In this work we report the results of ultrafast transient absorption studies which examined energy transfer between carotenoids and chlorophylls in Peridinin-Chlorophyll-a-Protein (PCP) light harvesting complex from the dinofiagellate Amphidinium carterae. Global analysis of the isotropic decay reveals that the peridinin lifetime in PCP is 2.3±0.2 ps. This time constant is the peridinin-Chla energy transfer, which is essentially entirely mediated by coupling of the peridinin S1 and Chla Qy transitions. Based on this lifetime we estimated an energy transfer timescale of ∼ 2.4 ps and a peridinin-Chla coupling of 46 cm-1. The magnitude of this coupling suggests a peridinin S1 transition dipole moment of ∼ 3 D. Global analysis of the depolarization measurements, shows, a small decrease in the depolarization from the initial 0.4 value to 0.36±0.03. This decrease occurs on the same timescale as the S2→S1 internal conversion, suggesting that either the S1 transition dipole is oriented ∼ 15° away from the S2 transition dipole, or, that a small amount of peridinin S2-peridinin S2 energy transfer occurs in competition with internal conversion, or some combination of the two.
|Number of pages||4|
|Journal||International Journal of Modern Physics B|
|Publication status||Published - 10 Dec 2001|