ISSN:
1432-2048
Keywords:
Blue light
;
ζ-carotene (cis-trans isomerization)
;
Euglena
;
Isomerization (ζ-carotene)
;
Light (blue)
;
Phototaxis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract When treated with blue light, intact cells of Euglena gracilis Klebs var. bacillaris Cori, bleached strain W3BUL, show a series of positive peaks at 384, 411, and 440 nm in the blue-light-minus-dark difference spectrum; bleached strain 1224-5/24 shows a series of positive peaks at 386, 417, and 448 nm under the same conditions. The same changes are observed in a 27,000xg supernatant from darkgrown W3. The absorption change appears to be a consequence of shifts in the absorption of carotenoids; it is not seen in cells of W3BUL grown on SAN 9789 (4-chloro-5-(methylamino)-2-(α,α, α-trifluoro-m-tolyl)-3(2H)pyridazinone) to deplete the carotenoids or in cells of W10BSmL, a mutant lacking carotenoids. Inhibitors of flavin-mediated reactions, reductants and valinomycin had no effect on the activity of the system. The activity in the 27,000xg supernatant was associated with material of a molecular weight more than 2.5×106 and was insensitive to heating for 2 min at 100° C but was reduced or eliminated on longer heat treatment or addition of Triton X-100, indicating a possible association with membrane material. Photoactivity is enriched in the lower density fractions of a flotation gradient, and correlates with the ζ-carotene content in all fractions. Similar spectral changes can be obtained by comparing the iodine catalyzed cis-to-trans isomerization of ζ-carotene in a CS2-CHCl3 solvent. The action spectrum for the absorbance change shows effectiveness peaks in the 370–390 and 420–448-nm regions, with no marked effectiveness past 500 nm. Thus the photosensitizer may not be a carotenoid (at least not a normally-occurring C40 carotenoid). These blue-lightinduced absorption changes and their action spectra are discussed in relation to such blue-light-mediated responses as carotenogenesis, chloroplast development and phototaxis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00388221
Permalink
