title: Ultrafast dynamics of isolated model photoactive yellow protein chromophores: "Chemical perturbation theory" in the laboratory.
abstract: Pump-probe and pump-dump probe experiments have been performed on several isolated model chromophores of the photoactive yellow protein (PYP). The observed transient absorption spectra are discussed in terms of the spectral signatures ascribed to solvation, excited-state twisting, and vibrational relaxation. It is observed that the protonation state has a profound effect on the excited-state lifetime of p-coumaric acid. Pigments with ester groups on the coumaryl tail end and charged phenolic moieties show dynamics that are significantly different from those of other pigments. Here, an unrelaxed ground-state intermediate could be observed in pump-probe signals. A similar intermediate could be identified in the sinapinic acid and in isomerization-locked chromophores by means of pump-dump probe spectroscopy; however, in these compounds it is less pronounced and could be due to ground-state solvation and/or vibrational relaxation. Because of strong protonation-state dependencies and the effect of electron donor groups, it is argued that charge redistribution upon excitation determines the twisting reaction pathway, possibly through interaction with the environment. It is suggested that the same pathway may be responsible for the initiation of the photocycle in native PYP.
authors.affiliation: Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands. mikasv@nat.vu.nl
authors.forename: Mikas
authors.initials: M
authors.lastname: Vengris
authors.forename: Delmar S
authors.initials: DS
authors.lastname: Larsen
authors.forename: Michael A
authors.initials: MA
authors.lastname: van der Horst
authors.forename: Olaf F A
authors.initials: OF
authors.lastname: Larsen
authors.forename: Klaas J
authors.initials: KJ
authors.lastname: Hellingwerf
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D013058:Mass Spectrometry; D019906:Nuclear Magnetic Resonance, Biomolecular; D020283:Photoreceptors, Microbial / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; C050162:photoactive yellow protein, Bacteria