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  • Articles: DFG German National Licenses  (4)
  • Acidity  (2)
  • Anabaena flos-aquae  (2)
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  • Articles: DFG German National Licenses  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Differential action of Hg2+ and Cd2+ on the phycobilisomes and chlorophyll a fluorescence, and photosystem II dependent electron transport in the cyanobacterium Anabaena flos-aquae (1993)
    Springer
    BioMetals 6 (1993), S. 125-132 
    Details
    ISSN: 1572-8773
    Keywords: Anabaena flos-aquae ; chlorophyll a ; fluorescence emission ; heavy metals ; Hill activity ; photosystem II ; phycobilisomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effect of equimolar concentrations of Hg2+ and Cd2+ on the whole cell absorption spectra, absorption spectra of the extracted phycocyanin (PC) and fluorescence emission spectra of phycobilisomes (PBS) was investigated in the cells of Anabaena flos-aquae. The PC component of the PBS was found to be extremely sensitive to the Hg2+ rather than the Cd2+ ions. Further, the results showed that Hg2+ and Cd2+ induced decrease in the rate of Hill activity (H2O - DCPIP) was partially restored by the electron donor NH2OH, not by the diphenyl carbazide. Similarly, chlorophyll a fluorescence emission in the presence of metals showed that addition of NH2OH could effectively reverse the metal induced alterations in the fluorescence emission intensity. These results, together, suggested that Hg2+ and Cd2+ caused damage to the photosystems (PS) II reaction center. However, a relatively higher stimulation of the chlorophyll a emission at 695 nm with a red shift of 4.0 nm in the presence of Hg2+, and Cd2+ induced preferential decrease in the emission intensity at 676 nm as compared with the peak at 695 nm were indicative of the differential action of Hg2+ and Cd2+ on the PS II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00140114
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Microcalorimetric studies of zeolite acidity (1992)
    Springer
    Catalysis letters 12 (1992), S. 201-211 
    Details
    ISSN: 1572-879X
    Keywords: Acidity ; gravimetry ; heat of adsorption ; H-Mordenite ; H-Y ; H-ZSM-5 ; microcalorimetry ; pyridine ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The acidity characteristics of H-ZSM-5, H-Mordenite and H-Y zeolite have been studied by microcalorimetric and gravimetric measurements of pyridine adsorption. H-ZSM-5 and H-Mordenite have Brønsted acid sites of primarily homogenous strength, with H-Mordenite having the stronger sites, whereas H-Y zeolite had Brønsted sites of varying strength. The effects of Na exchange level in H-Y zeolite and high temperature calcination for H-Mordenite have also been examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00767202
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Thermogravimetric and microcalorimetric studies of ZSM-5 acidity (1993)
    Springer
    Catalysis letters 18 (1993), S. 183-192 
    Details
    ISSN: 1572-879X
    Keywords: Acidity ; zeolites ; microcalorimetry ; thermogravimetry ; pyridine adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The combination of thermogravimetry, microcalorimetry and infrared spectroscopy studies of pyridine adsorption has been used to characterize the acidity of a ZSM-5 catalyst. The majority of the acid sites are Brønsted acid centers associated with framework Al species, with heats of pyridine adsorption equal to 140 kJ/mol. Non-framework Al species in the zeolite sample of this study eliminate an approximately equal number of Brønsted acid sites. These nonframework Al species also produce strong Lewis acid sites with pyridine adsorption heats greater than 140 kJ/mol, as well as weak adsorption sites (e.g., weak Bransted acid sites or hydrogen bonding sites) with heats equal to 90–140 kJ/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769437
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Hg2+ and Cd2+ induced inhibition of light induced proton efflux in the cyanobacteriumAnabaena flos-aquae (1992)
    Springer
    BioMetals 5 (1992), S. 163-167 
    Details
    ISSN: 1572-8773
    Keywords: Anabaena flos-aquae ; carbon fixation ; carbonic anhydrase ; heavy metals ; Hill activity ; oxygen evolution ; proton efflux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Light induced proton efflux in intact cells ofAnabaena flos-aquae is inhibited by the heavy metals Hg2+ and Cd2+. Furthermore, Hg2+ and Cd2+ reduced the14CO2 fixation, oxygen evolution and carbonic anhydrase activity responsible for H+ efflux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061323
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    Paper (German National Licenses)
    Fulltext
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