title: Mutations to R. sphaeroides Reaction Center Perturb Energy Levels and Vibronic Coupling but Not Observed Energy Transfer Rates.
abstract: The bacterial reaction center is capable of both efficiently collecting and quickly transferring energy within the complex; therefore, the reaction center serves as a convenient model for both energy transfer and charge separation. To spectroscopically probe the interactions between the electronic excited states on the chromophores and their intricate relationship with vibrational motions in their environment, we examine coherences between the excited states. Here, we investigate this question by introducing a series of point mutations within 12 Å of the special pair of bacteriochlorophylls in the Rhodobacter sphaeroides reaction center. Using two-dimensional spectroscopy, we find that the time scales of energy transfer dynamics remain unperturbed by these mutations. However, within these spectra, we detect changes in the mixed vibrational-electronic coherences in these reaction centers. Our results indicate that resonance between bacteriochlorophyll vibrational modes and excitonic energy gaps promote electronic coherences and support current vibronic models of photosynthetic energy transfer.
authors.forename: Moira L
authors.initials: ML
authors.lastname: Flanagan
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Long
authors.forename: Peter D
authors.initials: PD
authors.lastname: Dahlberg
authors.affiliation: Department of Chemistry, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Rolczynski
authors.affiliation: Department of Chemistry, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Sara C
authors.initials: SC
authors.lastname: Massey
authors.affiliation: Department of Chemistry, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Engel
mesh_terms: D004735:Energy Transfer; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D012242:Rhodobacter sphaeroides / Q000235:genetics*; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins