A Phytotoxicity Biosensor using Photosynthetic Membranes

1990 ◽  
Vol 25 (2) ◽  
pp. 175-186 ◽  
Author(s):  
Marc Purcell ◽  
Robert Carpentier
Keyword(s):  
Electron Transport ◽  
Small Volume ◽  
Chlorophyll Concentration ◽  
Photosynthetic Electron Transport ◽  
Inhibitory Effect ◽  
Thylakoid Membranes ◽  
Photoelectrochemical Cell ◽  
Synthetic Membranes ◽  
Low Concentrations ◽  
Artificial Electron Acceptor

Abstract The potential of a photoelectrochemical cell employing photo-synthetic membranes in an application as a phytotoxicity biosensor is demonstrated. In this cell, a small volume (80 μl) of isolated thylakoid membranes is used to produce a photocurrent. The reduced species produced during photosynthetic electron transport are oxidized by soluble electroactive mediators which are reoxidized by a platinum working electrode. The photocurrent generated was inhibited by relatively low concentrations of herbicides, nitrite, sulfite and several heavy metals due to their inhibitory effect on photosynthetic electron transport. The cell sensitivity was enhanced when chlorophyll concentration was reduced and artificial electron acceptor concentration was increased.

X-Ray Structure Analysis of a Cyanoacrylate Inhibitor of Photosystem II Electron Transport

1991 ◽  
Vol 46 (1-2) ◽  
pp. 93-98 ◽  
Author(s):  
Helen G. McFadden ◽  
Donald C. Craig ◽  
John L. Huppatz ◽  
John N. Phillips
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Chlorophyll Concentration ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Ps Ii ◽  
X Ray ◽  
High Affinity ◽  
Modelling Studies ◽  
Intramolecular Hydrogen

Abstract X-ray crystallographic data for the highly potent cyanoacrylate photosynthetic electron transport inhibitor, (Z)-ethoxyethyl 3-(4-chlorobenzylamino)-2-cyano-4-methylpent-2-enoate, are presented. This compound has a particularly high affinity for the photosystem II (PS II) herbicide receptor with a p I50 value of 9.5 (in the Hill reaction under uncoupled condi­tions with a chlorophyll concentration of 0.1 μg/ml). Data regarding the structure of small li­gands, such as this potent cyanoacrylate, which bind to the site with high affinity may be used to provide the basis for modelling studies of PS II/herbicide complexes. The X-ray data presented confirm the Z-stereochemistry of active cyanoacrylates and demonstrate the pres­ence of a planar core stabilized by an intramolecular hydrogen bond between the ester car­bonyl oxygen and a benzylamino hydrogen atom. In order to assess the importance of the benzylamino -NH -group in this type of cyanoacrylate, analogues containing a methylene group in its place were synthesized and found to be 100-and 1000-fold less active as Hill inhibitors.

Inhibition by Tetranitromethane of Photosynthetic Electron Transport from Water to Photosystem II in Chloroplasts

1980 ◽  
Vol 35 (3-4) ◽  
pp. 293-297 ◽  
Author(s):  
P. V. Sane ◽  
Udo Johanningmeier
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Ph Dependence ◽  
Photosynthetic Electron Transport ◽  
Donor Side ◽  
Ps Ii ◽  
Diphenyl Carbazide ◽  
Low Concentrations ◽  
Sh Group

Abstract Low concentrations (10 µM) of tetranitromethane inhibit noncyclic electron transport in spinach chloroplasts. A study of different partial electron transport reactions shows that tetranitromethane primarily interferes with the electron flow from water to PS II. At higher concentrations the oxidation of plastohydroquinone is also inhibited. Because diphenyl carbazide but not Mn2+ ions can donate electrons efficiently to PS II in the presence of tetranitromethane it is suggested that it blocks the donor side of PS II prior to donation of electrons by diphenyl carbazide. The pH dependence of the inhibition by this protein modifying reagent may indicate that a functional-SH group is essential for a protein, which mediates electron transport between the water splitting complex and the reaction center of PS II.

Mode of Inhibition of Photosynthetic Electron Transport by Substituted Diphenylethers

1981 ◽  
Vol 36 (9-10) ◽  
pp. 848-852 ◽  
Author(s):  
W. Draber ◽  
H. J. Knops ◽  
A. Trebst
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Thylakoid Membranes ◽  
Photosynthetic Electron Flow ◽  
Spinach Chloroplasts

Abstract Several substituted diphenylethers were found to be effective inhibitors of photosynthetic electron flow in isolated thylakoid membranes from spinach chloroplasts. T heir site of inhibition was localized with artificial acceptor and donor systems. The phenylether of an alkyl substituted nitrophenol is prim arely inhibiting electron flow after plastoquinone function whereas a dinitro-phenylether of a phenyl substituted nitrophenol is inhibiting before plastoquinone function. Therefore certain diphenylethers interfere with plastoquinone function at the oxidation or reduction site, depending on the substitution.

scholarly journals Synthesis and Inhibitory Effect on Photosynthetic Electron Transport of 1,3,5-Triazinylcarboxylic Acid Derivatives

2005 ◽  
Vol 30 (1) ◽  
pp. 39-43 ◽  
Author(s):  
Atsushi Fujimori ◽  
Yumi Ikeda ◽  
Ruiko Okano ◽  
Masaki Hiraki ◽  
Jack J. S. van Rensen ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Inhibitory Effect

Regulation of photosystem II by metabolic and environmental factors

1989 ◽  
Vol 323 (1216) ◽  
pp. 269-279 ◽  
Keyword(s):  
Electron Transport ◽  
Higher Plants ◽  
Photosynthetic Electron Transport ◽  
Thylakoid Membranes ◽  
Internal Factors ◽  
Regulatory Processes ◽  
Quenching Analysis ◽  
Intact Chloroplasts ◽  
Rate Of Dissipation

The thylakoid membranes of higher plants possess several mechanisms that control both the distribution and rate of dissipation of absorbed light. These mechanisms, which allow regulation of photosynthetic electron transport in response to alteration in external and internal factors, can be observed as the various processes that quench chlorophyll fluorescence. By using the 'light-doubling techniques’, together with analysis of quenching relaxation, it is possible to assess quantitatively the extents of these regulatory processes and to allow their interrelations to be studied. These techniques can be applied to in vitro systems or to leaves, and can be particularly useful when applied with electron-transport measurements and when models are used to aid interpretation. Results of quenching analysis at different light intensities in isolated thylakoids, intact chloroplasts, protoplasts, algae and leaves of a variety of species are presented.

scholarly journals Invitro Toxicity of Binary Mixtures of Glyphosate and 2, 2 Dichlorovinyl Dimethyl Phosphate on Bacterial Isolates

2021 ◽  
pp. 36-48
Author(s):  
C. O. Anuniru ◽  
J. N. Ogbulie ◽  
C. C. Opurum ◽  
E. S. Asiwe
Keyword(s):  
Binary Mixtures ◽  
Bacterial Species ◽  
Aquatic Organisms ◽  
Inhibitory Effect ◽  
In Vitro Toxicity ◽  
Triphenyltetrazolium Chloride ◽  
Dimethyl Phosphate ◽  
Low Concentrations ◽  
Artificial Electron Acceptor

The in vitro toxicity of glyphosate (Gly) and 2, 2 Dichlorovinyl dimethyl phosphate (DDVP) single compound and binary mixtures was assessed against Pseudomonas sp. and Bacillus sp. isolated from Otamiri River, Imo state, Nigeria was investigated. The toxicity response was assessed using the inhibitory effect of the single and binary mixtures on isolates dehydrogenase activity; and 2,3,5 triphenyltetrazolium chloride (TTC) was used as the artificial electron acceptor. The binary mixtures were composed using fixed ratios of glyphosate and 2, 2 Dichlorovinyl dimethyl phosphate in ratios of 20% Gly:80% DDVP, 40% Gly: 60% DDVP, 50% Gly: 50% DDVP, 60% Gly: 40% DDVP and 80% Gly: 20% DDVP. Results obtained showed that the isolates exhibited different degrees of logistic and sigmoidal toxicity trends with areas of hormesis at low concentrations of the toxicants. Furthermore, isobolographic analysis on the toxic interaction of the mixtures presented both synergism and antagonism, based on the relative ratio of the component mixtures. Increasing concentration of glyphosate in the binary mixture caused a shift in the interaction effect from antagonism to synergism. Our findings showed that isolates exhibited tolerance to glyphosate and 2,2 dichlorovinyl dimethyl phosphate and their binary mixtures exposure at concentration range of 0-1000mg/L; above which has deleterious effects on the aquatic organisms. It is evident that there are considerable differences in pesticide sensitivity among the bacterial species and that the presence of glyphosate and 2, 2-dichlorovinyl dimethyl phosphate in the aquatic environment may present toxicological risk to microbial diversity.

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