title: Defining the far-red limit of photosystem II in spinach.
abstract: The far-red limit of photosystem II (PSII) photochemistry was studied in PSII-enriched membranes and PSII core preparations from spinach (Spinacia oleracea) after application of laser flashes between 730 and 820 nm. Light up to 800 nm was found to drive PSII activity in both acceptor side reduction and oxidation of the water-oxidizing CaMn(4) cluster. Far-red illumination induced enhancement of, and slowed down decay kinetics of, variable fluorescence. Both effects reflect reduction of the acceptor side of PSII. The effects on the donor side of PSII were monitored using electron paramagnetic resonance spectroscopy. Signals from the S(2)-, S(3)-, and S(0)-states could be detected after one, two, and three far-red flashes, respectively, indicating that PSII underwent conventional S-state transitions. Full PSII turnover was demonstrated by far-red flash-induced oxygen release, with oxygen appearing on the third flash. In addition, both the pheophytin anion and the Tyr Z radical were formed by far-red flashes. The efficiency of this far-red photochemistry in PSII decreases with increasing wavelength. The upper limit for detectable photochemistry in PSII on a single flash was determined to be 780 nm. In photoaccumulation experiments, photochemistry was detectable up to 800 nm. Implications for the energetics and energy levels of the charge separated states in PSII are discussed in light of the presented results.
authors.affiliation: Department of Photochemistry, Angström Laboratory, Uppsala University, SE-751 20 Uppsala, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Thapper
authors.forename: Fikret
authors.initials: F
authors.lastname: Mamedov
authors.forename: Fredrik
authors.initials: F
authors.lastname: Mokvist
authors.forename: Leif
authors.initials: L
authors.lastname: Hammarström
authors.forename: Stenbjörn
authors.initials: S
authors.lastname: Styring
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D008027:Light; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018724:Spinacia oleracea / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D045332:Photosystem II Protein Complex; D010100:Oxygen
references.citation: Proc Natl Acad Sci U S A. 1957 Jan 15;43(1):133-43
references.pmid: 16589986
references.citation: Proc Natl Acad Sci U S A. 2007 Apr 24;104(17):7283-8
references.pmid: 17431035
references.citation: Biochemistry. 2006 Aug 1;45(30):9279-90
references.pmid: 16866374
references.citation: Biochemistry. 2007 Sep 18;46(37):10703-12
references.pmid: 17718509
references.citation: Biochemistry. 2007 Oct 30;46(43):12473-81
references.pmid: 17918957
references.citation: Biochim Biophys Acta. 2006 Jul;1757(7):841-51
references.pmid: 16859635
references.citation: Biochim Biophys Acta. 2005 Jul 15;1708(3):311-21
references.pmid: 15950173
references.citation: FEBS Lett. 1976 Jan 15;61(2):286-9
references.pmid: 174952
references.citation: Biochemistry. 2002 Jul 2;41(26):8518-27
references.pmid: 12081503
references.citation: Biochemistry. 2002 Mar 26;41(12):4117-26
references.pmid: 11900555
references.citation: Biochemistry. 2005 May 10;44(18):6723-8
references.pmid: 15865417
references.citation: Biochim Biophys Acta. 1981 Jul;636(2):201-9
references.pmid: 7284350
references.citation: Biochim Biophys Acta. 2005 Jun 30;1708(2):209-18
references.pmid: 15878422
references.citation: Biochemistry. 1999 Aug 10;38(32):10578-84
references.pmid: 10441155
references.citation: Biochim Biophys Acta. 2006 Mar;1757(3):155-7; discussion 158-60
references.pmid: 16638565
references.citation: Nature. 2005 Dec 15;438(7070):1040-4
references.pmid: 16355230
references.citation: Nature. 2001 Jun 21;411(6840):909-17
references.pmid: 11418848
references.citation: Science. 2004 Mar 19;303(5665):1831-8
references.pmid: 14764885
references.citation: Biochemistry. 2002 Feb 12;41(6):1981-9
references.pmid: 11827545
references.citation: Biochim Biophys Acta. 1991 Jan 3;1056(1):1-18
references.pmid: 1845842
references.citation: Biochemistry. 2003 Jul 8;42(26):8066-76
references.pmid: 12834358
references.citation: Proc Natl Acad Sci U S A. 1981 Jan;78(1):274-8
references.pmid: 16592949
references.citation: FEBS Lett. 2005 Jul 18;579(18):4017-9
references.pmid: 16004989
references.citation: Biochemistry. 1989 Dec 12;28(25):9557-65
references.pmid: 2692711
references.citation: C R Hebd Seances Acad Sci. 1964 May 4;258:4622-5
references.pmid: 14146826
references.citation: Biochemistry. 2004 Nov 2;43(43):13787-95
references.pmid: 15504041
references.citation: Photosynth Res. 2000;65(1):41-52
references.pmid: 16228469
references.citation: J Biol Chem. 1994 Feb 18;269(7):5115-21
references.pmid: 8106491
references.citation: Biochim Biophys Acta. 2001 Oct 30;1507(1-3):80-99
references.pmid: 11687209
references.citation: Plant Cell Physiol. 2005 Jun;46(6):837-42
references.pmid: 15769805
references.citation: Biochemistry. 2000 Aug 29;39(34):10478-86
references.pmid: 10956038