Abstract
The Mn cluster in photosystem II (PS II) is believed to play an important role in the UV photoinhibition of green plants, but the mechanism is still not clear at a molecular level. In this work, the photochemical stability of [MnIII(O)2MnIV(H2O) 2(Terpy)2](NO3)3 (Terpy = 2,2′:6′,2″-terpyridine), designated as Mn-oxo mixed-valence dimer, a well characterized functional model of the oxygen-evolving complex in PS II, was examined in aqueous solution by exposing the complex to excess light irradiation at six different wavelengths in the range of 250 to 700 nm. The photodamage of the Mn-oxo mixed-valence dimer was confirmed by the decrease of its oxygen-evolution activity measured in the presence of the chemical oxidant oxone. Ultraviolet light irradiation induced a new absorption peak at around 400-440 nm of the Mn-oxo mixed-valence dimer. Visible light did not have the same effect on the Mn-oxo mixed-valence dimer. We speculate that the spectral change may be caused by conversion of the Mn(III)O2Mn(IV) dimer into a new structure - Mn(IV)O2Mn(IV). In the processes, the appearance of a 514 nm fluorescence peak was observed in the solution and may be linked to the hydration or protonation of Terpy ligand in the Mn-oxo dimer. In comparing the response of the PS II functional model compound and the PS II complex to excess light radiation, our results support the idea that UV photoinhibition is triggered at the Mn4Ca center of the oxygen-evolution complex in PS II by forming a modified structure, possibly a Mn(IV) species, and that the reaction of Mn ions is likely the initial step.
| Original language | English |
|---|---|
| Pages (from-to) | 118-125 |
| Number of pages | 8 |
| Journal | Journal of Photochemistry and Photobiology B: Biology |
| Volume | 104 |
| Issue number | 1-2 |
| DOIs | |
| Publication status | Published - Jul 2011 |
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Keywords
- Manganese-oxo compound
- Oxygen evolution
- Photodamage
- Photoinhibition
- PS II
- UV effect
ASJC Scopus subject areas
- Radiation
- Radiology Nuclear Medicine and imaging
- Radiological and Ultrasound Technology
- Biophysics
Cite this
Photodamage of a Mn(III/IV)-oxo mixed-valence compound and photosystem II : Evidence that a high-valent manganese species is responsible for UV-induced photodamage of the oxygen-evolving complex in photosystem II. / Wei, Zi; Cady, Clyde W.; Brudvig, Gary W; Hou, Harvey J M.
In: Journal of Photochemistry and Photobiology B: Biology, Vol. 104, No. 1-2, 07.2011, p. 118-125.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Photodamage of a Mn(III/IV)-oxo mixed-valence compound and photosystem II
T2 - Evidence that a high-valent manganese species is responsible for UV-induced photodamage of the oxygen-evolving complex in photosystem II
AU - Wei, Zi
AU - Cady, Clyde W.
AU - Brudvig, Gary W
AU - Hou, Harvey J M
PY - 2011/7
Y1 - 2011/7
N2 - The Mn cluster in photosystem II (PS II) is believed to play an important role in the UV photoinhibition of green plants, but the mechanism is still not clear at a molecular level. In this work, the photochemical stability of [MnIII(O)2MnIV(H2O) 2(Terpy)2](NO3)3 (Terpy = 2,2′:6′,2″-terpyridine), designated as Mn-oxo mixed-valence dimer, a well characterized functional model of the oxygen-evolving complex in PS II, was examined in aqueous solution by exposing the complex to excess light irradiation at six different wavelengths in the range of 250 to 700 nm. The photodamage of the Mn-oxo mixed-valence dimer was confirmed by the decrease of its oxygen-evolution activity measured in the presence of the chemical oxidant oxone. Ultraviolet light irradiation induced a new absorption peak at around 400-440 nm of the Mn-oxo mixed-valence dimer. Visible light did not have the same effect on the Mn-oxo mixed-valence dimer. We speculate that the spectral change may be caused by conversion of the Mn(III)O2Mn(IV) dimer into a new structure - Mn(IV)O2Mn(IV). In the processes, the appearance of a 514 nm fluorescence peak was observed in the solution and may be linked to the hydration or protonation of Terpy ligand in the Mn-oxo dimer. In comparing the response of the PS II functional model compound and the PS II complex to excess light radiation, our results support the idea that UV photoinhibition is triggered at the Mn4Ca center of the oxygen-evolution complex in PS II by forming a modified structure, possibly a Mn(IV) species, and that the reaction of Mn ions is likely the initial step.
AB - The Mn cluster in photosystem II (PS II) is believed to play an important role in the UV photoinhibition of green plants, but the mechanism is still not clear at a molecular level. In this work, the photochemical stability of [MnIII(O)2MnIV(H2O) 2(Terpy)2](NO3)3 (Terpy = 2,2′:6′,2″-terpyridine), designated as Mn-oxo mixed-valence dimer, a well characterized functional model of the oxygen-evolving complex in PS II, was examined in aqueous solution by exposing the complex to excess light irradiation at six different wavelengths in the range of 250 to 700 nm. The photodamage of the Mn-oxo mixed-valence dimer was confirmed by the decrease of its oxygen-evolution activity measured in the presence of the chemical oxidant oxone. Ultraviolet light irradiation induced a new absorption peak at around 400-440 nm of the Mn-oxo mixed-valence dimer. Visible light did not have the same effect on the Mn-oxo mixed-valence dimer. We speculate that the spectral change may be caused by conversion of the Mn(III)O2Mn(IV) dimer into a new structure - Mn(IV)O2Mn(IV). In the processes, the appearance of a 514 nm fluorescence peak was observed in the solution and may be linked to the hydration or protonation of Terpy ligand in the Mn-oxo dimer. In comparing the response of the PS II functional model compound and the PS II complex to excess light radiation, our results support the idea that UV photoinhibition is triggered at the Mn4Ca center of the oxygen-evolution complex in PS II by forming a modified structure, possibly a Mn(IV) species, and that the reaction of Mn ions is likely the initial step.
KW - Manganese-oxo compound
KW - Oxygen evolution
KW - Photodamage
KW - Photoinhibition
KW - PS II
KW - UV effect
UR - http://www.scopus.com/inward/record.url?scp=79957991409&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79957991409&partnerID=8YFLogxK
U2 - 10.1016/j.jphotobiol.2011.01.017
DO - 10.1016/j.jphotobiol.2011.01.017
M3 - Article
VL - 104
SP - 118
EP - 125
JO - Journal of Photochemistry and Photobiology B: Biology
JF - Journal of Photochemistry and Photobiology B: Biology
SN - 1011-1344
IS - 1-2
ER -