title: Diurnal rhythm of beta-carotene in photosynthetic alga Gonyaulax polyedra.
abstract: Carotenoids comprise one of the most widespread classes of pigments found in nature. Polyene pigments from the dinoflagellate Gonyaulax polyedra were extracted every hour over a 24 hour period and the levels of beta-carotene during the day-phase were found to be twice as high as during the night-phase period. Using the thermal decomposition of 1,4-dimethylnaphthalene endoperoxide, the overall quenching ability of beta-carotene and G. polyedra carotenoids of singlet oxygen were found to be 2.04 x 10(9) M-1 s-1 and 4.75 x 10(9) M-1 s-1 respectively. Such a high quenching rate constant suggest a possible role for carotenoids as effective singlet oxygen quenchers in G. polyedra. The dose response curve for light-induced carotenoid synthesis shows a linear response up to 45 minutes of light exposure, after which night phase cells contain the same levels of beta-carotene as day-phase cells. Cells exposed to light pulses at different times during the night period display the highest beta-carotene induction in the middle of the night.
authors.affiliation: Instituto de Química, Departamento de Bioquímica, Universidade de São Paulo, Brazil.
authors.forename: P
authors.initials: P
authors.lastname: Di Mascio
authors.forename: H C
authors.initials: HC
authors.lastname: Hollnagel
authors.forename: M
authors.initials: M
authors.lastname: Sperança
authors.forename: P
authors.initials: P
authors.lastname: Colepicolo
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000302:isolation & purification / Q000378:metabolism*; D002338:Carotenoids / Q000302:isolation & purification / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002940:Circadian Rhythm / Q000502:physiology*; D004141:Dinoflagellida / Q000378:metabolism*; D009281:Naphthalenes / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry; D010775:Photic Stimulation; D010788:Photosynthesis / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013053:Spectrophotometry; D019207:beta Carotene
chemical_list: D000970:Antineoplastic Agents; D009281:Naphthalenes; D017382:Reactive Oxygen Species; D019207:beta Carotene; D002338:Carotenoids; C031969:1,4-dimethylnaphthalene; D010100:Oxygen