Ultrafast light-induced response of photoactive yellow protein chromophore analogues

Photochemical & Photobiological Sciences - Tập 6 - Trang 780-787 - 2007
Agathe Espagne1,2,3, Daniel H. Paik2,4, Pascale Changenet-Barret1, Pascal Plaza1, Monique M. Martin1, Ahmed H. Zewail2
1UMR CNRS-ENS 8640 P.A.S.T.E.U.R., Département de Chimie, Ecole Normale Supérieure, Paris, France
2Laboratory for Molecular Sciences, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, USA
3Service de Bioénergétique, CEA-Saclay, Gif-sur-Yvette Cedex, France
4JILA, University of Colorado, Boulder, USA

Tóm tắt

The fluorescence decays of several analogues of the photoactive yellow protein (PYP) chromophore in aqueous solution have been measured by femtosecond fluorescence up-conversion and the corresponding time-resolved fluorescence spectra have been reconstructed. The native chromophore of PYP is a thioester derivative of p-coumaric acid in its trans deprotonated form. Fluorescence kinetics are reported for a thioester phenyl analogue and for two analogues where the thioester group has been changed to amide and carboxylate groups. The kinetics are compared to those we previously reported for the analogues bearing ketone and ester groups. The fluorescence decays of the full series are found to lie in the 1–10 ps range depending on the electron-acceptor character of the substituent, in good agreement with the excited-state relaxation kinetics extracted from transient absorption measurements. Steady-state photolysis is also examined and found to depend strongly on the nature of the substituent. While it has been shown that the ultrafast light-induced response of the chromophore in PYP is controlled by the properties of the protein nanospace, the present results demonstrate that, in solution, the relaxation dynamics and pathway of the chromophore is controlled by its electron donor—acceptor structure: structures of stronger electron donor—acceptor character lead to faster decays and less photoisomerisation.

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