Energy conservation in the photochemical reactions of photosynthesis and its relation to delayed fluorescence

Crofts, Antony R.; Wraight, Colin A.; Fleischmann, D.E.

doi:10.1016/0014-5793(71)80031-5

Cited by 107 publications

(20 citation statements)

References 70 publications

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“…The almost isopotential nature of cytochrome b,, with quinone and succinate wound tend to promote such a situation. Some evidence supporting this role for cytochrome b,, has been provided by the studies of Jones [33]. Using chromatophores from the bluegreen mutant of Rps.…”

Section: Components Of the Light Reactionmentioning

confidence: 99%

“…The potential span between the midpoints of cytochromes b,, and cZg, is greater than that encountered a t energy conservation site I1 in mitochondria1 respiration between cytochrome b,,, (Em7.2 40 mV) and cytochrome c1 (Em7.2 225 mV) (see [16,17]) and hence would be capable of delivering the necessary energy to sustain the experimentally observed "phosphate potential" of about 15 kcal/mol in Rps. spheroides [32,33]; for transfer of two electrons this is energetically equivalent to an operating A E of approximately 300 mV.…”

Section: Components Of the Light Reactionmentioning

confidence: 99%

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Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Dutton

Jackson

1972

European Journal of Biochemistry

183

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1. The b-and c-type cytochromes in chromatophores from photosynthetically grown Rhodospirillum rubrum and Rhodopseudomonas spheroides have been characterized in situ in terms of their oxidation-reduction potential properties.I n R. rubrum only one cytochrome c measured a t 551-540 nm was resolved potentiometrically; the midpoint potential a t pH 7.2, Em7.2, is +293 mV. Three cytochrome species measured a t 562-540 nm were resolved; they had Em7.2 values + 170 mV, -5 mV and -105 mV and were tentatively identified with cytochrome b, cc' and b respectively; they contributed to the over-all absorbance change in the ratio 8 : 25 : 17, respectively. I n Rps. spheroides the Em7.0 of cytochrome c is + 295 mV. Three cytochromes tentatively considered to be of the b-type have Em7.2 values of + 155 mV, +50 mV and -90 mV; their approximate reduced minus oxidized maxima were determined to be 558-9 nm, 560 nm and 564 nm, respectively. The approximate relative absorbance ratio given at the reduced minus oxidized maxima was 8 : 21 : 14. 3. A working model for electron transfer in Rps. spheroides based on the measured thermodynamic and kinetic properties is presented.

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Section: Components Of the Light Reactionmentioning

confidence: 99%

Section: Components Of the Light Reactionmentioning

confidence: 99%

Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Dutton

Jackson

1972

European Journal of Biochemistry

183

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“…Treatments that result in changes of the transthylakoid ApH will affect luminescence in two ways. First, a ApH with a more acidic inside will lower the activation energy for recombinations in PS II and hence enhance the emission of luminescence [3], second, a ApH will also quench luminescence, through the same mechanism as it quenches prompt fluorescence, the so-called 'energy quenching' [4]. The net effect on luminescence by these two contradictory processes may differ with different conditions in the chloroplast .…”

Section: Introductionmentioning

confidence: 99%

Luminescence decay kinetics in relation to the relaxation of the transthylakoid ΔpH from high and low CO₂ adapted cells of Scenedesmus obliquus

1986

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Luminescence decay kinetics was shown to be. polyphasic with two relative maxima observed, when high CO, adapted cells of Scenedesmus obliquus were stressed by CO, deficiency. Low CO, adapted cells exhibited a single maximum. Luminescence from high CO, adapted cells under high CO, conditions decayed asymptotically without maxima. The magnitude of the transthylakoid dpH was shown to be. related to the intensity of luminescence in an antiparallel way. The relaxation kinetics of the dpH was shown to be complex, with an interval of increasing or maintained dpH. A working hypothesis is presented in order to explain polyphasic luminescence decay kinetics in terms of luminescence quenching by the transthylakoid dpH.Luminescence CO, accumulation pH gradient Thylakoid membrane

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“…is lower under phosphorylating than under nonphosphorylating conditions. Quantitative analyses of the signals in relation to ApR and AE is difficult, since one may be dealing with the product of two exponential functions (6). Nevertheless, the type of analysis presented in this paper may have some meaning, since it gives an estimate of the minimal value of the p.m.f.…”

Section: Discussionmentioning

confidence: 99%

“…' tion energy for the recombination process. According to a more detailed model (6), the free energy difference between donor and acceptor pools is dependent (in addition to the concentration of Z+ and Q-) both on the proton concentration difference (ApH) and the electrostatic potential difference (AE) across the thylakoid membrane. Since according to the chemiosmotic hypothesis, AE and ApH comprise the driving force for ATP formation (19), DLE should indeed be closely related to photophosphorylation.…”

mentioning

confidence: 99%

The Relation between Photophosphorylation and Delayed Light Emission in Chloroplasts

Neumann¹,

Barber²,

Gregory³

1973

Plant Physiol.

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One millisecond delayed light emission has been studied in isolated coupled lettuce (Lactuca sativa var. romaine) chloroplasts. Delayed light emission was increased upon addition of ferricyanide or 2,3, 5,6-tetramethyl-p-phenylene diamine. In the presence of ferricyanide, the magnitude of the signal was increased by the addition of ADP (in the absence of orthophosphate), ATP, DIO-9, or phlorizin. The signal was also increased by the addition of NaCI and by the addition of NH4Cl in the presence of a high NaCl concentration. The signal of delayed light emission was decreased by the addition of gramicidin, valinomycin, and by the addition of NH4Cl in the presence of a low NaCl concentration.Phosphorylation, whether started by addition of ADP or by addition of glucose plus hexokinase plus ATP, caused a significant decrease in delayed light emission. It was concluded that the magnitude of delayed light emission reflects the size of the proton motive force across the thylakoid membrane. Calibration of delayed light emission by creating KCI gradients indicated that the value for the electrochemical potential gradient for H+ in the presence of ferricyanide was at least 155 millivolts decreasing to 134 millivolts after the onset of phosphorylation.Goedheer (8) has suggested that DLE' in photosynthetic organisms results from back reactions of electrons and holes in acceptor and donor pools of photosystem II or bacterial reaction centers in a reversal of the light reactions. On the basis of studies involving the effect of uncouplers and phosphorylating agents on DLE in chloroplasts, Mayne (17) suggested that the high energy state of phosphorylation is an additional source of energy for DLE, in direct equilibrium with the photochemical act. Subsequently, Fleischmann (7) suggested that during the photoact charge separation across the thylakoid membrane would provide a store of energy in the form of electrical potential. This so-called membrane potential provides a source of energy in the dark for DLE by presumably lowering the activa- tion energy for the recombination process. According to a more detailed model (6), the free energy difference between donor and acceptor pools is dependent (in addition to the concentration of Z+ and Q-) both on the proton concentration difference (ApH) and the electrostatic potential difference (AE) across the thylakoid membrane. Since according to the chemiosmotic hypothesis, AE and ApH comprise the driving force for ATP formation (19), DLE should indeed be closely related to photophosphorylation. In the present work, we have further studied this relationship using coupled phosphorylating lettuce chloroplasts. In addition, following the method of Barber (4, 5), the magnitude of the minimal value of the p.m.f. was estimated during electron flow and when electron flow was coupled to phosphorylation. MATERIALS AND METHODSChloroplasts were isolated from lettuce leaves Lactuica satii'a var. romaine. One hundred grams of leaves were homogenized for 15 sec in a Waring Blendor in 130 ml of...

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Energy conservation in the photochemical reactions of photosynthesis and its relation to delayed fluorescence

Cited by 107 publications

References 70 publications

Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Luminescence decay kinetics in relation to the relaxation of the transthylakoid ΔpH from high and low CO₂ adapted cells of Scenedesmus obliquus

The Relation between Photophosphorylation and Delayed Light Emission in Chloroplasts

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Energy conservation in the photochemical reactions of photosynthesis and its relation to delayed fluorescence

Cited by 107 publications

References 70 publications

Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

Luminescence decay kinetics in relation to the relaxation of the transthylakoid ΔpH from high and low CO2 adapted cells of Scenedesmus obliquus

The Relation between Photophosphorylation and Delayed Light Emission in Chloroplasts

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Luminescence decay kinetics in relation to the relaxation of the transthylakoid ΔpH from high and low CO₂ adapted cells of Scenedesmus obliquus