The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Judith P. Armitage - One of the best experts on this subject based on the ideXlab platform.
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Photoresponses in Rhodobacter sphaeroides: role of photosynthetic Electron Transport.
Journal of bacteriology, 1997Co-Authors: Ruslan N. Grishanin, D E Gauden, Judith P. ArmitageAbstract:Rhodobacter sphaeroides responds to a decrease in light intensity by a transient stop followed by adaptation. There is no measurable response to increases in light intensity. We confirmed that photosynthetic Electron Transport is essential for a photoresponse, as (i) inhibitors of photosynthetic Electron Transport inhibit photoresponses, (ii) Electron Transport to oxidases in the presence of oxygen reduces the photoresponse, and (iii) the magnitude of the response is dependent on the photopigment content of the cells. The photoresponses of cells grown in high light, which have lower concentrations of light-harvesting photopigment and reaction centers, saturated at much higher light intensities than the photoresponses of cells grown in low light, which have high concentrations of light-harvesting pigments and reaction centers. We examined whether the primary sensory signal from the photosynthetic Electron Transport chain was a change in the electrochemical proton gradient or a change in the rate of Electron Transport itself (probably reflecting redox sensing). R. sphaeroides showed no response to the addition of the proton ionophore carbonyl cyanide 4-trifluoromethoxyphenylhydrazone, which decreased the electrochemical proton gradient, although a behavioral response was seen to a reduction in light intensity that caused an equivalent reduction in proton gradient. These results strongly suggest that (i) the photosynthetic apparatus is the primary photoreceptor, (ii) the primary signal is generated by a change in the rate of Electron Transport, (iii) the change in the electrochemical proton gradient is not the primary photosensory signal, and (iv) stimuli affecting Electron Transport rates integrate via the Electron Transport chain.
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Electron Transport-dependent taxis in Rhodobacter sphaeroides.
Journal of bacteriology, 1995Co-Authors: D E Gauden, Judith P. ArmitageAbstract:Rhodobacter sphaeroides showed chemotaxis to the terminal Electron acceptors oxygen and dimethyl sulfoxide, and the responses to these effectors were shown to be influenced by the relative activities of the different Electron Transport pathways. R. sphaeroides cells tethered by their flagella showed a step-down response to a decrease in the oxygen or dimethyl sulfoxide concentration when using them as terminal acceptors. Bacteria using photosynthetic Electron Transport, however, showed a step-down response to oxygen addition. Addition of the proton ionophore carbonyl cyanide 4-trifluoromethoxyphenylhydrazone did not cause a transient behavioral response, although it decreased the electrochemical proton gradient (delta p) and increased the rate of Electron Transport. However, removal of the ionophore, which caused an increase in delta p and a decrease in the Electron Transport rate, resulted in a step-down response. Together, these data suggest that behavioral responses of R. sphaeroides to Electron Transport effectors are caused by changes in the rate of Electron Transport rather than changes in delta p.
D E Gauden - One of the best experts on this subject based on the ideXlab platform.
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Photoresponses in Rhodobacter sphaeroides: role of photosynthetic Electron Transport.
Journal of bacteriology, 1997Co-Authors: Ruslan N. Grishanin, D E Gauden, Judith P. ArmitageAbstract:Rhodobacter sphaeroides responds to a decrease in light intensity by a transient stop followed by adaptation. There is no measurable response to increases in light intensity. We confirmed that photosynthetic Electron Transport is essential for a photoresponse, as (i) inhibitors of photosynthetic Electron Transport inhibit photoresponses, (ii) Electron Transport to oxidases in the presence of oxygen reduces the photoresponse, and (iii) the magnitude of the response is dependent on the photopigment content of the cells. The photoresponses of cells grown in high light, which have lower concentrations of light-harvesting photopigment and reaction centers, saturated at much higher light intensities than the photoresponses of cells grown in low light, which have high concentrations of light-harvesting pigments and reaction centers. We examined whether the primary sensory signal from the photosynthetic Electron Transport chain was a change in the electrochemical proton gradient or a change in the rate of Electron Transport itself (probably reflecting redox sensing). R. sphaeroides showed no response to the addition of the proton ionophore carbonyl cyanide 4-trifluoromethoxyphenylhydrazone, which decreased the electrochemical proton gradient, although a behavioral response was seen to a reduction in light intensity that caused an equivalent reduction in proton gradient. These results strongly suggest that (i) the photosynthetic apparatus is the primary photoreceptor, (ii) the primary signal is generated by a change in the rate of Electron Transport, (iii) the change in the electrochemical proton gradient is not the primary photosensory signal, and (iv) stimuli affecting Electron Transport rates integrate via the Electron Transport chain.
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Electron Transport-dependent taxis in Rhodobacter sphaeroides.
Journal of bacteriology, 1995Co-Authors: D E Gauden, Judith P. ArmitageAbstract:Rhodobacter sphaeroides showed chemotaxis to the terminal Electron acceptors oxygen and dimethyl sulfoxide, and the responses to these effectors were shown to be influenced by the relative activities of the different Electron Transport pathways. R. sphaeroides cells tethered by their flagella showed a step-down response to a decrease in the oxygen or dimethyl sulfoxide concentration when using them as terminal acceptors. Bacteria using photosynthetic Electron Transport, however, showed a step-down response to oxygen addition. Addition of the proton ionophore carbonyl cyanide 4-trifluoromethoxyphenylhydrazone did not cause a transient behavioral response, although it decreased the electrochemical proton gradient (delta p) and increased the rate of Electron Transport. However, removal of the ionophore, which caused an increase in delta p and a decrease in the Electron Transport rate, resulted in a step-down response. Together, these data suggest that behavioral responses of R. sphaeroides to Electron Transport effectors are caused by changes in the rate of Electron Transport rather than changes in delta p.
Navdeep S. Chandel - One of the best experts on this subject based on the ideXlab platform.
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Genetics of mitochondrial Electron Transport chain in regulating oxygen sensing.
Methods in Enzymology, 2007Co-Authors: Eric L. Bell, Navdeep S. ChandelAbstract:Oxygen is the terminal Electron acceptor in the mitochondrial Electron Transport chain and therefore is required for the generation of energy through oxidative phosphorylation. In environments of decreased oxygen levels (hypoxia), organisms have developed an adaptive response through the activation of the hypoxia-inducible transcription factor (HIF) to maintain their energetic demand. In order to sense hypoxic environments, cells have developed oxygen-sensing machinery that allows for the activation of HIF. The mitochondrial Electron Transport chain is required for the oxygen-sensing pathway. This chapter outlines methods used to explore the role of the Electron Transport chain and a by-product of Electron Transport, reactive oxygen species, in oxygen sensing.
Alexander N. Tikhonov - One of the best experts on this subject based on the ideXlab platform.
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Alternative pathways of photoinduced Electron Transport in chloroplasts
Russian Journal of Physical Chemistry B, 2009Co-Authors: Ilya V. Kuvykin, A. V. Vershubskii, Alexander N. TikhonovAbstract:The influence of the alternative pathways of Electron Transport in photosynthetic systems of the oxygen type on the kinetics of the photoinduced redox transitions of P700, ferredoxin, NADP, pH of the intrathylakoid space or lumen, and relative concentration of ATP was studied. The oxygen effect on the kinetics of photooxidation of P700 was analyzed. The retardation of the photooxidation of P700 at low oxygen concentrations can be explained by the “over-reduction” of the acceptor side of PS1 as a result of a decrease in the Electron outflow from PS1 to oxygen during hypoxia. The results of numerical experiments are in good agreement with known experimental data that the withdrawal of Electrons from PS1 (on the ferredoxin-NADP segment of the chain) can be the limiting stage in the noncyclic Electron Transport chain. The functioning of the cyclic Electron Transport chain provides additional synthesis of ATP molecules and weakens the excess reduction of the acceptor segment of PS1. The alternative pathway of Electron Transport, namely, Electron outflow from PS1 to oxygen also favors the optimum conditions for the functioning of the photosynthetic Electron Transport chain.
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EPR study of Electron Transport in the cyanobacterium Synechocystis sp. PCC 6803: oxygen-dependent interrelations between photosynthetic and respiratory Electron Transport chains.
Biochimica et Biophysica Acta, 2005Co-Authors: Boris V. Trubitsin, Vasilii V. Ptushenko, Olga A. Koksharova, Mahir D. Mamedov, Liya A. Vitukhnovskaya, Igor A. Grigor'ev, Alexey Yu. Semenov, Alexander N. TikhonovAbstract:Abstract In this work, we investigated Electron Transport processes in the cyanobacterium Synechocystis sp. PCC 6803, with a special emphasis focused on oxygen-dependent interrelations between photosynthetic and respiratory Electron Transport chains. Redox transients of the photosystem I primary donor P700 and oxygen exchange processes were measured by the EPR method under the same experimental conditions. To discriminate between the factors controlling Electron flow through photosynthetic and respiratory Electron Transport chains, we compared the P700 redox transients and oxygen exchange processes in wild type cells and mutants with impaired photosystem II and terminal oxidases (CtaI, CydAB, CtaDEII). It was shown that the rates of Electron flow through both photosynthetic and respiratory Electron Transport chains strongly depended on the transmembrane proton gradient and oxygen concentration in cell suspension. Electron Transport through photosystem I was controlled by two main mechanisms: (i) oxygen-dependent acceleration of Electron transfer from photosystem I to NADP+, and (ii) slowing down of Electron flow between photosystem II and photosystem I governed by the intrathylakoid pH. Inhibitor analysis of P700 redox transients led us to the conclusion that Electron fluxes from dehydrogenases and from cyclic Electron Transport pathway comprise 20–30% of the total Electron flux from the intersystem Electron Transport chain to P700+.
Eric L. Bell - One of the best experts on this subject based on the ideXlab platform.
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Genetics of mitochondrial Electron Transport chain in regulating oxygen sensing.
Methods in Enzymology, 2007Co-Authors: Eric L. Bell, Navdeep S. ChandelAbstract:Oxygen is the terminal Electron acceptor in the mitochondrial Electron Transport chain and therefore is required for the generation of energy through oxidative phosphorylation. In environments of decreased oxygen levels (hypoxia), organisms have developed an adaptive response through the activation of the hypoxia-inducible transcription factor (HIF) to maintain their energetic demand. In order to sense hypoxic environments, cells have developed oxygen-sensing machinery that allows for the activation of HIF. The mitochondrial Electron Transport chain is required for the oxygen-sensing pathway. This chapter outlines methods used to explore the role of the Electron Transport chain and a by-product of Electron Transport, reactive oxygen species, in oxygen sensing.