We have used time-resolved absorption and fluorescence spectroscopy with nanosecond resolution to study triplet energy transfer from chlorophylls to carotenoids in a protective process that prevents the formation of reactive singlet oxygen. The light-harvesting complexes studied were isolated from Chromera velia, belonging to a group Alveolata, and Xanthonema debile and Nannochloropsis oceanica, both from Stramenopiles. All three light-harvesting complexes are related to fucoxanthin-chlorophyll protein, but contain only chlorophyll a and no chlorophyll c. In addition, they differ in the carotenoid content. This composition of the complexes allowed us to study the quenching of chlorophyll a triplet states by different carotenoids in a comparable environment. The triplet states of chlorophylls bound to the light-harvesting complexes were quenched by carotenoids with an efficiency close to 100%. Carotenoid triplet states were observed to rise with a ~5 ns lifetime and were spectrally and kinetically homogeneous. The triplet states were formed predominantly on the red-most chlorophylls and were quenched by carotenoids which were further identified or at least spectrally characterized.

• Keywords
• Algae, Energy transfer, Light harvesting, Photoprotection, Photosynthesis, Transient spectroscopy,
• MeSH
• Anaerobiosis MeSH
• Time Factors MeSH
• Chlorophyll metabolism   MeSH
• Spectrometry, Fluorescence MeSH
• Photochemical Processes * MeSH
• Stramenopiles metabolism   MeSH
• Carotenoids metabolism   MeSH
• Kinetics MeSH
• Chlorophyll Binding Proteins metabolism   MeSH
• Light-Harvesting Protein Complexes metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Chlorophyll MeSH
• Carotenoids MeSH
• Chlorophyll Binding Proteins MeSH
• Light-Harvesting Protein Complexes MeSH