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  • 1
    ISSN: 1573-5079
    Keywords: Chlamydomonas reinhardtii ; mutagenesis ; photoinhibition ; Photosystem II ; repair cycle ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The work outlines the isolation of transformant Chlamydomonas reinhardtii cells that appear to be unable to repair Photosystem II from photoinhibitory damage. A physiological and biochemical characterization of three mutants is presented. The results show differential stability for the D1 reaction center protein in the three mutants compared to the wild type and suggest lesions that affect different aspects of the Photosystem II repair mechanism. In the ag16.2 mutant, significantly greater amounts of D1 accumulate in the thylakoid membrane than in the wild type under steady-state growth conditions, and D1 loss is significantly retarded in the presence of the protein biosynthesis inhibitor chloramphenicol. Moreover, aberrant electrophoretic mobility of D1 in the ag16.2 suggests that this protein is modified to an as yet unknown configuration. These results indicate that the biosynthesis and/or degradation of D1 is altered in this strain. A different type of mutation occurred in the kn66.7 and kn27.4 mutants of C. reinhardtii. The stability of D1 declined much faster as a function of light intensity in these mutants than in the wild type. Thereby, the threshold of photoinhibition in these mutants was significantly lower than that in the wild type. It appears that kn66.7 and kn27.4 are similar conditional mutants, with the only difference between them being the amplitude of the chloroplast response to the mutation and the differential sensitivity they display to the level of irradiance.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5079
    Keywords: chlorophyll antenna size ; damage and repair cycle ; Dunaliella salina ; photoinhibition ; photosynthesis ; Photosystem-II ; photosystem stoichiometry ; productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract High-light (HL) grown Dunaliella salina cells exhibit lower pigment content, a highly truncated chlorophyll (Chl) antenna size, and accumulation of photodamaged PS II centers in the chloroplast thylakoids (chronic photoinhibition). In HL-grown cells, the rate of photosynthesis saturated at higher irradiances and the quantum yield was lower compared to that of normally-pigmented low-light (LL) grown cells. In spite of these deficiencies, the light-saturated rate of photosynthesis for the HL-cells, when measured on a per chlorophyll basis, was ∼3 times greater than that of the LL-grown cells. To delineate the effect of photoinhibition from the Chl antenna size on quantum yield and rate of photosynthesis, HL-acclimated cells were switched to LL-conditions. Repair of photodamaged PS II, estimated from the recovery of functional PS II centers and from the increase in the quantum yield of photosynthesis, occurred with a half-time of ∼1 h. Chlorophyll accumulation in the cells occurred with a half-time of ∼4 h. The differential kinetics in repair versus Chl accumulation provided a ‘window of opportunity’, within about 2–3 h after the HL→LL shift, when cells exhibited a high quantum yield of photosynthesis, a small Chl antenna size and a light-saturated rate that was ∼6–9 times greater than that of the normally pigmented LL-grown cells. The work provides insight on the temporal sequence of events at the chloroplast and thylakoid membrane levels, leading from a chronic photoinhibition of PS II to repair and recovery. It is suggested that it is possible to maximize photosynthetic productivity and light utilization in mass microalgal cultures by minimizing the light-harvesting Chl antenna size of the photosystems.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical methods of operations research 51 (2000), S. 459-470 
    ISSN: 1432-5217
    Keywords: Key words: Newton-like method, variational inequality problems, superlinear convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract. In this paper, a Newton-like method for variational inequality problems is considered. One feature of the algorithm is that only the solution of linear systems of equations is required at each iteration and that the strict complementarity assumption is never invoked. Another is that under mild assumptions, the sequence produced by the Newton-like method Q-superlinearly converges to the solution of the VIP. Furthermore, a simpler version of this method is studied and it is shown that it is also superlinearly convergent.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2021-09-29
    Description: Highlights • DGT is a feasible technique for simultaneous measurement of REEs in soils. • REE elution efficiencies ranged from 86.5% to 93.8% using 2 M HCl. • DGT uptake was independent of solution pH (3–9) and ionic strength (3 mM- 100 mM). • Chelex®100 DGT had capacities of 5.39–6.75 μg cm−2 for measurement of mixed REEs. A new method for simultaneous measurement of fifteen rare earth elements (REEs) [La (Ⅲ), Ce (Ⅲ), Pr (Ⅲ), Nd (Ⅲ), Sm (Ⅲ), Eu (Ⅲ), Gd (Ⅲ), Tb (Ⅲ), Dy (Ⅲ), Ho (Ⅲ), Er (Ⅲ), Tm (Ⅲ), Yb (Ⅲ), Lu (Ⅲ), and Y (Ⅲ)] was established in this study using the diffusive gradients in thin films (DGT) technique with Chelex®100 binding gel. Five different types of ion exchange resins (Chelex®100, D418, D001-cc, 001 × 7, and HSTY®-SS) were selected for the initial investigation of their adsorption performance for REEs. The Chelex®100 binding gel had the greatest uptake efficiencies of 〉95% for the fifteen REE ions, which was used for all subsequent experiments. The binding gel exhibited rapid binding dynamics to REEs in mixed solution of the fifteen REE ions. Elution efficiencies ranging from 86.5% to 93.8% for these REEs were obtained based on extraction using 2.0 M HCl. The Chelex®100 DGT uptake of the fifteen REE ions increased linearly with the deployment time and found to be independent of pH (3–9) and ionic strength (3 mM–100 mM). The capacities of Chelex®100 DGT for measurement of the mixed elements were determined at a range of 5.39–6.75 μg cm−2. Application of the DGT for soil analysis showed that Chelex®100 DGT was a useful tool in simultaneous measurement of the fifteen REE ions, even in a soil with high concentrations of REEs. This study demonstrated the advantage of Chelex®100 DGT in simultaneous measurement of the fifteen REE ions due to high uptake efficiencies and a wide tolerance to environmental interference.
    Type: Article , PeerReviewed
    Format: text
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  • 5
    Publication Date: 2016-02-12
    Description: A large volume press coupled with in-situ energy-dispersive synchrotron X-ray was used to probe the change of silicon carbide (SiC) under high pressure and temperature ( P-T ) up to 8.1 GPa and 1100 K. The obtained pressure–volume–temperature data were fitted to a modified high- T Birch-Murnaghan equation of state, yielding values of a series of thermo-elastic parameters, such as the ambient bulk modulus K To  = 237(2) GPa, temperature derivative of the bulk modulus at a constant pressure (∂ K /∂ T ) P  = −0.037(4) GPa K −1 , volumetric thermal expansivity α(0, T ) =  a  +  bT with a  = 5.77(1) × 10 −6  K −1 and b  = 1.36(2) × 10 −8  K −2 , and pressure derivative of the thermal expansion at a constant temperature (∂ α /∂ P ) T  = 6.53 ± 0.64 × 10 −7  K −1  GPa −1 . Furthermore, we found the temperature derivative of the bulk modulus at a constant volume, ( ∂K T / ∂T ) V , equal to −0.028(4) GPa K −1 by using a thermal pressure approach. In addition, the elastic properties of SiC were determined by density functional theory through the calculation of Helmholtz free energy. The computed results generally agree well with the experimentally determined values.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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