Inhibition of Oxygen Evolution by Cacalol and Its Derivatives

1991 ◽  
Vol 46 (9-10) ◽  
pp. 777-780 ◽  
Author(s):  
B. Lotina-Hennsen ◽  
J. L. Roque-Reséndiz ◽  
M. Jiménez ◽  
M. Aguilar
Keyword(s):  
Electron Transport ◽  
Oxygen Evolution ◽  
Photosystem I ◽  
Atp Synthesis ◽  
The Other ◽  
Other Hand ◽  
Transport Inhibitors ◽  
Proton Uptake

Abstract The inhibition of ATP synthesis, proton uptake and electron transport (basal, phosphory-lating and uncoupled) from water to methylviologen indicates that cacalol and its derivatives act as electron transport inhibitors. Since on one hand photosystem I is not affected and elec­tron transport from DPC to QA is midly affected and on the other hand the electron transport from water to DCIP, and water to silicomolibdate are inhibited, we conclude that the site of inhibition of cacalol is located at the oxygen evolution level. Cacalol derivatives inhibit elec­tron flow between P680 to QA and probably also the QB site.

Inhibition of oxygen evolution by ivalin

1994 ◽  
Vol 72 (2) ◽  
pp. 177-181 ◽  
Author(s):  
Ernesto Bernal-Morales ◽  
Alfonso Romo De Vivar ◽  
Bertha Sanchez ◽  
Martha Aguilar ◽  
Blas Lotina-Hennsen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Sesquiterpene Lactone ◽  
Oxygen Evolution ◽  
Electron Flow ◽  
Atp Synthesis ◽  
Naturally Occurring ◽  
Transport Inhibitor ◽  
Proton Uptake ◽  
Key Words Oxygen

The inhibition of ATP synthesis, proton uptake, and electron transport (basal, phosphorylating, and uncoupled) from water to methylviologen by ivalin (a naturally occurring sesquiterpene lactone in Zaluzania triloba and Iva microcephala) indicates that it acts as electron transport inhibitor. Since photosystem I and electron transport from DPC to QA were not affected, while the electron flow of uncoupled photosystem II from H2O to DAD and from water to silicomolybdate was inhibited, we concluded that the site of inhibition of ivalin is located at the oxygen evolution level. Key words: oxygen evolution, ivalin, photosynthesis, sesquiterpene lactone.

Energy Conservation in Photoreductions by Photosystem II. Reversal of Dibromothymoquinone Inhibition of Hill-Reactions by Phenylenediamines

1973 ◽  
Vol 28 (11-12) ◽  
pp. 710-716 ◽  
Author(s):  
Achim Trebst ◽  
Susanne Reimer
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Water Oxidation ◽  
Photosynthetic Electron Transport ◽  
The Other ◽  
Ferricyanide Reduction ◽  
Other Hand ◽  
Transport Chain ◽  
Energy Conserving

Abstract The plastoquinone antagonist dibromothymoquinone interrupts the photosynthetic electron transport chain between photosystem II and I by inhibiting the oxidation of plastohydroquinone by photosystem I. The effect of phenylenediamines on NADP and ferricyanide photoreduction inhibited by dibromothymoquinone is studied in isolated chloroplasts. IV-substituted phenylene­ diamines fully restore NADPH and ATP formation as well as oxygen evolution in DBMIB inhibited NADP reduction, but are practically inactive in stimulating ferricyanide reduction by photo­ system II. On the other hand phenylenediamine and C-substituted phenylenediamines are only weakly active in restoring NADP reduction but are very active in stimulating ferricyanide reduc­ tion. The P/e2 ratio in restoration of NADP reduction by phenylenediamines is close to 1, whereas the P/e2 ratio in ferricyanide reduction is about 0.4 (the ratio is dependent on the DBMIB con­ centration). The reversal of the DBMIB inhibition in NADP reduction by phenylenediamines is attributed to a bypass of the inhibition site: Reduced phenylenediamines are electron donors for photosystem I after and oxidized phenylenediamines are electron acceptors for photosystem II be­ fore the DBMIB inhibition site. To explain the different rates and P/e2 ratios in the various systems it is assumed that all phenylenediamines are reduced at the expense of water oxidation by photo­ system II but via plastoquinone and on the inside of the membrane. Therefore two energy con­ serving steps (i. e. two proton releasing sites on the inside of the membrane) are involved, N-sub­ stituted phenylenediamines like TMPD reduced by photosystem II inside remain inside the mem­ brane and are reoxidized inside by photosystem I. This way they connect photosystem II bade onto photosystem I, electron transport rates are high and the P/e2 ratio is one in the restored NADP photoreduction. Phenylenediamine and C-substituted phenylenediamines on the other hand travel back to the outside through the membrane, and by doing so carry some of the protons released on the inside of the membrane by the energy conserving steps back to the outside. This way they are very active in stimulating the rate of ferricyanide photoreduction but the P/e2 ratio is only about 0.4. These phenylenediamines being removed from the inside are less active in restoring the rate of NADP reduction

Photosystem I-abhängige Phosphorylierung isolierter Chloroplasten mit Ascorbat/2.6-Dichlorphenolindophenol als Elektronendonator und Methylviologen als Elektronenakzeptor / Photosystem I Dependent Phosphorylation of Isolated Chloroplasts with Ascorbate/2,6-Dichlorophenolindophenol as Electron Donor and Methylviologen as Electron Acceptor

1972 ◽  
Vol 27 (4) ◽  
pp. 445-455 ◽  
Author(s):  
Heinrich Strotmann ◽  
Christa Von Gösseln
Keyword(s):  
Electron Transport ◽  
Linear System ◽  
Photosystem I ◽  
Electron Acceptor ◽  
Electron Flow ◽  
Phosphorylation Site ◽  
Cyclic System ◽  
Atp Production ◽  
Proton Uptake ◽  
Isolated Chloroplasts

Photosystem I related phosphorylation of isolated chloroplasts was investigated with special reference to the stoichiometry between ATP production and electron transprt (ATP: 2e⊖). The system studied contained DCMU to inhibit electron flow from photosystem II, ascorbate and DPIP to supply electrons to photosystem I, and methylviologen as electron acceptor. The following results were obtained:1. Basal electron transport is stimulated by the addition of the phosphorylating system, indicating that phosphorylation is really coupled to non-cyclic electron flow. The ratio ATP: 2e⊖ is 1, when the increase of electron flow obtained by the addition of ADP and phosphate is correlated to phosphorylation. This ratio is constant upon varying several parameters including DPIP concentration and light intensity.2. In the absence of methylviologen a DPIP catalyzed cyclic phosphorylation takes place (cf. I. c.7, 11, 12). Phosphorylation is not increased by the addition of methylviologen, indicating that both, the cyclic DPIP mediated and the non-cyclic system are coupled to the same phosphorylation site and limited by the same reaction step.3. In the absence of oxygen a methylviologen supported cyclic phosphorylation occurs. Comparing optimum rates, phosphorylation under these conditions is about twice as high as in the noncyclic system. Therefore we conclude that two phosphorylation sites are involved in methylviologen catalyzed cyclic electron transport. This system is sensitive against trypsin treatment of the chloroplasts, whereas the linear system is not.4. The two cyclic systems as well as the non-cyclic system are coupled to reversible proton uptake. Furthermore the linear system exhibits an irreversible uptake of hydrogen ions, which is stoichiometric to electron flow. From the reversible and the irreversible components of the pH changes the ratio of the proton pump to electron transprt can be calculated. Under steady state conditions the ration H⨁ : e⊖ approaches 1.

Synthesis, molecular and electron transport properties of 2-alkyltrinitrofluoren-9-ones

1985 ◽  
Vol 63 (1) ◽  
pp. 147-152 ◽  
Author(s):  
Beng S. Ong ◽  
Barkev Keoshkerian ◽  
Trevor I. Martin ◽  
Gordon K. Hamer
Keyword(s):  
Charge Transfer ◽  
Electron Transport ◽  
Transport Properties ◽  
Electron Affinity ◽  
Electron Donors ◽  
The Other ◽  
Bulky Substituent ◽  
Other Hand ◽  
Electron Transport Properties ◽  
Polymer Compatibility

2-Alkyltrinitrofluoren-9-ones 2 were conveniently synthesized by controlled nitration of 2-alkylfluoren-9-ones 5 with a mixture of red fuming HNO3 and concentrated H2SO4 at 0–25 °C. The precursors 5 were derived from the corresponding 2-acylfluorenes by appropriate reduction of the acyl function, followed by base-catalysed O2-oxidation at the C-9 position. The regiochemistry of nitration was interesting: with a sterically bulky substituent in 5, nitration occurred at C-4, -5, and -7 positions, affording 2-alkyl-4,5,7-trinitrofluoren-9-one in over 35% yield; on the other hand, 5 with a primary alkyl function underwent nitration predominantly at C-3, -5, and -7 positions. By virtue of its alkyl function, 2-alkyltrinitrofluoren-9-one 2 displayed better solubility and polymer compatibility characteristics than its non-alkylated analog, TNF. However, the charge transfer interactions of 2 with electron donors were weaker than those of TNF, despite the fact that they both have the same electron affinity. Both 2 and TNF exhibited good electron transport properties in poly(N-vinylcarbazole) matrices.

scholarly journals The cytochemical localization of succinic dehydrogenase in the sperm mitochondria of the gastropod Biomphalaria glabrata. A comparison of two methods.

1975 ◽  
Vol 23 (1) ◽  
pp. 75-79 ◽  
Author(s):  
B J Bogitsh
Keyword(s):  
Electron Transport ◽  
Nicotinamide Adenine Dinucleotide ◽  
Succinic Dehydrogenase ◽  
Biomphalaria Glabrata ◽  
The Other ◽  
Tetrazolium Salt ◽  
Cytochemical Localization ◽  
Mitochondrial Derivative ◽  
The Matrix ◽  
Transport Inhibitors

The mitochondrial derivative of the sperm of the gastropod pulmonate Biomphalaria glabrata was studies to ascertain succinic dehydrogenase localization cytochemically. Two techniques were compared. One technique depends on a tetrazolium salt that yields an osmiophilic formazan upon reduction. The other technique is dependent on the reduction of copper ferricyanide. The effects of several electron transport inhibitors were studied. The reaction product observed in the matrix of the mitochondrial derivative using the former technique is sensitive to rotenone and is believed to be nicotinamide adenine dinucleotide-dependent. The reaction product observed in the intracristal spaces using the copper ferricyanide method is insensitive to rotenone and is believed to cytochemically demonstrate succinic dehydrogenase in this material.

Interference of l,2,3,4-Tetramethoxy-5-(2-propenyl)benzene with Photosynthetic Electron Transport

1998 ◽  
Vol 53 (1-2) ◽  
pp. 55-59 ◽  
Author(s):  
A. Jimenez ◽  
R. Mata ◽  
B. Lotina-Hennsen ◽  
A. L. Anaya
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Atp Synthesis ◽  
Photosynthetic Electron Transport ◽  
Stem Bark ◽  
Hill Reaction ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Proton Uptake ◽  
Photosynthetic Activities

AbstractThe effect of 1,2,3,4-tetramethoxy-5-(2-propenyl)benzene, the major phytogrowth-inhibitory agent isolated from the leaves, stem bark and wood of Malmea depressa (Annonaceae), on several photosynthetic activities has been investigated using freshly lysed spinach chloroplasts. The results indicate that this compound inhibits proton-uptake, ATP synthesis and electron flow (basal, phosphorylating and uncoupled) in a concentration dependent manner, therefore acting as a Hill reaction inhibitor. Uncoupled electron transport through photosystem I from reduced dichlorophenol-indophenol to methylviologen is unaffected by this compound. On the other hand, uncoupled electron transport through photosystem II from water to dichlorophenol-indophenol, from water to silicomolibdate and from diphenylcarbazide to dichlorophenol-indophenol is inhibited by this phenylpropanoid, suggesting that the site of inhibition is located in the span from P680 to QA.

scholarly journals Correlation between Ca2+ uptake, Ca2+ efflux and phosphoenzyme level in sarcoplasmic-reticulum vesicles

1991 ◽  
Vol 274 (2) ◽  
pp. 427-432 ◽  
Author(s):  
J C Benech ◽  
A Galina ◽  
L de Meis
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Aqueous Medium ◽  
Atp Synthesis ◽  
Dimethyl Sulphoxide ◽  
The Other ◽  
Apparent Affinity ◽  
High Affinity ◽  
Ph Values ◽  
A Value ◽  
Other Hand

Previously [Inesi & de Meis (1989) J. Biol. Chem. 264, 5929-5936] it was shown that dimethyl sulphoxide (Me2SO) increases the amount of Ca2+ accumulated by sarcoplasmic-reticulum vesicles. This effect was related to a decrease in the enzyme affinity for ADP from less than 20 microM to 1 mM. In the present work the apparent affinity of the ADP-sensitive phosphoenzyme for ADP was determined by measuring the rate of ATP synthesis in vesicles previously loaded with Ca2+, at different pH values and in the presence and absence of Me2SO (20%, v/v) and KCl. In all conditions tested, addition of Me2SO never promoted an increase of the apparent Km for ADP to a value higher than 25 microM. ADP inhibits the phosphorylation of the enzyme by Pi. Two components, with Ki values of 80 microM and 8 mM, were detected when vesicles previously loaded with Ca2+ were used. The high-affinity component (Ki 80 microM) was abolished after addition of Me2SO to the medium. Empty vesicles, on the other hand, exhibited only the low-affinity component (Ki 8 mM). During ATP synthesis in a totally aqueous medium, there was a decrease in the phosphoenzyme formed by Pi, after addition of 80-100 microM-ADP to the medium. In the presence of Me2SO this decrease was smaller. The sum of the fractions of phosphoenzyme formed by ATP and by Pi during Ca2+ uptake was higher in the presence of Me2SO than in a totally aqueous medium. Me2SO decreased the passive efflux of Ca2+ measured in the presence of 0.1 mM-Pi and 0.1 mM-MgCl2. In a totally aqueous medium the same decrease was observed when Pi and MgCl2 concentrations were raised to 4 mM. These data suggest that ADP binds to two different enzyme conformations. The binding to one of these conformations (*E) inhibits the phosphorylation of the enzyme by Pi, increases the efflux of Ca2+ and decreases the amount of Ca2+ accumulated by the vesicles.

143 Stimulated glycolysis is able to maintain ATP levels and motility of bull spermatozoa submitted to mitochondrial depolarisation

2020 ◽  
Vol 32 (2) ◽  
pp. 198
Author(s):  
J. Losano ◽  
J. Padín ◽  
I. Méndez-López ◽  
D. Angrimani ◽  
N. Montez ◽  
...  
Keyword(s):  
Atp Synthesis ◽  
The Other ◽  
Atp Levels ◽  
Other Hand ◽  
Significant Difference ◽  
Carbonyl Cyanide ◽  
Bovine Spermatozoa ◽  
Kinetics Of ◽  
Glucose Supplementation

Studies have reported the importance of mitochondria in sperm metabolism. However, for some species, glycolysis appears to be as essential as oxidative phosphorylation in sperm physiology. On the other hand, these mechanisms have not been fully elucidated for bovine spermatozoa. Therefore, the aim of this study was to evaluate the role of mitochondria and glycolysis in ATP synthesis and sperm kinetics of bovine spermatozoa. For this purpose, sperm from seven bovine epididymides (n=7) was collected and diluted to a concentration of 100×106 spermatozoamL−1 in Tyrode's albumin lactate pyruvate medium. Then, each sample was divided into 10 aliquots and evaluated in a 2×5 factorial design, with the first factor being the presence or absence of glucose (5mM) to stimulate glycolysis and the second factor being treatment with the mitochondrial uncoupler carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP; 0, 0.1, 0.3, 1, and 3 µM) to deplete mitochondrial ATP. Sperm samples were subjected to measurements of ATP levels using a luminescence technique (CellTiter-Glokit, Promega), with ATP levels measured in duplicate. In addition, sperm samples were subjected to computerised analysis of total and progressive motilities (ISAS, Proiser). Statistical analysis was performed using SAS (SAS Institute Inc.), where the interaction between the factors was analysed using PROC GLM and the comparison between groups was performed using means analysis of variance (least significant difference test). It was considered significant at 5%. Adenosine triphosphate was lower at FCCP concentrations of 0.3 µM (180.3±31.9nM), 1 µM (220.2±40.4nM), and 3 µM (272.3±70.4nM) than at 0 µM (control; 448.6±63.7nM) and 0.1 µM (422.4±41.5nM) in the absence of glucose. However, in the groups treated with FCCP supplemented with glucose, ATP concentrations did not differ among the groups (0 µM: 577.2±70.4 nM; 0.1 µM: 610.8±57.8 nM; 0.3 µM: 606.2±64.2 nM; 1 µM: 670.9±61.9 nM; 3 µM: 696.1±68.5nM). Additionally, total motility was lower in FCCP-treated groups without glucose supplementation. On the other hand, total motility increased in the groups treated with 0.3, 0.1, 1, and 3 µM FCCP supplemented with glucose. A similar effect was verified for progressive motility. Based on these results, we can suggest that glucose supplementation is able to maintain ATP levels and motility in bull sperm undergoing FCCP-induced mitochondrial depolarisation.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

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