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  • 1
    Electronic Resource
    Electronic Resource
    Biological weighting function for xanthophyll de-epoxidation induced by ultraviolet radiation (2005)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 125 (2005), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The light-induced de-epoxidation of xanthophylls is an important photoprotective mechanism in plants and algae. Exposure to ultraviolet radiation (UVR, 280–400 nm) can change the extent of xanthophyll de-epoxidation, but different types of responses have been reported. The de-epoxidation of violaxanthin (V) to zeaxanthin (Z), via the intermediate antheraxanthin, during exposure to UVR and photosynthetically active radiation (PAR, 400–700 nm) was studied in the marine picoplankter Nannochloropsis gaditana (Eustigmatophyceae) Lubián. Exposures used a filtered xenon lamp, which gives PAR and UVR similar to natural proportions. Exposure to UVR plus PAR increased de-epoxidation compared with under PAR alone. In addition, de-epoxidation increased with the irradiance and with the inclusion of shorter wavelengths in the spectrum. The spectral dependence of light-induced de-epoxidation under UVR and PAR exposure was well described by a model of epoxidation state (EPS) employing a biological weighting function (BWF). This model fit measured EPS in eight spectral treatments using Schott long pass filters, with six intensities for each filter, with a R2 = 0.90. The model predicts that 56% of violaxanthin is de-epoxidated, of which UVR can induce as much as 24%. The BWF for EPS was similar in shape to the BWF for UVR inhibition of photosynthetic carbon assimilation in N. gaditana but with about 22-fold lower effectiveness. These results demonstrate a connection between the presence of de-epoxidated Z and the inhibition under UVR exposures in N. gaditana. Nevertheless, they also indicate that de-epoxidation is insufficient to prevent UVR inhibition in this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.2005.00538.x
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  • 2
    Electronic Resource
    Electronic Resource
    The correlation of the stability constants of 1,3-dicarbonylic monochelates of Iron(III) with the acid dissociation constants of the ligand (1990)
    Springer
    Journal of solution chemistry 19 (1990), S. 1191-1197 
    Details
    ISSN: 1572-8927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The variation of the logrithms of stability constants of iron(III) monochelated compounds with structurally similar 1,3-dicarbonylic compounds has been found to be an essentially linear function of the negative logarithms of the acid ionization constant of the ligands. An analytical correlation which could be useful to predict equilibrium constants of iron(III) chelates has been developed. From spectrophotometric and potentiometric data a quantitative evaluation of the stability of the complex has been carried out. Results have provided information regarding substituent effects on the equilibrium constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652544
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  • 3
    Electronic Resource
    Electronic Resource
    Nannochloropsis (Eustigmatophyceae) as source of commercially valuable pigments (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 249-255 
    Details
    ISSN: 1573-5176
    Keywords: pigments ; ketocarotenoids ; xanthophyll cycle ; microalgae culture ; Nannochloropsis ; Eustigmatophyceae ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pigment composition and its variation with culture agewere analyzed in six strains of Nannochloropsis(Eustigmatophyceae). The capacity for accumulationof the ketocarotenoids astaxanthin and canthaxanthinwas higher in N. salina and N. gaditanathan in the other strains studied here. Theinfluence of salinity (15 to 100 practical units) onpigment production was studied in N. gaditana,where a defined pattern of variation could not befound apart from a notable increase in zeaxanthin at100‰. In cultures grown in a photobioreactor and athigh cell densities of about 109 cells mL-1,pigment production reached: 350 mg L-1 forchlorophyll a, 50 mg L-1 for violaxanthin,5 mg L-1 for canthaxanthin, 3 mg L-1 forastaxanthin. The highest contents of canthaxanthin andastaxanthin obtained in experiments with N.gaditana were 19.4 and 14.6 ng pigment (106cells)-1, respectively, which accounts for 0.7%dry weight. By means of xanthophyll cycle inductionthrough exposure of cells to high irradiance and at40 °C, conversion of violaxanthin intozeaxanthin may attain up to 70% of the violaxanthincontent, which corresponds to 0.6% dry weight. Theresults indicate that interest in Nannochloropsis as a source of valuable pigments isnot related to its capacity for single pigmentaccumulation, but the availability of a range ofpigments such as chlorophyll a, zeaxanthin,canthaxanthin and astaxanthin, each with highproduction levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008170915932
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