Ultrafast photophysics of protochlorophyllide a
Speaker: Benjamin Dietzek (Friedrich-Schiller-University Jena)
Date: Wednesday, 28 April 2010, 11:00-12:00
Location: room AER19/3.11
The talk will present the results of a detailed spectroscopic study on the photoinduced excited-state dynamics of protochlorophyllide a (PChlide), the substrate of the enzyme protochlorophyllideoxidoreductase. In order to unravel the initial dynamics and its correlation with structural features of the analyte we combine resonance Raman investigations with ultrafast solvent-dependent transient absorption and transient anisotropy measurements. From this comparison we deduce that the presence of the cyclopentanone ring places an important role in the formation of an intramolecular charge-transfer state, which determines the photophysics of PChlide on a ps-time scale. However, the resonance Raman data reveal a strong band at 1703 cm−1, which can be attributed to the CO carbonyl vibration of the cyclopentanone ring, which is attached in conjugation to the π-electron path of the porphyrin ring system. The enhancement of this mode upon electronically resonant excitation suggests that this structural feature is already involved in the light-absorption of the molecule. The results presented are discussed in the light of the reaction model suggested for the photoreduction of PChlide a in the protochlorophyllide oxidoreductase.