Abstract
We have used the desiccation-tolerant lichen Flavoparmelia caperata, containing the green algal photobiont Trebouxia gelatinosa, to examine H/D isotope effects in Photosystem II in vivo. Artifact-free H/D isotope effects on both PSII primary charge separation and water oxidation yields were determined as a function of flash rate from chlorophyll-a variable fluorescence yields. Intact lichens could be reversibly dehydrated/re-hydrated with H2O/D2O repeatedly without loss of O2 evolution, unlike all isolated PSII preparations. Above a threshold flash rate, PSII charge separation decreases sharply in both D2O and H2O, reflecting loss of excitation migration and capture by PSII. Changes in H/D coordinates further slow charge separation in D2O (−23% at 120 Hz), attributed to reoxidation of the primary acceptor QA −. At intermediate flash rates (5–50 Hz) D2O decreases water oxidation efficiency (O2 evolution) by −2–5%. No significant isotopic difference is observed at slow flash rates (<5 Hz) where charge recombination dominates. Slower D2O diffusion, changes in hydrogen bonding networks, and shifts in the pKa's of ionizable residues may all contribute to these systematic variations of H/D isotope effects. Lichens’ reversible desiccation tolerance allows highly reproducible H/D exchange kinetics in PSII reactions to be studied in vivo for the first time.
| Original language | English |
|---|---|
| Pages (from-to) | 1039-1044 |
| Number of pages | 6 |
| Journal | Biochimica et Biophysica Acta - Bioenergetics |
| Volume | 1859 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - Oct 1 2018 |
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Keywords
- Isotope effects
- Lichens
- Photosystem II
- Water oxidation
ASJC Scopus subject areas
- Biophysics
- Biochemistry
- Cell Biology
Cite this
Desiccation tolerant lichens facilitate in vivo H/D isotope effect measurements in oxygenic photosynthesis. / Vinyard, David J.; Ananyev, Gennady M.; Dismukes, G Charles.
In: Biochimica et Biophysica Acta - Bioenergetics, Vol. 1859, No. 10, 01.10.2018, p. 1039-1044.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Desiccation tolerant lichens facilitate in vivo H/D isotope effect measurements in oxygenic photosynthesis
AU - Vinyard, David J.
AU - Ananyev, Gennady M.
AU - Dismukes, G Charles
PY - 2018/10/1
Y1 - 2018/10/1
N2 - We have used the desiccation-tolerant lichen Flavoparmelia caperata, containing the green algal photobiont Trebouxia gelatinosa, to examine H/D isotope effects in Photosystem II in vivo. Artifact-free H/D isotope effects on both PSII primary charge separation and water oxidation yields were determined as a function of flash rate from chlorophyll-a variable fluorescence yields. Intact lichens could be reversibly dehydrated/re-hydrated with H2O/D2O repeatedly without loss of O2 evolution, unlike all isolated PSII preparations. Above a threshold flash rate, PSII charge separation decreases sharply in both D2O and H2O, reflecting loss of excitation migration and capture by PSII. Changes in H/D coordinates further slow charge separation in D2O (−23% at 120 Hz), attributed to reoxidation of the primary acceptor QA −. At intermediate flash rates (5–50 Hz) D2O decreases water oxidation efficiency (O2 evolution) by −2–5%. No significant isotopic difference is observed at slow flash rates (<5 Hz) where charge recombination dominates. Slower D2O diffusion, changes in hydrogen bonding networks, and shifts in the pKa's of ionizable residues may all contribute to these systematic variations of H/D isotope effects. Lichens’ reversible desiccation tolerance allows highly reproducible H/D exchange kinetics in PSII reactions to be studied in vivo for the first time.
AB - We have used the desiccation-tolerant lichen Flavoparmelia caperata, containing the green algal photobiont Trebouxia gelatinosa, to examine H/D isotope effects in Photosystem II in vivo. Artifact-free H/D isotope effects on both PSII primary charge separation and water oxidation yields were determined as a function of flash rate from chlorophyll-a variable fluorescence yields. Intact lichens could be reversibly dehydrated/re-hydrated with H2O/D2O repeatedly without loss of O2 evolution, unlike all isolated PSII preparations. Above a threshold flash rate, PSII charge separation decreases sharply in both D2O and H2O, reflecting loss of excitation migration and capture by PSII. Changes in H/D coordinates further slow charge separation in D2O (−23% at 120 Hz), attributed to reoxidation of the primary acceptor QA −. At intermediate flash rates (5–50 Hz) D2O decreases water oxidation efficiency (O2 evolution) by −2–5%. No significant isotopic difference is observed at slow flash rates (<5 Hz) where charge recombination dominates. Slower D2O diffusion, changes in hydrogen bonding networks, and shifts in the pKa's of ionizable residues may all contribute to these systematic variations of H/D isotope effects. Lichens’ reversible desiccation tolerance allows highly reproducible H/D exchange kinetics in PSII reactions to be studied in vivo for the first time.
KW - Isotope effects
KW - Lichens
KW - Photosystem II
KW - Water oxidation
UR - http://www.scopus.com/inward/record.url?scp=85049306806&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85049306806&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2018.05.014
DO - 10.1016/j.bbabio.2018.05.014
M3 - Article
VL - 1859
SP - 1039
EP - 1044
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
SN - 0005-2728
IS - 10
ER -