Effects of N,N′-Dibutylurea on Photosynthetic Electron Transport Reactions in Isolated Chloroplasts

1998 ◽  
Vol 59 (3) ◽  
pp. 129-135 ◽  
Author(s):  
R. Querns ◽  
G.E. MacDonald ◽  
J.F. Gaffney ◽  
C.A. Chase ◽  
H.A. Moye ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Isolated Chloroplasts

Counteraction of Paraquat Toxicity at the Chloroplast Level

1987 ◽  
Vol 42 (7-8) ◽  
pp. 824-828 ◽  
Author(s):  
Brad L. Upham ◽  
Kriton K. Hatzios
Keyword(s):  
Electron Transport ◽  
Pisum Sativum ◽  
Photosynthetic Electron Transport ◽  
Heme Iron ◽  
Hill Reaction ◽  
Ion Toxicity ◽  
Plastoquinone Pool ◽  
Pisum Sativum L ◽  
Paraquat Toxicity ◽  
Isolated Chloroplasts

Six pyridyl derivatives [benzylviologen, 2-anilinopyridine, 1,2-bis(4-pyridyl)ethane, 1,2-bis(4- pyridyl)ethylene, 2-benzoylpyridine, and 2-benzylaminopyridine] and five heme-iron derivatives [hemoglobin, hemin, hematin, ferritin, and ferrocene] were screened for their potential to coun- teract paraquat (1,1′-dimethyl-4.4′-bipyridinium ion) toxicity on pea (Pisum sativum L.) isolated chloroplasts. The H2O -> methylviologen(MV)/O2 and H2O → ferredoxin(Fd)/NADP+ were two Hill reactions assayed with these compounds. Antagonists of paraquat toxicity should inhibit the first Hill reaction but not the latter. All pyridyl derivatives examined did not inhibit the reaction H2O → MV/O2. Ferritin and ferrocene were also ineffective as inhibitors of this reaction. Hemoglobin inhibited the reaction H2O → MV/O2 without inhibiting the reaction H2O → Fd/NADP+, providing protection to pea chloroplasts against paraquat. Hemin and hematin inhibited both Hill reactions examined. They also inhibited H2O → diaminodurene(DAD)ox and durohydro-quinone → MV/O2 Hill reactions but not the dichlorophenol indophenolred → MV/O2 and DADred → MV/O2 Hill reactions. These results suggest that hemin and hematin are inhibiting the photosynthetic electron transport in the plastoquinone-pool region.

The site of electron transport inhibition by bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide) in isolated chloroplasts

1982 ◽  
Vol 60 (4) ◽  
pp. 409-412 ◽  
Author(s):  
Rungsit Suwanketnikom ◽  
Kriton K. Hatzios ◽  
Donald Penner ◽  
Duncan Bell
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Acceptor ◽  
Photosynthetic Electron Transport ◽  
Primary Electron ◽  
Photochemical Reactions ◽  
Spinacea Oleracea ◽  
Primary Electron Acceptor ◽  
Isolated Chloroplasts

The effect of bentazon (3-isopropyl-1H-2,1,3-benzathiadiazin-(4)3H-one 2,2-dioxide) on various photochemical reactions of isolated spinach (Spinacea oleracea L.) chloroplasts was studied at concentrations 0, 5, 15, 45, and 135 μM. Bentazon at a concentration of 135 μM strongly inhibited uncoupled electron transport from water to ferricyanide or to methylviologen with inhibition percentages greater than 90%. Photosystem II mediated electron transport from water to oxidized diaminodurene, with 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) blocking photosystem I, was also strongly inhibited by bentazon at 135 μM but less with lower concentrations of bentazon. Photosystem I mediated transfer of electrons from diaminodurene to methylviologen, with 3,4-dichlorophenyl-1,1-dimethylurea (DCMU) blocking photosystem II, was not inhibited by bentazon at any concentration examined. Transfer of electrons from catechol to methylviologen in hydroxylamine-treated chloroplasts was inhibited by bentazon, and the inhibition percentages were again concentration dependent. The data indicate that the site of bentazon inhibition of the photosynthetic electron transport is at the reducing side of photosystem II, between the primary electron acceptor Q and plastoquinone.

Inhibition of Photosynthetic Electron Transport by Azaphenanthrenes

1974 ◽  
Vol 29 (9-10) ◽  
pp. 545-551 ◽  
Author(s):  
Walter Oettmeier ◽  
Rolf Grewe
Keyword(s):  
Electron Transport ◽  
Mechanism Of Action ◽  
Inhibitory Activity ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Iron Complexes ◽  
Lower Activity ◽  
Photosynthetic Electron Flow ◽  
Isolated Chloroplasts ◽  
Insight Into

Abstract Various mono-and diazaphenanthrenes were prepared and assayed for their activity as inhibi­tors of photosynthetic electron flow in isolated chloroplasts in order to get more insight into the mechanism of action of the well known inhibitor o-phenanthroline = 1,10-diazaphenanthrene. The results show that 1-, 4-and 5-azaphenanthrene are only slightly less active than 1,10-diazaphen-anthrene. In the case of the different diazaphenanthrenes, 1,4-, 1,7-and 5,6-diazaphenanthrene exhibited somewhat lower activity than 1,10-diaphenanthrene, whereas 2,9-and 4,7-diazaphen-anthrene were completely inactive. Substitution at C-atoms of 1,10-diazaphenanthrene leads to an increase in activity in the case of the 4-and 7-position, regardless of electropositive or electro­ negative substituents, whereas substitution at the 2-, 3-, 5-, 6-, 8-and 9-position leads to a de­ creased activity. The ability of 1,10-diazaphenanthrene to form iron complexes seems to be of little relevance to the inhibitory activity on photosynthetic electron transport. This follows also from the fact that other strong iron complexing agens, like 2.2'-bipyridine or 8-hydroxyquinoline, are not inhibitory

Investigations on a Galvanic Cell Driven by Photosynthetic Electron Transport

1978 ◽  
Vol 33 (5-6) ◽  
pp. 392-401 ◽  
Author(s):  
Wolfgang Haehnel ◽  
Adelheid Heupel ◽  
Dorothea Hengstermann
Keyword(s):  
Electron Transport ◽  
Open Circuit Potential ◽  
Photosynthetic Activity ◽  
Photosynthetic Electron Transport ◽  
Open Circuit ◽  
Galvanic Cell ◽  
Platinum Electrodes ◽  
High Effectiveness ◽  
Electron Carriers ◽  
Isolated Chloroplasts

Abstract A light-driven galvanic cell was constructed making use of the photosynthetic activity of isolated chloroplasts. Artificial mediators managed the transfer of electrons from the endogenous electron carriers to the platinum electrodes in each of the joined half-cells. In one the mediators were reduced by electrons originating from water. In the other the mediators were oxidized by photosystem I in the presence of an autoxidizable electron acceptor. The redox potential in the single half-cells has been studied as a function of the lipophilicity of the mediators and their concentration. Further­ more different autoxidizable acceptors and different treatments of the chloroplasts were investigated. The combined half-cells were separated by an ultrafiltration membrane. Upon illumination the system gave rise to an open circuit potential of up to 220 mV. This battery was charged with rates as high as photosynthetic electron transport rates. The results are discussed with respect to the arrangement of the cell and the properties of the components for high effectiveness and maximal potential differences.

On a new inhibitor of photosynthetic electron-transport in isolated chloroplasts

1970 ◽  
Vol 25 (10) ◽  
pp. 1157-1159 ◽  
Author(s):  
A. Trebst ◽  
E. Harth ◽  
W. Draber
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
High Concentration ◽  
Ferricyanide Reduction ◽  
The Hill ◽  
Photosystem I And Ii ◽  
Isolated Chloroplasts

A halogenated benzoquinone has been found to inhibit the photosynthetic electron transport system in isolated chloroplasts. 2·10-6ᴍ of dibromo-thymoquinone inhibit the Hill- reaction with NADP, methylviologen or anthraquinone to 100%, but do not effect the photoreduction of NADP at the expense of an artificial electron donor. The Hill - reaction with ferricyanide is inhibited even at the high concentration of 2·10-5ᴍ of dibromo-thymoquinone to only 60%. The remaining reduction in the presence of the inhibitor reflects the rate of ferricyanide reduction by photosystem II. It is concluded that the inhibition of electron transport by the quinone occurs between photosystem I and II and close to or at the functional site of plastoquinone.

scholarly journals The Cupric Ion as an Inhibitor of Photosynthetic Electron Transport in Isolated Chloroplasts

1972 ◽  
Vol 50 (6) ◽  
pp. 698-701 ◽  
Author(s):  
Arturo Cedeno-Maldonado ◽  
J. A. Swader ◽  
Robert L. Heath
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Cupric Ion ◽  
Isolated Chloroplasts

Conjugated Enamino Compounds, a New Molecular Probe for the Mechanism of Photosynthetic Electron Transport

1986 ◽  
Vol 41 (7-8) ◽  
pp. 751-757 ◽  
Author(s):  
Tadao Asami ◽  
Nobutaka Takahashi ◽  
Shigeo Yoshida
Keyword(s):  
Electron Transport ◽  
Binding Site ◽  
Photosynthetic Electron Transport ◽  
Biological Characteristics ◽  
Molecular Probe ◽  
Hill Reaction ◽  
The Hill ◽  
Isolated Chloroplasts ◽  
Good Probe

Abstract A series of 2-(1-alkylamino)vinylidene-1,3-cyclohexanedione was synthesized and assayed as inhibitors of the Hill reaction in isolated chloroplasts. The pI50 value of this series was dramatically changed by modification of the peripheral of its hydrophilic moiety and the maximum pI50 value of this series was almost equal to that of DCMU . The results suggest that this series may be a good probe for searching the environment of inhibitors binding site because of its chemical and biological characteristics and its ease of synthesis.

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