Spectral hole burning at the low-energy absorption edge of photosystem II core complexes

Hughes, Joseph L.; Smith, Paul J.; Pace, Ronald; Krausz, Elmars

doi:10.1016/j.jlumin.2006.01.012

Cited by 14 publications

(20 citation statements)

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“…Spectral hole burning measurements at low temperatures on spinach PSII core complexes have revealed that Q A -formation can be observed up to 730 nm (Hughes et al, 2006a(Hughes et al, , 2006b. Two different photochemical events leading to Q A reduction could be distinguished.…”

Section: Discussionmentioning

confidence: 99%

“…An absorption band, with a maximum at 689 nm, was linked to the lowest energy chlorophyll a pigments in CP47, and stretches out to 704 nm at 1.7K. For a second absorption with a maximum at 705 nm, 80 and 30% of Q A could still be reduced using 708-and 728-nm light, respectively (Hughes et al, 2006a(Hughes et al, , 2006b). This absorption was proposed to be linked directly to a charge separating state of the special pair chlorophylls (Hughes et al, 2006a(Hughes et al, , 2006b.…”

Section: Discussionmentioning

confidence: 99%

“…For a second absorption with a maximum at 705 nm, 80 and 30% of Q A could still be reduced using 708-and 728-nm light, respectively (Hughes et al, 2006a(Hughes et al, , 2006b). This absorption was proposed to be linked directly to a charge separating state of the special pair chlorophylls (Hughes et al, 2006a(Hughes et al, , 2006b. No Q A -formation could be observed with illumination at 750 nm at 1.7K (Hughes et al, 2006a).…”

Section: Discussionmentioning

confidence: 99%

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Defining the Far-Red Limit of Photosystem II in Spinach

et al. 2009

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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. Farred 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.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Defining the Far-Red Limit of Photosystem II in Spinach

et al. 2009

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“…With illumination in the 690-700 nm range, Q A -formation occurs with high quantum efficiency in a large fraction of centers (Hughes et al 2006b). Thus, despite their low transition energies, these trap states transfer energy at a rate that is competitive with fluorescence lifetimes (Hughes et al 2004(Hughes et al , 2005(Hughes et al , 2006c. This indicates that the longwavelength emitting states in PSII act as the ''linkers'' between the proximal antennae and the reaction center at low temperatures (Krausz et al 2005b).…”

Section: Optical Transition Energies Of Pigments In Photosystem IImentioning

confidence: 99%

Toward understanding molecular mechanisms of light harvesting and charge separation in photosystem II

Vassiliev

Bruce

2008

Photosynth Res

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Conversion of light energy in photosynthesis is extremely fast and efficient, and understanding the nature of this complex photophysical process is challenging. This review describes current progress in understanding molecular mechanisms of light harvesting and charge separation in photosystem II (PSII). Breakthroughs in X-ray crystallography have allowed the development and testing of more detailed kinetic models than have previously been possible. However, due to the complexity of the light conversion processes, satisfactory descriptions remain elusive. Recent advances point out the importance of variations in the photochemical properties of PSII in situ in different thylakoid membrane regions as well as the advantages of combining sophisticated time-resolved spectroscopic experiments with atomic level computational modeling which includes the effects of molecular dynamics.

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“…For wavelengths longer than 704 nm, excitation of inner antenna ceases [16] and a residual absorption that tails to $730 nm with a dipole strength corresponding to $0.1-0.2 chl a, has been assigned to the chargeseparating state of PSII [10]. A new approach to understanding the complex temperature and time dependence of low-temperature PSII fluorescence becomes enabled [15] via identification of this weak and low-energy chargeseparating state and a quantification via spectral hole-burning [9] of the relatively slow excitation transfer to the reaction centre from the inner antennae CP43 and CP47.…”

Section: Introductionmentioning

confidence: 99%