• Journal of Photoscience
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• v.9 no.2
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• pp.78-81
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• 2002

Fluorescence rise and decay curves of carotenoids were measured in solutions and in pigment protein complexes with a femtosecond time-resolved fluorescence spectroscopy. For linear carotenoids, the S$_2$ lifetimes showed the maximum value around n = 9-10. The conjugation of a keto-carbonyl group shortened the S$_2$lifetime and prolonged the S$_1$lifetime. The excitation relaxation dynamics within carotenoids and the excitation energy transfer kinetics from carotenoids to chlorophylls are discussed as a function of molecular structure of carotenoids.

• Journal of Photoscience
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• v.9 no.2
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• pp.122-125
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• 2002

Coherent oscillations in is fluorescence dynamics of W.-t. PYP and its site-directed mutants have been observed. Two oscillatory modes coupled with the ultrafast fluorescence due to the twisting of the excited chromophore were identified, a high ftequency mode (∼135 cm$\^$-1/) with ∼550 is damping time and a low frequency overdamped mode (-45 cm$\^$-1/) with ∼250 is damping time, respectively. Both modes disappear in the fluorescence dynamics of denatured PYP emphasizing the important role of the protein nanospace as the environment for photoreaction. The qualitative picture of fluorescence dynamics in site-directed mutants was rather similar to that in W.-t. PYP, i.e., similar oscillatory modes (∼130-140 cm$\^$-1/ and ∼40-70 cm$\^$-1/) have been observed. This indicates that the vibrational modes and electron-vibration couplings do not change dramatically due to the mutation though the damping time of low frequency mode a little decreases as the protein nanospace structure becomes looser and more disordered by mutation. On the other hand, in the case of some PYP analogues, the qualitative picture of fluorescence dynamics changes, showing the familiar picture of solvation effect whereas the oscillations are almost damped. Comparative analyses of these observations are presented.