Low-temperature time-resolved spectroscopic study of the major light-harvesting complex of Amphidinium carterae

The major light-harvesting complex of Amphidinium ( A. ) carterae , chlorophyll- a –chlorophyll- c 2 –peridinin–protein complex (acpPC), was studied using ultrafast pump-probe spectroscopy at low temperature (60 K). An efficient peridinin–chlorophyll- a energy transfer was observed. The stimulated emission signal monitored in the near-infrared spectral region was stronger when redder part of peridinin pool was excited, indicating that these peridinins have the S 1 /ICT (intramolecular charge-transfer) state with significant charge-transfer character. This may lead to enhanced energy transfer efficiency from “red” peridinins to chlorophyll- a . Contrary to the water-soluble antenna of A. carterae , peridinin–chlorophyll- a protein, the energy transfer rates in acpPC were slower under low-temperature conditions. This fact underscores the influence of the protein environment on the excited-state dynamics of pigments and/or the specificity of organization of the two pigment–protein complexes.