Comparative study of UV and visible light induced degradation of lipids in non-axenic senescent cells of Emiliania huxleyi
Irradiation of killed non-axenic cells of Emiliania huxleyi (Prymnesiophyceae) by PAR and UVR resulted in a strong photodegradation of most of the unsaturated lipid components (chlorophylls, unsaturated fatty acids and brassicasterol) of this haptophyte. This degradation, which mainly involves type...
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Veröffentlicht in: | Marine chemistry 2010-04, Vol.119 (1), p.139-152 |
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Sprache: | eng |
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Zusammenfassung: | Irradiation of killed non-axenic cells of
Emiliania huxleyi (Prymnesiophyceae) by PAR and UVR resulted in a strong photodegradation of most of the unsaturated lipid components (chlorophylls, unsaturated fatty acids and brassicasterol) of this haptophyte. This degradation, which mainly involves type II (i.e. singlet oxygen-mediated) photosensitized oxidation processes, was induced by both PAR and UVR. Alkenones were the sole unsaturated components of
E. huxleyi unaffected by photodegradation processes. This particular recalcitrance was attributed to the
trans configuration of their double bonds, which is less reactive toward singlet oxygen than the classical
cis configuration of the double bonds of the other lipids. UVR exposure also induced photosensitized stereomutation (
cis-trans isomerization) of the double bonds of some lipids (e.g. monounsaturated fatty acids and chlorophyll phytyl side-chain) and of some of their oxidation products affording (after reduction) some compounds (e.g. 9-hydroxyoctadec-
cis-10-enoic and 10-hydroxyoctadec-
cis-8-enoic acids arising from oleic acid oxidation and 11-hydroxyoctadec-
cis-12-enoic and 12-hydroxyoctadec-
cis-10-enoic acids arising from
cis-vaccenic acid oxidation) sufficiently specific to act as tracers of UVR-induced photodegradation
in situ. A strong photodegradation of specific bacterial monounsaturated fatty acids (e.g.
cis-vaccenic and 11-MeC
18:1ω12 acids) was also observed and attributed to the migration of singlet oxygen from phytodetritus to the attached heterotrophic bacteria. |
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ISSN: | 0304-4203 1872-7581 |
DOI: | 10.1016/j.marchem.2010.01.007 |