title: Effect of Pb2+ ions on photosynthetic apparatus.
abstract: Using model lead compounds Pb(NO3)2 and Pb(CH3CHOO)2, the mechanism and the site of action of Pb2+ ions in the photosynthetic apparatus of spinach chloroplasts were studied. Both compounds inhibited photosynthetic electron transport (PET) through photosystem 1 (PS1) and photosystem 2 (PS2), while Pb(NO3)2 was found to be more effective PET inhibitor. Using EPR spectroscopy the following sites of Pb2+ action in the photosynthetic apparatus were determined: the water-splitting complex and the Z•/D• intermediates on the donor side of PS2 and probably also the ferredoxin on the acceptor side of PS1, because cyclic electron flow in chloroplasts was impaired by treatment with Pb2+ ions. Study of chlorophyll fluorescence in suspension of spinach chloroplasts in the presence of Pb2+ ions confirmed their site of action in PS2. Using fluorescence spectroscopy also formation of complexes between Pb2+ and amino acid residues in photosynthetic proteins was confirmed and constants of complex formation among Pb2+ and aromatic amino acids were calculated for both studied lead compounds.
authors.affiliation: Faculty of Natural Sciences, Institute of Chemistry, Comenius University in Bratislava, Bratislava, Slovak Republic. sersen@fns.uniba.sk.
authors.forename: Frantisek
authors.initials: F
authors.lastname: Sersen
authors.forename: Katarina
authors.initials: K
authors.lastname: Kralova
authors.forename: Matus
authors.initials: M
authors.lastname: Pesko
authors.forename: Marek
authors.initials: M
authors.lastname: Cigan
mesh_terms: D002734:Chlorophyll / Q000737:chemistry; D002736:Chloroplasts / Q000187:drug effects* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D007477:Ions / Q000737:chemistry; D007854:Lead / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000187:drug effects*; D045332:Photosystem II Protein Complex / Q000187:drug effects*; D013050:Spectrometry, Fluorescence; D018724:Spinacia oleracea / Q000737:chemistry / Q000187:drug effects*; D014867:Water / Q000737:chemistry
chemical_list: D007477:Ions; D009566:Nitrates; D009942:Organometallic Compounds; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D014867:Water; D002734:Chlorophyll; D007854:Lead; C017461:lead nitrate; C008261:lead acetate