title: Molecular interactions of the redox-active accessory chlorophyll on the electron-donor side of photosystem II as studied by Fourier transform infrared spectroscopy.
abstract: A Fourier transform infrared (FTIR) difference spectrum upon photooxidation of the accessory chlorophyll (Chlz) of photosystem II (PS II) was obtained at 210 K with Mn-depleted PS II membranes in the presence of fericyanide and silicomolybdate. The observed Chlz+/Chlz spectrum showed two differential bands at 1747/1736 and 1714/1684 cm-1. The former was assigned to the free carbomethoxy C = 0 and the latter to the keto C = 0 that is hydrogen-bonded or in a highly polar environment. Also, the negative 1614 cm-1 band assignable to the macrocycle mode indicated 5-coordination of the central Mg. The negative 1660 cm-1 band, possibly due to the strongly hydrogen-bonded keto C = 0, may suggest oxidation of one more Chlz, although an alternative assignment, the amide I mode of proteins perturbed by Chlz oxidation, is also possible.
authors.affiliation: Photosynthesis Research laboratory, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Noguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005292:Ferricyanides; D045342:Light-Harvesting Protein Complexes; D008345:Manganese / Q000172:deficiency; D008982:Molybdenum; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D017655:Silicon Compounds; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D005292:Ferricyanides; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D017655:Silicon Compounds; C013250:silicomolybdate; C007931:hexacyanoferrate III; D002734:Chlorophyll; D008345:Manganese; D008982:Molybdenum