Probing the photochemical mechanism in photoactive yellow protein.

Selectively bridged model compounds related to the chromophore in photoactive yellow protein have been synthesized where the single bond adjacent to the benzene ring (bond 1) and where both bond 1 and the adjacent double bond (bond 2) are bridged. They were compared to the nonbridged reference compound regarding their photophysical properties using steady-state and time-resolved fluorescence at various temperatures. Quantum chemical calculations were additionally performed and showed that several conformers are populated in the ground state.

Solvatochromic behavior of donor-acceptor-polyenes: dimethylamino-cyano-diphenylbutadiene.

4-(Dimethylamino)-4'-cyano-1,4-diphenylbutadiene (DCB) and 4-(dimethylamino)-2,6-dimethyl-4'-cyano-1,4-diphenylbutadiene (DMDCB) have been characterized spectroscopically. Quantum chemical calculations were performed for comparison. Solvatochromic shifts of the fluorescence were strong and showed a linear dependence on the solvent polarity parameters, whereas shifts in the absorption spectra are very weak only correlate better with the polarizability of the solvents.