Abstract
Treatment of Photosystem II (PS II) with low concentrations of hydroxylamine is known to cause a two-flash delay in the O2-evolution pattern, and in the formation of the S2-state multiline EPR signal, due to the two-electron reduction of the S1-state by hydroxylamine to form the S-1-state. Past work has shown that these delays are not reversed by washing out the hydroxylamine nor by adding DCBQ or ferricyanide to oxidize the residual hydroxylamine, but are reversed by illumination with two saturating flashes followed by a 30-min dark incubation. We have examined the effects of treatments aimed at restoring the normal flash-induced O2-evolution pattern and S2-state multiline EPR signal after treatment of PS II with 40 μM hydroxylamine. In agreement with past work, we find that the two-flash delay in O2 evolution is not reversed when the hydroxylamine is removed by three cycles of centrifugation and resuspension in hydroxylamine-free buffer nor by adding ferricyanide or DCBQ to oxidize the unreacted hydroxylamine. However, the normal flash-induced O2-evolution pattern is restored by illumination with two saturating flashes followed by a 30-min dark incubation (after the sample was first treated with 40 μM hydroxylamine and the unreacted hydroxylamine was removed); illumination with one saturating flash followed by a 30-min dark incubation is only partially effective. These results show that ferricyanide and DCBQ are not effective at oxidizing the S-1-state to the S1-state. In contrast, adding hypochlorite (OCl-) after treatment with hydroxylamine restored the normal flash-induced O2-evolution pattern and also restored the formation of the S2-state multiline EPR signal by illumination at 200 K. We conclude that hypochlorite is capable of oxidizing the S-1-state to the S1-state. This is the first example of a chemical treatment that advances the delayed flash-induced O2 evolution pattern.
| Original language | English |
|---|---|
| Pages (from-to) | 441-448 |
| Number of pages | 8 |
| Journal | Photosynthesis Research |
| Volume | 38 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Jan 1993 |
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Keywords
- hydroxylamine
- hypochlorite
- manganese
- oxygen evolution
- Photosystem II
- S-states
ASJC Scopus subject areas
- Plant Science
Cite this
Chemical oxidation and reduction of the O2-evolution center in Photosystem II. / Lin, Chao; Brudvig, Gary W.
In: Photosynthesis Research, Vol. 38, No. 3, 01.1993, p. 441-448.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Chemical oxidation and reduction of the O2-evolution center in Photosystem II
AU - Lin, Chao
AU - Brudvig, Gary W
PY - 1993/1
Y1 - 1993/1
N2 - Treatment of Photosystem II (PS II) with low concentrations of hydroxylamine is known to cause a two-flash delay in the O2-evolution pattern, and in the formation of the S2-state multiline EPR signal, due to the two-electron reduction of the S1-state by hydroxylamine to form the S-1-state. Past work has shown that these delays are not reversed by washing out the hydroxylamine nor by adding DCBQ or ferricyanide to oxidize the residual hydroxylamine, but are reversed by illumination with two saturating flashes followed by a 30-min dark incubation. We have examined the effects of treatments aimed at restoring the normal flash-induced O2-evolution pattern and S2-state multiline EPR signal after treatment of PS II with 40 μM hydroxylamine. In agreement with past work, we find that the two-flash delay in O2 evolution is not reversed when the hydroxylamine is removed by three cycles of centrifugation and resuspension in hydroxylamine-free buffer nor by adding ferricyanide or DCBQ to oxidize the unreacted hydroxylamine. However, the normal flash-induced O2-evolution pattern is restored by illumination with two saturating flashes followed by a 30-min dark incubation (after the sample was first treated with 40 μM hydroxylamine and the unreacted hydroxylamine was removed); illumination with one saturating flash followed by a 30-min dark incubation is only partially effective. These results show that ferricyanide and DCBQ are not effective at oxidizing the S-1-state to the S1-state. In contrast, adding hypochlorite (OCl-) after treatment with hydroxylamine restored the normal flash-induced O2-evolution pattern and also restored the formation of the S2-state multiline EPR signal by illumination at 200 K. We conclude that hypochlorite is capable of oxidizing the S-1-state to the S1-state. This is the first example of a chemical treatment that advances the delayed flash-induced O2 evolution pattern.
AB - Treatment of Photosystem II (PS II) with low concentrations of hydroxylamine is known to cause a two-flash delay in the O2-evolution pattern, and in the formation of the S2-state multiline EPR signal, due to the two-electron reduction of the S1-state by hydroxylamine to form the S-1-state. Past work has shown that these delays are not reversed by washing out the hydroxylamine nor by adding DCBQ or ferricyanide to oxidize the residual hydroxylamine, but are reversed by illumination with two saturating flashes followed by a 30-min dark incubation. We have examined the effects of treatments aimed at restoring the normal flash-induced O2-evolution pattern and S2-state multiline EPR signal after treatment of PS II with 40 μM hydroxylamine. In agreement with past work, we find that the two-flash delay in O2 evolution is not reversed when the hydroxylamine is removed by three cycles of centrifugation and resuspension in hydroxylamine-free buffer nor by adding ferricyanide or DCBQ to oxidize the unreacted hydroxylamine. However, the normal flash-induced O2-evolution pattern is restored by illumination with two saturating flashes followed by a 30-min dark incubation (after the sample was first treated with 40 μM hydroxylamine and the unreacted hydroxylamine was removed); illumination with one saturating flash followed by a 30-min dark incubation is only partially effective. These results show that ferricyanide and DCBQ are not effective at oxidizing the S-1-state to the S1-state. In contrast, adding hypochlorite (OCl-) after treatment with hydroxylamine restored the normal flash-induced O2-evolution pattern and also restored the formation of the S2-state multiline EPR signal by illumination at 200 K. We conclude that hypochlorite is capable of oxidizing the S-1-state to the S1-state. This is the first example of a chemical treatment that advances the delayed flash-induced O2 evolution pattern.
KW - hydroxylamine
KW - hypochlorite
KW - manganese
KW - oxygen evolution
KW - Photosystem II
KW - S-states
UR - http://www.scopus.com/inward/record.url?scp=4644228799&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=4644228799&partnerID=8YFLogxK
U2 - 10.1007/BF00046772
DO - 10.1007/BF00046772
M3 - Article
AN - SCOPUS:4644228799
VL - 38
SP - 441
EP - 448
JO - Photosynthesis Research
JF - Photosynthesis Research
SN - 0166-8595
IS - 3
ER -