TRIPLET STATES OF CAROTENOIDS FROM PHOTOSYNTHETIC BACTERIA STUDIED BY NANOSECOND ULTRAVIOLET AND ELECTRON PULSE IRRADIATION

摘要: Abstract— Absorptions of the triplet excited states five carotenoids (15,15'-ds phytoene, all-trans C-carotene, spheroidene and spirilloxanthin), extracted from photosynthetic bacteria Rhodopseudomonas spheroides Rhodospirillum rubrum, have been detected in solution using pulse radiolysis laser flash photolysis. Triplet lifetimes, extinction coefficients, lowest energy levels quantum efficiencies formation determined. Comparison carotenoid with that O2('Δg) suggests spirilloxanthin, possibly alsoζ-carotene, would be expected to protect against photodynamic action caused by O2 ('Δg), but not cis or trans phytoene. The S→T intersystem crossing efficiences all polyenes were found low, being a few per cent less. In their protective role these can only therefore effectively reached via transfer another triplet, except case ('Δg). low crossover also mean light absorbed such possible as accessory pigments wasted over state.