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  • 1
    Electronic Resource
    Electronic Resource
    How Euglena tells up from down (1996)
    [s.l.] : Nature Publishing Group
    Nature 379 (1996), S. 590-590 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-The green, unicellular flagellate Euglena gracilis orientates itself in the water column by means of external stimuli such as light and gravity1'2. Although much is known about photo-orientation, we know little about gravity-dependent orientation of microorganisms. Here we show that gravitactic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/379590a0
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  • 2
    Electronic Resource
    Electronic Resource
    New evidence for the mechanism of phototactic orientation ofEuglena gracilis (1986)
    Springer
    Current microbiology 14 (1986), S. 157-163 
    Details
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract When rotated horizontally in a cuvette in a strong lateral light beam, the flagellateEuglena gracilis effectively corrects its course and shows negative phototaxis, provided the angular velocity does not exceed 200s−1. Faster rotations cannot be corrected effeciently. In two strong light beams of equal illuminance perpendicular to each other, the cells move along the resultant away from the light beams. Decreasing the illuminance of one beam causes increasing numbers of the organisms to orient with respect to the stronger light source. In two perpendicular low illuminance beams (〉200lx), the population splits into two components moving towards either light source. The percentage of cells in each component depends on the relative illuminances. The results can be explained by the shading hypothesis combined with a dichroic orientation of the photoreceptor molecules perpendicular to the long axis of the cells. Externally applied electric dc fields have no effect on positive or negative phototaxis; this supports the hypothesis that electrical potential changes are not involved in the sensory transduction chain of photoorientation inEuglena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01568368
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  • 3
    Electronic Resource
    Electronic Resource
    Photoinhibition by visible and ultraviolet radiation in the red macroalga Porphyra umbilicalis grown in the laboratory (1999)
    Springer
    Plant ecology 145 (1999), S. 351-358 
    Details
    ISSN: 1573-5052
    Keywords: oxygen measurements ; PAM fluorescence ; photoinhibition ; Porphyra ; rhodophyta ; ultraviolet radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic oxygen production and PAM fluorescence measurements were used to follow photoinhibition in the red macroalga Porphyra umbilicalis. Exposure to simulated solar radiation caused inhibition of the effective photosynthetic quantum yield from which the thalli partially recovered in the shade in subsequent hours. There were no significant differences between samples exposed to unfiltered radiation and those exposed to radiation from which increasing portions of UV radiation had been removed indicating that the thalli are well adapted to current levels of solar PAR and UV radiation. This notion was supported by the finding of high concentrations of UV screening pigments which were even enhanced by exposure to increased UV radiation. However, when exposed to (only) UV radiation about 50% higher than that encountered by the organisms in their natural habitat, the photosynthetic yield decreased slowly and did not show any recovery even when the degree of inhibition did not exceed 10%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009833520770
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of photoreceptor proteins of microorganisms by gradient gel electrophoresis and other biochemical separation methods (1994)
    Weinheim : Wiley-Blackwell
    Electrophoresis 15 (1994), S. 1051-1061 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Photoreceptor proteins for photoorientation in microorganisms are usually membrane bound and can be isolated by standard biochemical methods. Three examples are shown: the flagellates Euglena gracilis, Peridinium gatunense and the slime mold Dictyostelium discoideum. The photoreceptor of Euglena is attached to the basis of the flagellum and is composed of at least four chromoproteins which can be separated by gradient sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE) fast protein liquid chromatography (FPLC) and isoelectric focusing (IEF); it contains pterins and a flavin as chromophoric groups. The photoreceptor of Peridinium absorbs in the red wavelength band. Though not yet identified in detail, multiple receptors are probably involved, as indicated by fluorescence spectroscopy. Dictyostelium shows positive and negative phototaxis in its amoebal form and exclusively positive phototaxis in its pseudoplasmodial form. It is still open to discussion whether the two stages use separate photoreceptors. From amoebae two photoreceptor pigments have been isolated, showing an absorption which resembles the action spectrum, one membrane bound with a molecular mass of 45 kDa and one cytoplasmic fraction with a molecular mass of 27 kDa.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501501157
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  • 5
    Electronic Resource
    Electronic Resource
    Electrophoretic applications of phycobiliproteins (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 215-219 
    Details
    ISSN: 0173-0835
    Keywords: Cyanobacteria ; Fluorescent proteins ; Phycocyanin ; Phycoerythrin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Phycobiliproteins are homologous chromoproteins which constitute the phycobilisomes, the light harvesting complexes of the photosynthetic apparatus in cyanobacteria, rhodophyta and cryptophyta. In the present work, phycocyanin (PC) and Phycoerythrin (PE) from a Nostoc species are proposed as protein markers for electrophoretic techniques. Phycocyanin is a blue-colored phycobiliprotein; it carries phycocyanobilin as chromophoric group and is composed of two subunits, α and β, with Mr of 14000 and 17000, respectively. In contrast, the PE subunits, having a similar Mr of 21000, are deep rose chromoproteins and carry phycoerythrobilin residues. Both low molecular weight phycobiliproteins are also suitable for monitoring protien blotting and the focusing time of protein samples during isoelectric focusing as internal markers. The PE subunits which form a single broad band after sodium dodecyl sulfate-polyacrylamide gel electrophoresis have different isoelectric points, and they form two visible bands when they reach their isoelectric point. The phycobilisomes constitute up to 50% of the total protein in cyanobacteria and their content in PC or PE can be up- or down-regulated by using different light conditions (chromatic adaptation).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150190213
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