title: Toward an Understanding of the Excitonic Structure of the CP47 Antenna Protein Complex of Photosystem II Revealed via Circularly Polarized Luminescence.
abstract: Identification of the lowest energy pigments in the photosynthetic CP47 antenna protein complex of Photosystem II (PSII) is essential for understanding its excitonic structure, as well as excitation energy pathways in the PSII core complex. Unfortunately, there is no consensus concerning the nature of the low-energy state(s), nor chlorophyll (Chl) site energies in this important photosynthetic antenna. Although we raised concerns regarding the estimations of Chl site energies obtained from modeling studies of various types of CP47 optical spectra [Reinot, T; et al., Anal. Chem. Insights 2016, 11, 35-48] recent new assignments imposed by the shape of the circularly polarized luminescence (CPL) spectrum [Hall, J.; et al., Biochim. Biophys. Acta 2016, 1857, 1580-1593] necessitate our comments. We demonstrate that other combinations of low-energy Chls provide equally good or improved simultaneous fits of various optical spectra (absorption, emission, CPL, circular dichroism, and nonresonant hole-burned spectra), but more importantly, we expose the heterogeneous nature of the recently studied complexes and argue that the published composite nature of the CPL (contributed to by CPL685, CPL691, and CPL695) does not represent an intact CP47 protein. A positive CPL695is extracted for the intact protein, which, when simultaneously fitted with multiple other optical spectra, provides new information on the excitonic structure of intact and destabilized CP47 complexes and their lowest energy state(s).
authors.affiliation: Department of Chemistry and ‡Department of Physics, Kansas State University , Manhattan, Kansas 66506, United States.
authors.forename: Mahboobe
authors.initials: M
authors.lastname: Jassas
authors.affiliation: Department of Chemistry and ‡Department of Physics, Kansas State University , Manhattan, Kansas 66506, United States.
authors.forename: Tonu
authors.initials: T
authors.lastname: Reinot
authors.affiliation: Department of Chemistry and ‡Department of Physics, Kansas State University , Manhattan, Kansas 66506, United States.
authors.forename: Adam
authors.initials: A
authors.lastname: Kell
authors.affiliation: Department of Chemistry and ‡Department of Physics, Kansas State University , Manhattan, Kansas 66506, United States.
authors.forename: Ryszard
authors.identifier: 0000-0003-3302-9232
authors.initials: R
authors.lastname: Jankowiak
mesh_terms: D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D049449:Luminescence; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; C070970:photosystem II, chlorophyll-binding protein, CP-47