scholarly journals Effect of ionophores on carrier-mediated electron translocation in ferricyanide-containing liposomes

1979 ◽  
Vol 184 (1) ◽  
pp. 125-131 ◽  
Author(s):  
Mette Miller ◽  
Lars Chr. Petersen ◽  
Finn B. Hansen ◽  
Peter Nicholls
Keyword(s):  
Reduction Rate ◽  
Electron Donors ◽  
Oxidation Products ◽  
Ph Gradient ◽  
Ferricyanide Reduction ◽  
Electron Carrier ◽  
Carbonyl Cyanide ◽  
Biochemical Systems ◽  
Stimulation Of

Ferricyanide-containing liposomes were used as a system to compare the electron- and proton-translocating properties of six redox reagents commonly used as electron donors for biochemical systems. The effects of different ionophore combinations on the ferricyanide-reduction rate were generally consistent with the expected proton- and electron-translocating properties of the mediators. The transmembrane pH gradient produced by hydrogen carriers was demonstrated. Nigericin or valinomycin plus carbonyl cyanide p-trifluoromethoxyphenylhydrazone are capable of collapsing this gradient and of stimulating ferricyanide reduction mediated by this type of carrier. No pH gradient is produced with the electron carrier 1,1′-dibutylferrocene. In the presence of tetraphenylboron anion, which is needed for this carrier to act as an efficient mediator, addition of valinomycin alone is sufficient to obtain full stimulation of ferricyanide reduction. NNN′N′-Tetramethyl-p-phenylenediamine does not behave as a simple electron carrier. During NNN′N′-tetramethyl-p-phenylenediamine-mediated ferricyanide reduction protons are translocated across the membrane and accumulated in the vesicles. This is not due to the presence of demethylated impurities in the NNN′N′-tetramethyl-p-phenylenediamine sample, but may be the result of an accumulation of oxidation products other than the Wurster's Blue radical. These results suggest a reconsideration of studies on protonmotive forces across membranes where NNN′N′-tetramethyl-p-phenylenediamine is used as a mediator.

scholarly journals Mechanism of stimulation of endogenous fermentation in yeast by carbonyl cyanide m-chlorophenylhydrazone.

1987 ◽  
Vol 262 (29) ◽  
pp. 14154-14157
Author(s):  
A Noshiro ◽  
C Purwin ◽  
M Laux ◽  
K Nicolay ◽  
W A Scheffers ◽  
...  
Keyword(s):  
Carbonyl Cyanide ◽  
Stimulation Of

Microbial Perchlorate Reduction in Groundwater with Different Electron Donors

2013 ◽  
Vol 295-298 ◽  
pp. 1402-1407
Author(s):  
Rui Wang ◽  
Ming Chen ◽  
Jia Wen Zhang ◽  
Fei Liu ◽  
Hong Han Chen
Keyword(s):  
Removal Efficiency ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Reduction Rate ◽  
Electron Donors ◽  
Monod Equation ◽  
Hydrogen Addition ◽  
Perchlorate Reduction ◽  
Perchlorate Removal

Effects of different electron donors (acetate and hydrogen), acetate and perchlorate concentrations on microbial perchlorate reduction in groundwater were studied. The results showed that acetate and hydrogen addition as an electron donor can significantly improve perchlorate removal efficiency while a longer period was observed for hydrogen (15 d) than for acetate (8 d). The optical ratio of electron donor (acetate)-to-electron acceptor (perchlorate) was approximately 1.65 mg COD mg perchlorate-1. The highest specific reduction rate of perchlorate was achieved at the acetate-to-perchlorate ratio of 3.80 mg COD mg perchlorate-1. The perchlorate reduction rates corresponded well to the theoretical values calculated by the Monod equation and the parameters of Ks and Vm were determined to be 15.6 mg L-1 and 0.26 d-1, respectively.

Studies on the Mechanism of NAD-photoreduction by Chromatophores of the Facultative Phototroph, Rhodopseudomonas capsulata

1969 ◽  
Vol 24 (1) ◽  
pp. 67-76 ◽  
Author(s):  
J.-H. Klemme
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Molecular Hydrogen ◽  
Reaction System ◽  
Electron Donors ◽  
Rhodopseudomonas Capsulata ◽  
Antimycin A ◽  
Inhibitory Effects ◽  
Carbonyl Cyanide ◽  
Cyclic Photophosphorylation ◽  
Energy Dependent

The light-driven and the ATP-driven reduction of nicotinamide adenine dinucleotide (NAD) catalyzed by the chromatophore fraction of Rhodopseudomonas capsulata was investigated. Efficient electron donors for the photoreduction of NAD are molecular hydrogen and succinate. In the ATP-dependent reaction system, succinate is a more efficient electron donor than H2. The energydependent NAD-reduction is driven by ATP, but not by pyrophosphate or ADP. Oligomycin stimulates the NAD-photoreductions and completely inhibits the ATP-driven NAD-reductions. Rotenone and piericidin A are inhibitors for both the light-driven and the ATP-driven NAD-reductions. Antimycin A is an inhibitor only for the light-driven reductions. The H2-linked NAD-photoreduction is less sensitive to these inhibitors and to the uncoupler desaspidin than the succinate-linked reduction. Atebrine, carbonyl cyanide-m-chlorophenylhydrazone, 2,4-dinitrophenol and phenazonium methosulfate are inhibitors for the light-driven and the ATP-driven reductions. Some of the compounds used as inhibitors of the NAD-reduction were also investigated with concerns to their inhibitory effects on cyclic photophosphorylation and O2-linked oxidations of reduced NAD, succinate and H2. Based on the results of these inhibitor studies, the relationships between cyclic photophosphorylation, light-induced noncyclic electron transport and energy-dependent NAD-reduction are discussed.

Intracellular flavonoids as electron donors for extracellular ferricyanide reduction in human erythrocytes

2002 ◽  
Vol 32 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Mara Fiorani ◽  
Roberta De Sanctis ◽  
Roberta De Bellis ◽  
Marina Dachà
Keyword(s):  
Human Erythrocytes ◽  
Electron Donors ◽  
Ferricyanide Reduction

Stimulation of bioluminescence in lanternfishes (Myctophidae). II.

1972 ◽  
Vol 50 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Michel Anctil
Keyword(s):  
Hydrogen Peroxide ◽  
Spinal Cord ◽  
Electrical Stimulation ◽  
Light Responses ◽  
External Application ◽  
The Family ◽  
Biochemical Systems ◽  
Variable Success ◽  
Stimulation Of

Injections and applications of hydrogen peroxide, peroxidase, and other chemicals evoked luminescence with variable success in three Atlantic lanternfishes of the family Myctophidae: Benthosema glaciale, Myctophum punctatum, and Notoscopelus kroeyeri. Electrical stimulation of the spinal cord and of isolated photophores resulted in only a few brief light responses in the first two species. Epinephrine injections evoked luminescence in the gonostomatid Maurolicus muelleri while injection and external application of hydrogen peroxide failed to produce a response in this species and in the stomiatid Stomias boa ferox. These and earlier data are discussed in terms of methodology and physiological states of the fish, biochemical systems involved, and luminescence control.

scholarly journals Role of intracellular Ca2+ in stimulation-induced increases in transmitter release at the frog neuromuscular junction.

1994 ◽  
Vol 104 (2) ◽  
pp. 337-355 ◽  
Author(s):  
J E Zengel ◽  
M A Sosa ◽  
R E Poage ◽  
D R Mosier
Keyword(s):  
Neuromuscular Junction ◽  
Transmitter Release ◽  
Cyclopiazonic Acid ◽  
Progressive Increase ◽  
Repetitive Stimulation ◽  
Frog Neuromuscular Junction ◽  
Quantal Content ◽  
Carbonyl Cyanide ◽  
Stimulation Of

Under conditions of reduced quantal content, repetitive stimulation of a presynaptic nerve can result in a progressive increase in the amount of transmitter released by that nerve in response to stimulation. At the frog neuromuscular junction, this increase in release has been attributed to four different processes: first and second components of facilitation, augmentation, and potentiation (e.g., Zengel, J. E., and K. L. Magleby. 1982. Journal of General Physiology. 80:583-611). It has been suggested that an increased entry of Ca2+ or an accumulation of intraterminal Ca2+ may be responsible for one or more of these processes. To test this hypothesis, we have examined the role of intracellular Ca2+ in mediating changes in end-plate potential (EPP) amplitude during and after repetitive stimulation at the frog neuromuscular junction. We found that increasing the extracellular Ca2+ concentration or exposing the preparation to carbonyl cyanide m-chlorophenylhydrazone, ionomycin, or cyclopiazonic acid all led to a greater increase in EPP amplitude during conditioning trains of 10-200 impulses applied at a frequency of 20 impulses/s. These experimental manipulations, all of which have been shown to increase intracellular levels of Ca2+, appeared to act by increasing primarily the augmentation component of increased release. The results of this study are consistent with previous suggestions that the different components of increased release represent different mechanisms, and that Ca2+ may be acting at more than one site in the nerve terminal.

scholarly journals Selecting the best electron donor and operational temperature for the rapid biotransformation of the insensitive munitions compound 2,4-dinitroanisole (DNAN) by anaerobic sludge

2021 ◽  
Author(s):  
Natanna Melo ◽  
Osmar Menezes ◽  
Matheus Paraiso ◽  
Lourdinha Florêncio ◽  
Mário T. Kato ◽  
...  
Keyword(s):  
Reduction Rate ◽  
Anaerobic Treatment ◽  
Electron Donors ◽  
Anaerobic Sludge ◽  
Amino Groups ◽  
Manufacturing Plants ◽  
Insensitive Munitions ◽  
Operational Temperature ◽  
Abiotic Controls ◽  
The Military

Abstract 2,4-Dinitroanisole (DNAN) is a toxic compound increasingly used by the military that can be released to the environment on the soil of training fields and in the wastewater of manufacturing plants. DNAN's nitro groups are anaerobically reduced to amino groups by microorganisms when electron donors are available. Using anaerobic sludge as inoculum, we tested different electron donors for DNAN bioreduction at 20 and 30 °C: acetate, ethanol, pyruvate, hydrogen, and hydrogen + pyruvate. Biotic controls without external electron donors and abiotic controls with heat-killed sludge were also assayed. No DNAN conversion was observed in the abiotic controls. In all biotic treatments, DNAN was reduced to 2-methoxy-5-nitroaniline (MENA), which was further reduced to 2,4-diaminoanisole (DAAN). Ethanol or acetate did not increase DNAN reduction rate compared to the endogenous control. The electron donors that caused the fastest DNAN reductions were (rates at 30 °C): H2 and pyruvate combined (311.28 ± 10.02 μM·d−1·gSSV−1), followed by H2 only (207.19 ± 5.95 μM·d−1·gSSV−1), and pyruvate only (36.35 ± 2.95 μM·d−1·gSSV−1). Raising the temperature to 30 °C improved DNAN reduction rates when pyruvate, H2, or H2 + pyruvate were used as electrons donors. Our results can be applied to optimize the anaerobic treatment of DNAN-containing wastewater.

The alteration of mitotic events by ionophore A23187 and carbonyl cyanide n-chlorophenylhydrazone

1985 ◽  
Vol 75 (1) ◽  
pp. 347-355
Author(s):  
M.L. Ziegler ◽  
J.E. Sisken ◽  
S. Vedbrat
Keyword(s):  
Oxidative Phosphorylation ◽  
Intracellular Calcium ◽  
Calcium Ions ◽  
Hela Cells ◽  
Cytosolic Calcium ◽  
Ionophore A23187 ◽  
Chromosome Movement ◽  
Low Concentrations ◽  
Carbonyl Cyanide ◽  
Stimulation Of

A large quantity of published work indicates that calcium ions may be involved in the regulation of mitotic events and recent reports suggest that the onset of chromosome movement is dependent upon a transient increase in free cytosolic calcium ions. In this paper we examine the effects of two agents known to perturb intracellular calcium pools on mitosis in HeLa cells. These were the calcium-selective ionophore A23187 and carbonyl cyanide n-chlorophenylhydrazone (CCCP), which is a protonophoric inhibitor of oxidative phosphorylation. Owing to a stimulation of glycolysis, the latter agent does not decrease intracellular ATP in HeLa but does cause mitochondria to release calcium ions. Our data show that, at low concentrations, both agents prolong metaphase but differ in their effects on anaphase and cytokinesis. Studies with chlorotetracycline, a commonly used probe for membrane-associated calcium, verify that these agents do affect calcium pools under the conditions of our experiments. The data presented are consistent with the idea that increased cytosolic calcium levels can directly or indirectly affect mitotic events but, contrary to other suggestions, cause a prolongation of metaphase, i.e. they delay the onset of chromosome movement.

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