone spiroketals 1-4 have two interactions and inhibition site on the PSII electron transport chain. The first one involves the water splitting enzyme inhibition; and, the second on the acceptor site of PSII in a similar way that herbicide Diuron, studied by polaroghaphy and corroborated by fluorescence of the chlorophyll a of PSII. The culture medium and mycelium organic extracts from four morphological variants of E. gomezpompae were phytotoxic, and the culture medium extracts were more potent than mycelium extracts. They also act as Hill reaction inhibitors. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Femtosecond stage of electron transfer in reaction centers of the triple mutant SL178K/GM203D/LM214H of Rhodobacter sphaeroides.

    Science.gov (United States)

    Yakovlev, A G; Shkuropatova, T A; Shkuropatova, V A; Shuvalov, V A

    2010-04-01

    Coherent processes in an initial phase of charge transfer in reaction centers (RCs) of the triple mutant S(L178)K/G(M203)D/L(M214)H of Rhodobacter sphaeroides were investigated by difference (light - dark) absorption spectroscopy with 18 fsec time resolution. Electron transfer in the B cofactor branch is activated in this mutant, while the A-branch electron transfer is slowed in comparison with native RCs of Rba. sphaeroides. A bulk of absorption difference spectra was analyzed in the 940-1060 nm range (stimulated emission of excited bacteriochlorophyll dimer P* and absorption of bacteriochlorophyll anions B(A)(-) and beta(-), where beta is a bacteriochlorophyll substituting the native bacteriopheophytin H(A)) and in the 735-775 nm range (bleaching of the absorption band of the bacteriopheophytin H(B) in the B-branch) in the -0.1 to 4 psec range of delays with respect to the moment of photoexcitation of P at 870 nm. Spectra were measured at 293 and 90 K. The kinetics of P* stimulated emission at 940 nm shows its decay with a time constant of approximately 14 psec at 90 K and approximately 18 psec at 293 K, which is accompanied by oscillations with a frequency of approximately 150 cm(-1). A weak absorption band is found at 1018 nm that is formed approximately 100 fsec after excitation of P and reflects the electron transfer from P* to beta and/or B(A) with accumulation of the P(+)beta(-) and/or P(+)B(A)(-) states. The kinetics of DeltaA at 1018 nm contains the oscillations at approximately 150 cm(-1) and distinct low-frequency oscillations at 20-100 cm(-1); also, the amplitude of the oscillations at 150 cm(-1) is much smaller at 293 than at 90 K. The oscillations in the kinetics of the 1018 nm band do not contain a 32 cm(-1) mode that is characteristic for native Rba. sphaeroides RCs having water molecule HOH55 in their structure. The DeltaA kinetics at 751 nm reflects the electron transfer to H(B) with formation of the P(+)H(B)(-) state. The oscillatory part of

  7. Effects of Ni2+ toxicity on Hill reaction and membrane functionality in maize

    Directory of Open Access Journals (Sweden)

    Ghasemi F.

    2012-11-01

    Full Text Available Soil contamination with heavy metals has become a worldwide problem, leading to losses in agricultural yield and hazardous health effects as they enter the food chain . Nickel as an essential trace element, affect a number of biochemical and physiological processes in plants in toxic levels. The most common symptoms are chlorosis, and inhibited photosynthesis and respiration. Zea mays seeds were germinated and cultured on nutrient solution with nickel concentrations of 50-200 μmol for a period of two weeks. Studied physiological makers included photosynthetic pigments content, the rate of Hill reaction, K+ efflux and carbohydrate leakage from the roots to the external solution and cell death as a Ni-induced membrane damage. By increasing Ni concentration up to 100 μmol, the content of chlorophyll a increased, but decreased at 200 μmol Ni. No significant changes in chlorophyll b and carotinoids content observed.The rate of Hill reaction as an ability of chlorophyll a in the reaction center of PSII680 to split water, decreased by increasing Ni concentration. Different concentrations of nickel increased the K+ efflux and sugar leakage from roots to the culture and the cell death of root tips. The present results suggested that the disruption of photosynthesis by Ni cannot be attributed to any single factor and appears to result from its combined effects on chloroplast structure, chlorophyll content and photosynthetic protein complexes and treatment with different levels of nickel may induce structural damage and alterations in membrane properties by generation of reactive oxygen species.

  8. Correlated behavior of the EPR signal of cytochrome b-559 heme Fe(III) ligated by OH- and the multiline signal of the Mn cluster in PS-II membrane fragments.

    Science.gov (United States)

    Fiege, R; Shuvalov, V A

    1996-05-27

    EPR signals of Cyt b-559 heme Fe(III) ligated by OH- and the multiline signal of the Mn cluster in PS-II membrane fragments have been investigated. In 2,3-dicyano-5,6-dichloro-p-benzoquinone-oxidized PS-II membrane fragments the light-induced decrease of the EPR signal of the heme Fe(III)-OH- is accompanied by the appearance of the EPR multiline signal of the Mn cluster. Addition of F- ions, which act as a stronger ligand for heme Fe(III) than OH-, decreases to the same extent the dark- and light-induced signal of the heme Fe(III)-OH- and the light-induced multiline signal of the Mn cluster. These results are discussed in terms of the light-induced formation of a bound OH' radical shared between the Cyt b-559 heme Fe and the Mn cluster as a first step of water oxidation.

  9. Improved UV-B screening capacity does not prevent negative effects of ambient UV irradiance on PSII performance in High Arctic plants. Results from a six year UV exclusion study

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Mikkelsen, Teis Nørgaard; Ro-Poulsen, H.

    2010-01-01

    Long-term responses of ambient solar ultraviolet (UV) radiation were investigated on Salix arctica and Vaccinium uliginosum in a High Arctic heath ecosystem in Zackenberg, northeast Greenland. Over a period of six years, UV exclusion was conducted in the growing season by means of filters: 60% UV......-B reduction, 90% UV-B + UV-A reduction, UV transparent filter control, and an open control without filter. Plant responses were evaluated using specific leaf area, leaf content of UV-B absorbing compounds and PSII performance parameters derived from chlorophyll-a fluorescence induction curves. Based...... increased TRo/ABS = FV/FM and REo/ETo. These results demonstrate the current level of ambient UV-B to decrease PSII performance significantly in these High Arctic plants. It appears that the two plant species both have improved their UV-screening capacity, but through different strategies, although this did...

  10. Systematics of inclusive photon production in 158 center dot A GeVPb induced reactions on Ni, Nb, and Pb targets

    NARCIS (Netherlands)

    Aggarwal, MM; Agnihotri, A; Ahammed, Z; Angelis, ALS; Antonenko, [No Value; Arefiev, [No Value; Astakhov, [No Value; Avdeitchikov, [No Value; Awes, TC; Baba, PVKS; Badyal, SK; Baldine, A; Barabach, L; Barlag, C; Bathe, S; Batiounia, B; Bernier, T; Bhalla, KB; Bhatia, VS; Blume, C; Bock, R; Bohne, EM; Borocz, Z; Bucher, D; Buijs, A; Busching, H; Carlen, L; Chalyshev, [No Value; Chattopadhyay, S; Cherbatchev, R; Chujo, T; Claussen, A; Das, AC; Decowski, MP; Djordjadze, [No Value; Donni, P; Doubovik, [No Value; Dutt, S; Majumdar, MRD; El Chenawi, K; Eliseev, S; Enosawa, K; Foka, P; Fokin, S; Frolov, [No Value; Ganti, MS; Garpman, S; Gavrishchuk, O; Geurts, FJM; Ghosh, TK; Glasow, R; Gupta, SK; Guskov, B; Gustafsson, H.A.; Gutbrod, HH; Higuchi, R; Hrivnacova, [No Value; Ippolitov, M; Kalechofsky, H; Kamermans, R; Kampert, KH; Karadjev, K; Karpio, K; Kato, S; Kees, S; Kim, H; Kolb, BW; Kosarev, [No Value; Koutcheryaev, [No Value; Krumpel, T; Kugler, A; Kulinich, P; Kurata, M; Kurita, K; Kuzmin, N; Langbein, [No Value; Lebedev, A; Lee, YY; Lohner, H; Luquin, L; Mahapatra, DP; Manko, [No Value; Martin, M; Maximov, A; Mehdiyev, R; Mgebrichvili, G; Miake, Y; Mikhalev, D; Mir, MF; Mishra, GC; Miyamoto, Y; Morrison, D; Mukhopadhyay, DS; Myalkovski, [No Value; Naef, H; Nandi, BK; Nayak, SK; Nayak, TK; Neumaier, S; Nianine, A; Nikitine, [No Value; Nikolaev, S; Nilsson, P; Nishimura, S; Nomokonov, P; Nystrand, J; Obenshain, FE; Oskarsson, A; Otterlund, [No Value; Pachr, M; Parfenov, A; Pavliouk, S; Peitzmann, T; Petracek, [No Value; Plasil, F; Pinanaud, W; Purschke, ML; Raeven, B; Rak, J; Raniwala, R; Raniwala, S; Ramamurthy, VS; Rao, NK; Retiere, F; Reygers, K; Roland, G; Rosselet, L; Roufanov, [No Value; Roy, C; Rubio, JM; Sako, H; Sambyal, SS; Santo, R; Sato, S; Schlagheck, H; Shabratova, G; Shah, TH; Sibiriak, [No Value; Siemiarczuk, T; Silvermyr, D; Sinha, BC; Slavine, N; Soderstrom, K; Solomey, N; Sorensen, SP; Stankus, P; Stefanek, G; Steinberg, P; Stenlund, E; Stuken, D; Sumbera, M; Svensson, T; Trivedi, MD; Tsvetkov, A.; Twenhofel, C; Tykarski, L; Urbahn, J; Von Eijndhoven, N; Von Nieuwenhuizen, GJ; Vinogradov, A; Viyogi, YP; Vodopianov, A; Voros, S; Wyslouch, B; Yagi, K; Yokota, Y; Young, GR

    1999-01-01

    The multiplicity of inclusive photons has been measured on an event-by-event basis for 158.A GeV Pb induced reactions on Ni, Nb, and Pb targets. The systematics of the pseudorapidity densities at midrapidity (rho(max)) and the width of the pseudorapidity distributions have been studied for varying

  11. Gymnosperms have increased capacity for electron leakage to oxygen (Mehler and PTOX reactions) in photosynthesis compared with angiosperms.

    Science.gov (United States)

    Shirao, Masayoshi; Kuroki, Shu; Kaneko, Kaoru; Kinjo, Yuriko; Tsuyama, Michito; Förster, Britta; Takahashi, Shunichi; Badger, Murray R

    2013-07-01

    Oxygen plays an important role in photosynthesis by participating in a number of O2-consuming reactions. O2 inhibits CO2 fixation by stimulating photorespiration, thus reducing plant production. O2 interacts with photosynthetic electron transport in the chloroplasts' thylakoids in two main ways: by accepting electrons from PSI (Mehler reaction); and by accepting electrons from reduced plastoquinone (PQ) mediated by the plastid terminal oxidase (PTOX). In this study, we show, using 101 plant species, that there is a difference in the potential for photosynthetic electron flow to O2 between angiosperms and gymnosperms. We found, from measurements of Chl fluorescence and leaf absorbance at 830 nm, (i) that electron outflow from PSII, as determined by decay kinetics of Chl fluorescence after application of a saturating light pulse, is more rapid in gymnosperms than in angiosperms; (ii) that the reaction center Chl of PSI (P700) is rapidly and highly oxidized in gymnosperms during induction of photosynthesis; and (iii) that these differences are dependent on oxygen. Finally, rates of O2 uptake measured by mass spectrometry in the absence of photorespiration were significantly promoted by illumination in dark-adapted leaves of gymnosperms, but not in those of angiosperms. The light-stimulated O2 uptake was around 10% of the maximum O2 evolution in gymnosperms and 1% in angiosperms. These results suggest that gymnosperms have increased capacity for electron leakage to oxygen in photosynthesis compared with angiosperms. The involvement of the Mehler reaction and PTOX in the electron flow to O2 is discussed.

  12. Predawn and high intensity application of supplemental blue light decreases the quantum yield of PSII and enhances the amount of phenolic acids, flavonoids, and pigments in Lactuca sativa.

    Science.gov (United States)

    Ouzounis, Theoharis; Razi Parjikolaei, Behnaz; Fretté, Xavier; Rosenqvist, Eva; Ottosen, Carl-Otto

    2015-01-01

    To evaluate the effect of blue light intensity and timing, two cultivars of lettuce [Lactuca sativa cv. "Batavia" (green) and cv. "Lollo Rossa" (red)] were grown in a greenhouse compartment in late winter under natural light and supplemental high pressure sodium (SON-T) lamps yielding 90 (±10) μmol m(-2) s(-1) for up to 20 h, but never between 17:00 and 21:00. The temperature in the greenhouse compartments was 22/11°C day/night, respectively. The five light-emitting diode (LED) light treatments were Control (no blue addition), 1B 06-08 (Blue light at 45 μmol m(-2) s(-1) from 06:00 to 08:00), 1B 21-08 (Blue light at 45 μmol m(-2) s(-1) from 21:00 to 08:00), 2B 17-19 (Blue at 80 μmol m(-2) s(-1) from 17:00 to 19:00), and 1B 17-19 (Blue at 45 μmol m(-2) s(-1) from 17:00 to 19:00). Total fresh and dry weight was not affected with additional blue light; however, plants treated with additional blue light were more compact. The stomatal conductance in the green lettuce cultivar was higher for all treatments with blue light compared to the Control. Photosynthetic yields measured with chlorophyll fluorescence showed different response between the cultivars; in red lettuce, the quantum yield of PSII decreased and the yield of non-photochemical quenching increased with increasing blue light, whereas in green lettuce no difference was observed. Quantification of secondary metabolites showed that all four treatments with additional blue light had higher amount of pigments, phenolic acids, and flavonoids compared to the Control. The effect was more prominent in red lettuce, highlighting that the results vary among treatments and compounds. Our results indicate that not only high light level triggers photoprotective heat dissipation in the plant, but also the specific spectral composition of the light itself at low intensities. However, these plant responses to light are cultivar dependent.

  13. Predawn and high intensity application of supplemental blue light decreases the quantum yield of PSII and enhances the amount of phenolic acids, flavonoids, and pigments in Lactuca sativa.

    Directory of Open Access Journals (Sweden)

    Theoharis eOuzounis

    2015-02-01

    Full Text Available To evaluate the effect of blue light intensity and timing, two cultivars of lettuce [Lactuca sativa cv. ’Batavia’ (green and cv. ‘Lollo Rossa’ (red] were grown in a greenhouse compartment in late winter under natural light and supplemental high pressure sodium (SON-T lamps yielding 90 (±10 µmol m-2 s-1 for up to 20 hr, but never between 17:00 and 21:00. The temperature in the greenhouse compartments was 22/11°C day/night, respectively. The five light-emitting diode (LED light treatments were Control (no blue addition, 1B 06-08 (Blue light at 45 µmol m-2 s-1 from 06:00 to 08:00, 1B 21-08 (Blue light at 45 µmol m-2 s-1 from 21:00 to 08:00, 2B 17-19 (Blue at 80 µmol m-2 s-1 from 17:00 to 19:00, and (1B 17-19 Blue at 45 µmol m-2 s-1from 17:00 to 19:00. Total fresh and dry weight was not affected with additional blue light; however, plants treated with additional blue light were more compact. The stomatal conductance in the green lettuce cultivar was higher for all treatments with blue light compared to the Control. Photosynthetic yields measured with chlorophyll fluorescence showed different response between the cultivars; in red lettuce, the quantum yield of PSII decreased and the yield of non-photochemical quenching increased with increasing blue light, whereas in green lettuce no difference was observed. Quantification of secondary metabolites showed that all four treatments with additional blue light had higher amount of pigments, phenolic acids, and flavonoids compared to the Control. The effect was more prominent in red lettuce, highlighting that the results vary among treatments and compounds. Our results indicate that not only high light level triggers photoprotective heat dissipation in the plant, but also the specific spectral composition of the light itself at low intensities. However, these plant responses to light are cultivar dependent.

  14. Predawn and high intensity application of supplemental blue light decreases the quantum yield of PSII and enhances the amount of phenolic acids, flavonoids, and pigments in Lactuca sativa

    Science.gov (United States)

    Ouzounis, Theoharis; Razi Parjikolaei, Behnaz; Fretté, Xavier; Rosenqvist, Eva; Ottosen, Carl-Otto

    2015-01-01

    To evaluate the effect of blue light intensity and timing, two cultivars of lettuce [Lactuca sativa cv. “Batavia” (green) and cv. “Lollo Rossa” (red)] were grown in a greenhouse compartment in late winter under natural light and supplemental high pressure sodium (SON-T) lamps yielding 90 (±10) μmol m−2 s−1 for up to 20 h, but never between 17:00 and 21:00. The temperature in the greenhouse compartments was 22/11°C day/night, respectively. The five light-emitting diode (LED) light treatments were Control (no blue addition), 1B 06-08 (Blue light at 45 μmol m−2 s−1 from 06:00 to 08:00), 1B 21-08 (Blue light at 45 μmol m−2 s−1 from 21:00 to 08:00), 2B 17-19 (Blue at 80 μmol m−2 s−1 from 17:00 to 19:00), and 1B 17-19 (Blue at 45 μmol m−2 s−1 from 17:00 to 19:00). Total fresh and dry weight was not affected with additional blue light; however, plants treated with additional blue light were more compact. The stomatal conductance in the green lettuce cultivar was higher for all treatments with blue light compared to the Control. Photosynthetic yields measured with chlorophyll fluorescence showed different response between the cultivars; in red lettuce, the quantum yield of PSII decreased and the yield of non-photochemical quenching increased with increasing blue light, whereas in green lettuce no difference was observed. Quantification of secondary metabolites showed that all four treatments with additional blue light had higher amount of pigments, phenolic acids, and flavonoids compared to the Control. The effect was more prominent in red lettuce, highlighting that the results vary among treatments and compounds. Our results indicate that not only high light level triggers photoprotective heat dissipation in the plant, but also the specific spectral composition of the light itself at low intensities. However, these plant responses to light are cultivar dependent. PMID:25767473

  15. Intrahepatic B-cell follicles of chronically hepatitis C virus-infected individuals lack signs of an ectopic germinal center reaction.

    Science.gov (United States)

    Tucci, Felicia A; Broering, Ruth; Lutterbeck, Melanie; Schlaak, Joerg F; Küppers, Ralf

    2014-06-01

    Chronic infection with hepatitis C virus (HCV) often affects the B-cell compartment, leading to the occurrence of autoimmunity and B-cell lymphoproliferation, in particular mixed cryoglobulinemia and B-cell lymphomas. HCV presumably causes these lymphoproliferations by chronic antigenic stimulation and/or direct mutagenic effects on B cells. It has been speculated that the interaction of HCV with B cells and the expansion of antigen-triggered B cells happens in germinal center-like structures in the livers of HCV carriers. We studied rearranged immunoglobulin V(H) genes from seven B-cell follicles microdissected from the livers of three unselected chronic HCV patients. The follicles consisted of polyclonal naive and memory B-cell populations with only rare indication of minor clonal expansions and no evidence for active somatic hypermutation. Frequent detection of V(H) rearrangements using the VH1-69 gene segment nevertheless indicated that at least a fraction of the B cells is HCV-specific and/or autoreactive. Thus, the typical intrahepatic B-cell follicles in chronic HCV carriers do not function as ectopic germinal centers for clonal expansion and affinity maturation of B cells. Hence, autoreactive and HCV-specific B-cell clones might either develop in secondary lymphoid organs or in intrahepatic follicles only under particular, yet undefined, circumstances. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Retrospective analysis of non-laboratory-based adverse drug reactions induced by intravenous radiocontrast agents in a Joint Commission International-accredited academic medical center hospital in China

    Directory of Open Access Journals (Sweden)

    Chen QL

    2017-04-01

    Full Text Available Qin-lan Chen,1 Xiao-ying Zhao,2 Xiao-mi Wang,1 Na Lv,2 Ling-ling Zhu,3 Hui-min Xu,4 Quan Zhou4 1Radiology Nursing Unit, Division of Nursing, 2Department of Quality Management, 3Geriatric VIP Care Ward, Division of Nursing, 4Department of Pharmacy, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, People’s Republic of China Abstract: The authors retrospectively analyzed the pattern and characteristics of non-laboratory-based adverse drug reactions (ADRs induced by intravenous radiocontrast agents in a large-scale hospital in China during 2014–2015. There were 314 ADR cases among 118,208 patients receiving enhanced CT or MRI examinations. The frequency of moderate/severe ADRs defined by Chinese Society of Radiology (ie, severe vomiting, systematic urticaria, facial swelling, dyspnea, vasovagal reaction, laryngeal edema, seizure, trembling, convulsions, unconsciousness, shock, death, and other unexpected adverse reactions was rare (0.0431%, whereas the mild ADRs were uncommon (0.2225% and accounted for 83.76% of ADRs. Frequency of ADRs induced by iodinated contrast agents was related with examination site, sex, and type of patient settings (P<0.01 and was higher compared with gadolinium contrast agents (0.3676% vs 0.0504%, P<0.01. From 2014 to 2015, frequencies of total and moderate/severe ADRs induced by iodinated contrast agents decreased significantly (0.4410% vs 0.2947%, P<0.01; 0.0960% vs 0.0282%, P<0.01, respectively. Frequency of ADRs differed among different iodinated contrast and gadolinium contrast (P<0.05 agents. Iopromide’s ADR frequency in 2014 was significantly higher compared with iopamidol, ioversol, or iohexol (P<0.01. Frequency of moderate/severe ADRs induced by iodixanol was 4.1–5.4 times that of iohexol, iopromide, or iopamidol. Rash was the predominant ADR subtype (84.39% and occurred more frequently with iodixanol compared with iohexol, iopamidol, or ioversol (P<0

  17. Reaction-Based Reactive Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center

    Energy Technology Data Exchange (ETDEWEB)

    Burgos, W.D.

    2009-09-02

    This report summarizes research conducted in conjunction with a project entitled “Reaction-Based Reactive Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center”, which was funded through the Integrative Studies Element of the former NABIR Program (now the Environmental Remediation Sciences Program) within the Office of Biological and Environmental Research. Dr. William Burgos (The Pennsylvania State University) was the overall PI/PD for the project, which included Brian Dempsey (Penn State), Gour-Tsyh (George) Yeh (Central Florida University), and Eric Roden (formerly at The University of Alabama, now at the University of Wisconsin) as separately-funded co-PIs. The project focused on development of a mechanistic understanding and quantitative models of coupled Fe(III)/U(VI) reduction in FRC Area 2 sediments. The work builds on our previous studies of microbial Fe(III) and U(VI) reduction, and was directly aligned with the Scheibe et al. ORNL FRC Field Project at Area 2.

  18. Effects of acute O3 stress on PSII and PSI photochemistry of sensitive and resistant snap bean genotypes (Phaseolus vulgaris L.), probed by prompt chlorophyll "a" fluorescence and 820 nm modulated reflectance.

    Science.gov (United States)

    Salvatori, Elisabetta; Fusaro, Lina; Strasser, Reto J; Bussotti, Filippo; Manes, Fausto

    2015-12-01

    The response of PSII and PSI photochemistry to acute ozone (O3) stress was tested in a "model plant system", namely the O3 sensitive (S156) and O3 resistant (R123) genotype pairs of Phaseolus vulgaris L., during a phenological phase of higher O3 sensitivity (pod formation). The modulation of the photosynthetic activity during O3 stress was analysed by measuring gas exchanges, Prompt Fluorescence (PF, JIP-test) and 820 nm Modulated Reflectance (MR), a novel techniques which specifically detects the changes in the redox state of P700 and plastocyanin. The results showed that, coherently with genotypic-specific O3 sensitivity, the response of the two snap bean genotypes differed for the intensity and time of onset of the considered physiological changes. In fact, despite leaf injury and gas exchanges reduction appeared concurrently in both genotypes, S156 showed a PSII down regulation already after the first day of fumigation (DOF), and an enhancement of Cyclic Electron Flow of PSI after the second DOF, whereas R123 showed only slight adjustments until the third DOF, when the activity of both photosystems was down-regulated. Despite these differences, it is possible to distinguish in both genotypes an early O3 response of the photochemical apparatus, involving PSII only, and a following response, in which PSI activity and content are also modulated. The measurement of the MR signal, performed simultaneously with the PF measurements and the JIP-test analysis, has allowed a better understanding of the role that PSI plays in the O3 stress response of the S156/R123 model plant system. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  19. Cold-acclimation limits low temperature induced photoinhibition by promoting a higher photochemical quantum yield and a more effective PSII restoration in darkness in the Antarctic rather than the Andean ecotype of Colobanthus quitensis Kunt Bartl (Cariophyllaceae

    Directory of Open Access Journals (Sweden)

    Bascuñán-Godoy Luisa

    2012-07-01

    Full Text Available Abstract Background Ecotypes of Colobanthus quitensis Kunt Bartl (Cariophyllaceae from Andes Mountains and Maritime Antarctic grow under contrasting photoinhibitory conditions, reaching differential cold tolerance upon cold acclimation. Photoinhibition depends on the extent of photodamage and recovery capability. We propose that cold acclimation increases resistance to low-temperature-induced photoinhibition, limiting photodamage and promoting recovery under cold. Therefore, the Antarctic ecotype (cold hardiest should be less photoinhibited and have better recovery from low-temperature-induced photoinhibition than the Andean ecotype. Both ecotypes were exposed to cold induced photoinhibitory treatment (PhT. Photoinhibition and recovery of photosystem II (PSII was followed by fluorescence, CO2 exchange, and immunoblotting analyses. Results The same reduction (25% in maximum PSII efficiency (Fv/Fm was observed in both cold-acclimated (CA and non-acclimated (NA plants under PhT. A full recovery was observed in CA plants of both ecotypes under dark conditions, but CA Antarctic plants recover faster than the Andean ecotype. Under PhT, CA plants maintain their quantum yield of PSII, while NA plants reduced it strongly (50% and 73% for Andean and Antarctic plants respectively. Cold acclimation induced the maintenance of PsaA and Cyt b6/f and reduced a 41% the excitation pressure in Antarctic plants, exhibiting the lowest level under PhT. xCold acclimation decreased significantly NPQs in both ecotypes, and reduced chlorophylls and D1 degradation in Andean plants under PhT. NA and CA plants were able to fully restore their normal photosynthesis, while CA Antarctic plants reached 50% higher photosynthetic rates after recovery, which was associated to electron fluxes maintenance under photoinhibitory conditions. Conclusions Cold acclimation has a greater importance on the recovery process than on limiting photodamage. Cold acclimation determined the

  20. EPR spectroscopic characterization of the manganese center and a free radical in the oxalate decarboxylase reaction: identification of a tyrosyl radical during turnover.

    Science.gov (United States)

    Chang, Christopher H; Svedruzic, Drazenka; Ozarowski, Andrzej; Walker, Lee; Yeagle, Gregory; Britt, R David; Angerhofer, Alexander; Richards, Nigel G J

    2004-12-17

    Several molecular mechanisms for cleavage of the oxalate carbon-carbon bond by manganese-dependent oxalate decarboxylase have recently been proposed involving high oxidation states of manganese. We have examined the oxalate decarboxylase from Bacillus subtilis by electron paramagnetic resonance in perpendicular and parallel polarization configurations to test for the presence of such species in the resting state and during enzymatic turnover. Simulation and the position of the half-field Mn(II) line suggest a nearly octahedral metal geometry in the resting state. No spectroscopic signature for Mn(III) or Mn(IV) is seen in parallel mode EPR for samples frozen during turnover, consistent either with a large zero-field splitting in the oxidized metal center or undetectable levels of these putative high-valent intermediates in the steady state. A narrow, featureless g = 2.0 species was also observed in perpendicular mode in the presence of substrate, enzyme, and dioxygen. Additional splittings in the signal envelope became apparent when spectra were taken at higher temperatures. Isotopic editing resulted in an altered line shape only when tyrosine residues of the enzyme were specifically deuterated. Spectral processing confirmed multiple splittings with isotopically neutral enzyme that collapsed to a single prominent splitting in the deuterated enzyme. These results are consistent with formation of an enzyme-based tyrosyl radical upon oxalate exposure. Modestly enhanced relaxation relative to abiological tyrosyl radicals was observed, but site-directed mutagenesis indicated that conserved tyrosine residues in the active site do not host the unpaired spin. Potential roles for manganese and a peripheral tyrosyl radical during steady-state turnover are discussed.

  1. Energy transfer followed by electron transfer in a porphyrin macrocycle and central acceptor ligand: a model for a photosynthetic composite of the light-harvesting complex and reaction center.

    Science.gov (United States)

    Kuramochi, Yusuke; Sandanayaka, Atula S D; Satake, Akiharu; Araki, Yasuyuki; Ogawa, Kazuya; Ito, Osamu; Kobuke, Yoshiaki

    2009-01-01

    A system that models a photosynthetic composite of the light-harvesting complex and reaction center is reported in which light energy collected by cyclic antenna porphyrins is transferred to a central energy-acceptor porphyrin, followed by photoinduced electron transfer to a fullerene positioned above the ring plane. Pyridyl tripodal ligands appended with bis(phenylethynyl)porphyrinatozinc(II) (ZnP-Tripod) and additional fulleropyrrolidine moieties (C(60)-ZnP-Tripod) were synthesized as the reaction center units. The tripodal ligand was strongly accommodated by the light-harvesting porphyrin macrocycle N-(1-Zn)(3) (1-Zn = trisporphyrinatozinc(II)) by using three-point coordination of pyridyl to uncoordinated porphyrinatozinc sites to afford a stable 1:1 composite. The binding constants for ZnP-Tripod and C(60)-ZnP-Tripod in benzonitrile were estimated from steady-state fluorescence titrations to be 1.4x10(7) and 1.6x10(7) M(-1), respectively. The steady-state fluorescence titration, fluorescence lifetime, and transient absorption studies revealed that in both composites the excitation energy collected by the nine porphyrins of N-(1-Zn)(3) was efficiently transferred to a ZnP moiety by means of a through-space mechanism with a quantum yield of approximately 90%. Furthermore, in the composite with C(60)-ZnP-Tripod, the converged energy at the ZnP moiety induced electron transfer to the C(60) moiety, which afforded the stable charge-separated state (Phi(CS)>90%).

  2. Reaction Automata

    OpenAIRE

    Okubo, Fumiya; Kobayashi, Satoshi; YOKOMORI, Takashi

    2011-01-01

    Reaction systems are a formal model that has been introduced to investigate the interactive behaviors of biochemical reactions. Based on the formal framework of reaction systems, we propose new computing models called reaction automata that feature (string) language acceptors with multiset manipulation as a computing mechanism, and show that reaction automata are computationally Turing universal. Further, some subclasses of reaction automata with space complexity are investigated and their la...

  3. Analysis of the Electronic Structure of the Special Pair of a Bacterial Photosynthetic Reaction Center by 13 C Photochemically Induced Dynamic Nuclear Polarization Magic-Angle Spinning NMR Using a Double-Quantum Axis.

    Science.gov (United States)

    Najdanova, Marija; Gräsing, Daniel; Alia, A; Matysik, Jörg

    2018-01-01

    The origin of the functional symmetry break in bacterial photosynthesis challenges since several decades. Although structurally very similar, the two branches of cofactors in the reaction center (RC) protein complex act very differently. Upon photochemical excitation, an electron is transported along one branch, while the other remains inactive. Photochemically induced dynamic nuclear polarization (photo-CIDNP) magic-angle spinning (MAS) 13 C NMR revealed that the two bacteriochlorophyll cofactors forming the "Special Pair" donor dimer are already well distinguished in the electronic ground state. These previous studies are relying solely on 13 C-13 C correlation experiments as radio-frequency-driven recoupling (RFDR) and dipolar-assisted rotational resonance (DARR). Obviously, the chemical-shift assignment is difficult in a dimer of tetrapyrrole macrocycles, having eight pyrrole rings of similar chemical shifts. To overcome this problem, an INADEQUATE type of experiment using a POST C7 symmetry-based approach is applied to selectively isotope-labeled bacterial RC of Rhodobacter (R.) sphaeroides wild type (WT). We, therefore, were able to distinguish unresolved sites of the macromolecular dimer. The obtained chemical-shift pattern is in-line with a concentric assembly of negative charge within the common center of the Special Pair supermolecule in the electronic ground state. © 2017 The American Society of Photobiology.

  4. The effect of light and temperature on the dynamic state of Rhodobacter sphaeroides reaction centers proteins determined from changes in tryptophan fluorescence lifetime and P+QA-recombination kinetics.

    Science.gov (United States)

    Knox, Peter P; Gorokhov, Vladimir V; Korvatovskiy, Boris N; Lukashev, Eugene P; Goryachev, Sergey N; Paschenko, Vladimir Z; Rubin, Andrew B

    2018-02-06

    The temperature dependencies of the rate of dark recombination of separated charges between the photoactive bacteriochlorophyll and the primary quinone acceptor (Q A ) in photosynthetic reaction centers (RCs) of the purple bacteria Rhodobacter sphaeroides (Rb. sphaeroides) were investigated. Measurements were performed in water-glycerol and trehalose environments after freezing to -180 °C in the dark and under actinic light with subsequent heating. Simultaneously, the RC tryptophanyl fluorescence lifetime in the spectral range between 323 and 348 nm was measured under these conditions. A correlation was found between the temperature dependencies of the functional and dynamic parameters of RCs in different solvent mixtures. For the first time, differences in the average fluorescence lifetime of tryptophanyl residues were measured between RCs frozen in the dark and in the actinic light. The obtained results can be explained by the RC transitions between different conformational states and the dynamic processes in the structure of the hydrogen bonds of RCs. We assumed that RCs exist in two main microconformations - "fast" and "slow", which are characterized by different rates of P + and Q A - recombination reactions. The "fast" conformation is induced in frozen RCs in the dark, while the "slow" conformation of RC occurs when the RC preparation is frozen under actinic light. An explanation of the temperature dependencies of tryptophan fluorescence lifetimes in RC proteins was made under the assumption that temperature changes affect mainly the electron transfer from the indole ring of the tryptophan molecule to the nearest amide or carboxyl groups. Copyright © 2018. Published by Elsevier B.V.

  5. Translation of Ligand-Centered Hydrogen Evolution Reaction Activity and Mechanism of a Rhenium-Thiolate from Solution to Modified Electrodes: A Combined Experimental and Density Functional Theory Study.

    Science.gov (United States)

    Zhang, Wuyu; Haddad, Andrew Z; Garabato, Brady D; Kozlowski, Pawel M; Buchanan, Robert M; Grapperhaus, Craig A

    2017-02-20

    The homogeneous, nonaqueous catalytic activity of the rhenium-thiolate complex ReL3 (L = diphenylphosphinobenzenethiolate) for the hydrogen evolution reaction (HER) has been transferred from nonaqueous homogeneous to aqueous heterogeneous conditions by immobilization on a glassy carbon electrode surface. A series of modified electrodes based on ReL3 and its oxidized precursor [ReL3][PF6] were fabricated by drop-cast methods, yielding catalytically active species with HER overpotentials for a current density of 10 mA/cm(2), ranging from 357 to 919 mV. The overpotential correlates with film resistance as measured by electrochemical impedance spectroscopy and film morphology as determined by scanning and transmission electron microscopy. The lowest overpotential was for films based on the ionic [ReL3][PF6] precursor with the inclusion of carbon black. Stability measurements indicate a 2 to 3 h conditioning period in which the overpotential increases, after which no change in activity is observed within 24 h or upon reimmersion in fresh aqueous, acidic solution. Electronic spectroscopy results are consistent with ReL3 as the active species on the electrode surface; however, the presence of an undetected quantity of catalytically active degradation species cannot be excluded. The HER mechanism was evaluated by Tafel slope analysis, which is consistent with a novel Volmer-Heyrovsky-Tafel-like mechanism that parallels the proposed homogeneous HER pathway. Proposed mechanisms involving traditional metal-hydride processes vs ligand-centered reactivity were examined by density functional theory, including identification and characterization of relevant transition states. The ligand-centered path is energetically favored with protonation of cis-sulfur sites culminating in homolytic S-H bond cleavage with H2 evolution via H atom coupling.

  6. Drug Reactions

    Science.gov (United States)

    ... or diabetes. But medicines can also cause unwanted reactions. One problem is interactions, which may occur between ... more serious. Drug allergies are another type of reaction. They can be mild or life-threatening. Skin ...

  7. Comparative analysis of mutant plants impaired in the main regulatory mechanisms of photosynthetic light reactions - From biophysical measurements to molecular mechanisms.

    Science.gov (United States)

    Tikkanen, Mikko; Rantala, Sanna; Grieco, Michele; Aro, Eva-Mari

    2017-03-01

    Chlorophyll (chl) fluorescence emission by photosystem II (PSII) and light absorption by P700 reaction center chl a of photosystem I (PSI) provide easy means to probe the function of the photosynthetic machinery. The exact relationship between the measured optical variables and the molecular processes have, however, remained elusive. Today, the availability of mutants with distinct molecular characterization of photosynthesis regulatory processes should make it possible to gain further insights into this relationship, yet a systematic comparative analysis of such regulatory mutants has been missing. Here we have systematically compared the behavior of Dual-PAM fluorescence and P700 variables from well-characterized photosynthesis regulation mutants. The analysis revealed a very convincing relationship between the given molecular deficiency in the photosynthetic apparatus and the original fluorescence and P700 signals obtained by using varying intensities of actinic light and by applying a saturating pulse. Importantly, the specific information on the underlying molecular mechanism, present in these authentic signals of a given photosynthesis mutant, was largely nullified when using the commonly accepted parameters that are based on further treatment of the original signals. Understanding the unique relationship between the investigated molecular process of photosynthesis and the measured variable is an absolute prerequisite for comprehensive interpretation of fluorescence and P700 measurements. The data presented here elucidates the relationships between the main regulatory mechanisms controlling the photosynthetic light reactions and the variables obtained by fluorescence and P700 measurements. It is discussed how the full potential of optical photosynthesis measurements can be utilized in investigation of a given molecular mechanism. Copyright © 2017 The Authors. Published by Elsevier Masson SAS.. All rights reserved.

  8. Incidence of antiretroviral adverse drug reactions in pregnant women in two referral centers for HIV prevention of mother-to-child-transmission care and research in Rio de Janeiro, Brazil

    Directory of Open Access Journals (Sweden)

    Marilia Santini-Oliveira

    Full Text Available Mother-to-child transmission (MTCT of human immunodeficiency virus (HIV infection remains an important cause of new HIV infections worldwide, especially in low and middle-resource limited countries. Safety data from studies involving pregnant women and prenatal antiretroviral (ARV exposure are still needed once these studies are often small and with a limited duration to assess adverse drug reactions (ADR. The aim of this study was to estimate the incidence of ADR related to the use of antiretroviral therapy (ART in pregnant women in two referral centers in Rio de Janeiro State. A prospective study was carried out from February 2005 to May 2006. Women were classified according to their ART status during pregnancy diagnosis: ARV-experienced (ARTexp or ARV-naïve (ARTn. Two hundred fourteen HIV-infected pregnant women were included: 36 ARTexp and 178 ARTn. ARTexp women have not experienced ADR. Among ARTn, 20.2% presented ADR. Incidence rate of ADR was 70.8 per 1000 person-months and the most common ADRs observed were: gastrointestinal (belly or abdominal cramps, diarrhea, nausea and vomit in 16.3%, cutaneous (pruritus and rash in 6.2%, anemia (2.2% and hepatitis (1.7%. The frequency of obstetrical complications, pre-term delivery, low birth weight and birth abnormalities was low in this population. ADRs ranged from mild to moderate intensity, none of them being potentially fatal. Only in a few cases it was necessary to discontinue ART. In conclusion, the high effectiveness of ARV for HIV prevention of MTCT (PMTCT overcomes the risk of ADR.

  9. Heterologous Production of the Photosynthetic Reaction Center and Light Harvesting 1 Complexes of the Thermophile Thermochromatium tepidum in the Mesophile Rhodobacter sphaeroides and Thermal Stability of a Hybrid Core Complex.

    Science.gov (United States)

    Jun, D; Huang, V; Beatty, J T

    2017-10-15

    The photosynthetic complexes of the thermophile Thermochromatium tepidum are of considerable interest in biohybrid solar cell applications because of the ability of thermophilic proteins to tolerate elevated temperatures. Synthetic operons encoding reaction center (RC) and light harvesting 1 (LH1) pigment-protein complexes of T. tepidum were expressed in the mesophile Rhodobacter sphaeroides The T. tepidum RC (TRC) was assembled and was found to be functional with the addition of menadione to populate the QA pocket. The production of T. tepidum LH1 (TLH1) was increased by selection of a phototrophy-capable mutant after UV irradiation mutagenesis, which yielded a hybrid RC-TLH1 core complex consisting of the R. sphaeroides RC and T. tepidum TLH1, confirmed by the absorbance peak of TLH1 at 915 nm. Affinity chromatography partial purification and subsequent sucrose gradient analysis of the hybrid RC-TLH1 core complex indicated that this core complex assembled as a monomer. Furthermore, the RC-TLH1 hybrid core complex was more tolerant of a temperature of 70°C than the R. sphaeroides RC-LH1 core complexes in both the dimeric and monomeric forms; after 1 h, the hybrid complex retained 58% of the initial starting value, compared to values of 11% and 53% for the R. sphaeroides RC-LH1 dimer and monomer forms, respectively.IMPORTANCE This work is important because it is a new approach to bioengineering of photosynthesis proteins for potential use in biophotovoltaic solar energy capture. The work establishes a proof of principle for future biohybrid solar cell applications. Copyright © 2017 American Society for Microbiology.

  10. Reference: 630 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available of the RNAs encoding the PSII subunits are unaltered in the mutant. In vivo protein-labeling experiments sho...wed that the synthesis of CP43 (for chlorophyll a binding protein) was greatly reduced, but CP47, D1, and D2 were...3 was rapidly degraded in lpa2-1, and the turnover rates of D1 and D2 were higher in lpa2-1 than in wild-typ...e plants. The newly synthesized PSII proteins were assembled into PSII complexes, but the assembly of PSII w...hat LPA2 interacts with the PSII core protein CP43 but not with the PSII reaction center proteins D1 and D2. Moreover, dire

  11. Quantum - coherent dynamics in photosynthetic charge separation revealed by wavelet analysis

    NARCIS (Netherlands)

    Romero, Elisabet; Prior, Javier; Chin, Alex W.; Morgan, Sarah E.; Novoderezhkin, Vladimir I.; Plenio, Martin B.; van Grondelle, Rienk

    2017-01-01

    Experimental/theoretical evidence for sustained vibration-assisted electronic (vibronic) coherence in the Photosystem II Reaction Center (PSII RC) indicates that photosynthetic solar-energy conversion might be optimized through the interplay of electronic and vibrational quantum dynamics. This

  12. The triterpenes 3β-lup-20(29)-en-3-ol and 3β-lup-20(29)-en-3-yl acetate and the carbohydrate 1,2,3,4,5,6-hexa-O-acetyl-dulcitol as photosynthesis light reactions inhibitors.

    Science.gov (United States)

    Menezes-de-Oliveira, Djalma; Aguilar, Maria-Isabel; King-Díaz, Beatriz; Vieira-Filho, Sidney Augusto; Pains-Duarte, Lucinier; Silva, Grácia-Divina de Fátima; Lotina-Hennsen, Blas

    2011-12-01

    Three compounds were isolated from Maytenus acanthophylla Reissek (Celastraceae): the pentacyclic triterpenes lup-20(29)-en-3β-ol (lupeol, 1) and 3β-lup-20(29)-en-3-yl acetate (2) and the carbohydrate 1,2,3,4,5,6-hexa-O-acetyldulcitol (3); lupeol was also isolated from Xylosma flexuosa. The compounds' structures were elucidated by spectroscopic and spectrometric analysis. Compound 1 acts as an energy transfer inhibitor, interacting with isolated CF₁ bound to thylakoid membrane, and dulcitol hexaacetate 3 behaves as a Hill reaction inhibitor and as an uncoupler, as determined by polarography. Chlorophyll a (Chl a) fluorescence induction kinetics from the minimum yield F₀ to the maximum yield F(M )provides information of the filling up from electrons coming from water to plastoquinone pool with reducing equivalents. In this paper we have examined the effects of compounds 1 and 3 on spinach leaf discs. Compound 1 induces the appearance of a K-band, which indicates that it inhibits the water splitting enzyme. In vivo assays measuring the fluorescence of chl a in P. ixocarpa leaves sprayed with compound 1, showed the appearance of the K-band and the PSII reaction centers was transformed to "heat sinks" or silent reaction centers unable to reduce Q(A). However, 3 also induced the appearance of a K band and a new band I appears in P. ixocarpa plants, therefore it inhibits at the water splitting enzyme complex and at the PQH₂ site on b₆f complex. Compounds 1 and 3 did not affect chlorophyll a fluorescence of L. perenne plants.

  13. The Triterpenes 3β-Lup-20(29-en-3-ol and 3β-Lup-20(29-en-3-yl Acetate and the Carbohydrate 1,2,3,4,5,6-Hexa-O-acetyl-dulcitol as Photosynthesis Light Reactions Inhibitors

    Directory of Open Access Journals (Sweden)

    Blas Lotina-Hennsen

    2011-12-01

    Full Text Available Three compounds were isolated from Maytenus acanthophylla Reissek (Celastraceae: the pentacyclic triterpenes lup-20(29-en-3β-ol (lupeol, 1 and 3β-lup-20(29-en-3-yl acetate (2 and the carbohydrate 1,2,3,4,5,6-hexa-O-acetyldulcitol (3; lupeol was also isolated from Xylosma flexuosa. The compounds’ structures were elucidated by spectroscopic and spectrometric analysis. Compound 1 acts as an energy transfer inhibitor, interacting with isolated CF1 bound to thylakoid membrane, and dulcitol hexaacetate 3 behaves as a Hill reaction inhibitor and as an uncoupler, as determined by polarography. Chlorophyll a (Chl a fluorescence induction kinetics from the minimum yield F0 to the maximum yield FM provides information of the filling up from electrons coming from water to plastoquinone pool with reducing equivalents. In this paper we have examined the effects of compounds 1 and 3 on spinach leaf discs. Compound 1 induces the appearance of a K-band, which indicates that it inhibits the water splitting enzyme. In vivo assays measuring the fluorescence of chl a in P. ixocarpa leaves sprayed with compound 1, showed the appearance of the K-band and the PSII reaction centers was transformed to “heat sinks” or silent reaction centers unable to reduce QA. However, 3 also induced the appearance of a K band and a new band I appears in P. ixocarpa plants, therefore it inhibits at the water splitting enzyme complex and at the PQH2 site on b6f complex. Compounds 1 and 3 did not affect chlorophyll a fluorescence of L. perenne plants.

  14. Photo-protective mechanisms in reed canary grass to alleviate photo-inhibition of PSII on the Qinghai-Tibet Plateau.

    Science.gov (United States)

    Zhang, Chao; Zhang, Da-Wei; Sun, Yan-Ni; Arfan, Muhammad; Li, Da-Xu; Yan, Jia-Jun; You, Ming-Hong; Bai, Shi-Qie; Lin, Hong-Hui

    2017-08-01

    Due to its characteristic of high biomass yield potential, there is considerable interest in cultivating Phalaris arundinacea L. cv. 'chuancaoyin No.3' (reed canary grass) on the Qinghai-Tibet Plateau where there is an abundance of alpine steppe meadow and a potential large market for animal husbandry. In this study, we 1) investigate whether reed canary grass exhibits superior productive capacity to Elymus nutans 'Aba' (E. nutans), ordinary common pasture, during the long warm days of summer at high-altitude; and 2) compare the cold tolerance between reed canary grass and E. nutans, including photosynthesis, photo-inhibition, and photo-protection. The results suggest that reed canary grass exhibits higher photosynthetic capacity compared to E. nutans at latitudes of the cool temperate zone. Meanwhile, cold-induced photo-inhibition and photo-damage at high altitudes in reed canary grass were due to both stomatal and non-stomatal limitation, and the enhancement in photo-respiration, thermal dissipation, and Mehler reaction are important processes to minimize the negative effects of high elevation and a cold environment. Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.

  15. Accelerator Center for Energy Research (ACER)

    Data.gov (United States)

    Federal Laboratory Consortium — The Accelerator Center for Energy Research (ACER) exploits radiation chemistry techniques to study chemical reactions (and other phenomena) by subjecting samples to...

  16. Comparative study of the water oxidizing reactions and the millisecond delayed chlorophyll fluorescence in photosystem II at different pH.

    Science.gov (United States)

    Gasanov, Ralphreed; Aliyeva, Samira; Arao, Sachiko; Ismailova, Aygun; Katsuta, Nobuhiro; Kitade, Hidetoshi; Yamada, Shuji; Kawamori, Asako; Mamedov, Fikret

    2007-02-01

    Water splitting activity, the multiline EPR signal associated with S(2)-state of the CaMn(4)-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5-8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O(2) evolution and the multiline EPR signal were inhibited at acidic (pK approximately 5.3) and alkaline (pK approximately 8.1) pH values, and were maximal at pH 6.0-7.0. Our results indicate that the loss of O(2) evolution and the S(2)-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0-8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed.

  17. Kinetic Study on Aminolysis of O-2-Pyridyl Thionobenzoate in Acetonitrile: Effect of Changing Electrophilic Center from C=O to C=S on Reactivity and Reaction Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Young; Um, Ik-Hwan [Ewha Womans University, Seoul (Korea, Republic of)

    2016-09-15

    Pseudo-first-order rate constants (k{sub obsd}) for nucleophilic substitution reaction of O-2-pyridyl thionobenzoate (7) with a series of secondary amines in MeCN at 25.0 ± 0.1 .deg. C have been measured spectrophotometrically. The plots of k{sub obsd} vs. [amine] curve upward, indicating that the reaction proceeds through a stepwise mechanism with a zwitterionic tetrahedral intermediate (T{sup ±}), which decomposes to the products through uncatalyzed and catalyzed routes. It has been proposed that the uncatalyzed reaction proceeds through a six-membered cyclic transition state (TS), in which expulsion of the leaving group occurs in the rate-determining step. The catalyzed reaction from T{sup ±} proceeds through a concerted mechanism with a six-membered cyclic TS rather than via a stepwise pathway with an anionic intermediate T{sup -}. This is in contrast to the report that the corresponding reaction of 2-pyridyl benzoate (6, a C=O analogue of 7) proceeds through a forced concerted mechanism. Comparison of the second-order rate constants for the uncatalyzed reaction of 7 with those reported previously for the corresponding reaction of 6 has revealed that 7 is much more reactive than 6. Factors that affect the reactivity and reaction mechanism are discussed in detail.

  18. Cu-Free 1,3-Dipolar Cycloaddition Click Reactions To Form Isoxazole Linkers in Chelating Ligands for fac-[MI(CO)3]+ Centers (M = Re, 99mTc)

    OpenAIRE

    Bottorff, Shalina C.; Kasten, Benjamin B.; Stojakovic, Jelena; Moore, Adam L.; MacGillivray, Leonard R.; Benny, Paul D.

    2014-01-01

    Isoxazole ring formation was examined as a potential Cu-free alternative click reaction to CuI-catalyzed alkyne/azide cycloaddition. The isoxazole reaction was explored at macroscopic and radiotracer concentrations with the fac-[MI(CO)3]+ (M = Re, 99mTc) core for use as a noncoordinating linker strategy between covalently linked molecules. Two click assembly methods (click, then chelate and chelate, then click) were examined to determine the feasibility of isoxazole ring formation with either...

  19. cycloaddition reactions

    Indian Academy of Sciences (India)

    Unknown

    models of regioselectivity in pericyclic reactions. In addition, local hard and soft acid base (HSAB) princi- ples have been also employed to predict the observed regioselectivity.2 In recent years, the conceptual density functional theory has been remarkably successful in explaining the reactivity and site selectivity.3 The.

  20. Hydrogen-atom transfer in reactions of organic radicals with [Co-II(por)](center dot) (por = porphyrinato) and in subsequent addition of [Co(H)(por)] to olefins

    NARCIS (Netherlands)

    de Bruin, B.; Dzik, W.I.; Li, S.; Wayland, B.B.

    2009-01-01

    The mechanisms for hydrogen-atom transfer from the cyanoisopropyl radical C-center dot(CH3)(2)CN to [Co-II(por)](center dot) (yielding [Co-III(H)(por)] and CH2=C(CH3)(CN); por = porphyrinato) and the insertion of vinyl acetate (CH2=CHOAc) into the Co-H bond of [Co(H)(por)] (giving

  1. Functional heterogeneity of photosystem II in domain specific regions of the thylakoid membrane of spinach (Spinacia oleracea L.).

    Science.gov (United States)

    Veerman, John; McConnell, Michael D; Vasil'ev, Sergei; Mamedov, Fikret; Styring, Stenbjörn; Bruce, Doug

    2007-03-20

    A mild sonication and phase fractionation method has been used to isolate five regions of the thylakoid membrane in order to characterize the functional lateral heterogeneity of photosynthetic reaction centers and light harvesting complexes. Low-temperature fluorescence and absorbance spectra, absorbance cross-section measurements, and picosecond time-resolved fluorescence decay kinetics were used to determine the relative amounts of photosystem II (PSII) and photosystem I (PSI), to determine the relative PSII antenna size, and to characterize the excited-state dynamics of PSI and PSII in each fraction. Marked progressive increases in the proportion of PSI complexes were observed in the following sequence: grana core (BS), whole grana (B3), margins (MA), stroma lamellae (T3), and purified stromal fraction (Y100). PSII antenna size was drastically reduced in the margins of the grana stack and stroma lamellae fractions as compared to the grana. Picosecond time-resolved fluorescence decay kinetics of PSII were characterized by three exponential decay components in the grana fractions, and were found to have only two decay components with slower lifetimes in the stroma. Results are discussed in the framework of existing models of chloroplast thylakoid membrane lateral heterogeneity and the PSII repair cycle. Kinetic modeling of the PSII fluorescence decay kinetics revealed that PSII populations in the stroma and grana margin fractions possess much slower primary charge separation rates and decreased photosynthetic efficiency when compared to PSII populations in the grana stack.

  2. Structured near-infrared Magnetic Circular Dichroism spectra of the Mn4CaO5 cluster of PSII in T. vulcanus are dominated by Mn(IV) d-d 'spin-flip' transitions.

    Science.gov (United States)

    Morton, Jennifer; Chrysina, Maria; Craig, Vincent S J; Akita, Fusamichi; Nakajima, Yoshiki; Lubitz, Wolfgang; Cox, Nicholas; Shen, Jian-Ren; Krausz, Elmars

    2018-02-01

    Photosystem II passes through four metastable S-states in catalysing light-driven water oxidation. Variable temperature variable field (VTVH) Magnetic Circular Dichroism (MCD) spectra in PSII of Thermosynochococcus (T.) vulcanus for each S-state are reported. These spectra, along with assignments, provide a new window into the electronic and magnetic structure of Mn4CaO5. VTVH MCD spectra taken in the S2 state provide a clear g=2, S=1/2 paramagnetic characteristic, which is entirely consistent with that known by EPR. The three features, seen as positive (+) at 749nm, negative (-) at 773nm and (+) at 808nm are assigned as 4A→2E spin-flips within the d3 configuration of the Mn(IV) centres present. This assignment is supported by comparison(s) to spin-flips seen in a range of Mn(IV) materials. S3 exhibits a more intense (-) MCD peak at 764nm and has a stronger MCD saturation characteristic. This S3 MCD saturation behaviour can be accurately modelled using parameters taken directly from analyses of EPR spectra. We see no evidence for Mn(III) d-d absorption in the near-IR of any S-state. We suggest that Mn(IV)-based absorption may be responsible for the well-known near-IR induced changes induced in S2 EPR spectra of T. vulcanus and not Mn(III)-based, as has been commonly assumed. Through an analysis of the nephelauxetic effect, the excitation energy of S-state dependent spin-flips seen may help identify coordination characteristics and changes at each Mn(IV). A prospectus as to what more detailed S-state dependent MCD studies promise to achieve is outlined. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Usage Center

    DEFF Research Database (Denmark)

    Kleinaltenkamp, Michael; Plewa, Carolin; Gudergan, Siegfried

    2017-01-01

    -actor value cocreation, this paper is the first to comprehensively andcoherently conceptualize the notion of a usage center. In doing so, the authorsbuild an important foundation for future theorizing related to the potentialemergence of usage centers as well as the cocreation of individual andcollective...

  4. A combined experimental, theoretical, and Van't Hoff model study for identity methyl, proton, hydrogen atom, and hydride exchange reactions. Correlation with three-center four-, three-, and two-electron systems

    Science.gov (United States)

    Buck, Henk M.

    We have studied carbon transfer reactions following an SN2 reaction profile. With ab initio calculations and experimental geometries concerning the nature of the various complexes indicated as stable, intermediate, and transition state we were able to show the additional value of van't Hoff's tetrahedral configuration by changing its geometry via a trigonal pyramid into a trigonal bipyramid. The ratio of the apical bond and corresponding tetrahedral bond distances is then nearly 1.333. The relevance of this approach has also been shown for identity proton-(hydrogen atom-, and hydride-) in-line reactions. The use of this geometrical transmission will be demonstrated for the hydrogen bonding distances in e.g., DNA duplexes and other biological (supra) molecular systems.

  5. Cu-free 1,3-dipolar cycloaddition click reactions to form isoxazole linkers in chelating ligands for fac-[M(I)(CO)3]+ centers (M = Re, 99mTc).

    Science.gov (United States)

    Bottorff, Shalina C; Kasten, Benjamin B; Stojakovic, Jelena; Moore, Adam L; MacGillivray, Leonard R; Benny, Paul D

    2014-02-17

    Isoxazole ring formation was examined as a potential Cu-free alternative click reaction to Cu(I)-catalyzed alkyne/azide cycloaddition. The isoxazole reaction was explored at macroscopic and radiotracer concentrations with the fac-[M(I)(CO)3](+) (M = Re, (99m)Tc) core for use as a noncoordinating linker strategy between covalently linked molecules. Two click assembly methods (click, then chelate and chelate, then click) were examined to determine the feasibility of isoxazole ring formation with either alkyne-functionalized tridentate chelates or their respective fac-[M(I)(CO)3](+) complexes with a model nitrile oxide generator. Macroscale experiments, alkyne-functionalized chelates, or Re complexes indicate facile formation of the isoxazole ring. (99m)Tc experiments demonstrate efficient radiolabeling with click, then chelate; however, the chelate, then click approach led to faster product formation, but lower yields compared to the Re analogues.

  6. Transfer reactions with HELIOS

    Science.gov (United States)

    Wuosmaa, Alan H.

    2011-04-01

    Nucleon-transfer reactions have formed the backbone of nuclear-structure studies for several decades, providing a wealth of information about the energies, quantum numbers, and wave functions of single-particle states in nuclei throughout the nuclear chart. Current trends in nuclear-structure physics and the modern emphasis on properties of neutron-rich nuclei far from stability have renewed interest in such transfer reactions with radioactive beams. Here, the usual combination of light beam and heavy target cannot be used, and measurements must be performed in ``inverse kinematics,'' with a heavy, unstable beam incident on a light target. This arrangement introduces several technical difficulties, including the identification of the reaction products and the resolution of the states of interest in the residual nuclei. A new device, HELIOS (the HELIcal Orbit Spectrometer) at the ATLAS facility at Argonne National Laboratory, solves many of the problems encountered with inverse kinematics including particle identification and energy resolution in the center-of-mass frame. The device utilizes the uniform magnetic field of a large, superconducting solenoid to transport light reaction products from the target to a linear array of position-sensitive silicon detectors. The properties of HELIOS will be described, and examples from the initial research program that focuses on neutron transfer with the (d,p) reaction, using both stable and unstable beams with mass A = 11 to 136, will be presented. Work supported by the U. S. Department of Energy, Office of Nuclear Physics under contract numbers DE-FG02-04ER41320 (WMU) and DE-AC02-06CH11357 (ANL).

  7. Understanding the physics and chemistry of reaction mechanisms from atomic contributions: a reaction force perspective.

    Science.gov (United States)

    Vöhringer-Martinez, Esteban; Toro-Labbé, Alejandro

    2012-07-12

    Studying chemical reactions involves the knowledge of the reaction mechanism. Despite activation barriers describing the kinetics or reaction energies reflecting thermodynamic aspects, identifying the underlying physics and chemistry along the reaction path contributes essentially to the overall understanding of reaction mechanisms, especially for catalysis. In the past years the reaction force has evolved as a valuable tool to discern between structural changes and electrons' rearrangement in chemical reactions. It provides a framework to analyze chemical reactions and additionally a rational partition of activation and reaction energies. Here, we propose to separate these energies further in atomic contributions, which will shed new insights in the underlying reaction mechanism. As first case studies we analyze two intramolecular proton transfer reactions. Despite the atom based separation of activation barriers and reaction energies, we also assign the participation of each atom in structural changes or electrons' rearrangement along the intrinsic reaction coordinate. These participations allow us to identify the role of each atom in the two reactions and therfore the underlying chemistry. The knowledge of the reaction chemistry immediately leads us to suggest replacements with other atom types that would facilitate certain processes in the reaction. The characterization of the contribution of each atom to the reaction energetics, additionally, identifies the reactive center of a molecular system that unites the main atoms contributing to the potential energy change along the reaction path.

  8. Spallation reactions; Reactions de spallation

    Energy Technology Data Exchange (ETDEWEB)

    Cugon, J.

    1996-12-31

    Spallation reactions dominate the interactions of hadrons with nuclei in the GeV range (from {approx} 0.1 to {approx} 10 GeV). They correspond to a sometimes important ejection of light particles leaving most of the time a residue of mass commensurate with the target mass. The main features of the experimental data are briefly reviewed. The most successful theoretical model, namely the intranuclear cascade + evaporation model, is presented. Its physical content, results and possible improvements are critically discussed. Alternative approaches are shortly reviewed. (author). 84 refs.

  9. Kinematical coincidence method in transfer reactions

    CERN Document Server

    Acosta, L; Auditore, L; Berceanu, I; Cardella, G; Chatterjiee, M B; De Filippo, E; FrancalanzA, L; Gianì, R; Grassi, L; Grzeszczuk, A; La Guidara, E; Lanzalone, G; Lombardo, I; Loria, D; Minniti, T; Pagano, E V; Papa, M; Pirrone, S; Politi, G; Pop, A; Porto, F; Rizzo, F; Rosato, E; Russotto, P; Santoro, S; Trifirò, A; Trimarchi, M; Verde, G; Vigilante, M

    2012-01-01

    A new method to extract high resolution angular distributions from kinematical coincidence measurements in binary reactions is presented. Kinematic is used to extract the center of mass angular distribution from the measured energy spectrum of light particles. Results obtained in the case of 10Be+p-->9Be+d reaction measured with the CHIMERA detector are shown. An angular resolution of few degrees in the center of mass is obtained.

  10. Reaction of turbulence at the edge and in the center of the plasma column to pulsed impurity injection caused by the sputtering of the wall coating in L-2M stellarator

    Science.gov (United States)

    Batanov, G. M.; Berezhetskii, M. S.; Borzosekov, V. D.; Vasilkov, D. G.; Vafin, I. Yu.; Grebenshchikov, S. E.; Grishina, I. A.; Kolik, L. V.; Konchekov, E. M.; Larionova, N. F.; Letunov, A. A.; Logvinenko, V. P.; Malakhov, D. V.; Meshcheryakov, A. I.; Petrov, A. E.; Sarksian, K. A.; Skvortsova, N. N.; Stepakhin, V. D.; Kharchev, N. K.; Kharchevskii, A. A.; Kholnov, Yu. V.; Shchepetov, S. V.

    2017-08-01

    Impurity injection into plasma caused by the sputtering of the wall coating in the L-2M stellarator during auxiliary electron cyclotron resonance heating leads to a change in the level of plasma density fluctuations with frequencies above 0.25 MHz: suppression of long-wavelength ( k ⊥ = 2 cm-1) density fluctuations in the edge plasma, intensification of short-wavelength ( k ⊥ = 30 cm-1) and long-wavelength ( k ⊥ = 1 cm-1) fluctuations at the midradius of the plasma column, and intensification of short-wavelength fluctuations ( k ⊥ = 20 cm-1) in the plasma center (including the gyroresonance region). At the same time, the level of fluctuations with frequencies below 0.25 MHz remains unchanged. In the edge plasma, a decrease in the plasma potential and suppression of its fluctuations is observed during impurity injection, which also causes an increase in MHD activity.

  11. Discerning the effects of photoinhibition and photoprotection on the rate of oxygen evolution in Arabidopsis leaves.

    Science.gov (United States)

    Giovagnetti, Vasco; Ruban, Alexander V

    2015-11-01

    Higher plants possess a set of interconnected processes to regulate light harvesting. Non-photochemical quenching of chlorophyll a fluorescence (NPQ) is the fastest process activated to protect the photosystem (PS) II from the absorption of excess light energy. However, damage of PSII reaction centers (RCIIs) is often inevitable, a phenomenon known as photoinhibition. Both NPQ and photoinhibition undermine PSII quantum yield (ΦPSII). Recently, we devised a fluorescence-based methodology that uses the coefficient of photochemical quenching measured in the dark following illumination (qPd) to assess the intactness of RCIIs. This procedure enables to express ΦPSII as a function (ƒ) of NPQ and qPd, ΦPSII=ƒ(NPQ,qPd), thus allowing to efficiently discern between the effects of protective NPQ and photoinhibition upon the efficiency of electron transport. In this study, we addressed the relationship between qPd and ΦPSII measured by photosynthetic oxygen evolution in intact leaves of Arabidopsis. We found a linear correlation between qPd and ΦPSII of oxygen evolution (as well as Fv/Fm). This relates to the fact that qPd reflects the onset of photoinhibition. These results further demonstrate the validity of the qPd parameter and underlying theory in quantitatively assessing PSII efficiency solely by using this effective and simple fluorescence technique. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. The roles of cytochrome b559 in assembly and photoprotection of Photosystem II revealed by site-directed mutagenesis studies

    Directory of Open Access Journals (Sweden)

    Hsiu-An eChu

    2016-01-01

    Full Text Available Cytochrome b559 (Cyt b559 is one of the essential components of the Photosystem II reaction center (PSII. Despite recent accomplishments in understanding the structure and function of PSII, the exact physiological function of Cyt b559 remains unclear. Cyt b559 is not involved in the primary electron transfer pathway in PSII but may participate in secondary electron transfer pathways that protect PSII against photoinhibition. Site-directed mutagenesis studies combined with spectroscopic and functional analysis have been used to characterize Cyt b559 mutant strains and their mutant PSII complex in higher plants, green algae and cyanobacteria. These integrated studies have provided important in vivo evidence for possible physiological roles of Cyt b559 in the assembly and stability of PSII, protecting PSII against photoinhibition, and modulating photosynthetic light harvesting. This mini-review presents an overview of recent important progress in site-directed mutagenesis studies of Cyt b559 and implications for revealing the physiological functions of Cyt b559 in PSII.

  13. Excess Ca(2+) does not alleviate but increases the toxicity of Hg(2+) to photosystem II in Synechocystis sp. (Cyanophyta).

    Science.gov (United States)

    Zhang, Daoyong; Deng, Chunnuan; Pan, Xiangliang

    2013-11-01

    This study demonstrated that excess Ca(2+) increased the toxicity of Hg(2+) to PSII of cyanobacterium Synechocystis sp. using fast rise chlorophyll fluorescence test. Excess Ca(2+) increased the inhibitory effect of Hg(2+) on O2 evolution. Exposure to Hg(2+) caused increase in functional antenna size (ABS/RC), trapping rate of reaction center (TR0/RC), dissipated energy flux per reaction center (DI0/RC) and maximum quantum yield of non-photochemical deexcitation ( [Formula: see text] ), indicating that some reaction centers were transformed to dissipation sinks under Hg(2+) stress. Hg(2+) stress slowed down electron transport on both donor side and acceptor side and caused accumulation of P680(+). Excess Ca(2+) intensified all the Hg(2+) toxic effects on PSII function and led to dysfunction of PSII. The number of reaction centers that were transformed into dissipation sinks increased with increasing Ca(2+) concentration. Copyright © 2013 Elsevier Inc. All rights reserved.

  14. Quantum-coherent dynamics in photosynthetic charge separation revealed by wavelet analysis

    OpenAIRE

    Romero, Elisabet; Prior, Javier; Chin, Alex W.; Morgan, Sarah E.; Novoderezhkin, Vladimir I.; Plenio, Martin B.; van Grondelle, Rienk

    2017-01-01

    Experimental/theoretical evidence for sustained vibration-assisted electronic (vibronic) coherence in the Photosystem II Reaction Center (PSII RC) indicates that photosynthetic solar-energy conversion might be optimized through the interplay of electronic and vibrational quantum dynamics. This evidence has been obtained by investigating the primary charge separation process in the PSII RC by two-dimensional electronic spectroscopy (2DES) and Redfield modeling of the experimental data. However...

  15. Photo-catalytic oxidation of a di-nuclear manganese centre in an engineered bacterioferritin 'reaction centre'.

    Science.gov (United States)

    Conlan, Brendon; Cox, Nicholas; Su, Ji-Hu; Hillier, Warwick; Messinger, Johannes; Lubitz, Wolfgang; Dutton, P Leslie; Wydrzynski, Tom

    2009-09-01

    Photosynthesis involves the conversion of light into chemical energy through a series of electron transfer reactions within membrane-bound pigment/protein complexes. The Photosystem II (PSII) complex in plants, algae and cyanobacteria catalyse the oxidation of water to molecular O2. The complexity of PSII has thus far limited attempts to chemically replicate its function. Here we introduce a reverse engineering approach to build a simple, light-driven photo-catalyst based on the organization and function of the donor side of the PSII reaction centre. We have used bacterioferritin (BFR) (cytochrome b1) from Escherichia coli as the protein scaffold since it has several, inherently useful design features for engineering light-driven electron transport. Among these are: (i.) a di-iron binding site; (ii.) a potentially redox-active tyrosine residue; and (iii.) the ability to dimerise and form an inter-protein heme binding pocket within electron tunnelling distance of the di-iron binding site. Upon replacing the heme with the photoactive zinc-chlorin e6 (ZnCe6) molecule and the di-iron binding site with two manganese ions, we show that the two Mn ions bind as a weakly coupled di-nuclear Mn2II,II centre, and that ZnCe6 binds in stoichiometric amounts of 1:2 with respect to the dimeric form of BFR. Upon illumination the bound ZnCe6 initiates electron transfer, followed by oxidation of the di-nuclear Mn centre possibly via one of the inherent tyrosine residues in the vicinity of the Mn cluster. The light dependent loss of the MnII EPR signals and the formation of low field parallel mode Mn EPR signals are attributed to the formation of MnIII species. The formation of the MnIII is concomitant with consumption of oxygen. Our model is the first artificial reaction centre developed for the photo-catalytic oxidation of a di-metal site within a protein matrix which potentially mimics water oxidation centre (WOC) photo-assembly.

  16. An analysis of DTP- associated reactions by manufacturer, batch ...

    African Journals Online (AJOL)

    Local and systemic adverse reactions following immunisation with DTP. Results. Local reactions were significantly more common with both Rh6ne--Poulenc Rarer products. Conclusion. AJI adverse reaction rates compared favourably with those reported by the Centers for Disease. Control. S Atr Med J 1996; 86: 1288-1290.

  17. Anaphylaxis-Like Reactions

    Science.gov (United States)

    ... Home Conditions Anaphylaxis Anaphylaxis-Like Reactions Anaphylaxis-Like Reactions Make an Appointment Refer a Patient Ask a ... exposed to a foreign substance, some people suffer reactions identical to anaphylaxis, but no allergy (IgE antibody) ...

  18. Catalysis of Photochemical Reactions.

    Science.gov (United States)

    Albini, A.

    1986-01-01

    Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

  19. On Thermonuclear Reaction Rates

    OpenAIRE

    Haubold, H. J.; Mathai, A. M.

    1996-01-01

    Nuclear reactions govern major aspects of the chemical evolution of galaxies and stars. Analytic study of the reaction rates and reaction probability integrals is attempted here. Exact expressions for the reaction rates and reaction probability integrals for nuclear reactions in the cases of nonresonant, modified nonresonant, screened nonresonant and resonant cases are given. These are expressed in terms of H-functions, G-functions and in computable series forms. Computational aspects are als...

  20. Atmospheric gas phase reactions

    Science.gov (United States)

    Platt, Ulrich

    This chapter introduces the underlying physicochemical principles and the relevance of atmospheric gas phase reactions. In particular, reaction orders, the concept of elementary reactions, definition of and factors determining reaction rates (kinetic theory of chemical reactions), and photochemical reactions are discussed. Sample applications of the pertinent reaction pathways in tropospheric chemistry are presented, particularly reactions involving free radicals (OH, NO3, halogen oxides) and their roles in the self-cleaning of the troposphere. The cycles of nitrogen and sulfur species as well as the principles of tropospheric ozone formation are introduced. Finally, the processes governing the stratospheric ozone layer (Chapman Cycle and extensions) are discussed.

  1. Method for predicting enzyme-catalyzed reactions

    Science.gov (United States)

    Hlavacek, William S.; Unkefer, Clifford J.; Mu, Fangping; Unkefer, Pat J.

    2013-03-19

    The reactivity of given metabolites is assessed using selected empirical atomic properties in the potential reaction center. Metabolic reactions are represented as biotransformation rules. These rules are generalized from the patterns in reactions. These patterns are not unique to reactants but are widely distributed among metabolites. Using a metabolite database, potential substructures are identified in the metabolites for a given biotransformation. These substructures are divided into reactants or non-reactants, depending on whether they participate in the biotransformation or not. Each potential substructure is then modeled using descriptors of the topological and electronic properties of atoms in the potential reaction center; molecular properties can also be used. A Support Vector Machine (SVM) or classifier is trained to classify a potential reactant as a true or false reactant using these properties.

  2. The different effects of chilling stress under moderate light intensity on photosystem II compared with photosystem I and subsequent recovery in tropical tree species.

    Science.gov (United States)

    Huang, Wei; Zhang, Shi-Bao; Cao, Kun-Fang

    2010-03-01

    Tropical plants are sensitive to chilling temperatures above zero but it is still unclear whether photosystem I (PSI) or photosystem II (PSII) of tropical plants is mainly affected by chilling temperatures. In this study, the effect of 4 degrees C associated with various light densities on PSII and PSI was studied in the potted seedlings of four tropical evergreen tree species grown in an open field, Khaya ivorensis, Pometia tomentosa, Dalbergia odorifera, and Erythrophleum guineense. After 8 h chilling exposure at the different photosynthetic flux densities of 20, 50, 100, 150 micromol m(-2) s(-1), the maximum quantum yield of PSII (F (v) /F (m)) in all of the four species decreased little, while the quantity of efficient PSI complex (P (m)) remained stable in all species except E. guineense. However, after chilling exposure under 250 micromol m(-2) s(-1) for 24 h, F (v) /F (m) was severely photoinhibited in all species whereas P (m) was relative stable in all plants except E. guineense. At the chilling temperature of 4 degrees C, electron transport from PSII to PSI was blocked because of excessive reduction of primary electron acceptor of PSII. F (v) /F (m) in these species except E. guineense recovered to approximately 90% after 8 h recovery in low light, suggesting the dependence of the recovery of PSII on moderate PSI and/or PSII activity. These results suggest that PSII is more sensitive to chilling temperature under the moderate light than PSI in tropical trees, and the photoinhibition of PSII and closure of PSII reaction centers can serve to protect PSI.

  3. Wound care centers

    Science.gov (United States)

    ... wound care center; Diabetic ulcer - wound care center; Surgical wound - wound center; Ischemic ulcer - wound center ... types of non-healing wounds include: Pressure sores Surgical wounds Radiation sores Foot ulcers due to diabetes , poor ...

  4. [Adverse reactions to insulin].

    Science.gov (United States)

    Liñana, J J; Montoro, F J; Hernández, M D; Basomba, A

    1997-07-01

    The prevalence of allergic reactions to insuline has decreased during the last few years. Probably this is due to the use of the newly-developed recombinant human insuline. At present, adverse reactions to insuline occur in 5-10% of patients on therapy with insuline. Adverse reactions may be local (more frequent) or systemic (rare). Insuline resistance consists in a different type of immunological reaction. Diagnosis of allergy to insuline is based on clinical history and cutaneous and serological tests. Treatment depends upon the severity of the reaction. When insuline is indispensable despite a previous allergic reaction, a desensitization protocol may be implemented.

  5. Cyclic electron flow plays an important role in photoprotection of tropical trees illuminated at temporal chilling temperature.

    Science.gov (United States)

    Huang, Wei; Zhang, Shi-Bao; Cao, Kun-Fang

    2011-02-01

    Our previous study indicated that PSII is more sensitive to chilling and light stress than PSI in tropical trees, and Erythrophleum guineense is more sensitive to chilling stress than Dalbergia odorifera and Khaya ivorensis, but the underlying physiological mechanisms are unclear. Although recent studies have reported that cyclic electron flow (CEF) plays an important role in photoprotection, the role of CEF in protecting PSI and PSII of tropical tree species remains unclear. We investigated the effect of temporal chilling temperature on energy distribution in PSII, the redox state of P700 and CEF in the above-mentioned tropical evergreen tree species grown in an open field. Our results indicated that the overclosure of PSII reaction centers at chilling temperature led to excess excitation pressure in PSII. At the temporal chilling temperature under low light, PSI acceptor side limitation [Y(NA)] was lower than those at 25°C for all species. Although the effective quantum yield of CEF [Y(CEF)] was not significantly stimulated in E. guineense and K. ivorensis under temporal chilling at low light levels, the ratio of Y(CEF) to the effective quantum yield of PSII [Y(II)] significantly increased. Under chilling conditions Y(CEF)/Y(II) was stimulated much more in K. ivorensis and D. odorifera compared with that in the chilling-sensitive E. guineense. These results suggested that stimulation of Y(CEF)/Y(II) plays an important role in protecting PSI and PSII from photoinhibition caused by chilling stress.

  6. Heat stress: an overview of molecular responses in photosynthesis.

    Science.gov (United States)

    Allakhverdiev, Suleyman I; Kreslavski, Vladimir D; Klimov, Vyacheslav V; Los, Dmitry A; Carpentier, Robert; Mohanty, Prasanna

    2008-01-01

    The primary targets of thermal damage in plants are the oxygen evolving complex along with the associated cofactors in photosystem II (PSII), carbon fixation by Rubisco and the ATP generating system. Recent investigations on the combined action of moderate light intensity and heat stress suggest that moderately high temperatures do not cause serious PSII damage but inhibit the repair of PSII. The latter largely involves de novo synthesis of proteins, particularly the D1 protein of the photosynthetic machinery that is damaged due to generation of reactive oxygen species (ROS), resulting in the reduction of carbon fixation and oxygen evolution, as well as disruption of the linear electron flow. The attack of ROS during moderate heat stress principally affects the repair system of PSII, but not directly the PSII reaction center (RC). Heat stress additionally induces cleavage and aggregation of RC proteins; the mechanisms of such processes are as yet unclear. On the other hand, membrane linked sensors seem to trigger the accumulation of compatible solutes like glycinebetaine in the neighborhood of PSII membranes. They also induce the expression of stress proteins that alleviate the ROS-mediated inhibition of repair of the stress damaged photosynthetic machinery and are required for the acclimation process. In this review we summarize the recent progress in the studies of molecular mechanisms involved during moderate heat stress on the photosynthetic machinery, especially in PSII.

  7. Microfluidic chemical reaction circuits

    Science.gov (United States)

    Lee, Chung-cheng [Irvine, CA; Sui, Guodong [Los Angeles, CA; Elizarov, Arkadij [Valley Village, CA; Kolb, Hartmuth C [Playa del Rey, CA; Huang, Jiang [San Jose, CA; Heath, James R [South Pasadena, CA; Phelps, Michael E [Los Angeles, CA; Quake, Stephen R [Stanford, CA; Tseng, Hsian-rong [Los Angeles, CA; Wyatt, Paul [Tipperary, IE; Daridon, Antoine [Mont-Sur-Rolle, CH

    2012-06-26

    New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

  8. Allergic reactions (image)

    Science.gov (United States)

    Allergic reaction can be provoked by skin contact with poison plants, chemicals and animal scratches, as well as ... mildew, dust, nuts and shellfish, may also cause allergic reaction. Medications such as penicillin and other antibiotics are ...

  9. Cosmetic tattoo pigment reaction

    National Research Council Canada - National Science Library

    Greywal, Tanya; Cohen, Philip R

    2016-01-01

    BackgroundCutaneous reactions to tattoos are most commonly granulomatous or lichenoid.PurposeWe describe a woman who developed a lymphocytic reaction following a cosmetic tattoo procedure with black dye...

  10. Chemical transport reactions

    CERN Document Server

    Schäfer, Harald

    2013-01-01

    Chemical Transport Reactions focuses on the processes and reactions involved in the transport of solid or liquid substances to form vapor phase reaction products. The publication first offers information on experimental and theoretical principles and the transport of solid substances and its special applications. Discussions focus on calculation of the transport effect of heterogeneous equilibria for a gas motion between equilibrium spaces; transport effect and the thermodynamic quantities of the transport reaction; separation and purification of substances by means of material transport; and

  11. SUPPLEMENTARY INFORMATION Efficient click reaction towards ...

    Indian Academy of Sciences (India)

    sudarshana

    SUPPLEMENTARY INFORMATION. Efficient click reaction towards novel sulfonamide hybrids by molecular hybridization strategy as antiproliferative agents. DONG-JUN FU,a. YU-HUI HOU,a. SAI-YANG ZHANGb* and YAN-BING. ZHANGa*. aNew Drug Research & Development Center, School of Pharmaceutical Sciences,.

  12. Enhancement of reaction rates for catalytic benzaldehyde ...

    Indian Academy of Sciences (India)

    Enhancement of reaction rates for catalytic benzaldehyde hydrogenation and sorbitol dehydration in water solvent by addition of carbon dioxide. MASAYUKI SHIRAIa,b,∗, OSAMU SATOa, NORIHITO HIYOSHIa and. ARITOMO YAMAGUCHIa. aResearch Center for Compact Chemical System, National Institute of Advanced ...

  13. Photosystem II and photoinhibition

    NARCIS (Netherlands)

    Feikema, Willem Onno

    2006-01-01

    Plants harvest light energy and convert it into chemical energy. Light absorption by photosystems I and II (PSI and PSII) results in charge separations in their reaction centers (RCs), initiating a chain of redox reactions with PSI generating the reducing power for CO2 assimilation into sugars, and

  14. Reaction Time (Polish language)

    OpenAIRE

    Iermakov, Sergii

    2014-01-01

    Reaction time is the interval time between the presentation of a stimulus and the initiation of the muscular response to that stimulus.If there is only one possible response (simple reaction time) it will only take a short time to react. If there are several possible responses (choice reaction time) then it will take longer to determine which response to carry out.

  15. Laser enhanced chemical reactions

    Science.gov (United States)

    Included is the discussion of infrared diode lasers used to study time dependent dynamic events. Also, hot atom excitation of vibrational states of polyatomic molecules, bimolecular quenching and reactions of O(sup 1)D, bimolecular reaction studies of the OH + CO yields H + CO2 system, and the chemical dynamics of the reaction between chlorine atoms and deuterated cyclohexane are covered briefly.

  16. (MIRC) reaction w

    Indian Academy of Sciences (India)

    Sudesh Kumari

    as eco-friendly reaction media in catalyst free organic synthesis.7 Ethylene glycol has promising physical ... these properties it is used as a promising green media in many catalysed/ uncatalysed organic reactions ..... Ruijter E, Scheffelaar R and Orru R V A 2011 Multi- component Reaction Design in the Quest for Molecular ...

  17. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... Education Centers Carbon Monoxide Information Center Carbon Monoxide Information Center En Español The Invisible Killer Carbon monoxide, ... Install one and check its batteries regularly. View Information About CO Alarms Other CO Topics Safety Tips ...

  18. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... Education Safety Education Centers Carbon Monoxide Information Center Carbon Monoxide Information Center En Español The Invisible Killer Carbon monoxide, also known as CO, is called the "Invisible ...

  19. High-temperature sensitivity and its acclimation for photosynthetic electron reactions of desert succulents

    Energy Technology Data Exchange (ETDEWEB)

    Chetti, M.B.; Nobel, P.S. (Univ. of California, Los Angeles (USA))

    1987-08-01

    Photosynthetic electron reactions of succulent plants from hot deserts are able to tolerate extremely high temperatures and to acclimate to seasonal increase in temperature. In this study, we report the influence of relatively long, in vivo, high-temperature treatments on electron transport reactions for two desert succulents, Agave deserti and Opuntia ficus-indica, species which can tolerate 60{degree}C. Whole chain electron transport averaged 3{degree}C more sensitive to a 1-hour high-temperature treatment than did PSII (Photosystem II) which in turn averaged 3{degree}C more sensitive than did PSI. For plants maintained at day/night air temperatures of 30{degree}C/20{degree}C, treatment at 50{degree}C cause these reactions to be inhibited an average of 39% during the first hour, an additional 31% during the next 4 hours, and 100% by 12 hours. Upon shifting the plants from 30{degree}C/20{degree}C to 45{degree}C/35{degree}C, the high temperatures where activity was inhibited 50% increased 3{degree}C to 8{degree}C for the three electron transport reactions, the half-times for acclimation averaging 5 days for A. deserti and 4 days for O. ficus-indica. For the 45{degree}C/35{degree}C plants treated at 60{degree}C for 1 hour, PSI activity was reduced by 54% for A. deserti and 36% for O. ficus-indica. Acclimation leads to a toleration of very high temperatures without substantial disruption of electron transport for these desert succulents, facilitating their survival in hot deserts. Indeed, the electron transport reactions of these species tolerate longer periods at higher temperatures than any other vascular plants so far reported.

  20. Photo-oxidation of tyrosine in a bio-engineered bacterioferritin 'reaction centre'-a protein model for artificial photosynthesis.

    Science.gov (United States)

    Hingorani, Kastoori; Pace, Ron; Whitney, Spencer; Murray, James W; Smith, Paul; Cheah, Mun Hon; Wydrzynski, Tom; Hillier, Warwick

    2014-10-01

    The photosynthetic reaction centre (RC) is central to the conversion of solar energy into chemical energy and is a model for bio-mimetic engineering approaches to this end. We describe bio-engineering of a Photosystem II (PSII) RC inspired peptide model, building on our earlier studies. A non-photosynthetic haem containing bacterioferritin (BFR) from Escherichia coli that expresses as a homodimer was used as a protein scaffold, incorporating redox-active cofactors mimicking those of PSII. Desirable properties include: a di-nuclear metal binding site which provides ligands for bivalent metals, a hydrophobic pocket at the dimer interface which can bind a photosensitive porphyrin and presence of tyrosine residues proximal to the bound cofactors, which can be utilised as efficient electron-tunnelling intermediates. Light-induced electron transfer from proximal tyrosine residues to the photo-oxidised ZnCe6(•+), in the modified BFR reconstituted with both ZnCe6 and Mn(II), is presented. Three site-specific tyrosine variants (Y25F, Y58F and Y45F) were made to localise the redox-active tyrosine in the engineered system. The results indicate that: presence of bound Mn(II) is necessary to observe tyrosine oxidation in all BFR variants; Y45 the most important tyrosine as an immediate electron donor to the oxidised ZnCe6(•+) and that Y25 and Y58 are both redox-active in this system, but appear to function interchangebaly. High-resolution (2.1Å) crystal structures of the tyrosine variants show that there are no mutation-induced effects on the overall 3-D structure of the protein. Small effects are observed in the Y45F variant. Here, the BFR-RC represents a protein model for artificial photosynthesis. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  1. Womens Business Center

    Data.gov (United States)

    Small Business Administration — Women's Business Centers (WBCs) represent a national network of nearly 100 educational centers throughout the United States and its territories, which are designed...

  2. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... OnSafety Blog Safety Education Centers Neighborhood Safety Network Community Outreach Resource Center Toy ... Research & Statistics Technical Reports Injury Statistics NEISS ...

  3. Southern California Particle Center

    Data.gov (United States)

    Federal Laboratory Consortium — At the Southern California Particle Center, center researchers will investigate the underlying mechanisms that produce the health effects associated with exposure to...

  4. Natural isoforms of the Photosystem II D1 subunit differ in photoassembly efficiency of the water-oxidizing complex.

    Science.gov (United States)

    Vinyard, David J; Sun, Jennifer S; Gimpel, Javier; Ananyev, Gennady M; Mayfield, Stephen P; Charles Dismukes, G

    2016-05-01

    Oxygenic photosynthesis efficiency at increasing solar flux is limited by light-induced damage (photoinhibition) of Photosystem II (PSII), primarily targeting the D1 reaction center subunit. Some cyanobacteria contain two natural isoforms of D1 that function better under low light (D1:1) or high light (D1:2). Herein, rates and yields of photoassembly of the Mn4CaO5 water-oxidizing complex (WOC) from the free inorganic cofactors (Mn(2+), Ca(2+), water, electron acceptor) and apo-WOC-PSII are shown to differ significantly: D1:1 apo-WOC-PSII exhibits a 2.3-fold faster rate-limiting step of photoassembly and up to seven-fold faster rate to the first light-stable Mn(3+) intermediate, IM1*, but with a much higher rate of photoinhibition than D1:2. Conversely, D1:2 apo-WOC-PSII assembles slower but has up to seven-fold higher yield, achieved by a higher quantum yield of charge separation and slower photoinhibition rate. These results confirm and extend previous observations of the two holoenzymes: D1:2-PSII has a greater quantum yield of primary charge separation, faster [P680 (+) Q A (-) ] charge recombination and less photoinhibition that results in a slower rate and higher yield of photoassembly of its apo-WOC-PSII complex. In contrast, D1:1-PSII has a lower quantum yield of primary charge separation, a slower [P680 (+) Q A (-) ] charge recombination rate, and faster photoinhibition that together result in higher rate but lower yield of photoassembly at higher light intensities. Cyanobacterial PSII reaction centers that contain the high- and low-light D1 isoforms can tailor performance to optimize photosynthesis at varying light conditions, with similar consequences on their photoassembly kinetics and yield. These different efficiencies of photoassembly versus photoinhibition impose differential costs for biosynthesis as a function of light intensity.

  5. Hypersensitivity reactions to heparins.

    Science.gov (United States)

    Gonzalez-Delgado, Purificación; Fernandez, Javier

    2016-08-01

    This article provides an update on hypersensitivity reactions to heparins and novel oral anticoagulants, with special emphasis on diagnostic methods and management of patients. Although heparins are drugs widely used, hypersensitivity reactions are uncommon. Cutaneous delayed hypersensitivity reactions after subcutaneous administration affects up to 7.5% of patients. Heparin-induced thrombocytopenia is another unusual but severe condition in which early recognition is crucial. Immediate hypersensitivity reactions to heparins have been also reported, but with the novel oral anticoagulants are much more uncommon, although reports of exanthemas have been notified.Skin tests and subcutaneous provocation test are useful tools in the diagnosis of hypersensitivity reactions, except in heparin-induced thrombocytopenia in which biopsy of lesional skin and in-vitro tests are the modalities of choice to confirm the diagnosis.Management of hypersensitivity reactions includes finding an alternative depending on the type of reaction. Fondaparinux and novel oral anticoagulants may be safe alternatives. Delayed skin lesions after subcutaneous heparin are the most common type of hypersensitivity reactions, followed by life-threatening heparin-induced thrombocytopenia. Immediate reactions are uncommon. Allergologic studies may be useful to find an alternative option in patients with skin lesions in which heparin-induced thrombocytopenia has been previously excluded, as well as in heparin immediate reactions.

  6. Mechanism of interaction of Al3+ with the proteins composition of photosystem II.

    Directory of Open Access Journals (Sweden)

    Imed Hasni

    Full Text Available The inhibitory effect of Al3+on photosystem II (PSII electron transport was investigated using several biophysical and biochemical techniques such as oxygen evolution, chlorophyll fluorescence induction and emission, SDS-polyacrylamide and native green gel electrophoresis, and FTIR spectroscopy. In order to understand the mechanism of its inhibitory action, we have analyzed the interaction of this toxic cation with proteins subunits of PSII submembrane fractions isolated from spinach. Our results show that Al 3+, especially above 3 mM, strongly inhibits oxygen evolution and affects the advancement of the S states of the Mn4O5Ca cluster. This inhibition was due to the release of the extrinsic polypeptides and the disorganization of the Mn4O5Ca cluster associated with the oxygen evolving complex (OEC of PSII. This fact was accompanied by a significant decline of maximum quantum yield of PSII (Fv/Fm together with a strong damping of the chlorophyll a fluorescence induction. The energy transfer from light harvesting antenna to reaction centers of PSII was impaired following the alteration of the light harvesting complex of photosystem II (LHCII. The latter result was revealed by the drop of chlorophyll fluorescence emission spectra at low temperature (77 K, increase of F0 and confirmed by the native green gel electrophoresis. FTIR measurements indicated that the interaction of Al 3+ with the intrinsic and extrinsic polypeptides of PSII induces major alterations of the protein secondary structure leading to conformational changes. This was reflected by a major reduction of α-helix with an increase of β-sheet and random coil structures in Al 3+-PSII complexes. These structural changes are closely related with the functional alteration of PSII activity revealed by the inhibition of the electron transport chain of PSII.

  7. Reaction kinetics of polybutylene terephthalate polycondensation reaction

    NARCIS (Netherlands)

    Darda, P. J.; Hogendoorn, J. A.; Versteeg, G. F.; Souren, F.

    2005-01-01

    The kinetics of the forward polycondensation reaction of polybutylene terephthalate (PBT) has been investigated using thermogravimetric analysis (TGA). PBT - prepolymer with an initial degree of polymerization of 5.5 was used as starting material. The PBT prepolymer was prepared from dimethyl

  8. Reactions at Solid Surfaces

    CERN Document Server

    Ertl, Gerhard

    2009-01-01

    Expanding on the ideas first presented in Gerhard Ertl's acclaimed Baker Lectures at Cornell University, Reactions at Solid Surfaces comprises an authoritative, self-contained, book-length introduction to surface reactions for both professional chemists and students alike. Outlining our present understanding of the fundamental processes underlying reactions at solid surfaces, the book provides the reader with a complete view of how chemistry works at surfaces, and how to understand and probe the dynamics of surface reactions. Comparing traditional surface probes with more modern ones, and brin

  9. Desosamine in multicomponent reactions

    NARCIS (Netherlands)

    Achatz, Sepp; Dömling, Alexander

    2006-01-01

    Desosamine occurring ubiquitously in natural products is introduced into isocyanide based multicomponent reaction chemistry. Corresponding products are of potential interest for the design of novel antibiotics. © 2006.

  10. Diverse mechanisms for photoprotection in photosynthesis. Dynamic regulation of photosystem II excitation in response to rapid environmental change.

    Science.gov (United States)

    Derks, Allen; Schaven, Kristin; Bruce, Doug

    2015-01-01

    Photosystem II (PSII) of photosynthesis catalyzes one of the most challenging reactions in nature, the light driven oxidation of water and release of molecular oxygen. PSII couples the sequential four step oxidation of water and two step reduction of plastoquinone to single photon photochemistry with charge accumulation centers on both its electron donor and acceptor sides. Photon capture, excitation energy transfer, and trapping occur on a much faster time scale than the subsequent electron transfer and charge accumulation steps. A balance between excitation of PSII and the use of the absorbed energy to drive electron transport is essential. If the absorption of light energy increases and/or the sink capacity for photosynthetically derived electrons decreases, potentially deleterious side reactions may occur, including the production of reactive oxygen species. In response, a myriad of fast (second to minutes timescale) and reversible photoprotective mechanisms are observed to regulate PSII excitation when the environment changes more quickly than can be acclimated to by gene expression. This review compares the diverse photoprotective mechanisms that are used to dissipate (quench) PSII excitation within the antenna systems of higher land plants, green algae, diatoms, and cyanobacteria. The molecular bases of how PSII excitation pressure is sensed by the antenna system and how the antenna then reconfigures itself from a light harvesting to an energy dissipative mode are discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Reactions to Attitudinal Deviancy.

    Science.gov (United States)

    Levine, John M.; Allen, Vernon L.

    This paper presents a critical review of empirical and theoretical treatments of group reaction to attitudinal deviancy. Inspired by Festinger's (1950) ideas on resolution of attitudinal discrepancies in groups, Schachter (1951) conducted an experiment that has greatly influenced subsequent research and theory concerning reaction to attitudinal…

  12. ORGANIC REACTION MECHANISM CONTROVERSY ...

    African Journals Online (AJOL)

    Preferred Customer

    Chemists, educators and students are entitled to their mental constructs about reaction mechanism in the classroom. What pedagogical implications have these knowledge claims for teaching and learning reaction mechanisms in organic chemistry? This is the main interest of the paper. Thus three questions were critically ...

  13. Hydrogen evolution reaction catalyst

    Science.gov (United States)

    Subbaraman, Ram; Stamenkovic, Vojislav; Markovic, Nenad; Tripkovic, Dusan

    2016-02-09

    Systems and methods for a hydrogen evolution reaction catalyst are provided. Electrode material includes a plurality of clusters. The electrode exhibits bifunctionality with respect to the hydrogen evolution reaction. The electrode with clusters exhibits improved performance with respect to the intrinsic material of the electrode absent the clusters.

  14. Applications of Reaction Rate

    Science.gov (United States)

    Cunningham, Kevin

    2007-01-01

    This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…

  15. Alpha resonant scattering for astrophysical reaction studies

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, H.; Kahl, D.; Nakao, T. [Center for Nuclear Study (CNS), University of Tokyo, RIKEN campus, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Wakabayashi, Y.; Kubano, S. [The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Hashimoto, T. [Research Center for Nuclear Physics (RCNP), Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Hayakawa, S. [Istituto Nazionale Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS), Via S. Sofia 62, 95125 Catania (Italy); Kawabata, T. [Department of Physics, Kyoto University, Kita-Shirakawa, Kyoto 606-8502 (Japan); Iwasa, N. [Department of Physics, Tohoku University, Aoba, Sendai, Miyagi 980-8578 (Japan); Teranishi, T. [Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan); Kwon, Y. K. [Institute for Basic Science, 70, Yuseong-daero 1689-gil, Yuseong-gu, Daejeon 305-811 (Korea, Republic of); Binh, D. N. [30 MeV Cyclotron Center, Tran Hung Dao Hospital, Hoan Kiem District, Hanoi (Viet Nam); Khiem, L. H.; Duy, N. G. [Institute of Physics, Vietnam Academy of Science and Technology, 18 Hong Quoc Viet, Nghia do, Hanoi (Viet Nam)

    2014-05-02

    Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of {sup 7}Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the {sup 7}Be(α,γ) reaction, and proposed a new cluster band in {sup 11}C.

  16. Respiratory transfusion reactions

    Directory of Open Access Journals (Sweden)

    Ivica Marić

    2017-11-01

    Full Text Available Respiratory transfusion-related reactions are not very frequent, partly also because recognition and reporting transfusion reactions is still underemphasized. Tis article describes the most important respiratory transfusion reactions, their pathophysiology, clinical picture and treatment strategies. Respiratory transfusion related reactions can be primary or secondary. The most important primary transfusion-related reactions are TRALI - transfusion-related acute lung injury, TACO – transfusion-associated circulatory overload, and TAD - transfusion-associated dyspnea. TRALI is immuneassociated injury of alveolar basal membrane, which becomes highly permeable and causes noncardiogenic pulmonary edema. Treatment of TRALI is mainly supportive with oxygen, fluids (in case of hypotension and in cases of severe acute respiratory failure also mechanic ventilation. TACO is caused by volume overload in predisposed individuals, such as patients with heart failure, the elderly, infants, patients with anemia and patients with positive fluid balance. Clinical picture is that of a typical pulmonary cardiogenic edema, and the therapy is classical: oxygen and diuretics, and in severe cases also non-invasive or invasive mechanical ventilation. TAD is usually a mild reaction of unknown cause and cannot be classified as TACO or TRALI, nor can it be ascribed to patient’s preexisting diseases. Although the transfusion-related reactions are not very common, knowledge about them can prevent serious consequences. On the one hand preventive measures should be sought, and on the other early recognition is beneficial, so that proper treatment can take place.

  17. Autocatalysis in Reaction Networks

    OpenAIRE

    Deshpande, Abhishek; Gopalkrishnan, Manoj

    2013-01-01

    The persistence conjecture is a long-standing open problem in chemical reaction network theory. It concerns the behavior of solutions to coupled ODE systems that arise from applying mass-action kinetics to a network of chemical reactions. The idea is that if all reactions are reversible in a weak sense, then no species can go extinct. A notion that has been found useful in thinking about persistence is that of "critical siphon." We explore the combinatorics of critical siphons, with a view to...

  18. The Reaction Wheel Pendulum

    CERN Document Server

    Block, Daniel J; Spong, Mark W

    2007-01-01

    This monograph describes the Reaction Wheel Pendulum, the newest inverted-pendulum-like device for control education and research. We discuss the history and background of the reaction wheel pendulum and other similar experimental devices. We develop mathematical models of the reaction wheel pendulum in depth, including linear and nonlinear models, and models of the sensors and actuators that are used for feedback control. We treat various aspects of the control problem, from linear control of themotor, to stabilization of the pendulum about an equilibrium configuration using linear control, t

  19. Electron transfer reactions

    CERN Document Server

    Cannon, R D

    2013-01-01

    Electron Transfer Reactions deals with the mechanisms of electron transfer reactions between metal ions in solution, as well as the electron exchange between atoms or molecules in either the gaseous or solid state. The book is divided into three parts. Part 1 covers the electron transfer between atoms and molecules in the gas state. Part 2 tackles the reaction paths of oxidation states and binuclear intermediates, as well as the mechanisms of electron transfer. Part 3 discusses the theories and models of the electron transfer process; theories and experiments involving bridged electron transfe

  20. Find a Health Center

    Data.gov (United States)

    U.S. Department of Health & Human Services — HRSA Health Centers care for you, even if you have no health insurance – you pay what you can afford based on your income. Health centers provide services that...

  1. NIH Clinical Centers

    Data.gov (United States)

    Federal Laboratory Consortium — The NIH Clinical Center consists of two main facilities: The Mark O. Hatfield Clinical Research Center, which opened in 2005, houses inpatient units, day hospitals,...

  2. Center for Functional Nanomaterials

    Data.gov (United States)

    Federal Laboratory Consortium — The Center for Functional Nanomaterials (CFN) explores the unique properties of materials and processes at the nanoscale. The CFN is a user-oriented research center...

  3. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... Center Carbon Monoxide Information Center En Español The Invisible Killer Carbon monoxide, also known as CO, is called the "Invisible Killer" because it's a colorless, odorless, poisonous gas. ...

  4. MARYLAND ROBOTICS CENTER

    Data.gov (United States)

    Federal Laboratory Consortium — The Maryland Robotics Center is an interdisciplinary research center housed in the Institute for Systems Research (link is external)within the A. James Clark School...

  5. Hydrologic Engineering Center

    Data.gov (United States)

    Federal Laboratory Consortium — The Hydrologic Engineering Center (HEC), an organization within the Institute for Water Resources, is the designated Center of Expertise for the U.S. Army Corps of...

  6. Day Care Centers

    Data.gov (United States)

    Department of Homeland Security — This database contains locations of day care centers for 50 states and Washington D.C. and Puerto Rico. The dataset only includes center based day care locations...

  7. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available Skip to main content Languages 简体中文 English Bahasa ... Blog Safety Education Centers Neighborhood Safety Network Community Outreach Resource Center Toy Recall Statistics CO Poster ...

  8. Poison Control Centers

    Science.gov (United States)

    ... 1222 immediately. Name State American Association of Poison Control Centers Address AAPCC Central Office NOT A POISON ... not for emergency use. Arkansas ASPCA Animal Poison Control Center Address 1717 S. Philo Road, Suite 36 Urbana, ...

  9. RSW Cell Centered Grids

    Data.gov (United States)

    National Aeronautics and Space Administration — New cell centered grids are generated to complement the node-centered ones uploaded. Six tarballs containing the coarse, medium, and fine mixed-element and pure tet....

  10. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... Resources OnSafety Blog Safety Education Centers Neighborhood Safety Network Community Outreach Resource Center Toy Recall Statistics CO Poster Contest Pool Safely Business & Manufacturing Business & Manufacturing Business Education Small Business Resources ...

  11. Regulation of expression of genes for light-harvesting antenna proteins LH-I and LH-II; reaction center polypeptides RC-L, RC-M, and RC-H; and enzymes of bacteriochlorophyll and carotenoid biosynthesis in Rhodobacter capsulatus by light and oxygen.

    Science.gov (United States)

    Zhu, Y S; Hearst, J E

    1986-10-01

    RNA levels were measured by blot hybridization to study the coordinate and differential expression of Rhodobacter capsulatus genes for light-harvesting I antenna proteins LH-I and LH-II; reaction center (RC) polypeptides L, M, and H; and bacteriochlorophyll and carotenoid biosynthesis in response to light and O2. The genes for LH-II alpha and beta subunits only have one transcript, 0.5 kilobase (kb) long, whereas the genes for LH-I have two transcripts (0.5 and 2.6 kb). The small transcript (0.5 kb) is the mRNA only for LH-I beta and alpha polypeptides, whereas the large transcript (2.6 kb) codes for RC-L, RC-M, and the beta and alpha polypeptides of LH-I, as well as the product of an unknown open reading frame designated ORF C2397. These five genes thus comprise a single operon (designated the puf operon). The mRNA specifying the LH-II polypeptides is more abundant, more sensitive to changes in O2 concentration, and shows a variation over a wider range than that of the mRNA for LH-I, indicating that the genes for LH-II and LH-I/RC are regulated independently. The gene for RC-H (puhA) has at least two transcripts (1.2 and 1.4 kb) that initiate within ORF F1696 and respond differentially to light intensity. The expression of the genes coding for RC-L, RC-M, and RC-H is coordinately regulated by light intensity and O2 concentration. An increase in light intensity causes a decrease in the expression of the genes for LH-I, LH-II, and RC proteins. The genes coding for the enzymes in the bacteriochlorophyll biosynthetic pathways are regulated by light intensity and O2 in a manner similar to that of the genes for LH and RC proteins. The crt genes coding for the enzymes in carotenoid biosynthetic pathways, however, are regulated in an opposite fashion: high light intensity results in increased expression of crt genes. These results are interpreted based on the protective function of carotenoids under high light intensity in the presence of O2.

  12. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... and Bans Report an Unsafe Product Consumers Businesses Home Safety Education Safety Education Centers Carbon Monoxide Information Center Carbon ... All CO Safety Guides ")); jQuery(".node-type-safety-education-center ... Camping Equipment Home Heating Equipment On Safety Blogs: CO Safety More ...

  13. Autocatalysis in reaction networks.

    Science.gov (United States)

    Deshpande, Abhishek; Gopalkrishnan, Manoj

    2014-10-01

    The persistence conjecture is a long-standing open problem in chemical reaction network theory. It concerns the behavior of solutions to coupled ODE systems that arise from applying mass-action kinetics to a network of chemical reactions. The idea is that if all reactions are reversible in a weak sense, then no species can go extinct. A notion that has been found useful in thinking about persistence is that of "critical siphon." We explore the combinatorics of critical siphons, with a view toward the persistence conjecture. We introduce the notions of "drainable" and "self-replicable" (or autocatalytic) siphons. We show that: Every minimal critical siphon is either drainable or self-replicable; reaction networks without drainable siphons are persistent; and nonautocatalytic weakly reversible networks are persistent. Our results clarify that the difficulties in proving the persistence conjecture are essentially due to competition between drainable and self-replicable siphons.

  14. [Adverse reactions to vaccines].

    Science.gov (United States)

    Ito Tsuchiya, F M; Rosas Vargas, M A; Zepeda Ortega, B; Río del Navarro, Blanca Estela; Sienra Monge, Juan José Luis

    2007-01-01

    Vaccination is one of the medicine's achievements to control and/or eradicate certain infectious diseases. Vaccines contain antigenic doses derived from microorganisms and/or its toxins, besides they are composed of other substances such as aluminum, gelatin, egg proteins, mercury components (as thimerosal), and antibiotics; therefore, these substances can produce hypersensitivity reactions. The above-mentioned reactions can be evidenced with itch, edema, hives, asthmatic crisis, hypotension and even anaphylactic shock. Due to the importance of vaccination, especially in childhood, it is essential to know the benefits of vaccines, their impact in morbidity and mortality decrease of certain infected-contagious diseases, as well as the adverse effects and the allergic reactions to their application. As immunizations prevent natural infections, they might contribute to a free infectious environment that would allow atopic response. This paper reviews the allergic reactions to vaccines and their influence on the development of atopic disease.

  15. Bad Reaction to Cosmetics?

    Science.gov (United States)

    ... Consumers Protect Yourself Health Fraud Bad Reactions to Cosmetics? Tell FDA! Share Tweet Linkedin Pin it More ... Radiation-Emitting Products Vaccines, Blood & Biologics Animal & Veterinary Cosmetics Tobacco Products

  16. Reactor for exothermic reactions

    Science.gov (United States)

    Smith, Jr., Lawrence A.; Hearn, Dennis; Jones, Jr., Edward M.

    1993-01-01

    A liquid phase process for oligomerization of C.sub.4 and C.sub.5 isoolefins or the etherification thereof with C.sub.1 to C.sub.6 alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120.degree. to 300.degree. F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

  17. Firefighter Nozzle Reaction

    DEFF Research Database (Denmark)

    Chin, Selena K.; Sunderland, Peter B.; Jomaas, Grunde

    2017-01-01

    to anchor forces, the hose becomes straight. The nozzle reaction is found to equal the jet momentum flow rate, and it does not change when an elbow connects the hose to the nozzle. A forward force must be exerted by a firefighter or another anchor that matches the forward force that the jet would exert...... on a perpendicular wall. Three reaction expressions are derived, allowing it to be determined in terms of hose diameter, jet diameter, flow rate, and static pressure upstream of the nozzle. The nozzle reaction predictions used by the fire service are 56% to 90% of those obtained here for typical firefighting hand......Nozzle reaction and hose tension are analyzed using conservation of fluid momentum and assuming steady, inviscid flow and a flexible hose in frictionless contact with the ground. An expression that is independent of the bend angle is derived for the hose tension. If this tension is exceeded owing...

  18. Chemical burn or reaction

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/000059.htm Chemical burn or reaction To use the sharing features on ... the burned area from pressure and friction. Minor chemical burns will generally heal without further treatment. However, if ...

  19. Adverse reaction to tetrazepam.

    Science.gov (United States)

    Palacios Benito, R; Domínguez Ortega, J; Alonso Llamazares, A; Rodríguez Morales, A; Plaza Díaz, A; Chamorro Gómez, M; Martínez-Cócera, C

    2001-01-01

    Adverse reactions caused by benzodiazepines rarely occur. We present a case of a 70-year-old man who developed a maculopapular exanthema after the ingestion of tetrazepam. For his diagnosis, skin tests were performed, including prick and patch tests, not only with the benzodiazepine implicated in the reaction, but also with benzodiazepines of other groups. Single-blind oral challenge tests were also performed in the patient, in order to assess his tolerance to other benzodiazepines.

  20. Oxygen evolution reaction catalysis

    Science.gov (United States)

    Haber, Joel A.; Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Jones, Ryan J.; Guevarra, Dan W.; Shinde, Aniketa A.

    2016-09-06

    An Oxygen Evolution Reaction (OER) catalyst includes a metal oxide that includes oxygen, cerium, and one or more second metals. In some instances, the cerium is 10 to 80 molar % of the metals in the metal oxide and/or the catalyst includes two or more second metals. The OER catalyst can be included in or on an electrode. The electrode can be arranged in an oxygen evolution system such that the Oxygen Evolution Reaction occurs at the electrode.

  1. Photoinduced Multicomponent Reactions.

    Science.gov (United States)

    Garbarino, Silvia; Ravelli, Davide; Protti, Stefano; Basso, Andrea

    2016-12-12

    The combination of multicomponent approaches with light-driven processes opens up new scenarios in the area of synthetic organic chemistry, where the need for sustainable, atom- and energy-efficient reactions is increasingly urgent. Photoinduced multicomponent reactions are still in their infancy, but significant developments in this area are expected in the near future. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Respiratory hypersensitivity reactions to NSAIDs in Europe

    DEFF Research Database (Denmark)

    Makowska, J S; Burney, P; Jarvis, D

    2016-01-01

    . Questionnaires including questions about age, gender, presence of symptoms of asthma, allergic rhinitis, chronic rhinosinusitis, smoking status, and history of NSAID-induced hypersensitivity reactions were sent to participants by mail. Totally, 62 737 participants completed the questionnaires. RESULTS: The mean......BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most prevalent drugs inducing hypersensitivity reactions. The aim of this analysis was to estimate the prevalence of NSAID-induced respiratory symptoms in population across Europe and to assess its association with upper...... prevalence of NSAID-induced dyspnea was 1.9% and was highest in the three Polish centers [Katowice (4.9%), Krakow (4.8%), and Lodz (4.4%)] and lowest in Skopje, (0.9%), Amsterdam (1.1%), and Umea (1.2%). In multivariate analysis, the prevalence of respiratory reactions to NSAIDs was higher in participants...

  3. Enantio- and Stereoselective Construction of Atisane Scaffold via Organocatalytic Intramolecular Michael Reaction and Diels-Alder Reaction.

    Science.gov (United States)

    Sekita, Hiroko; Adachi, Kyohei; Kobayashi, Ippei; Sato, Yusuke; Nakada, Masahisa

    2017-05-05

    An enantio- and stereoselective construction of the atisane scaffold via organocatalytic intramolecular Michael reaction and Diels-Alder reaction is described. The organocatalytic intramolecular Michael reaction has been found to stereoselectively generate a trans-stereodiad comprising an all-carbon quaternary and a tertiary stereogenic centers. Use of the chiral secondary amine bearing thiourea with benzoic acid as additive is the key to obtaining the desired product with excellent ee in synthetically acceptable yield. The prepared chiral building block has been successfully converted to the compound including the atisane scaffold via the highly stereoselective intramolecular Diels-Alder reaction.

  4. Excitonic connectivity between photosystem II units: what is it, and how to measure it?

    Science.gov (United States)

    Stirbet, Alexandrina

    2013-10-01

    In photosynthetic organisms, light energy is absorbed by a complex network of chromophores embedded in light-harvesting antenna complexes. In photosystem II (PSII), the excitation energy from the antenna is transferred very efficiently to an active reaction center (RC) (i.e., with oxidized primary quinone acceptor Q(A)), where the photochemistry begins, leading to O2 evolution, and reduction of plastoquinones. A very small part of the excitation energy is dissipated as fluorescence and heat. Measurements on chlorophyll (Chl) fluorescence and oxygen have shown that a nonlinear (hyperbolic) relationship exists between the fluorescence yield (Φ(F)) (or the oxygen emission yield, (Φ(O2)) and the fraction of closed PSII RCs (i.e., with reduced Q(A)). This nonlinearity is assumed to be related to the transfer of the excitation energy from a closed PSII RC to an open (active) PSII RC, a process called PSII excitonic connectivity by Joliot and Joliot (CR Acad Sci Paris 258: 4622-4625, 1964). Different theoretical approaches of the PSII excitonic connectivity, and experimental methods used to measure it, are discussed in this review. In addition, we present alternative explanations of the observed sigmoidicity of the fluorescence induction and oxygen evolution curves.

  5. Loss-of-function of OsSTN8 suppresses the photosystem II core protein phosphorylation and interferes with the photosystem II repair mechanism in rice (Oryza sativa).

    Science.gov (United States)

    Nath, Krishna; Poudyal, Roshan Sharma; Eom, Joon-Seob; Park, Yu Shin; Zulfugarov, Ismayil S; Mishra, Sujata R; Tovuu, Altanzaya; Ryoo, Nayeoon; Yoon, Ho-Sung; Nam, Hong Gil; An, Gynheung; Jeon, Jong-Seong; Lee, Choon-Hwan

    2013-11-01

    STN8 kinase is involved in photosystem II (PSII) core protein phosphorylation (PCPP). To examine the role of PCPP in PSII repair during high light (HL) illumination, we characterized a T-DNA insertional knockout mutant of the rice (Oryza sativa) STN8 gene. In this osstn8 mutant, PCPP was significantly suppressed, and the grana were thin and elongated. Upon HL illumination, PSII was strongly inactivated in the mutants, but the D1 protein was degraded more slowly than in wild-type, and mobilization of the PSII supercomplexes from the grana to the stromal lamellae for repair was also suppressed. In addition, higher accumulation of reactive oxygen species and preferential oxidation of PSII reaction center core proteins in thylakoid membranes were observed in the mutants during HL illumination. Taken together, our current data show that the absence of STN8 is sufficient to abolish PCPP in osstn8 mutants and to produce all of the phenotypes observed in the double mutant of Arabidopsis, indicating the essential role of STN8-mediated PCPP in PSII repair. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

  6. Medications and Drug Allergic Reactions

    Science.gov (United States)

    ... drug allergic reactions TTR Share | Medications and Drug Allergic Reactions This article has been reviewed by Thanai Pongdee, ... your symptoms are severe, seek medical help immediately. Allergic Reactions Allergy symptoms are the result of a chain ...

  7. Light harvesting in photosystem II

    NARCIS (Netherlands)

    van Amerongen, H.; Croce, R.

    2013-01-01

    Water oxidation in photosynthesis takes place in photosystem II (PSII). This photosystem is built around a reaction center (RC) where sunlight-induced charge separation occurs. This RC consists of various polypeptides that bind only a few chromophores or pigments, next to several other cofactors. It

  8. Determination of the excitation migration time in Photosystem II - Consequences for the membrane organization and charge separation parameters

    NARCIS (Netherlands)

    Broess, Koen; Trinkunas, Gediminas; van Hoek, Arie; Croce, Roberta; van Amerongen, Herbert

    The fluorescence decay kinetics of Photosystem II (PSII) membranes from spinach with open reaction centers (RCs), were compared after exciting at 420 and 484 nm. These wavelengths lead to preferential excitation of chlorophyll (Chl) a and Chl b, respectively, which causes different initial

  9. Bibliographic index to photonuclear reaction data (1955--1992)

    Energy Technology Data Exchange (ETDEWEB)

    Asami, Tetsuo [Data Engineering, Inc., Yokohama (Japan); Nakagawa, Tsuneo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Dept. of Reactor Engineering

    1993-10-01

    Japanese Nuclear Data Committee (JNDC) has a plan to compile the evaluated data library for photon-induced nuclear reaction cross sections, and the work on the data evaluation is in progress at the present. In the evaluations for these data a bibliographic index for neutron nuclear data is required. As the bibliographic index to photonuclear reactions, several excellent compilations have been done at some research institutes in the world, and have contributed to various basic and applied researches on the photonuclear reactions. For example, there are the abstract sheets published by US National Bureau of Standards and the data index published regularly in Russia. On the other hand, the four-center network on nuclear data (US National Nuclear Data Center at Brookhaven, Russian Nuclear Data Center at Obninsk, NEA Data Bank at Paris and IAEA Nuclear Data Section at Vienna) compiles and exchanges the numerical data on photonuclear reactions as well as on neutron-induced ones, in the EXFOR format. Those numerical data are available for users. There is, however, no bibliographic index to photonuclear reactions, available for general users. Therefore, the present work to make a photonuclear reaction data index has been done urgently to contribute to the above-mentioned data evaluation. Although these data might be still incomplete and have some defects, we have decided to serve this as the first edition of our photonuclear reaction index.

  10. Chemical kinetics of gas reactions

    CERN Document Server

    Kondrat'Ev, V N

    2013-01-01

    Chemical Kinetics of Gas Reactions explores the advances in gas kinetics and thermal, photochemical, electrical discharge, and radiation chemical reactions. This book is composed of 10 chapters, and begins with the presentation of general kinetic rules for simple and complex chemical reactions. The next chapters deal with the experimental methods for evaluating chemical reaction mechanisms and some theories of elementary chemical processes. These topics are followed by discussions on certain class of chemical reactions, including unimolecular, bimolecular, and termolecular reactions. The rema

  11. Reaction Qualifications Revisited

    DEFF Research Database (Denmark)

    Lippert-Rasmussen, Kasper

    2009-01-01

    of merit. Specifically, it preserves symmetry between negative evaluations of antimeritocratic bases of selection and negative evaluations of qualifications rooted in comparable antimeritocratic reactions. So if employers should not select among applicants on the basis of their (the employers') racial...... preferences, recipients should not respond to the applicant actually hired on the basis of their (the recipients') racial preferences. My account decomposes the meritocratic ideal into four separate norms, one of which applies to recipients rather than to selectors. Finally, it defends the view that reaction...... reaction-qualifications are entirely irrelevant from the point of view of merit, the view expounded here implies that the ideal of meritocracy and the norm of non-discrimination are less closely tied than theorists like Andrew Mason and David Miller believe.  ...

  12. Allergic reactions in anaesthesia

    DEFF Research Database (Denmark)

    Krøigaard, M; Garvey, L H; Menné, T

    2005-01-01

    BACKGROUND: The aim of this retrospective survey of possible allergic reactions during anaesthesia was to investigate whether the cause suspected by anaesthetists involved corresponded with the cause found on subsequent investigation in the Danish Anaesthesia Allergy Centre (DAAC). METHODS: Case...... notes and anaesthetic charts from 111 reactions in 107 patients investigated in the DAAC were scrutinized for either suspicions of or warnings against specific substances stated to be the cause of the supposed allergic reaction. RESULTS: In 67 cases, one or more substances were suspected. In 49...... of these (73%) the suspected cause did not match the results of subsequent investigation, either a different substance being the cause or no cause being found. Only five cases (7%) showed a complete match between suspected cause and investigation result. In the remaining 13 cases (19%) there was a partial...

  13. Hipersensitivity Reactions to Corticosteroids.

    Science.gov (United States)

    Berbegal, L; DeLeon, F J; Silvestre, J F

    2016-03-01

    Corticosteroids are widely used drugs in the clinical practice, especially by topic application in dermatology. These substances may act as allergens and produce immediate and delayed hypersensitivity reactions. Allergic contact dermatitis is the most frequent presentation of corticosteroid allergy and it should be studied by patch testing in specific units. The corticosteroids included in the Spanish standard battery are good markers but not ideal. Therefore, if those makers are positive, it is useful to apply a specific battery of corticosteroids and the drugs provided by patients. Immediate reactions are relatively rare but potentially severe, and it is important to confirm the sensitization profile and to guide the use of alternative corticosteroids, because they are often necessary in several diseases. In this article we review the main concepts regarding these two types of hypersensitivity reactions in corticosteroid allergy, as well as their approach in the clinical practice. Copyright © 2015 Elsevier España, S.L.U. and AEDV. All rights reserved.

  14. Nanoparticle Reactions on Chip

    Science.gov (United States)

    Köhler, J. M.; Kirner, Th.; Wagner, J.; Csáki, A.; Möller, R.; Fritzsche, W.

    The handling of heterogenous systems in micro reactors is difficult due to their adhesion and transport behaviour. Therefore, the formation of precipitates and gas bubbles has to be avoided in micro reaction technology, in most cases. But, micro channels and other micro reactors offer interesting possibilities for the control of reaction conditions and transport by diffusion and convection due to the laminar flow caused by small Reynolds numbers. This can be used for the preparation and modification of objects, which are much smaller than the cross section of microchannels. The formation of colloidal solutions and the change of surface states of nano particles are two important tasks for the application of chip reactors in nanoparticle technology. Some concepts for the preparation and reaction of nanoparticles in modular chip reactor arrangements will be discussed.

  15. Adverse reactions to cosmetics

    Directory of Open Access Journals (Sweden)

    Dogra A

    2003-03-01

    Full Text Available Adverse reaction to cosmetics constitute a small but significant number of cases of contact dermatitis with varied appearances. These can present as contact allergic dermatitis, photodermatitis, contact irritant dermatitis, contact urticaria, hypopigmentation, hyperpigmentotion or depigmentation, hair and nail breakage. Fifty patients were included for the study to assess the role of commonly used cosmetics in causing adverse reactions. It was found that hair dyes, lipsticks and surprisingly shaving creams caused more reaction as compared to other cosmetics. Overall incidence of contact allergic dermatitis seen was 3.3% with patients own cosmetics. Patch testing was also done with the basic ingredients and showed positive results in few cases where casual link could be established. It is recommended that labeling of the cosmetics should be done to help the dermatologists and the patients to identify the causative allergen in cosmetic preparation.

  16. Velocity pump reaction turbine

    Science.gov (United States)

    House, P.A.

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  17. Knockout reactions: experimental aspects

    Energy Technology Data Exchange (ETDEWEB)

    Cortina Gil, D. [Santiago de Compostela Univ. (Spain)

    2007-07-01

    The availability of radioactive beams has given rise to intense activity in the field of direct reactions. The removal of one(two)-nucleon (referred to as nucleon knockout in this text) from a fast exotic projectile has been extensively investigated. This lecture provides a general overview of the experimental results achieved using this technique. The sensitivity of the method to different experimental aspects is illustrated with a few examples. Special attention is given to the application of nucleon-knockout reactions as a general purpose spectroscopic tool. (author)

  18. Relativistic Guiding Center Equations

    Energy Technology Data Exchange (ETDEWEB)

    White, R. B. [PPPL; Gobbin, M. [Euratom-ENEA Association

    2014-10-01

    In toroidal fusion devices it is relatively easy that electrons achieve relativistic velocities, so to simulate runaway electrons and other high energy phenomena a nonrelativistic guiding center formalism is not sufficient. Relativistic guiding center equations including flute mode time dependent field perturbations are derived. The same variables as used in a previous nonrelativistic guiding center code are adopted, so that a straightforward modifications of those equations can produce a relativistic version.

  19. Test Control Center (TCC)

    Data.gov (United States)

    Federal Laboratory Consortium — The Test Control Center (TCC) provides a consolidated facility for planning, coordinating, controlling, monitoring, and analyzing distributed test events. ,The TCC...

  20. Electron Microscopy Center (EMC)

    Data.gov (United States)

    Federal Laboratory Consortium — The Electron Microscopy Center (EMC) at Argonne National Laboratory develops and maintains unique capabilities for electron beam characterization and applies those...

  1. Center for Deployment Psychology

    Data.gov (United States)

    Federal Laboratory Consortium — The Center for Deployment Psychology was developed to promote the education of psychologists and other behavioral health specialists about issues pertaining to the...

  2. Great Lakes Science Center

    Data.gov (United States)

    Federal Laboratory Consortium — Since 1927, Great Lakes Science Center (GLSC) research has provided critical information for the sound management of Great Lakes fish populations and other important...

  3. Small Business Development Center

    Data.gov (United States)

    Small Business Administration — Small Business Development Centers (SBDCs) provide assistance to small businesses and aspiring entrepreneurs throughout the United States and its territories. SBDCs...

  4. Environmental Modeling Center

    Data.gov (United States)

    Federal Laboratory Consortium — The Environmental Modeling Center provides the computational tools to perform geostatistical analysis, to model ground water and atmospheric releases for comparison...

  5. Chemical Security Analysis Center

    Data.gov (United States)

    Federal Laboratory Consortium — In 2006, by Presidential Directive, DHS established the Chemical Security Analysis Center (CSAC) to identify and assess chemical threats and vulnerabilities in the...

  6. Audio Visual Center

    Data.gov (United States)

    Federal Laboratory Consortium — The Audiovisual Services Center provides still photographic documentation with laboratory support, video documentation, video editing, video duplication, photo/video...

  7. Differences between Drug-Induced and Contrast Media-Induced Adverse Reactions Based on Spontaneously Reported Adverse Drug Reactions.

    Science.gov (United States)

    Ryu, JiHyeon; Lee, HeeYoung; Suh, JinUk; Yang, MyungSuk; Kang, WonKu; Kim, EunYoung

    2015-01-01

    We analyzed differences between spontaneously reported drug-induced (not including contrast media) and contrast media-induced adverse reactions. Adverse drug reactions reported by an in-hospital pharmacovigilance center (St. Mary's teaching hospital, Daejeon, Korea) from 2010-2012 were classified as drug-induced or contrast media-induced. Clinical patterns, frequency, causality, severity, Schumock and Thornton's preventability, and type A/B reactions were recorded. The trends among causality tools measuring drug and contrast-induced adverse reactions were analyzed. Of 1,335 reports, 636 drug-induced and contrast media-induced adverse reactions were identified. The prevalence of spontaneously reported adverse drug reaction-related admissions revealed a suspected adverse drug reaction-reporting rate of 20.9/100,000 (inpatient, 0.021%) and 3.9/100,000 (outpatients, 0.004%). The most common adverse drug reaction-associated drug classes included nervous system agents and anti-infectives. Dermatological and gastrointestinal adverse drug reactions were most frequently and similarly reported between drug and contrast media-induced adverse reactions. Compared to contrast media-induced adverse reactions, drug-induced adverse reactions were milder, more likely to be preventable (9.8% vs. 1.1%, p contrast media-induced adverse reactions (56.6%, p = 0.066). Causality patterns differed between the two adverse reaction classes. The World Health Organization-Uppsala Monitoring Centre causality evaluation and Naranjo algorithm results significantly differed from those of the Korean algorithm version II (p contrast media-induced adverse reactions. The World Health Organization-Uppsala Monitoring Centre and Naranjo algorithm causality evaluation afforded similar results.

  8. cyclopropanation reaction with ketene

    Indian Academy of Sciences (India)

    Administrator

    Smith. 15. This has motivated a large number of research groups to develop new and wide-range methods to produce cyclopropanated products. Methylene insertion by a carbenoid species into the. C=C bond is one of the most widely used methods since the recognition of the Simmons–Smith reac- tion, which is a reaction ...

  9. Reaction product imaging

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, D.W. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    Over the past few years the author has investigated the photochemistry of small molecules using the photofragment imaging technique. Bond energies, spectroscopy of radicals, dissociation dynamics and branching ratios are examples of information obtained by this technique. Along with extending the technique to the study of bimolecular reactions, efforts to make the technique as quantitative as possible have been the focus of the research effort. To this end, the author has measured the bond energy of the C-H bond in acetylene, branching ratios in the dissociation of HI, the energetics of CH{sub 3}Br, CD{sub 3}Br, C{sub 2}H{sub 5}Br and C{sub 2}H{sub 5}OBr dissociation, and the alignment of the CD{sub 3} fragment from CD{sub 3}I photolysis. In an effort to extend the technique to bimolecular reactions the author has studied the reaction of H with HI and the isotopic exchange reaction between H and D{sub 2}.

  10. Reaction Formulation: A Bibliography.

    Science.gov (United States)

    Pedrini, D. T.; Pedrini, Bonnie C.

    Reaction formation was studied by Sigmund Freud. This defense mechanism may be related to repression, substitution, reversal, and compensation (or over-compensation). Alfred Adler considered compensation a basic process in his individual psychology. Anna Freud discussed some defense mechanisms, and Bibring, Dwyer, Huntington, and Valenstein…

  11. Explaining competitive reaction effects

    NARCIS (Netherlands)

    Leeflang, P.S.H.; Wittink, D.R.

    Changes in promotional expenditure decisions for a brand, as in other marketing decisions, should be based on the expected impact on purchase and consumption behavior as well as on the likely reactions by competitors. Purchase behavior may be predicted from estimated demand functions. Competitive

  12. Cluster knockout reactions

    Indian Academy of Sciences (India)

    2014-04-07

    Apr 7, 2014 ... Cluster knockout reactions are expected to reveal the amount of clustering (such as that of , d and even of heavier clusters such as 12C, 16O etc.) in the target nucleus. In simple terms, incident medium high-energy nuclear projectile interacts strongly with the cluster (present in the target nucleus) as if it ...

  13. Multicomponent reactions in polymer synthesis.

    Science.gov (United States)

    Kakuchi, Ryohei

    2014-01-03

    More participants, yet efficient reactions: Multicomponent reactions (MCRs) have found application in polymer chemistry both in the synthesis of multifunctional monomers and in post-polymerization modification. Examples include the Passerini three-component reaction, the Ugi four-component reaction, and the copper-catalyzed MCR. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Kinetics of Bio-Reactions

    DEFF Research Database (Denmark)

    Villadsen, John

    2015-01-01

    his chapter predicts the specific rates of reaction by means of a mathematical expression, the kinetics of the reaction. This expression can be derived through a mechanistic interpretation of an enzymatically catalyzed reaction, but it is essentially of empirical nature for cell reactions. The mo...

  15. What Is a Reaction Rate?

    Science.gov (United States)

    Schmitz, Guy

    2005-01-01

    The definition of reaction rate is derived and demonstrations are made for the care to be taken while using the term. Reaction rate can be in terms of a reaction property, the extent of reaction and thus it is possible to give a definition applicable in open and closed systems.

  16. Call Center Capacity Planning

    DEFF Research Database (Denmark)

    Nielsen, Thomas Bang

    The main topics of the thesis are theoretical and applied queueing theory within a call center setting. Call centers have in recent years become the main means of communication between customers and companies, and between citizens and public institutions. The extensively computerized infrastructu...

  17. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... main content Languages 简体中文 English Bahasa Indonesia 한국어 Español ภาษาไทย Tiếng Việt Text Size: Decrease Font Increase ... Monoxide Information Center Carbon Monoxide Information Center En Español The Invisible Killer Carbon monoxide, also known as ...

  18. Dimensioning large call centers

    NARCIS (Netherlands)

    S.C. Borst (Sem); A. Mandelbaum; M.I. Reiman

    2000-01-01

    textabstractWe develop a framework for asymptotic optimization of a queueing system. The motivation is the staffing problem of call centers with 100's of agents (or more). Such a call center is modeled as an M/M/N queue, where the number of agents~$N$ is large. Within our framework, we determine the

  19. HRSA: Find a Health Center

    Science.gov (United States)

    ... and Seasonal Head Start Center (MSHS) HELP: HRSA Contact Center is available at 877-464-4772, 8 a. ... p.m. ET, weekdays (except federal holidays) HRSA Contact Center Close × Center Name Close Close Panel OPOs Transplant ...

  20. PTSD: National Center for PTSD

    Medline Plus

    Full Text Available ... Locator Hospitals and Clinics Vet Centers Regional Benefits Offices Regional Loan Centers Cemetery Locations Search Enter your ... Clinic Locations Hospitals & Clinics Vet Centers Regional Benefits Offices Regional Loan Centers Cemetery Locations Contact Us FAQs ...

  1. Energy efficient data centers

    Energy Technology Data Exchange (ETDEWEB)

    Tschudi, William; Xu, Tengfang; Sartor, Dale; Koomey, Jon; Nordman, Bruce; Sezgen, Osman

    2004-03-30

    Data Center facilities, prevalent in many industries and institutions are essential to California's economy. Energy intensive data centers are crucial to California's industries, and many other institutions (such as universities) in the state, and they play an important role in the constantly evolving communications industry. To better understand the impact of the energy requirements and energy efficiency improvement potential in these facilities, the California Energy Commission's PIER Industrial Program initiated this project with two primary focus areas: First, to characterize current data center electricity use; and secondly, to develop a research ''roadmap'' defining and prioritizing possible future public interest research and deployment efforts that would improve energy efficiency. Although there are many opinions concerning the energy intensity of data centers and the aggregate effect on California's electrical power systems, there is very little publicly available information. Through this project, actual energy consumption at its end use was measured in a number of data centers. This benchmark data was documented in case study reports, along with site-specific energy efficiency recommendations. Additionally, other data center energy benchmarks were obtained through synergistic projects, prior PG&E studies, and industry contacts. In total, energy benchmarks for sixteen data centers were obtained. For this project, a broad definition of ''data center'' was adopted which included internet hosting, corporate, institutional, governmental, educational and other miscellaneous data centers. Typically these facilities require specialized infrastructure to provide high quality power and cooling for IT equipment. All of these data center types were considered in the development of an estimate of the total power consumption in California. Finally, a research ''roadmap'' was developed

  2. Reaction chemistry of cerium

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-01-01

    It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

  3. Reactions to dietary tartrazine.

    Science.gov (United States)

    David, T J

    1987-01-01

    Double blind challenges with tartrazine and benzoic acid were performed in hospital in 24 children whose parents gave a definite history of a purely behavioural immediate adverse reaction to one of these substances. The patients, whose ages ranged from 1.6 to 12.4 years, were on a diet that avoided these items, and in all there was a clear history that any lapse of the diet caused an obvious adverse behavioural reaction within two hours. In no patient was any change in behaviour noted either by the parents or the nursing staff after the administration of placebo or active substances. Twenty two patients returned to a normal diet without problems, but the parents of two children insisted on continuing the diet. While popular belief has it that additives may have harmful behavioural effects, objective verification is required to prevent overdiagnosis. PMID:3548601

  4. Enzyme catalysed tandem reactions.

    Science.gov (United States)

    Oroz-Guinea, Isabel; García-Junceda, Eduardo

    2013-04-01

    To transfer to the laboratory, the excellent efficiency shown by enzymes in Nature, biocatalysis, had to mimic several synthetic strategies used by the living organisms. Biosynthetic pathways are examples of tandem catalysis and may be assimilated in the biocatalysis field for the use of isolated multi-enzyme systems in the homogeneous phase. The concurrent action of several enzymes that work sequentially presents extraordinary advantages from the synthetic point of view, since it permits a reversible process to become irreversible, to shift the equilibrium reaction in such a way that enantiopure compounds can be obtained from prochiral or racemic substrates, reduce or eliminate problems due to product inhibition or prevent the shortage of substrates by dilution or degradation in the bulk media, etc. In this review we want to illustrate the developments of recent studies involving in vitro multi-enzyme reactions for the synthesis of different classes of organic compounds. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. CMLSnap : Animated reaction mechanisms

    OpenAIRE

    Holliday, Gemma L; Mitchell, John BO; Murray-Rust, Peter

    2004-01-01

    The authors thank the EPSRC for financial support of this project and Unilever for their support of the Centre for Molecular Science Informatics. Reactions with many steps can be represented by a single XML-based table of the atoms, bonds and electrons. For each step the complete Chemical Markup Language 1 representation of all components is obtained and a snapshot representing the end point of the step is generated. These snapshots can then be combined to give an animated description of t...

  6. Exclusive reactions in QCD

    OpenAIRE

    Pire, Bernard

    1996-01-01

    We review the theory of hard exclusive scattering in Quantum Chromodynamics. After recalling the classical counting rules which describe the leading scale dependence of form factors and exclusive cross-sections at fixed angle, the pedagogical example of the pion form factor is developped in some detail in order to show explicitely what factorization means in the QCD framework. The picture generalizes to many hard reactions which are at the heart of the ELFE project. We briefly present the con...

  7. Photochemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Moore, B.C. [Lawrence Berkeley Laboratory, Livermore, CA (United States)

    1993-12-01

    The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.

  8. Cryochemical chain reactions

    Science.gov (United States)

    Barkalov, I. M.; Kiryukhin, D. P.

    The possibility of a chemical reaction near absolute zero has appeared doubtful since the beginning of the 1970s. The existing ideas must be revised after the radiation polymerization of formaldehyde at 4.2 K has been observed. In glassy systems, we have examined chain processes that occur under sharp (by five to six orders) changes in molecular mobility of the medium in the region of matrix devitrification. Quite unusual mechano-energetic chains of chemical conversion arise in the studied systems submerged in liquid helium. The chemical transformation initiated by local brittle fracture travels over the sample as an autowave. A series of experimental and theoretical investigations devoted to this interesting phenomenon are described. There is no generalization in this new region of chemistry up to this time. Many journal articles and reviews have been previously published only in Russian. The cycles of investigations of chain cryochemical reactions are the subject of this review. We hope that the investigation of the extraordinary peculiarities of chain cryochemical reactions should produce new ideas in chemical theory and industry.

  9. Adverse cutaneous drug reaction

    Directory of Open Access Journals (Sweden)

    Nayak Surajit

    2008-01-01

    Full Text Available In everyday clinical practice, almost all physicians come across many instances of suspected adverse cutaneous drug reactions (ACDR in different forms. Although such cutaneous reactions are common, comprehensive information regarding their incidence, severity and ultimate health effects are often not available as many cases go unreported. It is also a fact that in the present world, almost everyday a new drug enters market; therefore, a chance of a new drug reaction manifesting somewhere in some form in any corner of world is unknown or unreported. Although many a times, presentation is too trivial and benign, the early identification of the condition and identifying the culprit drug and omit it at earliest holds the keystone in management and prevention of a more severe drug rash. Therefore, not only the dermatologists, but all practicing physicians should be familiar with these conditions to diagnose them early and to be prepared to handle them adequately. However, we all know it is most challenging and practically difficult when patient is on multiple medicines because of myriad clinical symptoms, poorly understood multiple mechanisms of drug-host interaction, relative paucity of laboratory testing that is available for any definitive and confirmatory drug-specific testing. Therefore, in practice, the diagnosis of ACDR is purely based on clinical judgment. In this discussion, we will be primarily focusing on pathomechanism and approach to reach a diagnosis, which is the vital pillar to manage any case of ACDR.

  10. Modelling Tethered Enzymatic Reactions

    Science.gov (United States)

    Solis Salas, Citlali; Goyette, Jesse; Coker-Gordon, Nicola; Bridge, Marcus; Isaacson, Samuel; Allard, Jun; Maini, Philip; Dushek, Omer

    Enzymatic reactions are key to cell functioning, and whilst much work has been done in protein interaction in cases where diffusion is possible, interactions of tethered proteins are poorly understood. Yet, because of the large role cell membranes play in enzymatic reactions, several reactions may take place where one of the proteins is bound to a fixed point in space. We develop a model to characterize tethered signalling between the phosphatase SHP-1 interacting with a tethered, phosphorylated protein. We compare our model to experimental data obtained using surface plasmon resonance (SPR). We show that a single SPR experiment recovers 5 independent biophysical/biochemical constants. We also compare the results between a three dimensional model and a two dimensional model. The work gives the opportunity to use known techniques to learn more about signalling processes, and new insights into how enzyme tethering alters cellular signalling. With support from the Mexican Council for Science and Technology (CONACyT), the Public Education Secretariat (SEP), and the Mexican National Autonomous University's Foundation (Fundacion UNAM).

  11. Spin distribution in neutron induced preequilibrium reactions

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D; Kawano, T; Chadwick, M; Devlin, M; Fotiades, N; Nelson, R O; Mitchell, G E; Garrett, P E; Agvaanluvsan, U; Becker, J A; Bernstein, L A; Macri, R; Younes, W

    2005-10-04

    The preequilibrium reaction mechanism makes an important contribution to neutron-induced reactions above E{sub n} {approx} 10 MeV. The preequilibrium process has been studied exclusively via the characteristic high energy neutrons produced at bombarding energies greater than 10 MeV. They are expanding the study of the preequilibrium reaction mechanism through {gamma}-ray spectroscopy. Cross-section measurements were made of prompt {gamma}-ray production as a function of incident neutron energy (E{sub n} = 1 to 250 MeV) on a {sup 48}Ti sample. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the Los Alamos Neutron Science Center facility. The prompt-reaction {gamma} rays were detected with the large-scale Compton-suppressed Germanium Array for Neutron Induced Excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The {gamma}-ray excitation functions were converted to partial {gamma}-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). Residual state population was predicted using the GNASH reaction code, enhanced for preequilibrium. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshback, Kerman, and Koonin (FKK). The multistep direct part of the FKK theory was calculated for a one-step process. The FKK preequilibrium spin distribution was incorporated into the GNASH calculations and the {gamma}-ray production cross sections were calculated and compared with experimental data. The difference in the partial {gamma}-ray cross sections using spin distributions with and without preequilibrium effects is significant.

  12. Relative Lyapunov Center Bifurcations

    DEFF Research Database (Denmark)

    Wulff, Claudia; Schilder, Frank

    2014-01-01

    Relative equilibria (REs) and relative periodic orbits (RPOs) are ubiquitous in symmetric Hamiltonian systems and occur, for example, in celestial mechanics, molecular dynamics, and rigid body motion. REs are equilibria, and RPOs are periodic orbits of the symmetry reduced system. Relative Lyapunov...... center bifurcations are bifurcations of RPOs from REs corresponding to Lyapunov center bifurcations of the symmetry reduced dynamics. In this paper we first prove a relative Lyapunov center theorem by combining recent results on the persistence of RPOs in Hamiltonian systems with a symmetric Lyapunov...

  13. Molecular beam studies of reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.T. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  14. Mechanisms for control of biological electron transfer reactions.

    Science.gov (United States)

    Williamson, Heather R; Dow, Brian A; Davidson, Victor L

    2014-12-01

    Electron transfer (ET) through and between proteins is a fundamental biological process. The rates and mechanisms of these ET reactions are controlled by the proteins in which the redox centers that donate and accept electrons reside. The protein influences the magnitudes of the ET parameters, the electronic coupling and reorganization energy that are associated with the ET reaction. The protein can regulate the rates of the ET reaction by requiring reaction steps to optimize the system for ET, leading to kinetic mechanisms of gated or coupled ET. Amino acid residues in the segment of the protein through which long range ET occurs can also modulate the ET rate by serving as staging points for hopping mechanisms of ET. Specific examples are presented to illustrate these mechanisms by which proteins control rates of ET reactions. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Organolanthanide reagents and the Mukaiyama reaction

    Energy Technology Data Exchange (ETDEWEB)

    Gong, L.

    1989-01-01

    The bis(pentamethylcyclopentadienyl) lutetium halide complex ((C/sub 5/Me/sub 5/)/sub 2/LuCl/center dot/THF) was synthesized and characterized. The crystal structure of this complex shows that the Lu is at the center of a distorted tetrahedron consisting of the centroids of two cyclopentadienyl rings, the oxygen atom of a tetrahydrofuran molecule and a chlorine atom. /sup 1/H NMR studies of toluene-d/sub 8/ solutions of (C/sub 5/Me/sub 5/LuCl(THF) + THF, (TMS/sub 2/CP)/sub 2/LuCl(THF) + THF, and (MeCp)/sub 2/LuCl(THF) + THF at various temperatures showed exchange processes between co- ordinated THF and free THF with average values of ..delta..G/sup ne/ of 13.0 /+-/ 0.3 kcal/mol, 11.1 /+-/ 0.1 kcal/mol and <11 kcal/mol at 0/degree/C, respectively. It has been found that under the influence of a catalytic amount (1--5 mol %) of (TMS/sub 2/Cp)/sub 2/YbCl dimer, silyl enol ethers (R/sub 1/R/sub 2/C = C(OR/sub 3/)OSiMe/sub 3/)) react with benzaldehyde smoothly in dichloromethane at room temperature, giving >99% of the aldol silyl ether (isolated yield: 90%) within 3 h. At /minus/78/degrees/C, the reaction gives kinetically controlled diastereoselectivity, which was not observed in the TiCl/sub 4/-mediated aldol reaction. The use of organoytterbium enolates shows promise result with respect to increased stereoselectivity, and indicates the importance of the bulky ligands on the metal center. In addition, Yb(III) species can retard retroaldol reaction owing to its mild Lewis acidity. 118 refs., 14 figs., 30 tabs.

  16. Center Innovation Fund Program

    Data.gov (United States)

    National Aeronautics and Space Administration — To stimulate and encourage creativity and innovation within the NASA Centers. The activities are envisioned to fall within the scope of NASA Space Technology or...

  17. FEMA Disaster Recovery Centers

    Data.gov (United States)

    Department of Homeland Security — This is a search site for FEMA's Disaster Recovery Centers (DRC). A DRC is a readily accessible facility or mobile office set up by FEMA where applicants may go for...

  18. Center for Contaminated Sediments

    Data.gov (United States)

    Federal Laboratory Consortium — The U.S. Army Corps of Engineers Center for Contaminated Sediments serves as a clearinghouse for technology and expertise concerned with contaminated sediments. The...

  19. National Automotive Center - NAC

    Data.gov (United States)

    Federal Laboratory Consortium — Encouraged by the advantages of collaboration, the U.S. Army Tank Automotive Research, Development and Engineering Center (TARDEC) worked with the Secretary of the...

  20. Cooperative Tagging Center (CTC)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Cooperative Tagging Center (CTC) began as the Cooperative Game Fish Tagging Program (GTP) at Woods Hole Oceanographic Institute (WHOI) in 1954. The GTP was...

  1. HUD Homeownership Centers

    Data.gov (United States)

    Department of Housing and Urban Development — HUD Homeownership Centers (HOCs) insure single family Federal Housing Administration (FHA) mortgages and oversee the selling of HUD homes. FHA has four Homeownership...

  2. Children's cancer centers

    Science.gov (United States)

    ... workers Mental health experts Therapists Child life workers Teachers Clergy Centers also offer many specific benefits such ... M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health ...

  3. USU Patient Simulation Center

    Data.gov (United States)

    Federal Laboratory Consortium — he National Capital Area (NCA) Medical Simulation Center is a state-of-the-art training facility located near the main USU campus. It uses simulated patients (i.e.,...

  4. Center for Hydrogen Storage.

    Science.gov (United States)

    2013-06-01

    The main goals of this project were to (1) Establish a Center for Hydrogen Storage Research at Delaware State University for the preparation and characterization of selected complex metal hydrides and the determination their suitability for hydrogen ...

  5. Advanced Missile Signature Center

    Data.gov (United States)

    Federal Laboratory Consortium — The Advanced Missile Signature Center (AMSC) is a national facility supporting the Missile Defense Agency (MDA) and other DoD programs and customers with analysis,...

  6. Mobility Data Analytics Center.

    Science.gov (United States)

    2016-01-01

    Mobility Data Analytics Center aims at building a centralized data engine to efficiently manipulate : large-scale data for smart decision making. Integrating and learning the massive data are the key to : the data engine. The ultimate goal of underst...

  7. World Trade Center

    Index Scriptorium Estoniae

    2006-01-01

    Esilinastus katastroofifilm "World Trade Center" : stsenarist Andrea Berloff : režissöör Oliver Stone : kunstnik Jan Roelfs : osades Nicholas Cage, Michael Pena, Stephen Dorff jpt : Ameerika Ühendriigid 2006. Ka filmi prototüüpidest

  8. Mental Health Screening Center

    Science.gov (United States)

    ... Releases & Announcements Public Service Announcements Partnering with DBSA Mental Health Screening Center These online screening tools are not ... you have any concerns, see your doctor or mental health professional. Depression Screening for Adult Depression Screening for ...

  9. Global Hydrology Research Center

    Data.gov (United States)

    National Aeronautics and Space Administration — The GHRC is the data management and user services arm of the Global Hydrology and Climate Center. It encompasses the data and information management, supporting...

  10. Facility Focus: Athletic Centers.

    Science.gov (United States)

    College Planning & Management, 2002

    2002-01-01

    Describes the designs of the Jesse Owens Memorial Stadium at Ohio State University and the fitness center of Scottsdale Community College in Arizona. Discusses design goals and unique features and includes photographs. (EV)

  11. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... CONSUMER PRODUCT SAFETY COMMISSION Search CPSC Search Menu Home Recalls Recall List CPSC Recall API Recall Lawsuits ... and Bans Report an Unsafe Product Consumers Businesses Home Safety Education Safety Education Centers Carbon Monoxide Information ...

  12. Accredited Birth Centers

    Science.gov (United States)

    ... Birthing Center-Cedar Park Accredited 1130 Cottonwood Creek Trail Building D Suite 2 Cedar Park, TX 78613 ... Health Accredited 29135 Ellensburg Avenue PO Box 1710 Gold Beach, OR 97444 541-425-5311 Accredited since ...

  13. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... Community Outreach Resource Center Toy Recall Statistics CO Poster Contest Pool Safely Business & Manufacturing Business & Manufacturing Business ... Featured Resources CPSC announces winners of carbon monoxide poster contest Video View the blog Clues You Can ...

  14. Beringin Youth Center

    OpenAIRE

    Putra, Yogi Pratama

    2016-01-01

    Development Kualanamu International Airport will have an impact on the growth of a region. Regional growth requires improving the quality of human resources in the area. Beringin Youth Development Center in addition to a youth facility and infrastructure is also useful to improve the quality of the resource the youth, with youth activities are creative. In addition to local youth activities, Beringin Youth Center can be used to perform youth international scale, with mess facil...

  15. Centering device for casings

    Energy Technology Data Exchange (ETDEWEB)

    Abdulzade, A.M.G.; Aliyev, R.K.; Karash, E.B.; Mamedov, T.R.G.; Puzanov, A.N.; Yakobashvili, M.V.

    1982-01-01

    A centering device is proposed for casings consisting of 2 rings connected by spring planks, and bushing with support element. In order to improve operating reliability of the centering device in the twisted well, the support element of the bushing is made in a cross section in the form of an ellipse and on the outer surface has spiral slits. A support element can be made of elastic material.

  16. Well sealing via thermite reactions

    Science.gov (United States)

    Lowry, William Edward; Dunn, Sandra Dalvit

    2016-11-15

    A platform is formed in a well below a target plug zone by lowering a thermite reaction charge into the well and igniting it, whereby the products of the reaction are allowed to cool and expand to form a platform or support in the well. A main thermite reaction charge is placed above the platform and ignited to form a main sealing plug for the well. In some embodiments an upper plug is formed by igniting an upper thermite reaction charge above the main thermite reaction charge. The upper plug confines the products of ignition of the main thermite reaction charge.

  17. Laser Candidate Reactions of O2F.

    Science.gov (United States)

    1980-07-01

    0039 9, PRFRORMING ORGANIZATION ’ NAME AND ADDRESS 1o. 0ROGRAM ELE MENT, PROJEC, TASK Rockwell International Science Center AREA 4 ,ORK WITNM S 1049...69, 4338 (1965). 15. R.W. Fessenden and R.H. Schuler, J. Chem. Phys., 44, 434 (1966). 16. P.N. Noble and G.C. Pimentel, J. Chem. Phys., 44, 3641...Systems," Physical Chemistry of Fast Reactions, Vol. 1, B.J. Levitt, Ed., Plenum Press, London, 1973, pp 245-330. 38. R.A. Dunie, Proc. Roy. Soc., A207

  18. Laser Spot Detection Based on Reaction Diffusion

    Directory of Open Access Journals (Sweden)

    Alejandro Vázquez-Otero

    2016-03-01

    Full Text Available Center-location of a laser spot is a problem of interest when the laser is used for processing and performing measurements. Measurement quality depends on correctly determining the location of the laser spot. Hence, improving and proposing algorithms for the correct location of the spots are fundamental issues in laser-based measurements. In this paper we introduce a Reaction Diffusion (RD system as the main computational framework for robustly finding laser spot centers. The method presented is compared with a conventional approach for locating laser spots, and the experimental results indicate that RD-based computation generates reliable and precise solutions. These results confirm the flexibility of the new computational paradigm based on RD systems for addressing problems that can be reduced to a set of geometric operations.

  19. A reaction diffusion model of pattern formation in clustering of adatoms on silicon surfaces

    Directory of Open Access Journals (Sweden)

    Trilochan Bagarti

    2012-12-01

    Full Text Available We study a reaction diffusion model which describes the formation of patterns on surfaces having defects. Through this model, the primary goal is to study the growth process of Ge on Si surface. We consider a two species reaction diffusion process where the reacting species are assumed to diffuse on the two dimensional surface with first order interconversion reaction occuring at various defect sites which we call reaction centers. Two models of defects, namely a ring defect and a point defect are considered separately. As reaction centers are assumed to be strongly localized in space, the proposed reaction-diffusion model is found to be exactly solvable. We use Green's function method to study the dynamics of reaction diffusion processes. Further we explore this model through Monte Carlo (MC simulations to study the growth processes in the presence of a large number of defects. The first passage time statistics has been studied numerically.

  20. Insect bite reactions

    Directory of Open Access Journals (Sweden)

    Sanjay Singh

    2013-01-01

    Full Text Available Insects are a class of living creatures within the arthropods. Insect bite reactions are commonly seen in clinical practice. The present review touches upon the medically important insects and their places in the classification, the sparse literature on the epidemiology of insect bites in India, and different variables influencing the susceptibility of an individual to insect bites. Clinical features of mosquito bites, hypersensitivity to mosquito bites Epstein-Barr virus NK (HMB-EBV-NK disease, eruptive pseudoangiomatosis, Skeeter syndrome, papular pruritic eruption of HIV/AIDS, and clinical features produced by bed bugs, Mexican chicken bugs, assassin bugs, kissing bugs, fleas, black flies, Blandford flies, louse flies, tsetse flies, midges, and thrips are discussed. Brief account is presented of the immunogenic components of mosquito and bed bug saliva. Papular urticaria is discussed including its epidemiology, the 5 stages of skin reaction, the SCRATCH principle as an aid in diagnosis, and the recent evidence supporting participation of types I, III, and IV hypersensitivity reactions in its causation is summarized. Recent developments in the treatment of pediculosis capitis including spinosad 0.9% suspension, benzyl alcohol 5% lotion, dimethicone 4% lotion, isopropyl myristate 50% rinse, and other suffocants are discussed within the context of evidence derived from randomized controlled trials and key findings of a recent systematic review. We also touch upon a non-chemical treatment of head lice and the ineffectiveness of egg-loosening products. Knockdown resistance (kdr as the genetic mechanism making the lice nerves insensitive to permethrin is discussed along with the surprising contrary clinical evidence from Europe about efficacy of permethrin in children with head lice carrying kdr-like gene. The review also presents a brief account of insects as vectors of diseases and ends with discussion of prevention of insect bites and some

  1. Low Energy Nuclear Reactions?

    CERN Multimedia

    CERN. Geneva; Faccini, R.

    2014-01-01

    After an introduction to the controversial problem of Low Energy Nuclear Reactions (LENR) catalyzed by neutrons on metallic hydride surfaces we present the results of an experiment, made in collaboration with ENEA Labs in Frascati, to search neutrons from plasma discharges in electrolytic cells. The negative outcome of our experiment goes in the direction of ruling out those theoretical models expecting LENR to occur in condensed matter systems under specific conditions. Our criticism on the theoretical foundations of such models will also be presented.

  2. Transfusion reactions in pediatric compared with adult patients: a look at rate, reaction type, and associated products.

    Science.gov (United States)

    Oakley, Fredrick D; Woods, Marcella; Arnold, Shanna; Young, Pampee P

    2015-03-01

    The majority of reports on transfusion reactions address adult patients. Less is known about the types, incidence, and other clinical details of transfusion reactions in pediatric populations. Furthermore, to our knowledge, there have been no previous reports directly comparing these aspects between adults and pediatric patient populations to assess if there are differences. Between the period of January 1, 2011, and February 1, 2013, all reported adult and pediatric transfusion reactions at Vanderbilt University Medical Center (VUMC) were evaluated by transfusion medicine clinical service. The information was subsequently shared with the hemovigilance database. Data provided to hemovigilance included age, sex, blood product associated with the reaction, severity of the reaction, and the type of transfusion reactions. These were collated with hospital and blood bank information system-acquired data on overall admission and product transfusion. A total of 133,671 transfusions were performed at VUMC during the study period including 20,179 platelet (PLT) transfusions, 31,605 plasma transfusions, 79,933 red blood cell (RBC) transfusions, and 2154 cryoprecipitate transfusions. Over the same period, 108 pediatric and 277 adult transfusion reactions were recorded. This corresponds to an incidence of 6.2 reactions per 1000 transfusions within the pediatric (age reactions per 1000 transfusions within the adult population. In both adult and pediatric populations, transfusion reactions were most commonly associated with PLT, followed by RBC, and then plasma transfusions. Within the pediatric population, subset analysis identified multiple differences when compared to the adult population, including an increased incidence of allergic transfusion reactions (2.7/1000 vs. 1.1/1000, p reactions (1.9/1000 vs. 0.47/1000, p reactions (0.29/1000 vs. 0.078/1000, p reaction incidence was the same between sexes in adults, in pediatric patients, reactions were more common in male

  3. Mass Transfer with Chemical Reaction.

    Science.gov (United States)

    DeCoursey, W. J.

    1987-01-01

    Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)

  4. Anaphylactic reactions to novel foods

    DEFF Research Database (Denmark)

    Ballardini, Natalia; Nopp, Anna; Hamsten, Carl

    2017-01-01

    an anaphylactic reaction. Cross-reactivity between chicken and crocodile meat was suspected to have triggered this reaction. Basophil activation and immunoglobulin E testing confirmed the boy's allergic reaction to crocodile meat proteins. Molecular analysis identified a crocodile a-parvalbumin, with extensive...

  5. Reactions inside nanoscale protein cages

    NARCIS (Netherlands)

    Bode, Saskia A.; Minten, Inge J.; Nolte, Roeland J.M.; Cornelissen, Jeroen Johannes Lambertus Maria

    2011-01-01

    Chemical reactions are traditionally carried out in bulk solution, but in nature confined spaces, like cell organelles, are used to obtain control in time and space of conversion. One way of studying these reactions in confinement is the development and use of small reaction vessels dispersed in

  6. "Infotonics Technology Center"

    Energy Technology Data Exchange (ETDEWEB)

    Fritzemeier, L. [Infotonics Technology Center Inc., Canandaigua, NY (United States); Boysel, M. B. [Infotonics Technology Center Inc., Canandaigua, NY (United States); Smith, D. R. [Infotonics Technology Center Inc., Canandaigua, NY (United States)

    2004-09-30

    During this grant period July 15, 2002 thru September 30, 2004, the Infotonics Technology Center developed the critical infrastructure and technical expertise necessary to accelerate the development of sensors, alternative lighting and power sources, and other specific subtopics of interest to Department of Energy. Infotonics fosters collaboration among industry, universities and government and operates as a national center of excellence to drive photonics and microsystems development and commercialization. A main goal of the Center is to establish a unique, world-class research and development facility. A state-of-the-art microsystems prototype and pilot fabrication facility was established to enable rapid commercialization of new products of particular interest to DOE. The Center has three primary areas of photonics and microsystems competency: device research and engineering, packaging and assembly, and prototype and pilot-scale fabrication. Center activities focused on next generation optical communication networks, advanced imaging and information sensors and systems, micro-fluidic systems, assembly and packaging technologies, and biochemical sensors. With targeted research programs guided by the wealth of expertise of Infotonics business and scientific staff, the fabrication and packaging facility supports and accelerates innovative technology development of special interest to DOE in support of its mission and strategic defense, energy, and science goals.

  7. Engineer Research and Development Center's Materials Testing Center (MTC)

    Data.gov (United States)

    Federal Laboratory Consortium — The Engineer Research and Development Center's Materials Testing Center (MTC) is committed to quality testing and inspection services that are delivered on time and...

  8. Entanglement with centers

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Chen-Te [Department of Physics and Center for Theoretical Sciences, National Taiwan University, Taipei 10617 (China)

    2016-01-13

    Entanglement is a physical phenomenon that each state cannot be described individually. Entanglement entropy gives quantitative understanding to the entanglement. We use decomposition of the Hilbert space to discuss properties of the entanglement. Therefore, partial trace operator becomes important to define the reduced density matrix from different centers, which commutes with all elements in the Hilbert space, corresponding to different entanglement choices or different observations on entangling surface. Entanglement entropy is expected to satisfy the strong subadditivity. We discuss decomposition of the Hilbert space for the strong subadditivity and other related inequalities. The entanglement entropy with centers can be computed from the Hamitonian formulations systematically, provided that we know wavefunctional. In the Hamitonian formulation, it is easier to obtain symmetry structure. We consider massless p-form theory as an example. The massless p-form theory in (2p+2)-dimensions has global symmetry, similar to the electric-magnetic duality, connecting centers in ground state. This defines a duality structure in centers. Because it is hard to exactly compute the entanglement entropy from partial trace operator, we propose the Lagrangian formulation from the Hamitonian formulation to compute the entanglement entropy with centers. From the Lagrangian method and saddle point approximation, the codimension two surface term (leading order) in the Einstein gravity theory or holographic entanglement entropy should correspond to non-tensor product decomposition (center is not identity). Finally, we compute the entanglement entropy of the SU(N) Yang-Mills lattice gauge theory in the fundamental representation using the strong coupling expansion in the extended lattice model to obtain spatial area term in total dimensions larger than two for N>1.

  9. Entanglement with centers

    Science.gov (United States)

    Ma, Chen-Te

    2016-01-01

    Entanglement is a physical phenomenon that each state cannot be described individually. Entanglement entropy gives quantitative understanding to the entanglement. We use decomposition of the Hilbert space to discuss properties of the entanglement. Therefore, partial trace operator becomes important to define the reduced density matrix from different centers, which commutes with all elements in the Hilbert space, corresponding to different entanglement choices or different observations on entangling surface. Entanglement entropy is expected to satisfy the strong subadditivity. We discuss decomposition of the Hilbert space for the strong subadditivity and other related inequalities. The entanglement entropy with centers can be computed from the Hamitonian formulations systematically, provided that we know wavefunctional. In the Hamitonian formulation, it is easier to obtain symmetry structure. We consider massless p-form theory as an example. The massless p-form theory in (2 p + 2)-dimensions has global symmetry, similar to the electric-magnetic duality, connecting centers in ground state. This defines a duality structure in centers. Because it is hard to exactly compute the entanglement entropy from partial trace operator, we propose the Lagrangian formulation from the Hamitonian formulation to compute the entanglement entropy with centers. From the Lagrangian method and saddle point approximation, the codimension two surface term (leading order) in the Einstein gravity theory or holographic entanglement entropy should correspond to non-tensor product decomposition (center is not identity). Finally, we compute the entanglement entropy of the SU( N) Yang-Mills lattice gauge theory in the fundamental representation using the strong coupling expansion in the extended lattice model to obtain spatial area term in total dimensions larger than two for N > 1.

  10. PTSD: National Center for PTSD

    Medline Plus

    Full Text Available ... Us FAQs Ask a Question Toll Free Numbers Homeless Veterans Chat VA » Health Care » PTSD: National Center ... Vet Centers) War Related Illness & Injury Study Center Homeless Veterans Returning Service Members Rural Veterans Seniors & Aging ...

  11. Vet Centers. Final rule.

    Science.gov (United States)

    2016-03-02

    The Department of Veterans Affairs (VA) adopts as final an interim final rule that amends its medical regulation that governs Vet Center services. The National Defense Authorization Act for Fiscal Year 2013 (the 2013 Act) requires Vet Centers to provide readjustment counseling services to broader groups of veterans, members of the Armed Forces, including a member of a reserve component of the Armed Forces, and family members of such veterans and members. This final rule adopts as final the regulatory criteria to conform to the 2013 Act, to include new and revised definitions.

  12. User Centered Design

    DEFF Research Database (Denmark)

    Egbert, Maria; Matthews, Ben

    2012-01-01

    The interdisciplinary approach of User Centered Design is presented here with a focus on innovation in the design and use of hearing technologies as well as on the potential of innovation in interaction. This approach is geared towards developing new products, systems, technologies and practices...... based on an understanding of why so few persons with hearing loss use the highly advanced hearing technologies. In integrating Conversation Analysis (“CA”), audiology and User Centered Design, three disciplines which are collaborating together for the first time, we are addressing the following...

  13. Evaluation of periprocedural hypersensitivity reactions.

    Science.gov (United States)

    Iammatteo, Melissa; Keskin, Taha; Jerschow, Elina

    2017-10-01

    Identifying the cause of periprocedural hypersensitivity reactions (HSRs) remains challenging because of the multitude of medications involved. Antibiotics are the most common cause in the United States, whereas neuromuscular blocking agents are most common in Europe. To identify causative agents for periprocedural HSRs. This study was a 7-year retrospective medical record review of patients evaluated between December 2009 and January 2017 at a drug allergy center in Bronx, New York for periprocedural HSRs, defined as occurring soon before, during, or soon after a medical procedure or operation with or without general anesthesia. Demographics, description of historical HSRs, results of testing to potential causative medications, and tolerance of subsequent anesthesia were reviewed. Thirty-four patients completed a comprehensive evaluation. Skin testing identified an IgE-mediated cause in 22 patients (64.7%). The most common causative class of medications was induction agents (n = 9 [36%]), with midazolam being the most frequently implicated (n = 6 [3 positive skin test results, 3 equivocal skin test results]). Cefazolin was the most common agent identified (n = 8 [32%]) followed by ondansetron (n = 3 [12%]). Sixteen of 22 contacted patients were exposed to subsequent anesthesia, including 3 patients with negative evaluations. One patient experienced a mild urticarial HSR. Induction agents were the most common causative agents in our patients, which differs from other studies. Given the variability in evaluations of periprocedural HSRs across the United States with data published on small sample sizes, there is a need to establish national guidelines to standardize evaluations and to create a national registry to allow for data sharing. Copyright © 2017 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

  14. Nuclear reactions an introduction

    CERN Document Server

    Paetz gen. Schieck, Hans

    2014-01-01

    Nuclei and nuclear reactions offer a unique setting for investigating three (and in some cases even all four) of the fundamental forces in nature. Nuclei have been shown – mainly by performing scattering experiments with electrons, muons, and neutrinos – to be extended objects with complex internal structures: constituent quarks; gluons, whose exchange binds the quarks together; sea-quarks, the ubiquitous virtual quark-antiquark pairs and, last but not least, clouds of virtual mesons, surrounding an inner nuclear region, their exchange being the source of the nucleon-nucleon interaction.   The interplay between the (mostly attractive) hadronic nucleon-nucleon interaction and the repulsive Coulomb force is responsible for the existence of nuclei; their degree of stability, expressed in the details and limits of the chart of nuclides; their rich structure and the variety of their interactions. Despite the impressive successes of the classical nuclear models and of ab-initio approaches, there is clearly no ...

  15. Reaction Time for Trimolecular Reactions in Compartment-based Reaction-Diffusion Models

    OpenAIRE

    Li, F; Chen, M; Erban, R; Cao, Y

    2016-01-01

    Trimolecular reaction models are investigated in the compartment-based (lattice-based) framework for stochastic reaction-diffusion modelling. The formulae for the first collision time and the mean reaction time are derived for the case where three molecules are present in the solution.

  16. The Glaser–Hay reaction

    DEFF Research Database (Denmark)

    Vilhelmsen, Mie Højer; Jensen, Jonas; Tortzen, Christian

    2013-01-01

    . This unfavorable change in reaction profile could be avoided by adding molecular sieves to the reaction mixture, thereby removing the water that is accumulated from the air and produced in the reaction in which dioxygen acts as the oxidizing agent. Not unexpectedly, the stirring rate, and hence uptake of air (O2......), was found to have a significant effect on the rate of the reaction: The percentage of alkyne remaining after a certain time decreased linearly with the rate of stirring. On the basis of systematic studies, the optimized conditions for the coupling reaction using CuCl/TMEDA as the catalyst system......The oxidative Glaser–Hay coupling of two terminal alkynes to furnish a butadiyne is a key reaction for acetylenic scaffolding. Although the reaction is performed under rather simple conditions [CuCl/TMEDA/O2 (air)], the mechanism is still under debate. Herein we present detailed studies...

  17. Ion-Molecule Reaction Dynamics.

    Science.gov (United States)

    Meyer, Jennifer; Wester, Roland

    2017-05-05

    We review the recent advances in the investigation of the dynamics of ion-molecule reactions. During the past decade, the combination of single-collision experiments in crossed ion and neutral beams with the velocity map ion imaging detection technique has enabled a wealth of studies on ion-molecule reactions. These methods, in combination with chemical dynamics simulations, have uncovered new and unexpected reaction mechanisms, such as the roundabout mechanism and the subtle influence of the leaving group in anion-molecule nucleophilic substitution reactions. For this important class of reactions, as well as for many fundamental cation-molecule reactions, the information obtained with crossed-beam imaging is discussed. The first steps toward understanding micro-solvation of ion-molecule reaction dynamics are presented. We conclude with the presentation of several interesting directions for future research.

  18. Data Analysis and Assessment Center

    Data.gov (United States)

    Federal Laboratory Consortium — The DoD Supercomputing Resource Center (DSRC) Data Analysis and Assessment Center (DAAC) provides classified facilities to enhance customer interactions with the ARL...

  19. Reações adversas causadas por fármacos que atuam no sistema nervoso: análise de registros de um centro de farmacovigilância do Brasil Adverse reaction caused by drugs acting in nervous system: records analysis of a farmacovigilance center in Brazil

    Directory of Open Access Journals (Sweden)

    Marta Maria de França Fonteles

    2009-01-01

    Full Text Available CONTEXTO: A morbimortalidade por uso de medicamentos é um grande problema de saúde. As reações adversas a medicamentos podem resultar em óbito, aumento de internações hospitalares e dos custos com a saúde. OBJETIVOS: Descrever e analisar as notificações de suspeitas de reações adversas causadas por medicamentos que atuam no sistema nervoso (RAM-SN, registradas no Centro de Farmacovigilância do Ceará, de janeiro de 1997 a março de 2008. MÉTODOS: As RAM-SN foram classificadas segundo os critérios da Organização Mundial da Saúde. Uma relação de causalidade entre o fármaco administrado e a reação adversa identificada foi realizada, bem como a análise da reação quanto à gravidade. RESULTADOS: Foram registradas 176 notificações de RAM-SN. A maioria (n = 145; 82,4% ocorreu no ambiente hospitalar. O principal notificador foi o farmacêutico. As RAM-SN foram classificadas como: possíveis (n = 110, prováveis (n = 37 e definidas (n = 17. Quanto à gravidade, foram consideradas: leves (n = 21, moderadas (n = 127, graves (n = 15 e fatais (n = 1. O caso fatal foi notificado por médico e envolveu medicamentos anestésicos. Geralmente, as reações adversas observadas foram causadas predominantemente por analgésicos, anestésicos e antiepilépticos. DISCUSSÃO: Os dados demonstram o valor potencial de se ter acesso a sistemas de farmacovigilância local para registrar possíveis riscos com o uso de fármacos.BACKGROUND: The morbi-mortality by the use of medicines is a major health problem. The drug adverse reactions may result in death, increased hospitalizations and healthcare costs. OBJECTIVES: Describe and analyze reports of suspected adverse reactions caused by drugs that act on the nervous system (SN-ADR, registered in the database of the Pharmacovigilance Centre of Ceará, from January 1997 to March 2008. METHODS: All the NS-ADRs were classified according to criteria of the World Health Organization. The causality

  20. Center for Infrastructure Defense

    OpenAIRE

    2013-01-01

    Includes an image of the main page on this date and compressed file containing additional web pages. The Center for Infrastructure Defense (CID) focuses on the continued operation of critical military and civilian infrastructure in the presence of accident, failure, and attack. Operations Research (OR) Department in the Graduate School of Operational and Information Sciences at the Naval Postgraduate School.

  1. Carbon Monoxide Information Center

    Medline Plus

    Full Text Available ... English Bahasa Indonesia 한국어 Español ภาษาไทย Tiếng Việt Text Size: Decrease Font Increase Font Contact CPSC Consumers: ... Guide View All CO Safety Guides ")); jQuery(".node-type-safety-education-center .region-sidebar-second").css('display', " ...

  2. Queering the Writing Center

    Science.gov (United States)

    Denny, Harry

    2010-01-01

    Composition classrooms and writing centers are spaces where negotiation of academic, social, cultural, and political identities are ubiquitous, yet research has not produced adequate theory and practice to help tutors and writers navigate identity production and its politics. This article seeks to begin conversations that might lead to better…

  3. vCenter troubleshooting

    CERN Document Server

    Mills, Chuck

    2015-01-01

    The book is designed for the competent vCenter administrator or anyone who is responsible for the vSphere environment. It can be used as a guide by vSphere architects and VMware consultants for a successful vSphere solution. You should have good knowledge and an understanding of core elements and applications of the vSphere environment.

  4. NASA NEESPI Data Center

    Science.gov (United States)

    Leptoukh, G.; Loboda, T.; Romanov, P.; Gerasimov, I.; Csiszar, I.

    2006-12-01

    The Northern Eurasia Earth Science Partnership Initiative (NEESPI) is an international program of coordinated research on the state and dynamics of ecosystems in Northern Eurasia and their interactions with the Earth's Climate system. The program is designed to enhance scientific knowledge of these ecosystems as well as to develop predictive capabilities to support informed decision-making and practical applications. The NASA NEESPI Data Center is a multi-sensor, online, easy access data archive and distribution system to provide advanced data management capabilities in support of the NEESPI scientific objectives. Its tools include data analysis and visualization, and other techniques for better science data usage. The NASA NEESPI Data Center portal integrates remote sensing data from MODIS, AIRS, OMI, and other instruments on board polar- orbiting satellites, along with customized data products from climatology data sets and models into a single one-stop-shopping interdisciplinary NASA-NEESPI data center. The presentation will provide status and the most recent achievements of the NASA NEESPI Data Center. In the recent months, the emphasis has been put on analyzing and then preparing steps for the online data analysis by bringing data to common grids while preserving available and statistically important information from the higher resolution inputs. The NESSPI instance of Giovanni, the popular online visualization and analysis tool, features the first batch of atmospheric, fire and snow data products, organized to provide quick and user-friendly exploration means.

  5. Johnson Space Center Overview

    Science.gov (United States)

    Gafka, Tammy; Terrier, Doug; Smith, James

    2011-01-01

    This slide presentation is a review of the work of Johnson Space Center. It includes a section on technology development areas, (i.e., composite structures, non-destructive evaluation, applied nanotechnology, additive manufacturing, and fracture and fatigue analytical methods), a section on structural analysis capabilities within NASA/JSC and a section on Friction stir welding and laser peening.

  6. National Health Information Center

    Science.gov (United States)

    ... you can: Educate the public about health risks Organize successful health promotion events and campaigns Get new ... Centers and Clearinghouses provide free public information and resources. Many offer toll-free numbers and websites. Their ... Department of Health and Human Services. Office of Disease Prevention and Health Promotion ...

  7. Precision Joining Center

    Energy Technology Data Exchange (ETDEWEB)

    Powell, J.W.; Westphal, D.A.

    1991-08-01

    A workshop to obtain input from industry on the establishment of the Precision Joining Center (PJC) was held on July 10--12, 1991. The PJC is a center for training Joining Technologists in advanced joining techniques and concepts in order to promote the competitiveness of US industry. The center will be established as part of the DOE Defense Programs Technology Commercialization Initiative, and operated by EG G Rocky Flats in cooperation with the American Welding Society and the Colorado School of Mines Center for Welding and Joining Research. The overall objectives of the workshop were to validate the need for a Joining Technologists to fill the gap between the welding operator and the welding engineer, and to assure that the PJC will train individuals to satisfy that need. The consensus of the workshop participants was that the Joining Technologist is a necessary position in industry, and is currently used, with some variation, by many companies. It was agreed that the PJC core curriculum, as presented, would produce a Joining Technologist of value to industries that use precision joining techniques. The advantage of the PJC would be to train the Joining Technologist much more quickly and more completely. The proposed emphasis of the PJC curriculum on equipment intensive and hands-on training was judged to be essential.

  8. Nicolaus Copernicus Astronomical Center

    Science.gov (United States)

    Murdin, P.

    2000-11-01

    Nicolaus Copernicus Astronomical Center is the largest astronomical institution in Poland, located in Warsaw and founded in 1956. At present it is a government-funded research institute supervised by the Polish Academy of Sciences and licensed by the government of Poland to award PhD and doctor habilitatus degrees in astronomy and astrophysics. In September 1999 staff included 21 senior scientist...

  9. LCA Center Denmark

    DEFF Research Database (Denmark)

    Hauschild, Michael Zwicky; Frydendal, Jeppe

    2006-01-01

    product-oriented environmental tools in companies, to ensure that the LCA efforts is based on a solid and scientific basis, and to maintain the well-established co-operation between all important actors in the LCA field in Denmark. A status is given on the achievements of LCA Center Denmark...

  10. Carolinas Energy Career Center

    Energy Technology Data Exchange (ETDEWEB)

    Classens, Anver; Hooper, Dick; Johnson, Bruce

    2013-03-31

    Central Piedmont Community College (CPCC), located in Charlotte, North Carolina, established the Carolinas Energy Career Center (Center) - a comprehensive training entity to meet the dynamic needs of the Charlotte region's energy workforce. The Center provides training for high-demand careers in both conventional energy (fossil) and renewable energy (nuclear and solar technologies/energy efficiency). CPCC completed four tasks that will position the Center as a leading resource for energy career training in the Southeast: • Development and Pilot of a New Advanced Welding Curriculum, • Program Enhancement of Non-Destructive Examination (NDE) Technology, • Student Support through implementation of a model targeted toward Energy and STEM Careers to support student learning, • Project Management and Reporting. As a result of DOE funding support, CPCC achieved the following outcomes: • Increased capacity to serve and train students in emerging energy industry careers; • Developed new courses and curricula to support emerging energy industry careers; • Established new training/laboratory resources; • Generated a pool of highly qualified, technically skilled workers to support the growing energy industry sector.

  11. User-Centered Design through Learner-Centered Instruction

    Science.gov (United States)

    Altay, Burçak

    2014-01-01

    This article initially demonstrates the parallels between the learner-centered approach in education and the user-centered approach in design disciplines. Afterward, a course on human factors that applies learner-centered methods to teach user-centered design is introduced. The focus is on three tasks to identify the application of theoretical and…

  12. [Therapeutic experience in a Chagas disease center].

    Science.gov (United States)

    Abramson, Raúl; Figueroa, Patricia

    2013-11-01

    American Trypanosomiasis or Chagas Disease is a major public health problem, endemic in the American continent since prehistoric times. Its natural course is towards chronicity in the immunocompetent host, often leading to severe cardiopathy or bowel involvement. Pharmacologic therapy is restricted to two drugs and only one of them is currently available in Chile. Both have poor effectiveness in the chronic stages of the disease and cause frequent adverse reactions. Many physicians avoid their use, despite published evidences about the usefulness. We herein report the experience of our Center in the treatment of Chronic Chagas Disease in adults using the drug nifurtimox, emphasizing its degree of acceptability and its secondary effects.

  13. Guideline for the diagnosis of drug hypersensitivity reactions: S2K-Guideline of the German Society for Allergology and Clinical Immunology (DGAKI) and the German Dermatological Society (DDG) in collaboration with the Association of German Allergologists (AeDA), the German Society for Pediatric Allergology and Environmental Medicine (GPA), the German Contact Dermatitis Research Group (DKG), the Swiss Society for Allergy and Immunology (SGAI), the Austrian Society for Allergology and Immunology (ÖGAI), the German Academy of Allergology and Environmental Medicine (DAAU), the German Center for Documentation of Severe Skin Reactions and the German Federal Institute for Drugs and Medical Products (BfArM).

    Science.gov (United States)

    Brockow, Knut; Przybilla, Bernhard; Aberer, Werner; Bircher, Andreas J; Brehler, Randolf; Dickel, Heinrich; Fuchs, Thomas; Jakob, Thilo; Lange, Lars; Pfützner, Wolfgang; Mockenhaupt, Maja; Ott, Hagen; Pfaar, Oliver; Ring, Johannes; Sachs, Bernhardt; Sitter, Helmut; Trautmann, Axel; Treudler, Regina; Wedi, Bettina; Worm, Margitta; Wurpts, Gerda; Zuberbier, Torsten; Merk, Hans F

    Drug hypersensitivity reactions are unpredictable adverse drug reactions. They manifest either within 1-6 h following drug intake (immediate reactions) with mild to life-threatening symptoms of anaphylaxis, or several hours to days later (delayed reactions), primarily as exanthematous eruptions. It is not always possible to detect involvement of the immune system (allergy). Waiving diagnostic tests can result in severe reactions on renewed exposure on the one hand, and to unjustified treatment restrictions on the other. With this guideline, experts from various specialist societies and institutions have formulated recommendations and an algorithm for the diagnosis of allergies. The key principles of diagnosing allergic/hypersensitivity drug reactions are presented. Where possible, the objective is to perform allergy diagnostics within 4 weeks-6 months following the reaction. A clinical classification of symptoms based on the morphology and time course of the reaction is required in order to plan a diagnostic work-up. In the case of typical symptoms of a drug hypersensitivity reaction and unequivocal findings from validated skin and/or laboratory tests, a reaction can be attributed to a trigger with sufficient confidence. However, skin and laboratory tests are often negative or insufficiently reliable. In such cases, controlled provocation testing is required to clarify drug reactions. This method is reliable and safe when attention is paid to indications and contraindications and performed under appropriate medical supervision. The results of the overall assessment are discussed with the patient and documented in an "allergy passport" in order to ensure targeted avoidance in the future and allow the use of alternative drugs where possible.

  14. Far-red light is needed for efficient photochemistry and photosynthesis.

    Science.gov (United States)

    Zhen, Shuyang; van Iersel, Marc W

    2017-02-01

    The efficiency of monochromatic light to drive photosynthesis drops rapidly at wavelengths longer than 685nm. The photosynthetic efficiency of these longer wavelengths can be improved by adding shorter wavelength light, a phenomenon known as the Emerson enhancement effect. The reverse effect, the enhancement of photosynthesis under shorter wavelength light by longer wavelengths, however, has not been well studied and is often thought to be insignificant. We quantified the effect of adding far-red light (peak at 735nm) to red/blue or warm-white light on the photosynthetic efficiency of lettuce (Lactuca sativa). Adding far-red light immediately increased quantum yield of photosystem II (ΦPSII) of lettuce by an average of 6.5 and 3.6% under red/blue and warm-white light, respectively. Similar or greater increases in ΦPSII were observed after 20min of exposure to far-red light. This longer-term effect of far-red light on ΦPSII was accompanied by a reduction in non-photochemical quenching of fluorescence (NPQ), indicating that far-red light reduced the dissipation of absorbed light as heat. The increase in ΦPSII and complementary decrease in NPQ is presumably due to preferential excitation of photosystem I (PSI) by far-red light, which leads to faster re-oxidization of the plastoquinone pool. This facilitates reopening of PSII reaction centers, enabling them to use absorbed photons more efficiently. The increase in ΦPSII by far-red light was associated with an increase in net photosynthesis (Pn). The stimulatory effect of far-red light increased asymptotically with increasing amounts of far-red. Overall, our results show that far-red light can increase the photosynthetic efficiency of shorter wavelength light that over-excites PSII. Copyright © 2016 Elsevier GmbH. All rights reserved.

  15. Chemical research on red pigments after adverse reactions to tattoo.

    Science.gov (United States)

    Tammaro, A; Toniolo, C; Giulianelli, V; Serafini, M; Persechino, S

    2016-03-01

    Currently, the incidence of tattooing is on the rise compared to the past, especially among adolescents, and it leads to the urgency of monitoring the security status of tattooing centers, as well as to inform people about the risks of tattoo practice. In our clinical experience, 20% of tattooed patients presented adverse reactions, like allergic contact dermatitis, psoriasis with Koebner's phenomena and granulomatous reactions, with the latter most prevalent and most often related to red pigment. Adverse reactions to tattoo pigments, especially the red one, are well known and described in literature. Great attention has to be focused on the pigments used, especially for the presence of new substances, often not well known. For this reason, we decided to perform a study on 12 samples of red tattoo ink, obtained by patients affected by different cutaneous reactions in the site of tattoo, to analyze their chemical composition.

  16. Metal Chelation in Asymmetric Diels-Alder Reaction (II)

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Kyoo Hyun; Chu, Chan Kook; Chang, Min Ho [Inha University, Incheon (Korea, Republic of)

    2004-03-15

    In the reaction, the inverse asymmetric induction has been observed by the use of either monovalent Lewis acids or divalent Lewis acids. The reaction of the acrylate of (S)-ethyl lactate with cyclopentadiene proceeded with 86% endo-S selectivity in the presence of TiCl{sub 4}, divalent Lewis acid, whereas did with 32% endo-R selectivity in the presence of BF{sub 3{center_dot}}Et{sub 2}O, monovalent Lewis acid. When a chiral dienophile which was prepared from benzyl ester of (S)-proline or methyl ester of (S)-indoline-2-carboxylic acid was employed in the reaction, a similar diastereofacial selectivity was also observed. Recently, we reported the similar selectivity in the reaction of methyl (2S,5S)-(5-t-butyldimethylsilyloxypiperidin- 2-yl)ethanoatewith cyclopentadiene.

  17. Preaggregation reactions of platelets.

    Science.gov (United States)

    Gear, A R

    1981-09-01

    Whether platelet volume increases during the morphological changes preceding aggregation has been investigated. Previous research is controversial; resistive-counting techniques reveal an increase, centrifugal methods do not. Platelets were sized with a computerized, resistive-particle counter before and after incubation with adenosine diphosphate (ADP). Resistive volume increased by 14% (p less than 0.001) in the absence of EDTA, and only 7% in its presence (ADP, 10 micro M). EDTA inhibited platelet volume changes, whether these were shrinking induced by warming or swelling by ADP. Handling of platelets, such as during centrifugation, also caused particle swelling. Particle density decreased after ADP exposure, without release of serotonin, suggesting uptake of water. Platelet shape was experimentally manipulated to test the hypothesis that resistive volume changes stem from artifacts of particle shape. Scanning electron microscopy confirmed that colchicine, chlorpromazine, and a temperature cycle of 0 degrees to 37 degrees all caused extensive alteration from the disc shape. Subsequent exposure to ADP increased resistive volume, and in the case of chlorpromazine, no long pseudopodia were extruded. It is concluded that preaggregation reactions of platelets can be associated with an increase in particle volume, and that earlier research based on centrifugation and the presence of ETA failed to reveal the increase because of inhibitory and apparent swelling effects.

  18. Adverse Reactions to Biologic Therapy.

    Science.gov (United States)

    Patel, Sheenal V; Khan, David A

    2017-05-01

    Biologic therapies are emerging as a significant therapeutic option for many with debilitating inflammatory and autoimmune conditions. As expansion in the number of FDA-approved agents continue to be seen, more unanticipated adverse reactions are likely to occur. Currently, the diagnostic tools, including skin testing and in vitro testing, to evaluate for immediate hypersensitivity reactions are insufficient. In this review, management strategies for common acute infusion reactions, injection site reactions, and immediate reactions suggestive of IgE-mediated mechanisms are discussed. Desensitization can be considered for reactions suggestive of IgE-mediated mechanisms, but allergists/immunologists should be involved in managing these patients. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. The Progression of Sequential Reactions

    Directory of Open Access Journals (Sweden)

    Jack McGeachy

    2010-01-01

    Full Text Available Sequential reactions consist of linked reactions in which the product of the first reaction becomes the substrate of a second reaction. Sequential reactions occur in industrially important processes, such as the chlorination of methane. A generalized series of three sequential reactions was analyzed in order to determine the times at which each chemical species reaches its maximum. To determine the concentration of each species as a function of time, the differential rate laws for each species were solved. The solution of each gave the concentration curve of the chemical species. The concentration curves of species A1 and A2 possessed discreet maxima, which were determined through slope-analysis. The concentration curve of the final product, A3, did not possess a discreet maximum, but rather approached a finite limit.

  20. The Paterno-Buchi reaction

    DEFF Research Database (Denmark)

    Brogaard, Rasmus Yding; Schalk, Oliver; Boguslavskiy, Andrey E.

    2012-01-01

    The Paternò-Büchi (PB) reaction between an excited carbonyl compound and an alkene has been widely studied, but so far little is known about the excited-state dynamics of the reaction. In this investigation, we used a compound in which a formyl and a vinyl group are attached to a [2.......2]paracyclophane in order to obtain a model system in pre-reactive conformation for the PB reaction. We studied the excited-state dynamics of the isolated molecule in a molecular beam using femtosecond time-resolved photoelectron spectroscopy and ab initio calculations. The results show that inter-system crossing...... within two picoseconds competes efficiently with the reaction in the singlet manifold. Thus, the PB reaction in this model system takes place in the triplet state on a time scale of nanoseconds. This result stresses the importance of triplet states in the excited-state pathway of the PB reaction...

  1. Multifrequency EPR and ENDOR spectroscopy of the S2-state of the manganese complex in photosystem II

    OpenAIRE

    Pudollek, Susanne

    2012-01-01

    Plants, green algae and cyanobacteria alike use oxygenic photosynthesis to transform harvested light into chemical energy. The oxygen which is released from oxidised water molecules forms the basis of animal and human life. The reaction cycle of catalytic dissociation of the water molecules takes place within a large protein complex called Photosystem II (PSII). Its catalytic center is the WaterOxidizing Complex (WOC) comprising four manganese and a calcium ion. The underlying reaction mechan...

  2. Nuclear astrophysics from direct reactions

    Energy Technology Data Exchange (ETDEWEB)

    Bertulani, C. [Department of Physics, Texas A and M University, Commerce, TX 75429 (United States)]. e-mail: carlos_bertulani@tamu-commerce.edu

    2008-12-15

    Accurate nuclear reaction rates are needed for primordial nucleosynthesis and hydrostatic burning in stars. The relevant reactions are extremely difficult to measure directly in the laboratory at the small astrophysical energies. In recent years direct reactions have been developed and applied to extract low-energy astrophysical S-factors. These methods require a combination of new experimental techniques and theoretical efforts, which are the subject of this presentation. (Author)

  3. Stochastic Modeling Of Biochemical Reactions

    Science.gov (United States)

    2006-11-01

    STOCHASTIC MODELING OF BIOCHEMICAL REACTIONS Abhyudai Singh and João Pedro Hespanha* Department of Electrical and Computer Engineering University of...procedure for con- structing approximate stochastic models for chemical reactions used for modeling biochemical processes such as gene regulatory networks... biochemical reactions , the modeling tools developed in this paper can be applied to a very general class of stochastic systems, in particular

  4. COMPUTATIONAL SCIENCE CENTER

    Energy Technology Data Exchange (ETDEWEB)

    DAVENPORT,J.

    2004-11-01

    The Brookhaven Computational Science Center brings together researchers in biology, chemistry, physics, and medicine with applied mathematicians and computer scientists to exploit the remarkable opportunities for scientific discovery which have been enabled by modern computers. These opportunities are especially great in computational biology and nanoscience, but extend throughout science and technology and include for example, nuclear and high energy physics, astrophysics, materials and chemical science, sustainable energy, environment, and homeland security.

  5. Nanomaterials Commercialization Center

    Science.gov (United States)

    2013-02-01

    October 2009, with input from the AFRL an additional technology thrust was added to the Technology Roadmap which focused on nanomaterials for new energy...NanoCenter’s Technology Advisory Committee, an additional technology thrust was added to the Technology Roadmap which focused on nanomaterials for new...the moisture sensor were questionable. Besides, we could not really tell the moisture value was from environment, clinician hands or user’s hip

  6. [Situational reactions in suicidologic practice].

    Science.gov (United States)

    Ambrumova, A G; Vrono, E M

    1985-01-01

    The paper is devoted to the description of suicidal manifestations in mentally normal adolescents among typical behavioural disorders characteristic of situational reactions of this age. Three types of suicido-dangerous situational responses of adolescents were specified with regard to their age and auto-and heteaggressiveness ratio: reaction of deprivation, explosive reaction and reaction of auto-elimination. Suicidogenic conflicts were analyzed and spheres of age-specific suicidal conflicts were defined. It is advisable that outpatient management of mentally normal adolescents with a history of a suicidal attempt be conducted in a special room of presentive suicidological service.

  7. Exploring the active center of human acetylcholinesterase with stereomers of an organophosphorus inhibitor with two chiral centers

    NARCIS (Netherlands)

    Ordentlich, A.; Barak, D.; Kronman, C.; Benschop, H.P.; Jong, L.P.A. de; Ariel, N.; Barak, R.; Segall, Y.; Velan, B.; Shafferman, A.

    1999-01-01

    The stereoselectivity of the phosphonylation reaction and the effects of adduct configuration on the aging process were examined for human acetylcholinesterase (HuAChE) and its selected active center mutants, using the four stereomers of 1,2,2-trimethylpropyl methylphosphonofluoridate (soman). The

  8. Dynamic Reaction Figures: An Integrative Vehicle for Understanding Chemical Reactions

    Science.gov (United States)

    Schultz, Emeric

    2008-01-01

    A highly flexible learning tool, referred to as a dynamic reaction figure, is described. Application of these figures can (i) yield the correct chemical equation by simply following a set of menu driven directions; (ii) present the underlying "mechanism" in chemical reactions; and (iii) help to solve quantitative problems in a number of different…

  9. Atmospheric oxidation of halogenated aromatics: comparative analysis of reaction mechanisms and reaction kinetics.

    Science.gov (United States)

    Kovacevic, Goran; Sabljic, Aleksandar

    2017-03-22

    Atmospheric transport is the major route for global distribution of semi-volatile compounds such as halogenated aromatics as well as their major exposure route for humans. Their major atmospheric removal process is oxidation by hydroxyl radicals. There is very little information on the reaction mechanism or reaction-path dynamics of atmospheric degradation of halogenated benzenes. Furthermore, the measured reaction rate constants are missing for the range of environmentally relevant temperatures, i.e. 230-330 K. A series of recent theoretical studies have provided those valuable missing information for fluorobenzene, chlorobenzene, hexafluorobenzene and hexachlorobenzene. Their comparative analysis has provided additional and more general insight into the mechanism of those important tropospheric degradation processes as well as into the mobility, transport and atmospheric fate of halogenated aromatic systems. It was demonstrated for the first time that the addition of hydroxyl radicals to monohalogenated as well as to perhalogenated benzenes proceeds indirectly, via a prereaction complex and its formation and dynamics have been characterized including the respective transition-state. However, in fluorobenzene and chlorobenzene reactions hydroxyl radical hydrogen is pointing approximately to the center of the aromatic ring while in the case of hexafluorobenzene and hexachlorobenzene, unexpectedly, the oxygen is directed towards the center of the aromatic ring. The reliable rate constants are now available for all environmentally relevant temperatures for the tropospheric oxidation of fluorobenzene, chlorobenzene, hexafluorobenzene and hexachlorobenzene while pentachlorophenol, a well-known organic micropollutant, seems to be a major stable product of tropospheric oxidation of hexachlorobenzene. Their calculated tropospheric lifetimes show that fluorobenzene and chlorobenzene are easily removed from the atmosphere and do not have long-range transport potential while

  10. Progress in microscopic direct reaction modeling of nucleon induced reactions

    Energy Technology Data Exchange (ETDEWEB)

    Dupuis, M.; Bauge, E.; Hilaire, S.; Lechaftois, F.; Peru, S.; Pillet, N.; Robin, C. [CEA, DAM, DIF, Arpajon (France)

    2015-12-15

    A microscopic nuclear reaction model is applied to neutron elastic and direct inelastic scatterings, and pre-equilibrium reaction. The JLM folding model is used with nuclear structure information calculated within the quasi-particle random phase approximation implemented with the Gogny D1S interaction. The folding model for direct inelastic scattering is extended to include rearrangement corrections stemming from both isoscalar and isovector density variations occurring during a transition. The quality of the predicted (n,n), (n,n{sup '}), (n,xn) and (n,n{sup '}γ) cross sections, as well as the generality of the present microscopic approach, shows that it is a powerful tool that can help improving nuclear reactions data quality. Short- and long-term perspectives are drawn to extend the present approach to more systems, to include missing reactions mechanisms, and to consistently treat both structure and reaction problems. (orig.)

  11. Mechanism and kinetics in reactions of caffeic acid with radicals by pulse radiolysis and calculation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xifeng; Cai, Zhongli; Katsumura, Yosuke [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab

    2000-03-01

    The interaction of caffeic acid with e{sub aq}{sup -}, (CH{sub 3}){sub 2}(OH) CCH{sub 2}{sup {center_dot}}, CO{sub 2}{sup {center_dot}}{sup -}, H{sup {center_dot}}, {center_dot}OH and N{sub 3}{sup {center_dot}} radicals were studied by {gamma}-, pulse radiolysis and molecular orbital calculation. UV-visible spectra of electron/{center_dot}OH adducts, semi-quinone radicals of caffeic ions, and the stable products from the reactions were derived. The rate constants were determined. The attacked sites and the most favorable structures of the transient radicals were predicted. Reaction mechanisms were proposed. (author)

  12. Standard Gibbs free energies of reactions of ozone with free radicals in aqueous solution: quantum-chemical calculations.

    Science.gov (United States)

    Naumov, Sergej; von Sonntag, Clemens

    2011-11-01

    Free radicals are common intermediates in the chemistry of ozone in aqueous solution. Their reactions with ozone have been probed by calculating the standard Gibbs free energies of such reactions using density functional theory (Jaguar 7.6 program). O(2) reacts fast and irreversibly only with simple carbon-centered radicals. In contrast, ozone also reacts irreversibly with conjugated carbon-centered radicals such as bisallylic (hydroxycylohexadienyl) radicals, with conjugated carbon/oxygen-centered radicals such as phenoxyl radicals, and even with nitrogen- oxygen-, sulfur-, and halogen-centered radicals. In these reactions, further ozone-reactive radicals are generated. Chain reactions may destroy ozone without giving rise to products other than O(2). This may be of importance when ozonation is used in pollution control, and reactions of free radicals with ozone have to be taken into account in modeling such processes.

  13. Adverse Reactions to Hallucinogenic Drugs.

    Science.gov (United States)

    Meyer, Roger E. , Ed.

    This reports a conference of psychologists, psychiatrists, geneticists and others concerned with the biological and psychological effects of lysergic acid diethylamide and other hallucinogenic drugs. Clinical data are presented on adverse drug reactions. The difficulty of determining the causes of adverse reactions is discussed, as are different…

  14. Pharmacogenetics of hypersensitivity drug reactions.

    Science.gov (United States)

    Negrini, Simone; Becquemont, Laurent

    2017-04-01

    Adverse drug reactions are a significant cause of morbidity and mortality and represent a major burden on the healthcare system. Some of those reactions are immunologically mediated (hypersensitivity reactions) and can be clinically subdivided into two categories: immediate reactions (IgE-related) and delayed reactions (T-cell-mediated). Delayed hypersensitivity reactions include both systemic syndromes and organ-specific toxicities and can be triggered by a wide range of chemically diverse drugs. Recent studies have demonstrated a strong genetic association between human leukocyte antigen alleles and susceptibility to delayed drug hypersensitivity. Most notable examples include human leukocyte antigen (HLA)-B*57:01 allele and abacavir hypersensitivity syndrome or HLA-B*15:02 and HLA-B*58:01 alleles related to severe cutaneous reactions induced by carbamazepine and allopurinol, respectively. This review aims to explore our current understanding in the field of pharmacogenomics of HLA-associated drug hypersensitivities and its translation into clinical practice for predicting adverse drug reactions. Copyright © 2017 Société française de pharmacologie et de thérapeutique. Published by Elsevier Masson SAS. All rights reserved.

  15. Engineering reactors for catalytic reactions

    Indian Academy of Sciences (India)

    Extensive studies have been conducted to establish sound basis for design and engineering of reactors for practising such catalytic reactions and for realizing improvements in reactor performance. In this article, application of recent (and not so recent) developments in engineering reactors for catalytic reactions is ...

  16. Incomplete fusion reactions in Ho

    Indian Academy of Sciences (India)

    It is now generally recognized that several reaction mechanisms are operative in heavy- ion-induced reactions below 10 MeV/amu. Predominant among these are, complete fusion. (CF), deep-inelastic collision (DIC), and quasi-elastic collisions. As the projectile energy increases to 5–10 MeV/amu and above, it turns out that ...

  17. Free Radical Reactions in Food.

    Science.gov (United States)

    Taub, Irwin A.

    1984-01-01

    Discusses reactions of free radicals that determine the chemistry of many fresh, processed, and stored foods. Focuses on reactions involving ascorbic acid, myoglobin, and palmitate radicals as representative radicals derived from a vitamin, metallo-protein, and saturated lipid. Basic concepts related to free radical structure, formation, and…

  18. Semiconductor Photocatalysis for Chemoselective Radical Coupling Reactions.

    Science.gov (United States)

    Kisch, Horst

    2017-04-18

    Photocatalysis at semiconductor surfaces is a growing field of general photocatalysis because of its importance for the chemical utilization of solar energy. By analogy with photoelectrochemistry the basic mechanism of semiconductor photocatalysis can be broken down into three steps: photogenerated formation of surface redox centers (electron-hole pairs), interfacial electron transfer from and to substrates (often coupled with proton-transfer), and conversion of primary redox intermediates into the products. Sun driven water cleavage and carbon dioxide fixation are still in the state of basic research whereas aerial degradation reactions of pollutants have reached practical application for the cleaning of air. In addition, a great variety of organic transformations (not syntheses) have been reported. They include cis-trans isomerizations, valence isomerizations, cycloaddition reactions, intramolecular or intermolecular C-N and C-C couplings, partial oxidations, and reductions. In all cases, well-known products were formed but very rarely also isolated. As compared to conventional homogeneous organic synthesis, the photocatalytic reaction mode is of no advantage, although the opposite is quite often claimed in the literature. It is also noted that a high quantum yield does not implicate a high product yield, since it is measured at very low substrate conversion in order to minimize secondary photoreactions. That is especially important in semiconductor photocatalysis since photocorrosion of the photocatalyst often prevents long-time irradiation, as is the case for colloidal metal sulfide semiconductors, which in general are photochemically too unstable to be used in synthesis. In this Account, we first classify the numerous organic photoreactions catalyzed by semiconductor powders. The classification is based on easily obtainable experimental facts, namely the nature of the light absorbing reaction component and the reaction stoichiometry. Next we discuss the

  19. A value set for documenting adverse reactions in electronic health records.

    Science.gov (United States)

    Goss, Foster R; Lai, Kenneth H; Topaz, Maxim; Acker, Warren W; Kowalski, Leigh; Plasek, Joseph M; Blumenthal, Kimberly G; Seger, Diane L; Slight, Sarah P; Wah Fung, Kin; Chang, Frank Y; Bates, David W; Zhou, Li

    2017-12-14

    To develop a comprehensive value set for documenting and encoding adverse reactions in the allergy module of an electronic health record. We analyzed 2 471 004 adverse reactions stored in Partners Healthcare's Enterprise-wide Allergy Repository (PEAR) of 2.7 million patients. Using the Medical Text Extraction, Reasoning, and Mapping System, we processed both structured and free-text reaction entries and mapped them to Systematized Nomenclature of Medicine - Clinical Terms. We calculated the frequencies of reaction concepts, including rare, severe, and hypersensitivity reactions. We compared PEAR concepts to a Federal Health Information Modeling and Standards value set and University of Nebraska Medical Center data, and then created an integrated value set. We identified 787 reaction concepts in PEAR. Frequently reported reactions included: rash (14.0%), hives (8.2%), gastrointestinal irritation (5.5%), itching (3.2%), and anaphylaxis (2.5%). We identified an additional 320 concepts from Federal Health Information Modeling and Standards and the University of Nebraska Medical Center to resolve gaps due to missing and partial matches when comparing these external resources to PEAR. This yielded 1106 concepts in our final integrated value set. The presence of rare, severe, and hypersensitivity reactions was limited in both external datasets. Hypersensitivity reactions represented roughly 20% of the reactions within our data. We developed a value set for encoding adverse reactions using a large dataset from one health system, enriched by reactions from 2 large external resources. This integrated value set includes clinically important severe and hypersensitivity reactions. This work contributes a value set, harmonized with existing data, to improve the consistency and accuracy of reaction documentation in electronic health records, providing the necessary building blocks for more intelligent clinical decision support for allergies and adverse reactions.

  20. Beyond Control Centers

    Science.gov (United States)

    Trimble, Jay

    2017-01-01

    For NASA's Resource Prospector (RP) Lunar Rover Mission, we are moving away from a control center concept, to a fully distributed operation utilizing control nodes, with decision support from anywhere via mobile devices. This operations concept will utilize distributed information systems, notifications, mobile data access, and optimized mobile data display for off-console decision support. We see this concept of operations as a step in the evolution of mission operations from a central control center concept to a mission operations anywhere concept. The RP example is part of a trend, in which mission expertise for design, development and operations is distributed across countries and across the globe. Future spacecraft operations will be most cost efficient and flexible by following this distributed expertise, enabling operations from anywhere. For the RP mission we arrived at the decision to utilize a fully distributed operations team, where everyone operates from their home institution, based on evaluating the following factors: the requirement for physical proximity for near-real time command and control decisions; the cost of distributed control nodes vs. a centralized control center; the impact on training and mission preparation of flying the team to a central location. Physical proximity for operational decisions is seldom required, though certain categories of decisions, such as launch abort, or close coordination for mission or safety-critical near-real-time command and control decisions may benefit from co-location. The cost of facilities and operational infrastructure has not been found to be a driving factor for location in our studies. Mission training and preparation benefit from having all operators train and operate from home institutions.

  1. Limits for Stochastic Reaction Networks

    DEFF Research Database (Denmark)

    Cappelletti, Daniele

    Reaction systems have been introduced in the 70s to model biochemical systems. Nowadays their range of applications has increased and they are fruitfully used in dierent elds. The concept is simple: some chemical species react, the set of chemical reactions form a graph and a rate function...... of reactions. Let the rates of degradation of the intermediate species be functions of a parameter N that tends to innity. We consider a reduced system where the intermediate species have been eliminated, and nd conditions on the degradation rate of the intermediates such that the behaviour of the reduced...... is stated in the setting of multiscale reaction systems: the amounts of all the species and the rates of all the reactions of the original model can scale as powers of N. A similar result also holds for the deterministic case, as shown in Appendix IA. In Paper II, we focus on the stationary distributions...

  2. Reaction rates for reaction-diffusion kinetics on unstructured meshes

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2017-02-01

    The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model.

  3. Effective reaction rates for diffusion-limited reaction cycles.

    Science.gov (United States)

    Nałęcz-Jawecki, Paweł; Szymańska, Paulina; Kochańczyk, Marek; Miękisz, Jacek; Lipniacki, Tomasz

    2015-12-07

    Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme-substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%.

  4. Reaction rates for reaction-diffusion kinetics on unstructured meshes.

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2017-02-14

    The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model.

  5. Memorial Center - Milwaukee

    Directory of Open Access Journals (Sweden)

    Saarinen, Eero

    1959-12-01

    Full Text Available El Memorial Center de Milwaukee ha sido erigido en la parte más alta de la ciudad, coronando una enorme colina que domina ampliamente el conjunto urbano y un hermoso lago. Su emplazamiento, al final de un puente de grandes dimensiones, exigía que fuese tratado en armonía con éste, habiéndose adoptado por ello el sistema de colocar la edificación reposando sobre una planta totalmente diáfana que deja vista la estructura, cuyos esbeltos soportes dan sensación de monumentalidad.

  6. COMPUTATIONAL SCIENCE CENTER

    Energy Technology Data Exchange (ETDEWEB)

    DAVENPORT, J.

    2005-11-01

    The Brookhaven Computational Science Center brings together researchers in biology, chemistry, physics, and medicine with applied mathematicians and computer scientists to exploit the remarkable opportunities for scientific discovery which have been enabled by modern computers. These opportunities are especially great in computational biology and nanoscience, but extend throughout science and technology and include, for example, nuclear and high energy physics, astrophysics, materials and chemical science, sustainable energy, environment, and homeland security. To achieve our goals we have established a close alliance with applied mathematicians and computer scientists at Stony Brook and Columbia Universities.

  7. Self-Access Centers: Maximizing Learners' Access to Center Resources

    Science.gov (United States)

    McMurry, Benjamin L.; Tanner, Mark W.; Anderson, Neil J.

    2009-01-01

    Although some students have discovered how to use self-access centers effectively, the majority appear to be unaware of available resources. A website and database of materials were created to help students locate materials and use the Self-Access Study Center (SASC) at Brigham Young University's English Language Center (ELC) more effectively.…

  8. Sustainable Biofuels Development Center

    Energy Technology Data Exchange (ETDEWEB)

    Reardon, Kenneth F. [Colorado State Univ., Fort Collins, CO (United States)

    2015-03-01

    The mission of the Sustainable Bioenergy Development Center (SBDC) is to enhance the capability of America’s bioenergy industry to produce transportation fuels and chemical feedstocks on a large scale, with significant energy yields, at competitive cost, through sustainable production techniques. Research within the SBDC is organized in five areas: (1) Development of Sustainable Crops and Agricultural Strategies, (2) Improvement of Biomass Processing Technologies, (3) Biofuel Characterization and Engine Adaptation, (4) Production of Byproducts for Sustainable Biorefining, and (5) Sustainability Assessment, including evaluation of the ecosystem/climate change implication of center research and evaluation of the policy implications of widespread production and utilization of bioenergy. The overall goal of this project is to develop new sustainable bioenergy-related technologies. To achieve that goal, three specific activities were supported with DOE funds: bioenergy-related research initiation projects, bioenergy research and education via support of undergraduate and graduate students, and Research Support Activities (equipment purchases, travel to attend bioenergy conferences, and seminars). Numerous research findings in diverse fields related to bioenergy were produced from these activities and are summarized in this report.

  9. Promoting adverse drug reaction reporting: comparison of different approaches

    Directory of Open Access Journals (Sweden)

    Inês Ribeiro-Vaz

    2016-01-01

    Full Text Available ABSTRACT OBJECTIVE To describe different approaches to promote adverse drug reaction reporting among health care professionals, determining their cost-effectiveness. METHODS We analyzed and compared several approaches taken by the Northern Pharmacovigilance Centre (Portugal to promote adverse drug reaction reporting. Approaches were compared regarding the number and relevance of adverse drug reaction reports obtained and costs involved. Costs by report were estimated by adding the initial costs and the running costs of each intervention. These costs were divided by the number of reports obtained with each intervention, to assess its cost-effectiveness. RESULTS All the approaches seem to have increased the number of adverse drug reaction reports. We noted the biggest increase with protocols (321 reports, costing 1.96 € each, followed by first educational approach (265 reports, 20.31 €/report and by the hyperlink approach (136 reports, 15.59 €/report. Regarding the severity of adverse drug reactions, protocols were the most efficient approach, costing 2.29 €/report, followed by hyperlinks (30.28 €/report, having no running costs. Concerning unexpected adverse drug reactions, the best result was obtained with protocols (5.12 €/report, followed by first educational approach (38.79 €/report. CONCLUSIONS We recommend implementing protocols in other pharmacovigilance centers. They seem to be the most efficient intervention, allowing receiving adverse drug reactions reports at lower costs. The increase applied not only to the total number of reports, but also to the severity, unexpectedness and high degree of causality attributed to the adverse drug reactions. Still, hyperlinks have the advantage of not involving running costs, showing the second best performance in cost per adverse drug reactions report.

  10. National Center on Family Homelessness

    Science.gov (United States)

    ... You are here Home National Center on Family Homelessness Center A staggering 2.5 million children are ... raise awareness of the current state of child homelessness in the United States, documents the number of ...

  11. PTSD: National Center for PTSD

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  12. PTSD: National Center for PTSD

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    Full Text Available ... Toll Free Numbers Media Contact Locator Hospitals and Clinics Vet Centers Regional Benefits Offices Regional Loan Centers ... Creative Arts Festival Golden Age Games Summer Sports Clinic Training - Exposure - Experience (TEE) Tournament Wheelchair Games Winter ...

  13. Center for Veterinary Medicine (CVM)

    Data.gov (United States)

    Federal Laboratory Consortium — As seen on the center's logo, the mission statement for FDA's Center for Veterinary Medicine (CVM) reads: "Protecting Human and Animal Health." To achieve this broad...

  14. PTSD: National Center for PTSD

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    Full Text Available ... a Question Toll Free Numbers Media Contact Locator Hospitals and Clinics Vet Centers Regional Benefits Offices Regional ... TEE) Tournament Wheelchair Games Winter Sports Clinic Locations Hospitals & Clinics Vet Centers Regional Benefits Offices Regional Loan ...

  15. PTSD: National Center for PTSD

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    Full Text Available ... America's Freedoms Special Events Adaptive Sports Program Creative Arts Festival Golden Age Games Summer Sports Clinic Training - ... Community Providers and Clergy Co-Occurring Conditions Continuing Education Publications List of Center Publications Articles by Center ...

  16. PTSD: National Center for PTSD

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    Full Text Available ... Conditions Continuing Education Publications List of Center Publications Articles by Center Staff Clinician’s Trauma Update PTSD Research ... Search Tips Modify Your Search How to Obtain Articles Alerts User Guide Purpose and Scope Find Assessment ...

  17. PTSD: National Center for PTSD

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    Full Text Available ... Room Public Affairs News Releases Speeches Videos Publications National Observances Veterans Day Memorial Day Celebrating America's Freedoms ... PTSD: National Center for PTSD » Public » Videos PTSD: National Center for PTSD Menu Menu PTSD PTSD Home ...

  18. Italy INAF Data Center Report

    Science.gov (United States)

    Negusini, M.; Sarti, P.

    2013-01-01

    This report summarizes the activities of the Italian INAF VLBI Data Center. Our Data Center is located in Bologna, Italy and belongs to the Institute of Radioastronomy, which is part of the National Institute of Astrophysics.

  19. PTSD: National Center for PTSD

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    Full Text Available ... Plans, Budget, & Performance VA Center for Innovation (VACI) Agency Financial Report (AFR) Budget Submission Recovery Act Resources ... Locations Contact Us FAQs Ask a Question Toll Free Numbers VA » Health Care » PTSD: National Center for ...

  20. Center for Prostate Disease Research

    Data.gov (United States)

    Federal Laboratory Consortium — The Center for Prostate Disease Research is the only free-standing prostate cancer research center in the U.S. This 20,000 square foot state-of-the-art basic science...

  1. Daugherty Memorial Assessment Center (DMAC)

    Data.gov (United States)

    Federal Laboratory Consortium — Daugherty Memorial Assessment Center (DMAC) is a 39,000-square-foot facility that doubles the warfare center's high-secured performance assessment capabilities. DMAC...

  2. PTSD: National Center for PTSD

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    Full Text Available ... Community Providers and Clergy Co-Occurring Conditions Continuing Education Publications List of Center Publications Articles by Center ... Type List of Materials By Type Assessments Continuing Education Handouts Manuals Mobile Apps Publications Toolkits Videos Web ...

  3. PTSD: National Center for PTSD

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    Full Text Available ... Free Numbers Media Contact Locator Hospitals and Clinics Vet Centers Regional Benefits Offices Regional Loan Centers Cemetery ... A-Z Health Topic Finder My Health e Vet Prescriptions Refills Schedule a VA Appointment Crisis Prevention ...

  4. PTSD: National Center for PTSD

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    Full Text Available ... Media Room Public Affairs News Releases Speeches Videos Publications National Observances Veterans Day Memorial Day Celebrating America's ... Providers and Clergy Co-Occurring Conditions Continuing Education Publications List of Center Publications Articles by Center Staff ...

  5. Dialysis centers - what to expect

    Science.gov (United States)

    ... in a treatment center. This article focuses on hemodialysis at a treatment center. ... JT, Blake PG, Ing TS, eds. Handbook of Dialysis . 5th ed. ... TA. Hemodialysis. In: Skorecki K, Chertow GM, Marsden PA, Taal ...

  6. National Center for Biotechnology Information

    Science.gov (United States)

    ... to NCBI Sign Out NCBI National Center for Biotechnology Information Search database All Databases Assembly Biocollections BioProject ... Search Welcome to NCBI The National Center for Biotechnology Information advances science and health by providing access ...

  7. PTSD: National Center for PTSD

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    Full Text Available ... Topics For Veterans For Researchers Research Oversight Special Groups Caregivers Combat Veterans & their Families Readjustment Counseling (Vet Centers) War Related Illness & Injury Study Center Homeless Veterans Returning Service Members Rural Veterans Seniors & Aging Veterans Volunteers Women Veterans ...

  8. PTSD: National Center for PTSD

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    Full Text Available ... Conditions Continuing Education Publications List of Center Publications Articles by Center Staff Clinician’s Trauma Update PTSD Research Quarterly Publications Search Using the PILOTS Database What ...

  9. Center for Beam Physics, 1992

    Energy Technology Data Exchange (ETDEWEB)

    1993-06-01

    This report contains the following information on the center for beam physics: Facilities; Organizational Chart; Roster; Profiles of Staff; Affiliates; Center Publications (1991--1993); and 1992 Summary of Activities.

  10. Contact Center Manager Administration (CCMA)

    Data.gov (United States)

    Social Security Administration — CCMA is the server that provides a browser-based tool for contact center administrators and supervisors. It is used to manage and configure contact center resources...

  11. PTSD: National Center for PTSD

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    Full Text Available ... Clinic Locations Hospitals & Clinics Vet Centers Regional Benefits Offices Regional Loan Centers Cemetery Locations Contact Us ... PTSD PTSD Home For the Public Public Section Home PTSD Overview ...

  12. VT Designated Village Centers Boundary

    Data.gov (United States)

    Vermont Center for Geographic Information — This community revitalization program helps maintain or evolve small to medium-sized historic centers with existing civic and commercial buildings. The designation...

  13. VT Designated Growth Center Boundary

    Data.gov (United States)

    Vermont Center for Geographic Information — Growth centers aim to align public infrastructure and private building investments with a local framework of policies and regulations to ensure that 20 years of...

  14. PTSD: National Center for PTSD

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    Full Text Available ... and Media Research Topics For Veterans For Researchers Research Oversight Special Groups Caregivers Combat Veterans & their Families Readjustment Counseling (Vet Centers) War Related Illness & Injury Study Center Homeless Veterans Returning Service Members Rural Veterans ...

  15. PTSD: National Center for PTSD

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    Full Text Available ... Community Providers and Clergy Co-Occurring Conditions Continuing Education Publications List of Center Publications Articles by Center Staff Clinician’s Trauma Update PTSD Research ...

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  17. PTSD: National Center for PTSD

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  18. PTSD: National Center for PTSD

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    Full Text Available ... Arts Festival Golden Age Games Summer Sports Clinic Training - Exposure - Experience (TEE) Tournament Wheelchair Games Winter Sports Clinic Locations Hospitals & Clinics Vet Centers Regional Benefits Offices Regional Loan Centers Cemetery Locations Contact Us ...

  19. PTSD: National Center for PTSD

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    Full Text Available ... Readjustment Counseling (Vet Centers) War Related Illness & Injury Study Center Homeless Veterans Returning Service Members Rural Veterans ... Strat Plan FY 2014-2020 VA Plans, Budget, & Performance VA Claims Representation RESOURCES ... Veterans Health Administration Veterans Benefits Administration ...

  20. PTSD: National Center for PTSD

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  1. PTSD: National Center for PTSD

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    Full Text Available ... America's Freedoms Special Events Adaptive Sports Program Creative Arts Festival Golden Age Games Summer Sports Clinic Training - ... Readjustment Counseling (Vet Centers) War Related Illness & Injury Study Center Homeless Veterans Returning Service Members Rural Veterans ...

  2. Cyanide reaction with ninhydrin: elucidation of reaction and interference mechanisms.

    Science.gov (United States)

    Drochioiu, Gabi; Mangalagiu, Ionel; Avram, Ecaterina; Popa, Karin; Dirtu, Alin Constantin; Druta, Ioan

    2004-10-01

    A new sensitive spectrophotometric method has recently been developed for the trace determination of cyanide with ninhydrin. Cyanide ion was supposed to act as a specific base catalyst. Nevertheless, this paper demonstrates that the reported assay is based on a novel reaction of cyanide with 2,2-dihydroxy-1,3-indanedione, which affords purple or blue colored salts of 2-cyano-1,2,3-trihydroxy-2H indene. Hydrindantin is merely an intermediary of the reaction. The formation of a stable and isolable ninhydrin-cyanide compound has been confirmed by its preparation in crystalline form. Also, it is thoroughly characterized by elemental as well as MS, IR, UV/VIS and 1H NMR analyses. The Ruhemann's sequence of reactions of cyanide with ninhydrin has been reconsidered and an adequate mechanism of the reaction is proposed. As a consequence, the interference of oxidizers as well as copper, silver and mercury ions with the cyanide determination has been elucidated.

  3. Rapid biocatalytic polytransesterification: reaction kinetics in an exothermic reaction

    Science.gov (United States)

    Chaudhary; Beckman; Russell

    1998-08-20

    Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. We have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization. Rate of polymerization increases with the concentration of monomers. This is also reflected by the increase in the temperature of the reaction mixture. Using time-temperature-conversion contours, a differential method of kinetic analysis was used to calculate the energy of activation ( approximately 15.1 Kcal/mol). Copyright 1998 John Wiley & Sons, Inc.

  4. Metal halide hydrates as lewis acid catalysts for the conjugated friedel-crafts reactions of indoles and activated olefins

    Energy Technology Data Exchange (ETDEWEB)

    Schwalm, Cristiane S.; Ceschi, Marco Antonio; Russowsky, Dennis, E-mail: dennis@iq.ufrgs.b [Universidade Federal do Rio Grande do Sul (IQ/UFRGS), Porto Alegre, RS (Brazil). Inst. de Quimica

    2011-07-01

    Metal halide hydrates such as SnCl{sub 2{center_dot}}2H{sub 2}O, MnCl{sub 2{center_dot}}4H{sub 2}O, SrCl{sub 2{center_dot}}6H{sub 2}O, CrCl{sub 2{center_dot}}6H{sub 2}O, CoCl{sub 2{center_dot}}6H{sub 2}O e CeCl{sub 3{center_dot}}7H{sub 2}O were investigated as mild Lewis acids catalysts for the conjugate Friedel-Crafts reaction between indoles and activated olefins. The reactions were carried out with aliphatic unsaturated ketones over a period of days at room temperature, while chalcones reacted only under reflux conditions. The reactions with nitrostyrene s were either performed in solvent or under solventless conditions. In all cases reasonable to good yields were obtained. (author)

  5. Cell death in a harmful algal bloom causing species Alexandrium tamarense upon an algicidal bacterium induction.

    Science.gov (United States)

    Zhang, Huajun; Lv, Jinglin; Peng, Yun; Zhang, Su; An, Xinli; Xu, Hong; Zhang, Jun; Tian, Yun; Zheng, Wei; Zheng, Tianling

    2014-09-01

    Harmful algal blooms occur throughout the world, destroying aquatic ecosystems and threatening human health. The culture supernatant of the marine algicidal bacteria DHQ25 was able to lysis dinoflagellate Alexandrium tamarense. Loss of photosynthetic pigments, accompanied by a decline in Photosystem II (PSII) photochemical efficiency (Fv/Fm), in A. tamarense was detected under bacterial supernatant stress. Transmission electron microscope analysis showed obvious morphological modifications of chloroplast dismantling as a part of the algicidal process. The PSII electron transport chain was seriously blocked, with its reaction center damaged. This damage was detected in a relative transcriptional level of psbA and psbD genes, which encode the D1 and D2 proteins in the PSII reaction center. And the block in the electron transport chain of PSII might generate excessive reactive oxygen species (ROS) which could destroy the membrane system and pigment synthesis and activated enzymic antioxidant systems including superoxide dismutase (SOD) and catalase (CAT). This study indicated that marine bacteria with indirect algicidal activity played an important role in the changes of photosynthetic process in a harmful algal bloom species.

  6. DEKRA technology center - competency center for the automotive industry; DEKRA Technology Center - Kompetenzzentrum fuer die Automobilindustrie

    Energy Technology Data Exchange (ETDEWEB)

    Loeschner, W.; Bahnert, J. [DEKRA Automobil Test Center (Germany)

    2003-04-01

    Within the DEKRA Group, the DEKRA Automobil Test Center in Klettwitz near Dresden is part of the DEKRA Technology Center and comes under the test area of the Automobil GmbH. In tandem with the DEKRA Crash Center in Neumuenster it constitutes the Competency Center for the automotive and automotive parts supply industry. (orig.) [German] Das DEKRA Automobil Test Center in Klettwitz bei Dresden ist Teil des DEKRA Technology Center und im DEKRA Konzern in den Pruefbereich der Automobil GmbH eingegliedert. Zusammen mit der DEKRA Unfallforschung in Stuttgart und dem DEKRA Crashzentrum in Neumuenster bildet es das Kompetenzzentrum fuer die Automobil- und Zulieferindustrie. (orig.)

  7. Immunopharmacology and adverse drug reactions.

    Science.gov (United States)

    Rieder, M J

    1993-04-01

    Adverse drug reactions are common and troublesome complications of contemporary pharmacotherapy. Adverse drug reactions are frequently, and often incorrectly, referred to as "allergy". Although there are multiple mechanisms for adverse drug reactions, adverse drug reactions mediated by the immune system account for a disproportionate number of fatal and serious adverse reactions, and constitute a major clinical problem for patients and physicians. The immune system has evolved in multicellular organisms as a defence against infection. Interactions between drugs and the immune system occur as inadvertent consequences of the protective function of the immune system, with drug molecules or drug-carrier haptens being recognized as "non-self" by the immune system. The classical mechanisms for drug hypersensitivity described by Gell and Coombs (Types 1 to 4) include IgE-mediated, cytotoxic, immune complex-mediated and delayed mechanism. These mechanisms provide elegant models for drug-immune interactions that can provide mechanistic explanations for events such as urticaria associated with penicillins. However, these mechanisms do not account for many of the immunologically mediated adverse reactions commonly encountered in clinical practice. Over the last two decades, there has been an increasing awareness of the importance of reactive drug metabolites and drug-protein interactions in the initiation of immunologic events mediating adverse drug reactions. Reactive drug metabolites may produce direct and profound effects on various functions of the immune system. Although some adverse reactions mediated by the immune system occur with equal frequency among adults and children, some of these reactions appear to be markedly more common among children than adults.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. Explicit formulas for reaction probability in reaction-diffusion experiments

    OpenAIRE

    Feres, Renato; Wallace, Matthew; Stern, Ari; Yablonsky, Gregory

    2015-01-01

    A computational procedure is developed for determining the conversion probability for reaction-diffusion systems in which a first-order catalytic reaction is performed over active particles. We apply this general method to systems on metric graphs, which may be viewed as 1-dimensional approximations of 3-dimensional systems, and obtain explicit formulas for conversion. We then study numerically a class of 3-dimensional systems and test how accurately they are described by model formulas obtai...

  9. COMPUTATIONAL SCIENCE CENTER

    Energy Technology Data Exchange (ETDEWEB)

    DAVENPORT, J.

    2006-11-01

    Computational Science is an integral component of Brookhaven's multi science mission, and is a reflection of the increased role of computation across all of science. Brookhaven currently has major efforts in data storage and analysis for the Relativistic Heavy Ion Collider (RHIC) and the ATLAS detector at CERN, and in quantum chromodynamics. The Laboratory is host for the QCDOC machines (quantum chromodynamics on a chip), 10 teraflop/s computers which boast 12,288 processors each. There are two here, one for the Riken/BNL Research Center and the other supported by DOE for the US Lattice Gauge Community and other scientific users. A 100 teraflop/s supercomputer will be installed at Brookhaven in the coming year, managed jointly by Brookhaven and Stony Brook, and funded by a grant from New York State. This machine will be used for computational science across Brookhaven's entire research program, and also by researchers at Stony Brook and across New York State. With Stony Brook, Brookhaven has formed the New York Center for Computational Science (NYCCS) as a focal point for interdisciplinary computational science, which is closely linked to Brookhaven's Computational Science Center (CSC). The CSC has established a strong program in computational science, with an emphasis on nanoscale electronic structure and molecular dynamics, accelerator design, computational fluid dynamics, medical imaging, parallel computing and numerical algorithms. We have been an active participant in DOES SciDAC program (Scientific Discovery through Advanced Computing). We are also planning a major expansion in computational biology in keeping with Laboratory initiatives. Additional laboratory initiatives with a dependence on a high level of computation include the development of hydrodynamics models for the interpretation of RHIC data, computational models for the atmospheric transport of aerosols, and models for combustion and for energy utilization. The CSC was formed to

  10. Industrial Assessment Center Program

    Energy Technology Data Exchange (ETDEWEB)

    Kolarik, William J.

    2007-02-26

    Over the five-year period (2002-2006) the Oklahoma State University Industrial Assessment Center (IAC) performed energy assessments for 106 different clients, writing 835 recommendations, for a total of $23,937,099 in potential estimated annual savings. IAC clients served consisted of small and medium-sized manufacturers ranging from food manufactures to foundries. The OSU IAC served clients in Oklahoma, Kansas, Missouri, Arkansas, and Texas. In addition to client service, student training and instruction was a major accomplishment. The OSU IAC employed (and trained) 12 baccalaureate-level students, 17 masters-level graduate students, and 7 doctoral-level graduate students. Most are practicing in the energy management area. Training was focused on both energy assessment and safety. Safety training was both center-based training as well as on-site training. Energy management related training was focused on classroom (for academic credit) work at both the undergraduate and graduate level. IEM 4923 (Energy and Water Management) was developed to serve both the IAC as well as non-IAC students. It was delivered once per year, with enrollments of typically 10 to 20 students. This course was required for IAC student employees, both undergraduate and graduate. This course was patterned after the AEE CEM (five-day) course for practicing professionals. IEM 4923 required each student to attend at least one on-site assessment and write at least one recommendation for their client’s report. Hence, a hands-on approach was practiced. Advance level courses were used to train graduate students. Two courses played major roles here: IEM 5923 (Advanced Energy and Water Management) and IEM 5943 (Hazardous Material and Waste). Graduate student participation in these courses helped the IAC to gain additional perspectives in on-site assessment and resulting recommendations. Numerous hands-on demonstration/training was conducted by directors and graduate students in order to gain

  11. Identification of possible adverse drug reactions in clinical notes

    DEFF Research Database (Denmark)

    Warrer, Pernille; Jensen, Peter Bjødstrup; Aagaard, Lise

    2015-01-01

    Objective: Through manual review of clinical notes for patients with type 2 diabetes mellitus attending a Danish diabetes center, the aim of the study was to identify adverse drug reactions (ADRs) associated with three classes of glucose-lowering medicines: "Combinations of oral blood-glucose low......Objective: Through manual review of clinical notes for patients with type 2 diabetes mellitus attending a Danish diabetes center, the aim of the study was to identify adverse drug reactions (ADRs) associated with three classes of glucose-lowering medicines: "Combinations of oral blood...... information is generally available for causality assessment. However, manual review of clinical notes is too time-consuming for routine use and hence there is a need for developing information technology (IT) tools for automatic screening of patient records with the purpose to detect information about...

  12. Direct reactions with exotic nuclei

    Directory of Open Access Journals (Sweden)

    Obertelli A.

    2014-03-01

    Full Text Available Direct reactions have been a unique tool to address the nuclear many-body problem from the experimental side. They are now routinely used in inverse kinematics with radioactive ion beams (RIB. However, weakly bound nuclei have recently raised questions on the applicability of reaction formalisms benchmarked on stable nuclei to the study of single-particle properties and correlations in these unstable systems. The study of the most exotic species produced at low intensity have triggered new technical developments to increase the sensitivity of the setup, with a focused attention to direct reactions such as transfer at low incident energy or knockout at intermediate energies.

  13. Palladium-catalyzed coupling reactions

    CERN Document Server

    Molnár, Árpád

    2013-01-01

    This handbook and ready reference brings together all significant issues of practical importance for interested readers in one single volume. While covering homogeneous and heterogeneous catalysis, the text is unique in focusing on such important aspects as using different reaction media, microwave techniques or catalyst recycling. It also provides a comprehensive treatment of modern-day coupling reactions and emphasizes those topics that show potential for future development, such as continuous flow systems, water as a reaction medium, and catalyst immobilization, among others. With i

  14. Polypharmacy Treatment of Hypertensionin Public Health Centers

    Directory of Open Access Journals (Sweden)

    Vasanthi A/P Nayagam

    2016-12-01

    Full Text Available Background: Hypertension is one of the most prominent global diseases. Despite the availability of effective therapies, hypertension remains poorly controlled in Indonesia. In many cases, patient’s noncompliance may be attributable to the low patients’ knowledge, attitude, and life-style practices such as polypharmacy. Polypharmacy is defined as the administration of many drugs at in one prescription. Polypharmacy increases expenses, possible adverse reaction to a single agent, incidence of drug interactions, and decreases patient’s compliance This study aimed to identify the practice of polypharmacy in hypertension treatment in primary health centers. Methods: A cross-sectional descriptive observational study was carried out on 60 patients from two primary health centers in Jatinangor, West Java, Indonesia in October 2013. Sociodemographic profile, degree of hypertension, types of antihypertensive drugs, concomitant drugs given together with antihypertensive drugs, and treatment compliance data were collected and presented in tables and figures. Results: The incidence of hypertension was more common among male patients compared to female patients. Thirty-three patients (55% have low compliance to their medication. Twenty-nine patients (48% received single drug and 31 patients (52% received more than one drugs. Conclusions: The percentage of polypharmacy practice in treating hypertension in primary health centers is 52%. The most frequently prescribed anti-hypertensive are angiotensin-converting enzyme (ACE inhibitors and calcium-channel blockers (CCB. Most of hypertensive patients have low compliance to therapy.

  15. On chains of centered valuations

    Directory of Open Access Journals (Sweden)

    Rachid Chibloun

    2003-01-01

    Full Text Available We study chains of centered valuations of a domain A and chains of centered valuations of A [X1,…,Xn] corresponding to valuations of A. Finally, we make some applications to chains of valuations centered on the same ideal of A [X1,…,Xn] and extending the same valuation of A.

  16. Centers for Enhancement of Education.

    Science.gov (United States)

    Biggerstaff, Ed

    The Center for Enhancement of Education organizes seven specialized centers within the School of Education and Human Services to provide faculty and students with the opportunity for research, development, and public service activities that complement and supplement classroom teaching. Each of the seven centers stresses one of the following…

  17. PTSD: National Center for PTSD

    Medline Plus

    Full Text Available ... Us FAQs Ask a Question Toll Free Numbers Homeless Veterans Chat VA » Health Care » PTSD: National Center for ... Vet Centers) War Related Illness & Injury Study Center Homeless Veterans Returning Service Members Rural Veterans Seniors & Aging Veterans ...

  18. Centering in on Professional Choices.

    Science.gov (United States)

    Harris, Muriel

    2001-01-01

    Examines the author's involvement with writing centers as an example of how educators can look at the choices made within their areas of expertise to see why the choices attract them. Notes that in her case, the flexible, collaborative, individualized, non-evaluative, experimental, non-hierarchical, student-centered nature of writing centers is an…

  19. Analysis of a questionnaire on adverse reactions to blood donation in Japan.

    Science.gov (United States)

    Inaba, S; Takanashi, M; Matsuzaki, K; Ono, Y; Nakajima, K; Shibata, R; Tadokoro, K; Ishikawa, Y; Kinukawa, N

    2013-02-01

    In 2007, the Japanese Red Cross Blood Center performed a large-scale questionnaire study of post-donation adverse reactions. The questionnaire was distributed to 98,389 donors, and the answers were returned by 55,231 (56.1%). In total, 2,877 (5.2%) complained of an adverse reaction. Assuming that there were no adverse reactions for the 46,150 donors who did not reply, the rate of adverse reaction can be speculated to be 2.8%. Our study strongly suggests that blood centers have long underestimated the risks of vaso-vagal reactions. Taking at least 6h of careful rest after donation would be a helpful counter measure. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Adverse reactions and other factors that impact subsequent blood donation visits.

    Science.gov (United States)

    Custer, Brian; Rios, Jorge A; Schlumpf, Karen; Kakaiya, Ram M; Gottschall, Jerome L; Wright, David J

    2012-01-01

    The importance of adverse reactions in terms of donor safety recently has received significant attention, but their role in subsequent donation behavior has not been thoroughly investigated. Six REDS-II blood centers provided data for this analysis. Summary minor and major adverse reaction categories were created. The influence of adverse reactions on donation was examined in two ways: Kaplan-Meier curves were generated to determine the cumulative pattern of first return, and adjusted odds ratios (AORs) for demographic and other factors positively and negatively associated with return were estimated using multivariable logistic regression. Donors who had major reactions had longer times to return than donors with minor or no reactions. The AOR of returning for donors with major reactions was 0.32 (95% confidence interval [CI], 0.28-0.37) and with minor reactions 0.59 (95% CI, 0.56-0.62) when compared to donors who did not have reactions. Conversely, the most important factors positively associated with return were the number of donations in the previous year and increasing age. Subsequent return, whether a major, minor, or no reaction occurred, varied by blood center. Factors that are associated with the risk of having adverse reactions were not substantial influences on the return after adverse reactions. Having an adverse reaction leads to significantly lower odds of subsequent donation irrespective of previous donation history. Factors that have been associated with a greater risk of adverse reactions were not important positive or negative predictors of return after a reaction. © 2011 American Association of Blood Banks.

  1. Reaction Control Engine for Space Launch Initiative

    Science.gov (United States)

    2002-01-01

    Engineers at the Marshall Space Flight Center (MSFC) have begun a series of engine tests on a new breed of space propulsion: a Reaction Control Engine developed for the Space Launch Initiative (SLI). The engine, developed by TRW Space and Electronics of Redondo Beach, California, is an auxiliary propulsion engine designed to maneuver vehicles in orbit. It is used for docking, reentry, attitude control, and fine-pointing while the vehicle is in orbit. The engine uses nontoxic chemicals as propellants, a feature that creates a safer environment for ground operators, lowers cost, and increases efficiency with less maintenance and quicker turnaround time between missions. Testing includes 30 hot-firings. This photograph shows the first engine test performed at MSFC that includes SLI technology. Another unique feature of the Reaction Control Engine is that it operates at dual thrust modes, combining two engine functions into one engine. The engine operates at both 25 and 1,000 pounds of force, reducing overall propulsion weight and allowing vehicles to easily maneuver in space. The low-level thrust of 25 pounds of force allows the vehicle to fine-point maneuver and dock while the high-level thrust of 1,000 pounds of force is used for reentry, orbit transfer, and coarse positioning. SLI is a NASA-wide research and development program, managed by the MSFC, designed to improve safety, reliability, and cost effectiveness of space travel for second generation reusable launch vehicles.

  2. Supernova Science Center

    Energy Technology Data Exchange (ETDEWEB)

    S. E. Woosley

    2008-05-05

    The Supernova Science Center (SNSC) was founded in 2001 to carry out theoretical and computational research leading to a better understanding of supernovae and related transients. The SNSC, a four-institutional collaboration, included scientists from LANL, LLNL, the University of Arizona (UA), and the University of California at Santa Cruz (UCSC). Intitially, the SNSC was funded for three years of operation, but in 2004 an opportunity was provided to submit a renewal proposal for two years. That proposal was funded and subsequently, at UCSC, a one year no-cost extension was granted. The total operational time of the SNSC was thus July 15, 2001 - July 15, 2007. This document summarizes the research and findings of the SNSC and provides a cummulative publication list.

  3. Citizen centered design

    Directory of Open Access Journals (Sweden)

    Ingrid Mulder

    2015-11-01

    Full Text Available Today architecture has to design for rapidly changing futures, in a citizen-centered way. That is, architecture needs to embrace meaningful design. Societal challenges ask for a new paradigm in city-making, which combines top-down public management with bottom-up social innovation to reach meaningful design. The biggest challenge is indeed to embrace a new collaborative attitude, a participatory approach, and to have the proper infrastructure that supports this social fabric. Participatory design and transition management are future-oriented, address people and institutions. Only through understanding people in context and the corresponding dynamics, one is able to design for liveable and sustainable urban environments, embracing the human scale.

  4. The Center is Everywhere

    CERN Document Server

    Weinberg, David H

    2012-01-01

    "The Center is Everywhere" is a sculpture by Josiah McElheny, currently (through October 14, 2012) on exhibit at the Institute of Contemporary Art, Boston. The sculpture is based on data from the Sloan Digital Sky Survey (SDSS), using hundreds of glass crystals and lamps suspended from brass rods to represent the three-dimensional structure mapped by the SDSS through one of its 2000+ spectroscopic plugplates. This article describes the scientific ideas behind this sculpture, emphasizing the principle of the statistical homogeneity of cosmic structure in the presence of local complexity. The title of the sculpture is inspired by the work of the French revolutionary Louis Auguste Blanqui, whose 1872 book "Eternity Through The Stars: An Astronomical Hypothesis" was the first to raise the spectre of the infinite replicas expected in an infinite, statistically homogeneous universe. Puzzles of infinities, probabilities, and replicas continue to haunt modern fiction and contemporary discussions of inflationary cosmo...

  5. The Atomki accelerator center

    Science.gov (United States)

    Vajda, I.; Fülöp, Zs.; Biri, S.

    2017-06-01

    Particle accelerators are the driving forces of nuclear physics laboratories and MTA Atomki, the Institute for Nuclear Research of the Hungarian Academy of Sciences is no exception. The Atomki Accelerator Center (AAC) incorporates several low-energy charged-particle accelerators, offering the possibility of choosing ions with various charge states, energies and beam intensities. Currently, the AAC has six main facilities: a cyclotron (K=20), two Van de Graaff accelerators (1 MV, 5 MV), an ECR ion source, an electromagnetic isotope separator and a 2 MV Tandetron installed in 2015. The accelerators, spanning a range of beam energies from 50 eV to 27 MeV, have been designed for a broad range of research projects and applications in various fields - mainly in nuclear and atomic physics, materials science, environmental research and archaeology. The structure of the laboratory with a short description of the most important topics, education and outreach activities are presented.

  6. Concurrent engineering research center

    Science.gov (United States)

    Callahan, John R.

    1995-01-01

    The projects undertaken by The Concurrent Engineering Research Center (CERC) at West Virginia University are reported and summarized. CERC's participation in the Department of Defense's Defense Advanced Research Project relating to technology needed to improve the product development process is described, particularly in the area of advanced weapon systems. The efforts committed to improving collaboration among the diverse and distributed health care providers are reported, along with the research activities for NASA in Independent Software Verification and Validation. CERC also takes part in the electronic respirator certification initiated by The National Institute for Occupational Safety and Health, as well as in the efforts to find a solution to the problem of producing environment-friendly end-products for product developers worldwide. The 3M Fiber Metal Matrix Composite Model Factory Program is discussed. CERC technologies, facilities,and personnel-related issues are described, along with its library and technical services and recent publications.

  7. Interface-confined oxide nanostructures for catalytic oxidation reactions.

    Science.gov (United States)

    Fu, Qiang; Yang, Fan; Bao, Xinhe

    2013-08-20

    Heterogeneous catalysts, often consisting of metal nanoparticles supported on high-surface-area oxide solids, are common in industrial chemical reactions. Researchers have increasingly recognized the importance of oxides in heterogeneous catalysts: that they are not just a support to help the dispersion of supported metal nanoparticles, but rather interact with supported metal nanoparticles and affect the catalysis. The critical role of oxides in catalytic reactions can become very prominent when oxides cover metal surfaces forming the inverse catalysts. The source of the catalytic activity in homogeneous catalysts and metalloenzymes is often coordinatively unsaturated (CUS) transition metal (TM) cations, which can undergo facile electron transfer and promote catalytic reactions. Organic ligands and proteins confine these CUS cations, making them highly active and stable. In heterogeneous catalysis, however, confining these highly active CUS centers on an inorganic solid so that they are robust enough to endure the reaction environment while staying flexible enough to perform their catalysis remains a challenge. In this Account, we describe a strategy to confine the active CUS centers on the solid surface at the interface between a TM oxide (TMO) and a noble metal (NM). Among metals, NMs have high electron negativity and low oxygen affinity. This means that TM cations of the oxide bind strongly to NM atoms at the interface, forming oxygen-terminated-bilayer TMO nanostructures. The resulting CUS sites at the edges of the TMO nanostructure are highly active for catalytic oxidation reactions. Meanwhile, the strong interactions between TMOs and NMs prevent further oxidation of the bilayer TMO phases, which would otherwise result in the saturation of oxygen coordination and the deactivation of the CUS cations. We report that we can also tune the oxide-metal interactions to modulate the bonding of reactants with CUS centers, optimizing their catalytic performance. We

  8. Microdroplet fusion mass spectrometry for fast reaction kinetics.

    Science.gov (United States)

    Lee, Jae Kyoo; Kim, Samuel; Nam, Hong Gil; Zare, Richard N

    2015-03-31

    We investigated the fusion of high-speed liquid droplets as a way to record the kinetics of liquid-phase chemical reactions on the order of microseconds. Two streams of micrometer-size droplets collide with one another. The droplets that fused (13 μm in diameter) at the intersection of the two streams entered the heated capillary inlet of a mass spectrometer. The mass spectrum was recorded as a function of the distance x between the mass spectrometer inlet and the droplet fusion center. Fused droplet trajectories were imaged with a high-speed camera, revealing that the droplet fusion occurred approximately within a 500-μm radius from the droplet fusion center and both the size and the speed of the fused droplets remained relatively constant as they traveled from the droplet fusion center to the mass spectrometer inlet. Evidence is presented that the reaction effectively stops upon entering the heated inlet of the mass spectrometer. Thus, the reaction time was proportional to x and could be measured and manipulated by controlling the distance x. Kinetic studies were carried out in fused water droplets for acid-induced unfolding of cytochrome c and hydrogen-deuterium exchange in bradykinin. The kinetics of the former revealed the slowing of the unfolding rates at the early stage of the reaction within 50 μs. The hydrogen-deuterium exchange revealed the existence of two distinct populations with fast and slow exchange rates. These studies demonstrated the power of this technique to detect reaction intermediates in fused liquid droplets with microsecond temporal resolution.

  9. Involvement of a hypersensitive-like reaction in tolerance to fire ...

    African Journals Online (AJOL)

    SAM

    2014-07-09

    Jul 9, 2014 ... programmed cell death; PEP, plastid encoded RNA polymerase-PEP enzyme; PQ, plastoquinone; PSI, photosystem I; PSII, photosystem II; PTK ... dria and chloroplast are required in programmed cell death (PCD) of guard cells ..... roplasts are believed to have evolved from prokaryotic ancestors, and they ...

  10. Educational Stress: Sources, Reactions, Preventions.

    Science.gov (United States)

    Kaiser, Jeffrey S.; Polczynski, James J.

    1982-01-01

    Effects of stress on educators and efforts to understand and cope with stress are discussed. Sources of stress, common reactions to stress, the effects of stress on educator performance, and suggested preventive methods are examined. (JN)

  11. Reactions with light exotic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenthäler, R.; Faria, P.N. de; Pires, K.C.C.; Lepine-Szily, A.; Guimaraes, V.; Mendes Junior, D.R.; Assuncao, M.; Barioni, A.; Morcelle, V.; Morais, M.C.; Camargo Junior, O.; Alcantara Nuñez, J. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Fisica; Moro, A.M. [Departamento de FAMN, Universidad de Sevilla, Sevilla (Spain); Arazi, A. [Laboratorio Tandar, Departamento de Fisica, Comision Nacional de Energia Atomica (CNEA), Buenos Aires (Argentina); Rodriguez-Gallardo, M. [Instituto de Estructura de la Materia, CSIC, Madrid (Spain)

    2014-07-01

    Experimental cross sections for the {sup 6}He+{sup 120}Sn are analysed. Elastic scattering angular distributions and alpha particle production cross sections have been measured and are compared with the total reaction cross sections. (author)

  12. Fluctuations in catalytic surface reactions

    CERN Document Server

    Imbihl, R

    2003-01-01

    The internal reaction-induced fluctuations which occur in catalytic CO oxidation on a Pt field emitter tip have been studied using field electron microscopy (FEM) as a spatially resolving method. The structurally heterogeneous Pt tip consists of facets of different orientations with nanoscale dimensions. The FEM resolution of roughly 2 nm corresponds to a few hundred reacting adsorbed particles whose variations in the density are imaged as brightness fluctuations. In the bistable range of the reaction one finds fluctuation-induced transitions between the two stable branches of the reaction kinetics. The fluctuations exhibit a behaviour similar to that of an equilibrium phase transition, i.e. the amplitude diverges upon approaching the bifurcation point terminating the bistable range of the reaction. Simulations with a hybrid Monte Carlo/mean-field model reproduce the experimental observations. Fluctuations on different facets are typically uncorrelated but within a single facet a high degree of spatial cohere...

  13. Transfer reactions in nuclear astrophysics

    Science.gov (United States)

    Bardayan, D. W.

    2016-08-01

    To a high degree many aspects of the large-scale behavior of objects in the Universe are governed by the underlying nuclear physics. In fact the shell structure of nuclear physics is directly imprinted into the chemical abundances of the elements. The tranquility of the night sky is a direct result of the relatively slow rate of nuclear reactions that control and determines a star’s fate. Understanding the nuclear structure and reaction rates between nuclei is vital to understanding our Universe. Nuclear-transfer reactions make accessible a wealth of knowledge from which we can extract much of the required nuclear physics information. A review of transfer reactions for nuclear astrophysics is presented with an emphasis on the experimental challenges and opportunities for future development.

  14. Analysis of kinetic reaction mechanisms

    CERN Document Server

    Turányi, Tamás

    2014-01-01

    Chemical processes in many fields of science and technology, including combustion, atmospheric chemistry, environmental modelling, process engineering, and systems biology, can be described by detailed reaction mechanisms consisting of numerous reaction steps. This book describes methods for the analysis of reaction mechanisms that are applicable in all these fields. Topics addressed include: how sensitivity and uncertainty analyses allow the calculation of the overall uncertainty of simulation results and the identification of the most important input parameters, the ways in which mechanisms can be reduced without losing important kinetic and dynamic detail, and the application of reduced models for more accurate engineering optimizations. This monograph is invaluable for researchers and engineers dealing with detailed reaction mechanisms, but is also useful for graduate students of related courses in chemistry, mechanical engineering, energy and environmental science and biology.

  15. Method for conducting exothermic reactions

    Science.gov (United States)

    Smith, Jr., Lawrence; Hearn, Dennis; Jones, Jr., Edward M.

    1993-01-01

    A liquid phase process for oligomerization of C.sub.4 and C.sub.5 isoolefins or the etherification thereof with C.sub.1 to C.sub.6 alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120.degree. to 300.degree. F. wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

  16. Engineering reactors for catalytic reactions

    Indian Academy of Sciences (India)

    Chemical Engineering and Process Development Division, CSIR - National Chemical Laboratory,. Pune 411 008, India ... Abstract. Catalytic reactions are ubiquitous in chemical and allied industries. ... strategies and recent advances in process intensification/ multifunctional reactors are discussed to illustrate the approach.

  17. Thermodynamics of random reaction networks.

    Directory of Open Access Journals (Sweden)

    Jakob Fischer

    Full Text Available Reaction networks are useful for analyzing reaction systems occurring in chemistry, systems biology, or Earth system science. Despite the importance of thermodynamic disequilibrium for many of those systems, the general thermodynamic properties of reaction networks are poorly understood. To circumvent the problem of sparse thermodynamic data, we generate artificial reaction networks and investigate their non-equilibrium steady state for various boundary fluxes. We generate linear and nonlinear networks using four different complex network models (Erdős-Rényi, Barabási-Albert, Watts-Strogatz, Pan-Sinha and compare their topological properties with real reaction networks. For similar boundary conditions the steady state flow through the linear networks is about one order of magnitude higher than the flow through comparable nonlinear networks. In all networks, the flow decreases with the distance between the inflow and outflow boundary species, with Watts-Strogatz networks showing a significantly smaller slope compared to the three other network types. The distribution of entropy production of the individual reactions inside the network follows a power law in the intermediate region with an exponent of circa -1.5 for linear and -1.66 for nonlinear networks. An elevated entropy production rate is found in reactions associated with weakly connected species. This effect is stronger in nonlinear networks than in the linear ones. Increasing the flow through the nonlinear networks also increases the number of cycles and leads to a narrower distribution of chemical potentials. We conclude that the relation between distribution of dissipation, network topology and strength of disequilibrium is nontrivial and can be studied systematically by artificial reaction networks.

  18. Thermodynamics of Random Reaction Networks

    Science.gov (United States)

    Fischer, Jakob; Kleidon, Axel; Dittrich, Peter

    2015-01-01

    Reaction networks are useful for analyzing reaction systems occurring in chemistry, systems biology, or Earth system science. Despite the importance of thermodynamic disequilibrium for many of those systems, the general thermodynamic properties of reaction networks are poorly understood. To circumvent the problem of sparse thermodynamic data, we generate artificial reaction networks and investigate their non-equilibrium steady state for various boundary fluxes. We generate linear and nonlinear networks using four different complex network models (Erdős-Rényi, Barabási-Albert, Watts-Strogatz, Pan-Sinha) and compare their topological properties with real reaction networks. For similar boundary conditions the steady state flow through the linear networks is about one order of magnitude higher than the flow through comparable nonlinear networks. In all networks, the flow decreases with the distance between the inflow and outflow boundary species, with Watts-Strogatz networks showing a significantly smaller slope compared to the three other network types. The distribution of entropy production of the individual reactions inside the network follows a power law in the intermediate region with an exponent of circa −1.5 for linear and −1.66 for nonlinear networks. An elevated entropy production rate is found in reactions associated with weakly connected species. This effect is stronger in nonlinear networks than in the linear ones. Increasing the flow through the nonlinear networks also increases the number of cycles and leads to a narrower distribution of chemical potentials. We conclude that the relation between distribution of dissipation, network topology and strength of disequilibrium is nontrivial and can be studied systematically by artificial reaction networks. PMID:25723751

  19. Drug Reactions in Oral Mucosa

    Directory of Open Access Journals (Sweden)

    Emine Derviş

    2012-12-01

    Full Text Available Both immunologic and nonimmunologic drug reactions can be seen in oral mucosa. Since considerable number of these reactions heals spontaneously without being noticed by the patients, exact frequency of the lesions is unknown. Most common lesions are xerostomia, taste disorders, mucosal ulcerations and edema. In this article, oral lesions resulting from drug intake similar to those from oral lesions of local and systemic diseases, and diagnostic problems caused by these similarities, have been reviewed.

  20. Radiation reaction and relativistic hydrodynamics.

    Science.gov (United States)

    Berezhiani, V I; Hazeltine, R D; Mahajan, S M

    2004-05-01

    By invoking the radiation reaction force, first perturbatively derived by Landau and Lifschitz, and later shown by Rohrlich to be exact for a single particle, we construct a set of fluid equations obeyed by a relativistic plasma interacting with the radiation field. After showing that this approach reproduces the known results for a locally Maxwellian plasma, we derive and display the basic dynamical equations for a general magnetized plasma in which the radiation reaction force augments the direct Lorentz force.