High resolution frequency selective photochemistry of phycobilisomes at cryogenic temperatures

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Abstract
Highly frequency selective photochemistry at cryogenic temperatures is used to gain information on the excited state dynamics of large biomolecular aggregates, the phycobilisomes from the blue–green alga (cyanobacterium) Masticogladus laminosus. In particular, we show that in spite of the well organized structure of these aggregates disorder on a microscopic level dominates the optical spectra. The hole burning reaction in the resonantly excited chromophores is most probably due to a conformational change in the neighborhood of the chromophore. From the widths of the holes energy transfer times between different pigments on the order of 16 ps are determined. These transfer times are independent of the excitation energy.