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Pallotti F, Lenaz G. Isolation and Subfractionation of Mitochondria from Animal Cells and Tissue Culture Lines. Methods Cell Biol 2007; 80:3-44. [PMID: 17445687 DOI: 10.1016/s0091-679x(06)80001-4] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Francesco Pallotti
- Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi dell'Insubria, 21100 Varese, Italy
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Forti G, Agostiano A, Barbato R, Bassi R, Brugnoli E, Finazzi G, Garlaschi FM, Jennings RC, Melandri BA, Trotta M, Venturoli G, Zanetti G, Zannoni D, Zucchelli G. Photosynthesis research in Italy: a review. PHOTOSYNTHESIS RESEARCH 2006; 88:211-40. [PMID: 16755326 DOI: 10.1007/s11120-006-9054-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2005] [Accepted: 02/24/2006] [Indexed: 05/10/2023]
Abstract
This historical review was compiled and edited by Giorgio Forti, whereas the other authors of the different sections are listed alphabetically after his name, below the title of the paper; they are also listed in the individual sections. This review deals with the research on photosynthesis performed in several Italian laboratories during the last 50 years; it includes research done, in collaboration, at several international laboratories, particularly USA, UK, Switzerland, Hungary, Germany, France, Finland, Denmark, and Austria. Wherever pertinent, references are provided, especially to other historical papers in Govindjee et al. [Govindjee, Beatty JT, Gest H, Allen JF (eds) (2005) Discoveries in Photosynthesis. Springer, Dordrecht]. This paper covers the physical and chemical events starting with the absorption of a quantum of light by a pigment molecule to the conversion of the radiation energy into the stable chemical forms of the reducing power and of ATP. It describes the work done on the structure, function and regulation of the photosynthetic apparatus in higher plants, unicellular algae and in photosynthetic bacteria. Phenomena such as photoinhibition and the protection from it are also included. Research in biophysics of photosynthesis in Padova (Italy) is discussed by G.M. Giacometti and G. Giacometti (2006).
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Affiliation(s)
- Giorgio Forti
- Istituto di Biofisica del CNR, Sezione di Milano e Dipartimento di Biologia dell'Università degli Studi di Milano, Via Celoria 26, Milan 20133, Italy.
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Pallotti F, Lenaz G. Isolation and subfractionation of mitochondria from animal cells and tissue culture lines. Methods Cell Biol 2002; 65:1-35. [PMID: 11381588 DOI: 10.1016/s0091-679x(01)65002-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- F Pallotti
- Department of Neurology, Columbia University, New York, New York 10032, USA
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Casadio R, Melandri AB, Melandri BA. Limited cooperativity in the coupling between electron flow and photosynthetic ATP synthesis A comparative study in chromatophores phosphorylating at very different rates. FEBS Lett 2001. [DOI: 10.1016/0014-5793(78)80361-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Rottenberg H, Moreno-Sanchez R. The proton pumping activity of H(+)-ATPases: an improved fluorescence assay. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1183:161-70. [PMID: 8399374 DOI: 10.1016/0005-2728(93)90014-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A new method for the estimation of steady-state delta pH, and the rate of acidification, by H(+)-ATPases (and other proton transporters) in inverted membrane vesicles is described. The method is based on a combination of two widely used fluorescent delta pH probes, 9-aminoacridine and 9-amino-6-chloro-2-methoxyacridine. It is demonstrated that 9-amino-6-chloro-2-methoxyacridine fluorescence quenching, which is very sensitive to small pH gradients, is not sensitive to the magnitude of large pH gradient, while 9-aminoacridine, which does not sense small gradients, is very sensitive to large pH gradients. A proper mixture of the two probes provides a method which is equally sensitive to pH gradients from very small values up to 3.5 pH units. The probe response was evaluated by titrations of the fluorescence signal with nigericin and adjusted by changing the concentration ratio and the emission wavelength. In liposomes, submitochondrial particles and bacterial vesicles an almost linear dependence of quenching on delta pH over the entire range can be obtained with this method. It is demonstrated that the new method can be used to obtain more reliable estimates of the rate of acidification as well as the magnitude of delta pH, whereas each of these and similar probes, by themselves are not as reliable. A determination of the ratio delta Gp/delta muH over a wide range of values reveal that this ratio is not constant but decreases with delta Gp. This finding should be taken into consideration when attempting to estimate the H+/ATP ratio form the measurement of delta Gp/delta muH.
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Affiliation(s)
- H Rottenberg
- Pathology Department M.S. 435, Hahnemann University, Philadelphia, PA 19102
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Fato R, Cavazzoni M, Castelluccio C, Parenti Castelli G, Palmer G, Degli Esposti M, Lenaz G. Steady-state kinetics of ubiquinol-cytochrome c reductase in bovine heart submitochondrial particles: diffusional effects. Biochem J 1993; 290 ( Pt 1):225-36. [PMID: 8382478 PMCID: PMC1132405 DOI: 10.1042/bj2900225] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In an attempt to establish the relative importance of diffusional and chemical control in the reactivity of the two of the two substrates, ubiquinol and cytochrome c, we have undertaken as extensive characterization of the steady-state kinetics of ubiquinol-cytochrome c reductase (EC 1.10.2.2) when present in open submitochondrial particles from bovine heart. The kinetic pattern follows a Ping Pong mechanism; contrary to the situation found with the isolated enzyme [Speck and Margoliash (1984) J. Biol. Chem. 259, 1064-1072, and confirmed in our laboratory], no substrate inhibition by oxidized cytochrome c was observed with the membrane-bound enzyme. Endogenous oxidized ubiquinone-10 is unable to exert product inhibition under the conditions employed. In the Ping Pong mechanism for this enzyme, the reaction scheme can be clearly divided into two parts, and the Kmin. (kcat./km) value for one substrate is independent of the rate constant for the second substrate. Both ubiquinol-1 and ubiquinol-2 can be used as electron donors reacting with the enzyme from within the lipid bilayer [Fato, Castelluccio, Palmer and Lenaz (1988) Biochim. Biophys. Acta 932, 216-222]; the kmin. values for ubiquinols, when calculated on the basis of their membranous concentrations, are significantly lower than the kmin. for cytochrome c. The temperature-dependence of the kinetic parameters was investigated by titrating each of the substrates under quasi-saturating concentrations of the second substrate. Arrhenius plots of Vmax. extrapolated from both cytochrome c and ubiquinol titrations were linear, when care was taken to verify the quasi-saturating concentrations of the fixed co-substrate. The Arrhenius plots for the kmin. values for both ubiquinol and cytochrome c were linear, but the activation energy was much higher for the former, particularly when calculated for ubiquinol dissolved in the lipid phase; the very low value of activation energy of the kmin. for cytochrome c is strong support for diffusion control being present in the reaction of cytochrome c with the membranous enzyme. In contrast to the soluble enzyme, ubiquinone titrations of submitochondrial particles at low cytochrome c concentrations deviated from hyperbolic behaviour. Changing the medium viscosity with either poly(ethylene glycol) or sucrose had a strong effect on the cytochrome c kmin., whereas the change in the ubiquinol kmin. was much smaller. From the viscosity studies the extent of diffusional control could be calculated, revealing that the reaction with cytochrome c was mostly diffusion-limited. The viscosity of the membrane was changed by incorporating cholesterol; no significant effect on the ubiquinol kmin. ascribable to diffusion control could be recognized.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R Fato
- Department of Biochemistry, University of Bologna, Italy
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Grzesiek S, Otto H, Dencher NA. delta pH-induced fluorescence quenching of 9-aminoacridine in lipid vesicles is due to excimer formation at the membrane. Biophys J 1989; 55:1101-9. [PMID: 2765648 PMCID: PMC1330576 DOI: 10.1016/s0006-3495(89)82907-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The fluorescence of 9-aminoacridine (9-AA) is quenched in vesicular suspensions containing negatively charged lipid headgroups (e.g., phosphatidylserine) upon imposition of a transmembrane (inside acidic) pH-gradient. It is shown that this fluorescence loss is accompanied by the formation of 9-AA dimers that undergo a transition in the dimer excited state to a dimer-excimer state. This result has been obtained on the basis of the specific dimer fluorescence excitation and hypochromic absorbance spectra that are redshifted by maximally 275 cm-1 (4.4 nm) with respect to the corresponding monomer spectra, as well as by the detection of the characteristic broad excimer emission band, centered at 560 nm. The existence of the spectrally distinct dimer-excimer is further corroborated by fluorescence life-time measurements that indicate an increased lifetime of up to 24 ns for this complex as compared with the normal monomer fluorescence lifetime of 16 ns. The formation of this dimer-excimer complex from the monomers can be reversed completely and the original monomeric spectral properties restored after the abolishment of the electrochemical proton gradient. In addition to the delta pH-induced dimer redshift in absorbance and fluorescence excitation, a further small redshift in monomer absorbance, fluorescence excitation, and emission spectra is observed due solely to the presence of the negatively charged phospholipid headgroups.
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Affiliation(s)
- S Grzesiek
- Department of Physics, Freie Universität Berlin, Federal Republic of Germany
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Ohta M, Nozawa T, Hatano M, Hayashi H, Tasumi M, Shimada K. 31P-NMR studies of photophosphorylation in chromatophores from Chromatium vinosum. BIOCHIMICA ET BIOPHYSICA ACTA (BBA) - MOLECULAR CELL RESEARCH 1989. [DOI: 10.1016/0167-4889(89)90074-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Grzesiek S, Dencher NA. The 'delta pH'-probe 9-aminoacridine: response time, binding behaviour and dimerization at the membrane. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 938:411-24. [PMID: 3349072 DOI: 10.1016/0005-2736(88)90139-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The fluorescence quenching of 9-aminoacridine (9-AA) after imposition of a transmembrane pH gradient (inside acidic) in liposomes has been investigated for a number of different lipid systems. The initial fluorescence decrease after a rapid pH jump, induced in the extravesicular medium by a stopped-flow mixing technique, was ascribed to a response of 9-AA to the imposed pH gradient and not to changes in the vesicular system itself. Time constants for this fluorescence quenching are in the range of several hundred milliseconds at 25 degrees C. Fluorescence recovery which should be correlated to the dissipation of the pH gradient occurs in the 100 s time range and is 10-30-times faster than the delta pH decay monitored with the entrapped hydrophilic pH-indicator dye pyranine. The quenching was severely hindered below the lipid phase transition of dipalmitoylphosphatidylglycerol. No delta pH-induced quenching was obtained in lipid vesicles containing only zwitterionic, net uncharged phosphatidylcholine headgroups. For the occurrence of quenching, the presence of negatively charged headgroups, i.e. phosphatidylglycerol or phosphatidylserine, was necessary. The extent of quenching, at a specific pH difference applied, had a cooperative dependency (Hill coefficient approximately 2) on the number of negative headgroups in the membrane and on the concentration of unquenched (unbound) 9-AA molecules. The concentration of quenched 9-AA molecules was furthermore proportional to the number of dimer-excimer complexes of 9-AA which are formed during the quenching process.
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Affiliation(s)
- S Grzesiek
- Department of Physics, Freie Universität Berlin, Germany
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11
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Calibration of the carotenoid band shift and the response of the external membrane potential probe oxonol VI with diffusion potentials in (proteo)liposomes and chloroplasts. ACTA ACUST UNITED AC 1986. [DOI: 10.1016/0302-4598(86)80045-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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12
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Calanni Rindina F, Baracca A, Solaini G, Rabbi A, Parenti Castelli G. Effects of cholesterol on the kinetics of mitochondrial ATPase. FEBS Lett 1986; 198:353-6. [PMID: 2937653 DOI: 10.1016/0014-5793(86)80435-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Enrichment of the inner mitochondrial membrane with cholesterol induces an increase in ATPase activity with a decrease in the Km for ATP. Cholesterol also abolishes the discontinuity normally found in the Arrhenius plot of ATPase activity. Since no change is detected in the rate of proton translocation through the ATPase membrane sector, it is concluded that cholesterol incorporation induces changes in the hydrolytic step of ATPase via a conformational change transmitted from the membrane sector to the catalytic sector F1.
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‘Backlash’ and the coupling between electron transport and proton translocation in bacterial chromatophores. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1986. [DOI: 10.1016/0005-2728(86)90043-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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14
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Knaff DB. Active transport in phototrophic bacteria. PHOTOSYNTHESIS RESEARCH 1986; 10:507-514. [PMID: 24435399 DOI: 10.1007/bf00118317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Phototrophic bacteria utilize light-driven, cyclic electron flow to pump protons out of their cytoplasm, creating an electrochemical proton gradient, ΔμH+, outside acid and positive. These bacteria exchange external protons for internal cations (Na(+), K(+) and Ca(+2)), allowing the cells to maintain a nearly constant internal pH while maintaining the electrical component of ΔμH+. Na(+)/H(+) exchange also establishes an electrochemical Na(+) gradient. Phototrophic bacteria are able to utilize these electrochemical gradients as energy sources for the uptake of a wide variety of metabolites (e.g., sugars, organic acids and amino acids) via metabolite/cation symports.
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Affiliation(s)
- D B Knaff
- Department of Chemistry and Biochemistry, Texas Tech University, 79409-4260, Lubbock, Texas, (U.S.A.)
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Itoh S, Nishimura M. Rate of redox reactions related to surface potential and other surface-related parameters in biological membranes. Methods Enzymol 1986; 125:58-86. [PMID: 3713540 DOI: 10.1016/s0076-6879(86)25008-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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16
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Kopacz SJ, Mueller DM, Lee CP. Photoaffinity labelling of submitochondrial membranes with the 3-azido analogue of 9-amino-3-chloro-7-methoxyacridine. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 807:177-88. [PMID: 3978094 DOI: 10.1016/0005-2728(85)90121-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
9-Amino-3-azido-7-methoxyacridine has been synthesized and shown to be a suitable photoaffinity probe for the site(s) of interaction of 9-amino-3-chloro-7-methoxyacridine with submitochondrial membranes. Both the excitation and emission spectra of the azido analogue covalently bound to membranes in the energized state display distinctive differences from the spectra of labelled, non-energized membranes (i.e., in the absence of oxidizable substrate, or its presence when uncoupler (FCCP) is also present during photolysis). Enzymatic analyses indicate that the probe interacts with the ATPase and the respiratory chain enzymes; energization appears to afford some protection against inactivation. Electrophoresis of the labelled membranes and isolation of their lipid and protein components indicate that the spectral differences are attributable to differing interactions with the lipid components of energized, relative to non-energized, membranes. Similar results have been obtained with the 3-azido analogue of quinacrine (Mueller, D.M., Hudson, R.A. and Lee, C.P. (1982) Biochemistry 21, 1445-1453), which differs significantly, however, in the extent of its interactions with the enzymes of the respiratory chain and the ATPase. These results indicate that the energy-linked fluorescence responses of 9-aminoacridines with submitochondrial membranes arise from direct interactions with membrane components and may involve redistribution of the probe molecules and/or alteration of their microenvironments upon energization.
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Casadio R, Melandri BA. Calibration of the response of 9-amino acridine fluorescence to transmembrane pH differences in bacterial chromatophores. Arch Biochem Biophys 1985; 238:219-28. [PMID: 3872628 DOI: 10.1016/0003-9861(85)90159-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The spectral characteristics of absorption and fluorescence emission of 9-amino acridine are not altered by the interaction with bacterial chromatophores, except for the attenuation of both the absorption and emission following the formation of a protonic gradient. The lifetime of fluorescence of the dye is significantly affected in the presence of membranes, and even more following illumination. The shortening of the lifetime induced by light is reversible and prevented by nigericin and K+. The onset kinetics of the fluorescence quenching following the generation of an artificial transmembrane pH difference is temperature dependent, with an activation energy of 17 +/- 3 kcal/mol. The effect of pH on the rate constants is consistent with a model assuming that the diffusion of the unprotonated species is the limiting step in the quenching phenomenon. The response of 9-amino acridine to artificially imposed delta pH's has been utilized as a calibration method for the measurements of the light-induced protonic gradient. The apparent inner volume of chromatophores, evaluated from the extraplation of the response at delta pH = 0, was found to be much larger (15- to 40-fold) than the true osmotic volume, indicating that most of the dye is bound to the membrane when accumulated into the inner lumen.
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Melandri BA, Mehlhorn RJ, Packer L. Light-induced proton gradients and internal volumes in chromatophores of Rhodopseudomonas sphaeroides. Arch Biochem Biophys 1984; 235:97-105. [PMID: 6093711 DOI: 10.1016/0003-9861(84)90258-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
To test the predictions of the chemiosmotic hypothesis, it is essential to have sensitive and accurate measures of the aqueous volume and pH within membrane compartments. One unique feature of the present investigation is the application of electron spin resonance probes to determine internal aqueous volume and pH changes in bacterial chromatophores under virtually identical conditions. Volumes of the chromatophores ranged from 6 to 16 microliter/mg bacteriochlorophyll among different preparations, and were sensitive to the osmolarity of the suspending buffer. pH gradients reached two units in illuminated chromatophores as determined with ESR methods, and increased when KCl and valinomycin were added to the assay. Measurements with the fluorescent dye 9-amino-acridine yielded similar pH gradients, provided that an operational vesicle volume, which corrected for the binding of the dye to the membrane, was used in the calculation. The sensitivity of the ESR method allowed the measurement of pH gradients resulting from only a few light flashes. A plot of pH gradients versus number of flashes was linear up to about 30 flashes, and intercepted the origin. This result is consistent with proton release into the bulk aqueous phase after only a single light flash. This ability to measure small pH gradients offers new opportunities for the study of energy-transducing mechanisms.
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AZZONE GIOVANNIFELICE, PIETROBON DANIELA, ZORATTI MARIO. Determination of the Proton Electrochemical Gradient across Biological Membranes. CURRENT TOPICS IN BIOENERGETICS 1984. [DOI: 10.1016/b978-0-12-152513-2.50008-8] [Citation(s) in RCA: 103] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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20
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9-Aminoacridine, a fluorescent probe of the thiamine carrier in yeast cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 1983. [DOI: 10.1016/0005-2736(83)90341-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Lenaz G, Esposti MD, Parenti Castelli G. DCCD inhibits proton translocation and electron flow at the second site of the mitochondrial respiratory chain. Biochem Biophys Res Commun 1982; 105:589-95. [PMID: 6284158 DOI: 10.1016/0006-291x(82)91475-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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23
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Haraux F, de Kouchkovsky Y. Further investigation on the lateral and transversal proton currents at the thylakoid membrane level by hydrogen-deuterium exchange. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1982. [DOI: 10.1016/0005-2728(82)90294-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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24
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Clark AJ, Jackson JB. The measurement of membrane potential during photosynthesis and during respiration in intact cells of Rhodopseudomonas capsulata by both electrochromism and by permeant ion redistribution. Biochem J 1981; 200:389-97. [PMID: 7340838 PMCID: PMC1163547 DOI: 10.1042/bj2000389] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
1. The membrane potential in intact cells of Rhodopseudomonas capsulata during photosynthesis and during dark respiration has been measured by two independent methods. 2. The light-induced and O2-induced shifts in the carotenoid absorption spectrum were measured in the intact cells. The shift was calibrated with K+-diffusion potentials in chromatophores derived from those cells. The light-induced and O2-induced membrane potentials were -290 mV and -230 mV respectively. 3. The energized uptake of butyltriphenylphosphonium ions was measured in the same batch of cells. The light-induced and O2-induced membrane potentials calculated from the Nernst equation were -160 mV and -120 mV respectively. 4. It is concluded that the two kinds of probe measure the electric potentials across different domains of the cytoplasmic membrane, but it is difficult to reconcile the existence of such domains with simple electrical analogues of the membrane and aqueous phases.
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Horne WC, Norman NE, Schwartz DB, Simons ER. Changes in cytoplasmic pH and in membrane potential in thrombin-stimulated human platelets. EUROPEAN JOURNAL OF BIOCHEMISTRY 1981; 120:295-302. [PMID: 7318826 DOI: 10.1111/j.1432-1033.1981.tb05703.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The response of human platelets to stimulation by a specific aggregant such as thrombin has been postulated to proceed sequentially via induction of response at the membrane, followed by execution of shape change, secretion, and aggregation of the platelets. We have shown earlier that the platelet response includes a depolarization of the membrane which starts within less than 5 s and is thrombin-dose-dependent up to 4.5 nM alpha-thrombin. This depolarization may be measured by the distribution of either a fluorescent or a tritium-labeled lipophilic cation. We present here an adaptation of techniques for intracellular pH measurements to the human platelet. These show that stimulation with thrombin also induces a rapid change in the platelet transmembrane pH gradient as measured using either a weak base or a fluorescein derivative as a probe. The pH gradient undergoes a time-dependent and thrombin-dose-dependent change which parallels that exhibited by the membrane potential and by serotonin secretion.
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Cirillo VP, Gromet-Elhanan Z. Steady-state measurements of delta pH and delta psi in Rhodospirillum rubrum chromatophores by two different methods. Comparison with phosphorylation potential. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 636:244-53. [PMID: 6793067 DOI: 10.1016/0005-2728(81)90098-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The pH gradient, delta pH, and the membrane potential, delta psi, formed during light-induced electron transport in Rhodospirillum rubrum chromatophores were measured by two independent methods: (a) using specific electrodes to monitor light-dependent uptake of NH4Cl and SCN- at chromatophore concentrations of about 0.1 mg bacteriochlorophyll/ml and (b) using 9-aminoacridine and 8-anilinonaphthalenesulfonic acid as fluorescent probes for delta pH and delta psi, respectively, at chromatophore concentrations of about 0.01 mg bacteriochlorophyll/ml. The light intensity was measured and set at a level which saturated the highest bacteriochlorophyll concentration used. The steady-state values obtained with each method under phosphorylating conditions were compared with the phosphorylation potential maintained by the chromatophores under identical conditions. The results indicate that under all conditions employed the ratio H+/ATP is greater than 2, and varies between 2.4 and 3.4 depending on the method used for estimation of the electrochemical proton gradient.
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BACCARINI-MELANDRI A, CASADIO R, MELANDRI B. Electron Transfer, Proton Translocation, and ATP Synthesis in Bacterial Chromatophores. CURRENT TOPICS IN BIOENERGETICS 1981. [DOI: 10.1016/b978-0-12-152512-5.50010-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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29
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Effects of the medium composition on the components of the electrochemical proton gradient in Rhodopseudomonas sphaeroides. Arch Microbiol 1981. [DOI: 10.1007/bf00414600] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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30
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Melandri BA, Venturoli G, de Santis A, Baccarini-Melandri A. The induction kinetics of bacterial photophosphorylation. Threshold effects by the phosphate potential and correlation with the amplitude of the carotenoid absorption band shift. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 592:38-52. [PMID: 7397138 DOI: 10.1016/0005-2728(80)90112-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
1. ATP synthesis (monitored by luciferin-luciferase) can be elicited by a single turnover flash of saturating intensity in chromatophores from Rhodopseudomonas capsulata, Kb1. The ATP yield from the first to the fourth turnover is strongly influenced by the phosphate potential: at high phosphate potential (-11.5 kcal/mol) no ATP is formed in the first three turnovers while at lower phosphate potential (-8.2 kcal/mol) and the yield in the first flash is already one half of the maximum, which is reached after 2-3 turnovers. 2. The response to ionophores indicates that the driving force for ATP synthesis in the first 20 turnovers is mainly given by a membrane potential. The amplitude of the carotenoid band shift shows that during a train of flashes an increasing delta psi is built up, which reaches a stationary level after a few turnovers; at high phosphate potential, therefore, more turnovers of the same photosynthetic unit are required to overcome an energetic threshold. 3. After several (six to seven) flashes the ATP yield becomes constant, independently from the phosphate potential; the yield varies, however, as a function of dark time (td) between flashes, with an optimum for td = 160-320 ms. 4. The decay kinetics of the high energy state generated by a long (125 ms) flash have been studied directly measuring the ATP yield produced in post-illumination by one single turnover flash, under conditions of phosphate potential (-10 kcal/mol), which will not allow ATP formation by one single turnover. The high energy state decays within 20 s after the illumination. The decay rate is strongly accelerated by 10(-8) M valinomycin. 5. Under all the experimental conditions described, the amplitude of the carotenoid signal correlates univocally with the ATP yield per flash, demonstrating that this signal monitores accurately an energetic state of the membrane directly involved in ATP synthesis. 6. Although values of the carotenoid signal much larger than the minimal threshold are present, relax slowly, and contribute to the energy input for phosphorylation, no ATP is formed unless electron flow is induced by a single turnover flash. 7. The conclusions drawn are independent from the assumption that a delta psi between bulk phases is evaluable from the carotenoid signal.
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Haraux F, de Kouchkovsky Y. Measurement of chloroplast internal protons with 9-aminoacridine. Probe binding, dark proton gradient, and salt effects. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 592:153-68. [PMID: 6249352 DOI: 10.1016/0005-2728(80)90122-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A defined ratio, gamma, of the total proton uptake to the concentration change of free internal H+ is observed for illuminated envelope-free chloroplasts (Haraux, F. and de Kouchkovsky, Y. (1979) Biochim. Biophys. Acta, 546, 455-471). Proton uptake is measured by the external pH shift, free internal H+ by 9-aminoacridine fluorescence quenching. Extension of this work leads to the following conclusions, which, in the case of 9-aminoacridine behaviour, should apply to any kind of diffusible protonizable delta pH probe: 1. The gamma constancy is preserved when the internal volume (Vi) is modulated by chlorophyll and osmolarity changes: thus, 9-aminoacridine behaves as expected from the delta pH distribution of an amine of high pK; previous doubts on this point are attributed to the lack of control of the external proton uptake. 2. With variable 9-aminoacridine concentration, however, some variation of gamma confirms the existence of slight light-induced probe-membrane interactions. 3. According to the diffuse layer theory, salts decrease the negative potential at the 'plane of closest approach' of the thylakoids, thereby releasing the excess 9-aminoacridine in this diffuse layer, which increases its fluorescence. Although of equal valency, NH4+ is more potent than K+, suggesting competition between amines for specific anionic binding sites. 4. Two categories of membrane modifications are induced by salts: in addition to the above-mentioned electrical effect, mono- and divalent cations at high concentration increase the chloroplast proton binding capacity. La3+ is only able to release the excess dye in the diffuse layer and leaves gamma unchanged. Therefore the probe-membrane interactions should have limited importance for steady-state delta pH measurement. 5. A Donnan-type dark pH difference, which could seriously bias these delta pH estimates, is found experimentally to be less than 2 (no significant gamma change when Vi varies) and even theoretically less than 1 (on the basis of the concentration of the non-diffusible internal protonizable groups). Similarly, the predictable errors of Vi and its possible light-induced variations must have a small effect on delta pH under present experimental conditions.
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Slooten L, Branders C. The influence of energy-transfer inhibitors on proton permeability and photophosphorylation in normal and preilluminated Rhodospirillum rubrum chromatophores. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 547:79-90. [PMID: 37903 DOI: 10.1016/0005-2728(79)90097-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
(1) Chromatophores were preilluminated in the presence of phenazine methosulphate or diaminodurene, and without phosphorylation substrates; next they were transferred to fresh medium and assayed for light-induced proton uptake, light-induced 9-aminoacridin fluorescence quenching, and photophosphorylation. (2) Preillumination in the presence of phenazine methosulphate or diaminodurene causes an inhibition of the photophosphorylation rate. The presence of ADP + MgCl2 + phosphate, or ADP + MgCl2 + arsenate during preillumination provides full protection against this effect. (3) Preilluminated chromatophores are leaky for protons. The leak is expressed as an accelerated dark decay, and a diminished extent of succinate-supported, light-induced proton uptake. The extent of light-induced 9-aminoacridin fluorescence quenching is also diminished. (4) The proton leak can be closed by oligomycin and by dicyclohexyl carbodiimide (at concentrations similar to those used to inhibit photophosphorylation), but not by aurovertin. Closure of the proton leak results in partial restoration of the photophosphorylation rate. (5) The inhibition of phosphorylation by oligomycin or dicyclohexyl carbodiimide is time-dependent. In untreated chromatophores, the time-dependence is determined by the extent of membrane energization. In preilluminated chromatophores, the time-dependence is determined in addition by the extent to which the proton leaks have been closed. The reasons for this are briefly discussed.
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Kell DB. On the functional proton current pathway of electron transport phosphorylation. An electrodic view. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 549:55-99. [PMID: 38839 DOI: 10.1016/0304-4173(79)90018-1] [Citation(s) in RCA: 242] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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34
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Haraux F, De Kouchkovsky Y. Quantitative estimation of the photosynthetic proton binding inside the thylakoids by correlating internal acidification to external alkalinisation and to oxygen evolution in chloroplasts. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 546:455-71. [PMID: 36908 DOI: 10.1016/0005-2728(79)90081-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The external alkalinisation delta pHe, or the rate of oxygen evolution vO2, of a suspension of envelope-free chlorplasts was correlated with their internal acidification, estimated from the transmembrane delta pHei. Knowing the external buffer value, the concentration of the total protons moved Hi was calculated from the delta pHe, measured with a glass electrode ([Hi] was also obtained from vO2), and the free proton concentration [Hi+] was determined from delta pHei, measured with 9-aminoacridine. This gives a ratio gamma i = theta [Hi]/theta [Hi+], which is independent of the thylakoids internal volume. Within a large pHi range, scanned by varying the light intensity, gamma i was kept reasonably constant; it was hardly sensitive to pHi. This apparent invariability implies a continuous change of the internal buffer value beta i with pHi, since beta i/gamma i = -2.3.....10pHi, a relationship which inlcudes neither the total concentration of protonizable groups [Ai] nor pKi. As gamma i approximately Ki[Ai]/(Ki + [Hi+i]2, to keep gamma i constant when pHi drops, pKi and [Ai] must increase. This may be achieved by a progressive unmasking of anionic functions, initially inaccessible in the membrane. The relative slowness of this process may explain why gamma i calculated from the initial kinetics was sometimes smaller in high than in low light, where it always equalled that measured from the steady-state amplitude at all intensities. A small deficit of [Hi+] deduced from what could have been expected from delta pHe may reflect a limited binding of protons in the membrane itself, about 1 H+ for 30--130 chlorophylls (gamma i could be between 70 and 240, more frequently around 100); these numbers varied depending on the samples, but were constant for a given preparation.
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Elema RP, Michels PA, Konings WN. Response of 9-aminoacridine fluorescence to transmembrane pH-gradients in chromatophores from Rhodopseudomonas sphaeroides. EUROPEAN JOURNAL OF BIOCHEMISTRY 1978; 92:381-7. [PMID: 33044 DOI: 10.1111/j.1432-1033.1978.tb12757.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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36
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Dell'Antone P, Cusinato O, Volpato O. Mechanism of acridine uptake by submitochondrial particles. Arch Biochem Biophys 1978; 191:413-25. [PMID: 33593 DOI: 10.1016/0003-9861(78)90379-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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37
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Kerber NL, Pucheu NL, García AF. PMS photo-inhibition in Rhodospirillum rubrum membranes in the presence of permeant entities affecting either the deltapsi or the deltapH components of the protonmotive force. FEBS Lett 1978; 94:265-8. [PMID: 29789 DOI: 10.1016/0014-5793(78)80952-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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38
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Kano K, Fendler JH. Pyranine as a sensitive pH probe for liposome interiors and surfaces. pH gradients across phospholipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 509:289-99. [PMID: 26400 DOI: 10.1016/0005-2736(78)90048-2] [Citation(s) in RCA: 274] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pyranine is shown to be a convenient and sensitive probe for reporting pH values, pHi, at the interior of anionic and at the outer surface of cationic liposomes. It is well shielded from the phospholipid headgroups by water molecules in the interior of anionic liposomes, but it is bound to the surface of cationic liposomes. Hydrogen ion concentrations outside the liposomes, 'bulk pH values', pHo, were measured by a combination electrode. While pHi = pHo for neutral, pHi less than pHo for anionic and pHi greater than pHo for cationic liposomes prepared in 5.0 . 10(-3) M phosphate buffers. pKa values for the ionization of pyranine were 7.22 +/- 0.04 and 6.00 +/- 0.05 in water and at the external surface of cationic liposomes. The surface potential for cationic liposomes containing dipalmitoyl-DL-alpha-phosphatidylcholine, cholesterol and octadecylamine in the molar ratio of 1.00 : 0.634 : 1.01, were calcuated to be +72.2 mV. Proton permeabilities were measured for single and multicompartment anionic liposomes. Transfer of anionic liposomes prepared at a given pH to a solution of different pH resulted in a pH gradient if sodium phosphate or borate were used as buffers. In the presence of sodium acetate proton equilibration is promptly established.
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Searle GF, Barber J. The involvement of the electrical double layer in the quenching of 9-aminoacridine fluorescence by negatively charged surfaces. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 502:309-20. [PMID: 26393 DOI: 10.1016/0005-2728(78)90052-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The addition of 9-aminoacridine monohydrochloride to carboxymethyl-cellulose particles or azolectin liposomes suspended in a low cation medium results in a quenching of its fluorescence. This quenching can be released on the addition of cations. The effectiveness of cations is related only to their valency in the series of salts tested, being monovalent less than divalent less than trivalent, and is independent of the associated anions. These results indicate an electrical rather than a chemical effect, and the relative effectiveness of the various cations can be predicted by the application of classical electrical double layer theory. Fluorescence quenching can also be released on protonation of the fixed negatively charged ionisable groups, and the quenching release curve follows the ionisation curve of these groups. We postulate that when 9-aminoacridine molecules are in the electrical diffuse layer adjacent to the charged surface their fluorescence is quenched, probably due to aggregate formation. As cations are added the 9-aminoacridine concentration at the surface falls as it is displaced into the bulk solution, where it shows a high fluorescence yield with a fluorescence lifetime of 16.3 ns. The fluorescence quenching is associated with an absorbance decrease, which is pronounced with carboxymethyl-cellulose particles and can probably be attributed to self-shielding. The negative charges carried by lipoprotein membranes are primarily due to carboxyl and phosphate groups. Therefore these results with carboxymethyl-cellulose (carboxyl) and azolectin (phosphate) support our earlier suggestion that 9-aminoacridine may be used to probe the electrical double layer associated with negatively charged biological membranes.
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40
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Kell DB, Ferguson SJ, John P. Measurement by a flow dialysis technique of the steady-state proton-motive force in chromatophores from Rhodospirillum rubrum. Comparison with phosphorylation potential. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 502:111-26. [PMID: 416847 DOI: 10.1016/0005-2728(78)90136-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
1. In the light a transmembrane electrical potential of 100 mV has been estimated to occur in chromatophores from Rhodospirillum rubrum. The potential was determined by measuring the steady-state distribution of the permeant SCN- across the chromatophore membrane using a flow dialysis technique. The potential was not observed in the dark, nor in the presence of antimycin. It was dissipated on the addition of carbonyl cyanide p-trifluoromethoxyphenylhydrazone. The potential was reduced by between 15 and 20 mV when ADP and Pi were added. Hydrolysis of ATP by the chromatophores generated a membrane potential of about 80 mV. 2. Using a flow dialysis technique light-dependent uptake of methylamine was observed only in the presence of concentrations of SCN- that were 500-fold higher than were used to measure the membrane potential. It is concluded that the pH gradient across the illuminated chromatophore membrane is insignificant except in the presence of relatively high concentrations of a permeant anion like thiocyanate. Further evidence that a negligible pH gradient was generated by the chromatophores is that addition of K+ and nigericin to illuminated chromatophores did not stimulate uptake of SCN-. 3. In the light of chromatophores established and maintained a phosphorylation potential of up to 14 kcal/mol. If a phosphorylation potential of this magnitude is to be poised against a proton-motive force that comprises solely a membrane potential of approx. 100 mV, then at least five protons must be translocated for each ATP synthesised via a chemiosmotic mechanism.
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41
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Michels PA, Konings WN. The electrochemical proton gradient generated by light in membrane vesicles and chromatophores from Rhodopseudomonas sphaeroides. EUROPEAN JOURNAL OF BIOCHEMISTRY 1978; 85:147-55. [PMID: 25184 DOI: 10.1111/j.1432-1033.1978.tb12222.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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42
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Azzone GF, Pozzan T, Viola E, Arslan P. Proton electrochemical gradient and phosphate potential in submitochondrial particles. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 501:317-29. [PMID: 23158 DOI: 10.1016/0005-2728(78)90037-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The aerobic uptake of inorganic ions, such as 86Rb+ or 125I-, by submitochondrial particles, is about one order of magnitude lower than the uptake of organic ions, such as acridines or 8-anilino-1-naphthalene sulphonate. The values of deltapH, the transmembrane pH differential, and deltapsi, the transmembrane membrane potential are between 60 and 100 mV when calculated on the inorganic ions and between 150 and 240 mV when calculated on the organic ions. The discrepancy between the deltapH and deltapsi values from organic and inorganic ions is large at high but not at low ion/protein ratios. 2. In the absence of weak bases and strong acids the values of deltamuH, the proton electrochemical potential difference, are close to 100 mV and the magnitude of deltapH and deltapsi are similar. Weak bases decrease deltapH and enhance deltapsi. Strong acids decrease deltapsi and enhance deltapH. Interchangeability of deltapH with deltapsi occurs at low concentrations of weak bases and strong acids. High concentrations of weak bases and strong acids cause depression of deltamuH. 3. Concentrations of weak bases capable of abolishing deltapH, do not affect ATP synthesis. Concentrations of strong acids capable of abolishing deltapsi affect only slightly ATP synthesis. Concentrations of weak bases and strong acids capable of causing a decline of deltapH + deltapsi inhibit ATP synthesis. 4. Depression of deltamuH is paralleled by inhibition of ATP synthesis and decline of deltaGp, the phosphate potential. Abolition of ATP synthesis occurs only when deltamuH is below 20 mV. The deltaGp/deltamuH ratio increases hyperbolically with the decrease of deltamuH.
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Madeira VM. Proton gradient formation during transport of Ca2+ by sarcoplasmic reticulum. Arch Biochem Biophys 1978; 185:316-25. [PMID: 24412 DOI: 10.1016/0003-9861(78)90173-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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44
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45
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Dell'Antone P, Volpato O. H+ gradient in submitochondrial particles generated by an electroneutral H+/Mn2+ exchange. FEBS Lett 1977; 81:243-8. [PMID: 21812 DOI: 10.1016/0014-5793(77)80527-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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46
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Searle GF, Barber J, Mills JD. 9-amino-acridine as a probe of the electrical double layer associated with the chloroplast thylakoid membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1977; 461:413-25. [PMID: 20138 DOI: 10.1016/0005-2728(77)90230-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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47
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Baccarini Melandri A, Casadio R, Melandri BA. Thermodynamics and kinetics of photophosphorylation in bacterial chromatophores and their relation with the transmembrane electrochemical potential difference of protons. EUROPEAN JOURNAL OF BIOCHEMISTRY 1977; 78:389-402. [PMID: 913405 DOI: 10.1111/j.1432-1033.1977.tb11751.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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48
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Takamiya K, Dutton PL. The influence of transmembrane potentials of the redox equilibrium between cytochrome c2 and the reaction center in Rhodopseudomonas sphaeroides chromatophores. FEBS Lett 1977; 80:279-84. [PMID: 196931 DOI: 10.1016/0014-5793(77)80457-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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49
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Tillberg JE, Giersch C, Heber U. CO2 reduction by intact chloroplasts under a diminished proton gradient. BIOCHIMICA ET BIOPHYSICA ACTA 1977; 461:31-47. [PMID: 18173 DOI: 10.1016/0005-2728(77)90067-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
9-Aminoacridine has been used to monitor the intrathylakoid pH of photosynthetically competent intact chloroplasts. Values obtained from 9-aminoacridine accumulation in the chloroplasts must be corrected for light-dependent binding of 9-aminoacridine to the thylakoid membranes. During nitrite reduction by intact chloroplasts, the intrathylakoid proton concentration increased. It decreased somewhat during CO2 reduction. However, low concentrations of uncoupling amines such as NH3 or cyclohexylamine, which rapidly penetrated the chloroplast envelope and decreased the intrathylakoid proton concentration, failed to reduce, and actually stimulated, rates of CO2-dependent oxygen evolution even under rate-limiting light. In contrast, low concentrations of carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) OR NIGERICIN, WHICH INHIBITED CO2 reduction, even appeared to increase the intrathylakoid proton concentration. As indicated by measurements of the 515 nm signal of the chloroplasts, the light-induced membrane potential was not much affected by low concentrations of the uncoupling amines, but was decreased by FCCP and by high concentrations of the amines. Even in the presence of high concentrations of NH4C1, ATP/ADP ratios of illuminated chloroplasts remained far above the ratios observed in the dark. In contrast, low concentrations of FCCP were sufficient to reduce ATP/ADP ratios to the dark value even under high intensity illumination. The observations are difficult to explain within the framework of the chemiosmotic hypothesis as presently discussed.
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Casadio R, Melandri BA. The behavior of 9-aminoacridine as an indicator of transmembrane pH difference in liposomes of natural bacterial phospholipids. J Bioenerg Biomembr 1977; 9:17-29. [PMID: 18457 DOI: 10.1007/bf00745040] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The behavior of 9-aminoacridine as an indicator of pH differences artificially set across a membrane has been reexamined in liposomes prepared from bacterial phospholipids extracted from chromatophores of Rhodopseudomonas capsulata grown photoheterotrophically. The dye behaves as an ideal indicator for pH differences lower than about three units; at higher pH's the expected linear dependence of Q/(100-Q) vs. pH is no longer strictly observed. Similarly a linear dependence upon the volume of the liposomes added has been verified. The amine ceases to respond to pH changes when the pH of the external medium exceeds the value of 10, corresponsing to the pKa of 9-aminoacridine. The apparent volume of the inner phase of liposomes, as calculated from fluorescence quenching, but not the slope of dependence of fluorescence on pH, appears to be affected by several factors, including the ionic composition, the osmolarity of the external medium, and the microscopic structure of the liposomes. Millimolar concentrations of earth-alkaline cations diminish the apparent internal volume of liposomes, in agreement with the complexing effect of these ions on phospholipid bilayers. The osmotic response of the apparent inner volume has also been verified; this parameter decreases linearly with the reciprocal of the external osmolarity, as expected from the van't Hoff relation; an osmolarity exceeding 0.3 M is, however, necessary in order to observe this effect.
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