Ultrafast carotenoid-chlorophyll interactions in fucoxanthin-chlorophyll protein (FCP)

FCP, or Fucoxanthin Chlorophyll Protein, is a Light Harvesting Complex that can be found in diatoms and brown algae. One of its interesting features is its ability to efficiently capture blue-green light, which is due to the presence of specific chromophores such as fucoxanthin, chlorophyll a, and chlorophyll c. Recently, researchers were able to solve the crystallographic structure of FCP, providing insight into the arrangement of pigments within the protein scaffold. This information helps with interpreting the spectroscopic characteristics of FCP, but also raises questions about potential interactions between fucoxanthin and chlorophyll c, which have yet to be experimentally observed despite their spatial proximity. To investigate this possibility, two-dimensional electronic spectroscopy was used to study the rapid relaxation dynamics of FCP. The experiments showed an immediate spread of the excitation between fucoxanthin and chlorophyll c, indicating that there is a significant coupling between the chromophores.