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Oxygen Uptake Photosensitized by Disorganized Chlorophyll in Model Systems and Thylakoids of Greening Barley
Author(s) -
Caspi Varda,
Malkin Shmuel,
Marder Jonathan B.
Publication year - 2000
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2000)0710441oupbdc2.0.co2
Subject(s) - greening , singlet oxygen , thylakoid , chemistry , chlorophyll , sodium azide , oxygen , photochemistry , ascorbic acid , azide , chlorophyll a , biochemistry , chloroplast , biology , organic chemistry , food science , ecology , gene
Light‐dependent oxygen uptake was observed and studied in thylakoids from early greening barley in comparison to oxygen uptake in chlorophyll solutions and in thylakoids from fully green leaves. Substantial oxygen uptake was observed in chlorophyll solutions supplemented with tryptophan, histidine, ascorbic acid or linoleic acid. This uptake was diminished by adding azide, β‐carotene and α‐tocopherol, which are specific singlet‐oxygen quenchers. Illuminated thylakoids from greening barley also exhibited marked oxygen uptake that, likewise, was strongly quenched by azide. In comparison, azide was found not to affect oxygen uptake that is associated with the methyl viologen‐catalyzed Mehler reaction. It is reasoned that in the first two cases the oxygen uptake arises from chlorophyll‐photosensitized activation of oxygen to the singlet state and its consumption by exogenous or endogenous substrates. In greening, we propose that disorganized chlorophyll photosensitizes the oxygen uptake.