title: Critical assessment of the emission spectra of various photosystem II core complexes.
abstract: We evaluate low-temperature (low-T) emission spectra of photosystem II core complexes (PSII-cc) previously reported in the literature, which are compared with emission spectra of PSII-cc obtained in this work from spinach and for dissolved PSII crystals from Thermosynechococcus (T.) elongatus. This new spectral dataset is used to interpret data published on membrane PSII (PSII-m) fragments from spinach and Chlamydomonas reinhardtii, as well as PSII-cc from T. vulcanus and intentionally damaged PSII-cc from spinach. This study offers new insight into the assignment of emission spectra reported on PSII-cc from different organisms. Previously reported spectra are also compared with data obtained at different saturation levels of the lowest energy state(s) of spinach and T. elongatus PSII-cc via hole burning in order to provide more insight into emission from bleached and/or photodamaged complexes. We show that typical low-T emission spectra of PSII-cc (with closed RCs), in addition to the 695 nm fluorescence band assigned to the intact CP47 complex (Reppert et al. J Phys Chem B 114:11884-11898, 2010), can be contributed to by several emission bands, depending on sample quality. Possible contributions include (i) a band near 690-691 nm that is largely reversible upon temperature annealing, proving that the band originates from CP47 with a bleached low-energy state near 693 nm (Neupane et al. J Am Chem Soc 132:4214-4229, 2010; Reppert et al. J Phys Chem B 114:11884-11898, 2010); (ii) CP43 emission at 683.3 nm (not at 685 nm, i.e., the F685 band, as reported in the literature) (Dang et al. J Phys Chem B 112:9921-9933, 2008; Reppert et al. J Phys Chem B 112:9934-9947, 2008); (iii) trap emission from destabilized CP47 complexes near 691 nm (FT1) and 685 nm (FT2) (Neupane et al. J Am Chem Soc 132:4214-4229, 2010); and (iv) emission from the RC pigments near 686-687 nm. We suggest that recently reported emission of single PSII-cc complexes from T. elongatus may not represent intact complexes, while those obtained for T. elongatus presented in this work most likely represent intact PSII-cc, since they are nearly indistinguishable from emission spectra obtained for various PSII-m fragments.
authors.affiliation: Department of Chemistry, Kansas State University, Manhattan, KS, 66506, USA.
authors.forename: Jinhai
authors.initials: J
authors.lastname: Chen
authors.forename: Adam
authors.initials: A
authors.lastname: Kell
authors.forename: Khem
authors.initials: K
authors.lastname: Acharya
authors.forename: Christopher
authors.initials: C
authors.lastname: Kupitz
authors.forename: Petra
authors.initials: P
authors.lastname: Fromme
authors.forename: Ryszard
authors.initials: R
authors.lastname: Jankowiak
mesh_terms: D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000737:chemistry*; D002734:Chlorophyll / Q000737:chemistry; D003460:Crystallization; D000458:Cyanobacteria / Q000737:chemistry*; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D013045:Species Specificity; D013050:Spectrometry, Fluorescence; D018724:Spinacia oleracea / Q000737:chemistry*; D013696:Temperature
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll
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