title: Simulations of the two-dimensional electronic spectroscopy of the photosystem II reaction center.
abstract: We report simulations of the two-dimensional electronic spectroscopy of the Q(y) band of the D1-D2-Cyt b559 photosystem II reaction center at 77 K. We base the simulations on an existing Hamiltonian that was derived by simultaneous fitting to a wide range of linear spectroscopic measurements and described within modified Redfield theory. The model obtains reasonable agreement with most aspects of the two-dimensional spectra, including the overall peak shapes and excited state absorption features. It does not reproduce the rapid equilibration from high energy to low energy excitonic states evident by a strong cross-peak below the diagonal. We explore modifications to the model to incorporate new structural data and improve agreement with the two-dimensional spectra. We find that strengthening the system-bath coupling and lowering the degree of disorder significantly improves agreement with the cross-peak feature, while lessening agreement with the relative diagonal/antidiagonal width of the 2D spectra. We conclude that two-dimensional electronic spectroscopy provides a sensitive test of excitonic models of the photosystem II reaction center and discuss avenues for further refinement of such models.
authors.affiliation: Department of Physics and Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA.
authors.forename: K L M
authors.initials: KL
authors.lastname: Lewis
authors.forename: F D
authors.initials: FD
authors.lastname: Fuller
authors.forename: J A
authors.initials: JA
authors.lastname: Myers
authors.forename: C F
authors.initials: CF
authors.lastname: Yocum
authors.forename: S
authors.initials: S
authors.lastname: Mukamel
authors.forename: D
authors.initials: D
authors.lastname: Abramavicius
authors.forename: J P
authors.initials: JP
authors.lastname: Ogilvie
mesh_terms: D003198:Computer Simulation; D004735:Energy Transfer; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011487:Protein Conformation; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D045332:Photosystem II Protein Complex