Photoisomerization and photoionization of the photoactive yellow protein chromophore in solution.
Dispersed pump-dump-probe spectroscopy has the ability to characterize and identify the underlying ultrafast dynamical processes in complicated chemical and biological systems. This technique builds on traditional pump-probe techniques by exploring both ground- and excited-state dynamics and characterizing the connectivity between constituent transient states. We have used the dispersed pump-dump-probe technique to investigate the ground-state dynamics and competing excited-state processes in the excitation-induced ultrafast dynamics of thiomethyl p-coumaric acid, a model chromophore for the photoreceptor photoactive yellow protein. Our results demonstrate the parallel formation of two relaxation pathways (with multiple transient states) that jointly lead to two different types of photochemistry: cis-trans isomerization and detachment of a hydrated electron. The relative transition rates and quantum yields of both pathways have been determined. We find that the relaxation of the photoexcited chromophores involves multiple, transient ground-state intermediates and the chromophore in solution does not generate persistent photoisomerized products, but instead undergoes photoionization resulting in the generation of detached electrons and radicals. These results are of great value in interpreting the more complex dynamical changes in the optical properties of the photoactive yellow protein.
Larsen
Delmar S
DS
Faculty of Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands. dslarsen@nat.vu.nl
Vengris
Mikas
M
van Stokkum
Ivo H M
IH
van der Horst
Michael A
MA
de Weerd
Frank L
FL
Hellingwerf
Klaas J
KJ
van Grondelle
Rienk
R
D003373:Coumaric Acids / Q000138:chemical synthesis / Q000737:chemistry*; D003374:Coumarins / Q000138:chemical synthesis / Q000737:chemistry*; D007536:Isomerism; D010777:Photochemistry; D011789:Quantum Theory; D013057:Spectrum Analysis; D013223:Statistics as Topic
D003373:Coumaric Acids; D003374:Coumarins; C492954:thiomethyl p-coumaric acid