title: Characterization of the low-temperature triplet state of chlorophyll in photosystem II core complexes: Application of phosphorescence measurements and Fourier transform infrared spectroscopy.
abstract: Phosphorescence measurements at 77 K and light-induced FTIR difference spectroscopy at 95 K were applied to study of the triplet state of chlorophyll a ((3)Chl) in photosystem II (PSII) core complexes isolated from spinach. Using both methods, (3)Chl was observed in the core preparations with doubly reduced primary quinone acceptor QA. The spectral parameters of Chl phosphorescence resemble those in the isolated PSII reaction centers (RCs). The main spectral maximum and the lifetime of the phosphorescence corresponded to 955±1 nm and of 1.65±0.05 ms respectively; in the excitation spectrum, the absorption maxima of all core complex pigments (Chl, pheophytin a (Pheo), and β-carotene) were observed. The differential signal at 1667(-)/1628(+)cm(-1) reflecting a downshift of the stretching frequency of the 13(1)-keto C=O group of Chl was found to dominate in the triplet-minus-singlet FTIR difference spectrum of core complexes. Based on FTIR results and literature data, it is proposed that (3)Chl is mostly localized on the accessory chlorophyll that is in triplet equilibrium with P680. Analysis of the data suggests that the Chl triplet state responsible for the phosphorescence and the FTIR difference spectrum is mainly generated due to charge recombination in the reaction center radical pair P680(+)PheoD1(-), and the energy and temporal parameters of this triplet state as well as the molecular environment and interactions of the triplet-bearing Chl molecule are similar in the PSII core complexes and isolated PSII RCs.
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russian Federation.
authors.forename: Alexey A
authors.initials: AA
authors.lastname: Zabelin
authors.affiliation: A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr., 33, Moscow 119071, Russian Federation; Biology Department, M.V. Lomonosov Moscow State University, Vorobyovy Gory, Moscow 119992, Russian Federation.
authors.forename: Konstantin V
authors.initials: KV
authors.lastname: Neverov
authors.affiliation: A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr., 33, Moscow 119071, Russian Federation; Biology Department, M.V. Lomonosov Moscow State University, Vorobyovy Gory, Moscow 119992, Russian Federation.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Krasnovsky
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russian Federation.
authors.forename: Valentina A
authors.initials: VA
authors.lastname: Shkuropatova
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russian Federation.
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Shuvalov
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russian Federation. Electronic address: ashkur@mail.ru.
authors.forename: Anatoly Ya
authors.initials: AY
authors.lastname: Shkuropatov
mesh_terms: D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism; D008163:Luminescent Measurements / Q000379:methods*; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011809:Quinones / Q000737:chemistry / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D018724:Spinacia oleracea / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
chemical_list: D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D011809:Quinones; D002734:Chlorophyll
keywords: Chlorophyll a; Core complex; FTIR spectroscopy; Phosphorescence; Photosystem II; Triplet state