Low-temperature turnover control of photosystem II using novel metal- containing redox-active herbicides

Laba Karki, K. V. Lakshmi, Veronika A. Szalai, Gary W. Brudvig

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

A novel approach of using metal-containing redox-active herbicides to prepare and study the light-induced intermediates of the photosystem II (PSII) photocycle is described. The redox-active herbicides feature an iron(III) ethylenediaminetetracetate [Fe(III)-(EDTA)] electron-acceptor group linked to a Q(B)-site binding dimethylphenylurea moiety by a hydrocarbon spacer. Like the nitroxyl-based redox-active herbicides previously described (Bocarslt, J. R.; Brudvig, G. W. J. Am. Chem. Soc. 1992, 114, 9762-9767), metal-containing herbicides accept electrons from the donor side of PSII while bound to the Q(B) site and restrict the S-state cycling to two stable charge separations. The use of Fe(III)-(EDTA) as an electron acceptor allows turnover at low temperatures. EPR studies of PSII upon continuous illumination at 225 K with 0.7 mM of redox-active herbicide, Fe(III)-(EDTA) linked by an ethane spacer to a dimethylphenyl urea group (4), produced a stable two-step S1 to S3 advance of the O2-evolving complex (OEC) and a stoichiometric reduction of the Fe(III)-(EDTA) moiety of the herbicide, while a control sample with 0.02 mM DCMU [3-(3,4-dichlorophenyl)-1,1-dimethyl-urea] and 0.7 mM of 4 exhibited only a one-step S1 to S2 advance of the OEC without significant reduction of the Fe(III)-(EDTA) moiety of the herbicide. Similar EPR results were obtained for 7, Fe(III)-(EDTA) linked to the dimethylphenylurea group by a pentane spacer. O2-evolution inhibition studies show that appending the Fe(III)-(EDTA) moiety to the phenylurea herbicide causes a significant decrease in the binding affinity compared to that of DCMU. On the basis of O2-evolution studies with various herbicide derivatives and different PSII sample types, the observed decrease in binding affinities is attributed to the degree of accessibility of the Q(B)-binding pocket to the herbicides and to electrostatic and hydrophilicity factors. The present study describes the use of hovel metal-containing herbicides in studying long-range electron transfer in PSII and in trapping photogenerated two-electron oxidized intermediate states of the O2-evolving complex.

Original languageEnglish
Pages (from-to)5180-5188
Number of pages9
JournalJournal of the American Chemical Society
Volume122
Issue number21
DOIs
Publication statusPublished - May 31 2000

Fingerprint

Photosystem II Protein Complex
Herbicides
Temperature control
Oxidation-Reduction
Metals
Ethylenediaminetetraacetic acid
Temperature
Electrons
Diuron
Urea
Paramagnetic resonance
Ethane
Hydrophilicity
Binding sites
Hydrocarbons
Fe(III)-EDTA
Lighting
Static Electricity
Hydrophobic and Hydrophilic Interactions
Electrostatics

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Low-temperature turnover control of photosystem II using novel metal- containing redox-active herbicides. / Karki, Laba; Lakshmi, K. V.; Szalai, Veronika A.; Brudvig, Gary W.

In: Journal of the American Chemical Society, Vol. 122, No. 21, 31.05.2000, p. 5180-5188.

Research output: Contribution to journalArticle

@article{c406f265940643118d01adf46bf90d2a,
title = "Low-temperature turnover control of photosystem II using novel metal- containing redox-active herbicides",
abstract = "A novel approach of using metal-containing redox-active herbicides to prepare and study the light-induced intermediates of the photosystem II (PSII) photocycle is described. The redox-active herbicides feature an iron(III) ethylenediaminetetracetate [Fe(III)-(EDTA)] electron-acceptor group linked to a Q(B)-site binding dimethylphenylurea moiety by a hydrocarbon spacer. Like the nitroxyl-based redox-active herbicides previously described (Bocarslt, J. R.; Brudvig, G. W. J. Am. Chem. Soc. 1992, 114, 9762-9767), metal-containing herbicides accept electrons from the donor side of PSII while bound to the Q(B) site and restrict the S-state cycling to two stable charge separations. The use of Fe(III)-(EDTA) as an electron acceptor allows turnover at low temperatures. EPR studies of PSII upon continuous illumination at 225 K with 0.7 mM of redox-active herbicide, Fe(III)-(EDTA) linked by an ethane spacer to a dimethylphenyl urea group (4), produced a stable two-step S1 to S3 advance of the O2-evolving complex (OEC) and a stoichiometric reduction of the Fe(III)-(EDTA) moiety of the herbicide, while a control sample with 0.02 mM DCMU [3-(3,4-dichlorophenyl)-1,1-dimethyl-urea] and 0.7 mM of 4 exhibited only a one-step S1 to S2 advance of the OEC without significant reduction of the Fe(III)-(EDTA) moiety of the herbicide. Similar EPR results were obtained for 7, Fe(III)-(EDTA) linked to the dimethylphenylurea group by a pentane spacer. O2-evolution inhibition studies show that appending the Fe(III)-(EDTA) moiety to the phenylurea herbicide causes a significant decrease in the binding affinity compared to that of DCMU. On the basis of O2-evolution studies with various herbicide derivatives and different PSII sample types, the observed decrease in binding affinities is attributed to the degree of accessibility of the Q(B)-binding pocket to the herbicides and to electrostatic and hydrophilicity factors. The present study describes the use of hovel metal-containing herbicides in studying long-range electron transfer in PSII and in trapping photogenerated two-electron oxidized intermediate states of the O2-evolving complex.",
author = "Laba Karki and Lakshmi, {K. V.} and Szalai, {Veronika A.} and Brudvig, {Gary W.}",
year = "2000",
month = "5",
day = "31",
doi = "10.1021/ja994138x",
language = "English",
volume = "122",
pages = "5180--5188",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "21",

}

TY - JOUR

T1 - Low-temperature turnover control of photosystem II using novel metal- containing redox-active herbicides

AU - Karki, Laba

AU - Lakshmi, K. V.

AU - Szalai, Veronika A.

AU - Brudvig, Gary W.

PY - 2000/5/31

Y1 - 2000/5/31

N2 - A novel approach of using metal-containing redox-active herbicides to prepare and study the light-induced intermediates of the photosystem II (PSII) photocycle is described. The redox-active herbicides feature an iron(III) ethylenediaminetetracetate [Fe(III)-(EDTA)] electron-acceptor group linked to a Q(B)-site binding dimethylphenylurea moiety by a hydrocarbon spacer. Like the nitroxyl-based redox-active herbicides previously described (Bocarslt, J. R.; Brudvig, G. W. J. Am. Chem. Soc. 1992, 114, 9762-9767), metal-containing herbicides accept electrons from the donor side of PSII while bound to the Q(B) site and restrict the S-state cycling to two stable charge separations. The use of Fe(III)-(EDTA) as an electron acceptor allows turnover at low temperatures. EPR studies of PSII upon continuous illumination at 225 K with 0.7 mM of redox-active herbicide, Fe(III)-(EDTA) linked by an ethane spacer to a dimethylphenyl urea group (4), produced a stable two-step S1 to S3 advance of the O2-evolving complex (OEC) and a stoichiometric reduction of the Fe(III)-(EDTA) moiety of the herbicide, while a control sample with 0.02 mM DCMU [3-(3,4-dichlorophenyl)-1,1-dimethyl-urea] and 0.7 mM of 4 exhibited only a one-step S1 to S2 advance of the OEC without significant reduction of the Fe(III)-(EDTA) moiety of the herbicide. Similar EPR results were obtained for 7, Fe(III)-(EDTA) linked to the dimethylphenylurea group by a pentane spacer. O2-evolution inhibition studies show that appending the Fe(III)-(EDTA) moiety to the phenylurea herbicide causes a significant decrease in the binding affinity compared to that of DCMU. On the basis of O2-evolution studies with various herbicide derivatives and different PSII sample types, the observed decrease in binding affinities is attributed to the degree of accessibility of the Q(B)-binding pocket to the herbicides and to electrostatic and hydrophilicity factors. The present study describes the use of hovel metal-containing herbicides in studying long-range electron transfer in PSII and in trapping photogenerated two-electron oxidized intermediate states of the O2-evolving complex.

AB - A novel approach of using metal-containing redox-active herbicides to prepare and study the light-induced intermediates of the photosystem II (PSII) photocycle is described. The redox-active herbicides feature an iron(III) ethylenediaminetetracetate [Fe(III)-(EDTA)] electron-acceptor group linked to a Q(B)-site binding dimethylphenylurea moiety by a hydrocarbon spacer. Like the nitroxyl-based redox-active herbicides previously described (Bocarslt, J. R.; Brudvig, G. W. J. Am. Chem. Soc. 1992, 114, 9762-9767), metal-containing herbicides accept electrons from the donor side of PSII while bound to the Q(B) site and restrict the S-state cycling to two stable charge separations. The use of Fe(III)-(EDTA) as an electron acceptor allows turnover at low temperatures. EPR studies of PSII upon continuous illumination at 225 K with 0.7 mM of redox-active herbicide, Fe(III)-(EDTA) linked by an ethane spacer to a dimethylphenyl urea group (4), produced a stable two-step S1 to S3 advance of the O2-evolving complex (OEC) and a stoichiometric reduction of the Fe(III)-(EDTA) moiety of the herbicide, while a control sample with 0.02 mM DCMU [3-(3,4-dichlorophenyl)-1,1-dimethyl-urea] and 0.7 mM of 4 exhibited only a one-step S1 to S2 advance of the OEC without significant reduction of the Fe(III)-(EDTA) moiety of the herbicide. Similar EPR results were obtained for 7, Fe(III)-(EDTA) linked to the dimethylphenylurea group by a pentane spacer. O2-evolution inhibition studies show that appending the Fe(III)-(EDTA) moiety to the phenylurea herbicide causes a significant decrease in the binding affinity compared to that of DCMU. On the basis of O2-evolution studies with various herbicide derivatives and different PSII sample types, the observed decrease in binding affinities is attributed to the degree of accessibility of the Q(B)-binding pocket to the herbicides and to electrostatic and hydrophilicity factors. The present study describes the use of hovel metal-containing herbicides in studying long-range electron transfer in PSII and in trapping photogenerated two-electron oxidized intermediate states of the O2-evolving complex.

UR - http://www.scopus.com/inward/record.url?scp=0034738168&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0034738168&partnerID=8YFLogxK

U2 - 10.1021/ja994138x

DO - 10.1021/ja994138x

M3 - Article

AN - SCOPUS:0034738168

VL - 122

SP - 5180

EP - 5188

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 21

ER -