title: Bacteriophytochrome Photoisomerization Proceeds Homogeneously Despite Heterogeneity in Ground State.
abstract: Phytochromes are red/far-red photoreceptors that are widely distributed in plants and prokaryotes. Ultrafast photoisomerization of a double bond in a biliverdin cofactor or other linear tetrapyrrole drives their photoactivity, but their photodynamics are only partially understood. Multiexponential dynamics were observed in previous ultrafast spectroscopic studies and were attributed to heterogeneous populations of the pigment-protein complex. In this work, two-dimensional photon echo spectroscopy was applied to study dynamics of the bacteriophytochromes RpBphP2 and PaBphP. Two-dimensional photon echo spectroscopy can simultaneously resolve inhomogeneity in ensembles and fast dynamics by correlating pump wavelength with the emitted signal wavelength. The distribution of absorption and emission energies within the same state indicates an ensemble of heterogeneous protein environments that are spectroscopically distinct. However, the lifetimes of the dynamics are uniform across the ensemble, suggesting a homogeneous model involving sequential intermediates for the initial photodynamics of isomerization.
authors.affiliation: Department of Chemistry, The James Franck Institute, Institute for Biophysical Dyanmics, The University of Chicago, Chicago, Illinois.
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
authors.affiliation: Graduate Program in Biophysical Science, The James Franck Institute, Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois.
authors.forename: Moira L
authors.initials: ML
authors.lastname: Flanagan
authors.affiliation: Department of Chemistry, The James Franck Institute, Institute for Biophysical Dyanmics, The University of Chicago, Chicago, Illinois.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: McGillicuddy
authors.affiliation: Department of Chemistry, The James Franck Institute, Institute for Biophysical Dyanmics, The University of Chicago, Chicago, Illinois.
authors.forename: Haibin
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, The James Franck Institute, Institute for Biophysical Dyanmics, The University of Chicago, Chicago, Illinois.
authors.forename: Alan Ruvim
authors.initials: AR
authors.lastname: Ginzburg
authors.affiliation: Department of Biochemistry and Molecular Biology, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Biochemistry and Molecular Biology, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois.
authors.forename: Keith
authors.initials: K
authors.lastname: Moffat
authors.affiliation: Department of Chemistry, The James Franck Institute, Institute for Biophysical Dyanmics, The University of Chicago, Chicago, Illinois. Electronic address: gsengel@uchicago.edu.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Engel
mesh_terms: D007536:Isomerism; D055668:Photochemical Processes; D010834:Phytochrome / Q000737:chemistry*
chemical_list: D010834:Phytochrome