Energy transfer and dynamics of photosynthetic antenna complexes and biological model systems: A study by photochemical hole-burning

Abstract

Photochemical hole-burning (PHB) experiments have been performed on two types of complex organic systems. Results on the Q y O-O transition of bacteriochlorophyll-a (BChl-a) in triethylamine (TEA) between 0.4 and 4.2 K, obtained with a diode laser at 780 nm, show that the homogeneous line width, Γ hom, follows a T 1.3±0.1 dependence. Such a power law has been found for many organic glassy systems at low temperatures. The absolute value of Γ hom in a solution of water and detergent is almost one order of magnitude larger than in TEA, which suggests that energy transfer takes place between BChl-a molecules within a micelle. Holes burnt in the 800 nm band of the B800-850 antenna pigment-protein complex of purple bacteria Rhodobacter sphaeroides show no variation in hole width between 1.2 and 30 K. The results yield an energy transfer time of 2.3 ± 0.4 ps between the aggregated BChl 800 and BChl 850 molecules. The same value is found for intact chromatophores at 1.2 K.