Ubiquinone and photochemical activity in Rhodospirillum rubrum.

Abstract— An analytical procedure was developed for quantitatively determining the ubiquinone content of bacterial photosynthetic material. High sensitivity was obtained by supplementing growth media with¹⁴C-labelled p-hydroxybenzoic acid which was specifically incorporated into the benzoquinones, ubiquinone and rhodoquinone. Sufficiently radioactive p-hydroxybenzoic acid was used so that 10 picomoles of ubiquinone could be quantitatively measured. High accuracy was obtained by using a carrier technique which was employed during the extraction and isolation of quinones for analyses. Purification of quinones was achieved by selective solvent extraction and thin layer chromatography in two different solvent systems. This analytical procedure was employed to determine the ubiquinone content of R. rubrum chromatophores following hydrocarbon solvent extraction to remove ubiquinone from the chromatophores. Ubiquinone was found to exist in at least two pools: a loosely bound pool which easily extracted with hydrocarbon solvents, and a tightly bound pool which required addition of some polar solvent for its removal. It was demonstrated that ubiquinone would not exchange readily between these two pools. Careful analyses of all protein fractions showed that less than 0.06 ubiquinone per primary electron donor unit (P865) could be covalently bound to these components. From the average of a number of measurements, the tightly bound ubiquinone was determined as very nearly one-half ubiquinone per phototrap (0.48 ± 0.05 S.D.). Removal of the tightly bound ubiquinone was linearly related to the loss of primary photochemical capacity. These results are consistent with the ‘duplex model’ for primary photochemical events but would seem to rule out an iron-ubiquinone complex where the ubiquinone can function only between the semiquinone and the fully oxidized oxidation state.     

Bakteriochlorophyll aGg und Bakteriophäophytin aP in den photosynthetischen Reaktionszentren von rhodospirillum rubrum G-9+

Bacteriochlorophyll a_Gg and Bacteriopheophytin a_p in Photosynthetic Reaction Centers from Rhodospirillum rubrum G-9⁺ In photosynthetically active reaction centers from Rhodospirillum rubrum G-9⁺, the magnesium complex bacteriochlorophyll a contains geranylgeraniol as the alcohol component, while the metal-free bacteriopheophytin a contains phytol instead. These pigments bacteriochlorophyll a_Gg ( 4 ) and bacteriopheophytin a_P ( 1 ) were isolated from reaction center preparations in a ratio of 2:1 and (after demetallation of 4 ) identified as bacteriopheophytin a_Gg ( 2 ), and a_P ( 1 ) by comparison with authentic samples (UV./VIS., CD. and mass spectra as well as mixed HPLC.).     

COMPLEX CHARGE RECOMBINATION KINETICS OF THE PHOTOTRAP IN RHODOSPIRILLUM RUBRUM*

Abstract— The dark decay kinetics of excited phototraps in chromatophores prepared from Rhodospirillum rubrum have been quantitatively measured under two different conditions where a direct return of the electron(s) from ubiquinone to the primary donor bacteriochlorophyll cation radical is expected. One of these experimental conditions was with a frozen sample (whole cells, chromatophores, and extracted chromatophores) at 77 K, while the other was a room temperature measurement of a sample of chromatophores from which the loosely bound ubiquinone was first removed by extraction with organic solvents. Results with the latter system were also compared to those obtained with chromatophores plus 1 mM o-phenanthroline. In all cases the kinetics of charge recombination were not pseudo-first order but showed a biphasic pattern. The data at low temperature could be exactly fit by assuming that two major pseudo-first order processes were occurring with half times of 6.5 and 19 ms, 22% decaying by the faster process and 78% by the slower process. Both types of experiments at room temperature could also be fit by assuming two major pseudo-first order processes were occurring, but with somewhat slower half times, 22 and 59 ms. In this case, 20% decayed by the faster process and 80% by the slower process. An equation was developed to fit the data assuming that one ubiquinone molecule was the electron acceptor for two donor units (the duplex model), the dark decay thus taking place in two sequential steps with 50% of the oxidized donor units becoming reduced in each step. The experimental data could be exactly fit using this equation and the above parameters. The data are viewed as best supporting the duplex model for explaining primary photochemical events in these bacteria.     

A COMPARISON OF DECAY KINETICS OF PHOTO-PRODUCED ABSORBANCE,EPR, AND LUMINESCENCE CHANGES IN CHROMATOPHORES OF RHODOSPIRRILLUM RUBRUM*

–Quantitative comparison of the decay rate for absorbance photochanges in chromatophores of R. rubrum at the major wavelengths of peaks and troughs (280, 365, 385, 433, 605, 763, 790, 810, 850, 865, 890 nm) reveal no major differences under a variety of sample conditions. In addition, the decay kinetics of EPR phtochange at the two environmental potentials used in this study are identical with the absorbance ph;otochange decay. Decay curves for fresh chromatophores, aged chromatophores, and fresh chromatophores at high ionic strength display a variety of half times and curve shapes. All of these data however, may be fit (within 10 per cent) by the equation x=αe^8.2t+βe^0.18t by merely varying the values of α and β. This is interpreted as meaning that any single trapping site may exist in one of two major forms each of which decays following a first order or pseudo-first order reaction. Although the change in decay pattern upon aging is not reversible, that due to high ionic strength is. The time dependencies for two light emission phenomena have been measured as well as their response to the oxidation state of molecules at the trapping site. A major component of long-lived luminescence follows pseudo-second order kinetics with a half time of 38 msec. A very long lived luminescence shows an increse with time which is nearly proportional to the decay of absorbance photochanges.     

Near‐IR Absorbing Solar Cell Sensitized With Bacterial Photosynthetic Membranes

Current interest in natural photosynthesis as a blueprint for solar energy conversion has led to the development of a biohybrid photovoltaic cell in which bacterial photosynthetic membrane vesicles (chromatophores) have been adsorbed to a gold electrode surface in conjunction with biological electrolytes (quinone [Q] and cytochrome c; Magis et al. [2010] Biochim. Biophys. Acta 1798 , 637–645). Since light‐driven current generation was dependent on an open circuit potential, we have tested whether this external potential could be replaced in an appropriately designed dye‐sensitized solar cell (DSSC). Herein, we show that a DSSC system in which the organic light‐harvesting dye is replaced by robust chromatophores from Rhodospirillum rubrum, together with Q and cytochrome c as electrolytes, provides band energies between consecutive interfaces that facilitate a unidirectional flow of electrons. Solar I–V testing revealed a relatively high I _sc (short‐circuit current) of 25 μA cm^?2 and the cell was capable of generating a current utilizing abundant near‐IR photons (maximum at ca 880 nm) with greater than eight‐fold higher energy conversion efficiency than white light. These studies represent a powerful demonstration of the photoexcitation properties of a biological system in a closed solid‐state device and its successful implementation in a functioning solar cell.     

Ubiquinone‐Rhodol (UQ‐Rh) for Fluorescence Imaging of NAD(P)H through Intracellular Activation

The nicotinamide adenine dinucleotide (NAD) derivatives NADH and NADPH are critical components of cellular energy metabolism and operate as electron carriers. A novel fluorescent ubiquinone‐rhodol derivative (UQ‐Rh) was developed as a probe for NAD(P)H. By using the artificial promoter [(η⁵‐C₅Me₅)Ir(phen)(H₂O)]²⁺, intracellular activation and imaging of NAD(P)H were successfully demonstrated. In contrast to bioorthogonal chemistry, this “bioparallel chemistry” approach involves interactions with native biological processes and could potentially be used to control or investigate cellular systems.     

Performance of trickle-bed bioreactors for converting synthesis gas to methane

Carbon monoxide, H₂, and CO₂ in synthesis gas can be converted to CH₄ by employing a triculture ofRhodospirillum rubrum, Methanosarcina barken, andMethanobacterium formicicum. Trickle-bed reactors have been found to be effective for this conversion because of their high mass-transfer coefficients. This paper compares results obtained for the conversion of synthesis gas to CH₄ in 5-cm- and 16.5-cm-diameter trickle-bed reactors. Mass-transfer and scale-up parameters are defined, and light requirements forR. rubrum are considered in bioreactor design.

     

Fluorometric determination of <Emphasis Type="Italic">Vibrio parahaemolyticus</Emphasis> using an F<Subscript>0</Subscript>F<Subscript>1</Subscript>-ATPase-based aptamer and labeled chromatophores

An F₀F₁-ATPase-based aptasensor is described for the fluorometric determination of Vibrio parahaemolyticus. Chromatophores containing F₀F₁-ATPases were first prepared from Rhodospirillum rubrum cells. Then, an aptamer-functionalized chromatophore acts as the capture probe, and a chromatophore labeled with the pH probe fluorescein acts as the signalling probe. In the presence of V. parahaemolyticus, the rotation rate of F₀F₁-ATPase is decreased due to the formation of the aptamer-chromatophore complex. This leads to a retarded proton flux out of the chromatophores. As a result, the pH value inside the chromatophores is reduced, and the fluorescence of the pH probe F1300 is accordingly decreased. The relative fluorescence varies linearly over the 15 to 1.5?×?10⁶ cfu·mL^?1 Vibrio parahaemolyticus concentration range, and the limit of detection is 15 cfu·mL^?1. The method was applied to analyze artificially contaminated salmon samples where it showed excellent perfomance.

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Graphical abstract In this assay, aptamer functionalized chromatophores act as a capture probe, and the fluoresce in labeled chromatophores as signalling probe. The formation of aptamer-chromatophore complex leads to a retarded proton flux out of the chromatophores. As a result, the pH value inside the chromatophores is reduced, and fluorescence intensity is accordingly decreased.

     

Identification of the Active Sites on Metallic MoO2−x Nano-Sea-Urchin for Atmospheric CO2 Photoreduction Under UV,Visible, and Near-Infrared Light Illumination

We report an oxygen vacancy (V_o)-rich metallic MoO_2−x nano-sea-urchin with partially occupied band, which exhibits super CO₂ (even directly from the air) photoreduction performance under UV, visible and near-infrared (NIR) light illumination. The V_o-rich MoO_2−x nano-sea-urchin displays a CH₄ evolution rate of 12.2 and 5.8 μmol g_catalyst⁻¹ h⁻¹ under full spectrum and NIR light illumination in concentrated CO₂, which is ca. 7- and 10-fold higher than the V_o-poor MoO_2−x, respectively. More interestingly, the as-developed V_o-rich MoO_2−x nano-sea-urchin can even reduce CO₂ directly from the air with a CO evolution rate of 6.5 μmol g_catalyst⁻¹ h⁻¹ under NIR light illumination. Experiments together with theoretical calculations demonstrate that the oxygen vacancy in MoO_2−x can facilitate CO₂ adsorption/activation to generate *COOH as well as the subsequent protonation of *CO towards the formation of CH₄ because of the formation of a highly stable Mo−C−O−Mo intermediate.     

Voltammetric Probing of Molecular Assemblies of Ubiquinone-10 at the Air–Water Interfaces

The redox properties of ubiquinone 10 (UQ10) placed at the air–water interface were studied using the horizontal touching method with a thin mercury film (TMFE) working electrode and cyclic voltammetry. Changes of pH of the subphase affected the formal potential of the ubiquinone/ubiquinol system exhibiting the participation of protons in the overall reduction of UQ10. The protonation of the semiquinone transition product was found to be the rate determining step. This explains the dependence of the rate constant value on pH. The highest values of rate constants were found at pH over 13. Under these conditions the mechanism of the process is different. The concentration of protons is small, and the availability of the counter ions (i.e., K⁺) becomes crucial for the kinetics of reduction. Their role is to neutralize the negative charge of the redox group following its reduction. The logarithm of rate constants was found to decrease linearly with the increase of surface concentration of ubiquinone. This reflects the influence of intermolecular interactions in the monolayer on the kinetics of the electrode process.     

GLOW CURVES FROM PHOTOSYNTHETIC BACTERIA*

Abstract— Cells and chromatophores of the photosynthetic bacterium Rhodopseudomonas viridis were frozen in the dark and illuminated while frozen or were illuminated during freezing. Upon being heated they emitted light. The conditions under which glow curves could be produced and the kinetics of the light emission indicate that the glows resulted from the thermal release of electrons from secondary electron acceptors and their recombination with oxidized reaction center bacteriochlorophyll b. Glow curves could not be obtained with Rhodospirillum rubrum.     

PHOTODYNAMIC ACTION OF HEMATOPORPHYRIN ON YEAST CELLS—A KINETIC APPROACH

Abstract— By a technique which combines rapid mixing of cells and hematoporphyrin (HP) with a short duration of illumination, the photodynamic inactivation of yeast cells was investigated, particularly, in seeking for the information of the location of HP at the time of action. The fluence-survival curves obtained under the conditions where the reaction mixture was kept in the dark for Is, 60s and even 35 min before illumination were indistinguishable from each other, indicating no interaction between cells and sensitizers took place in about 30 min in such a way that the photodynamic efficiency could be modified. It is unlikely that HP acted intracellularly, since the protective effect of N^?₃ was observed at concentrations as low as 0.5 mM. Furthermore, the rate constant k_p related to the protective effect of NJ, was estimated to be 1 × 10⁸M^?1 s^?1 under the assumption that ¹O₂ was the active intermediate and had a lifetime of 2 μs under the present conditions. This value of k_p is rather close to that of k_q, the quenching rate constant of N^?₃ for ¹O₂, of which the accepted value is 2 × 10⁸M^?1s^?1 in the homogeneous aqueous system. This information, together with the absence of uptake of HP by cells and a well response of survival upon illumination to the D₂O fraction of the reaction mixture, provide strong bases for the argument that direct interaction of HP with yeast cells is of minor importance in the photodynamic processes, and the photodynamic action is largely mediated by an intermediate (¹0₂) generated in bulk medium.     

SPECTROSCOPIC ANALYSIS OF BACTERIOCHLOROPHYLLS IN VITRO AND IN VIVO*

Abstract— Chromatophores from Rhodopseudonionas spheroides were treated with potassium iridic chloride so as to destroy the major complement of bacteriochlorophyll (BChl) without harming the photochemically active P870. A band at 802 mμ, attributed to a pigment P800, survived this treatment along with P870. Extraction of such chromatophores with a mixture of acetone and methanol removed the absorption bands of P800 and P870; a corresponding amount of BChl was found in the extract. The yield of BChl was too great to have been derived from either P800 or P870 alone; analysis of extinction cofficients and band areas of these pigments indicates that they are both specialized fornis of BChl, in a molecular ratio of 2P800:1P870. Bleaching of P870, without attenuation of the absorption band of P800, could be effected by adding potassium ferricyanide to the iridic chloride-treated chromatophores. Extraction of chromatophores in this condition gave a reduced yield of BChl, consistent with a 2:1 ratio of P800 to P870 under the assumption that the BChl in the extract was derived in this case from P800 alone. An absorption band at 600 mμ in iridic chloride-treated chromatophores, characteristic of BChl and ascribed to P800 and P870, is partly bleached and shifted to shoiter wavelengths upon illumination. This reversible effect, and a similar one near 375 mμ (corresponding to the Soret band maximum of BChl), has the combined attributes of the blue-shift of P800 and the bleaching of P870 seen in a spectrally resolved form near 800 and 865 mμ respectively. The 600 mμ band is bleached by about 30 per cent, again consistent with a ratio of 2P800:1P870. These data, in conjunction with information published elsewhere, support the view that two molecules of P800 and one of P870 are associated jointly with a photosynthetic reaction center. It was observed that the long wave absorption bands of BChl in vivo are sometimes narrower than the narrowest bands that have been observed for BChl in dilute organic solutions. Sharpness of these bands is most conspicuous in some forms absorbing near 800 mμ.     

Highly Converged Valence Bands and Ultralow Lattice Thermal Conductivity for High-Performance SnTe Thermoelectrics

A two-step optimization strategy is used to improve the thermoelectric performance of SnTe via modulating the electronic structure and phonon transport. The electrical transport of self-compensated SnTe (that is, Sn_1.03Te) was first optimized by Ag doping, which resulted in an optimized carrier concentration. Subsequently, Mn doping in Sn_1.03−xAg_xTe resulted in highly converged valence bands, which improved the Seebeck coefficient. The energy gap between the light and heavy hole bands, i.e. ΔE_v decreases to 0.10 eV in Sn_0.83Ag_0.03Mn_0.17Te compared to the value of 0.35 eV in pristine SnTe. As a result, a high power factor of ca. 24.8 μW cm⁻¹ K⁻² at 816 K in Sn_0.83Ag_0.03Mn_0.17Te was attained. The lattice thermal conductivity of Sn_0.83Ag_0.03Mn_0.17Te reached to an ultralow value (ca. 0.3 W m⁻¹ K⁻¹) at 865 K, owing to the formation of Ag₇Te₄ nanoprecipitates in SnTe matrix. A high thermoelectric figure of merit (z T≈1.45 at 865 K) was obtained in Sn_0.83Ag_0.03Mn_0.17Te.     

Spectroscopic properties of Nd ions in nano-perovskite CaTiO3

In this work, we present for the first time the spectroscopic properties of perovskite nanocrystals CaTiO₃: Nd³⁺, measured at room and liquid nitrogen temperature. Samples were prepared by the sol–gel method and annealed at 700 and 1000 °C. The concentration of Nd³⁺ ranged from 0.5% to 5%. Average nanocrystallite size primarily depends on the annealed temperature and is about 25 and 50 nm for 700 and 1000 °C, respectively. The absorption, emission and excitation spectra (monitored at 1078 nm) as well as the decay time profile of the emission from the ⁴F_3/2 energy level of Nd³⁺ are obtained. The increasing amount of Nd³⁺ ions decreases the lifetime of the ⁴F_3/2 level and that changes from 146 μs for 0.5% to 50 μs for 5% of Nd³⁺ concentration. The strongest emission was observed at two regions: 1050–1120 nm and 865–930 nm and was assigned to the ⁴F_3/2→⁴I_11/2 and ⁴F_3/2→⁴I_9/2 transitions, respectively. The spectroscopic quality parameter of neodymium in the CaTiO₃ lattice has been calculated from the emission spectra. The influence of luminescent properties depending on the annealing temperature and concentration of neodymium ions is discussed.     

Highly Converged Valence Bands and Ultralow Lattice Thermal Conductivity for High‐Performance SnTe Thermoelectrics

A two‐step optimization strategy is used to improve the thermoelectric performance of SnTe via modulating the electronic structure and phonon transport. The electrical transport of self‐compensated SnTe (that is, Sn_1.03Te) was first optimized by Ag doping, which resulted in an optimized carrier concentration. Subsequently, Mn doping in Sn_1.03?xAg_xTe resulted in highly converged valence bands, which improved the Seebeck coefficient. The energy gap between the light and heavy hole bands, i.e. ΔE_v decreases to 0.10 eV in Sn_0.83Ag_0.03Mn_0.17Te compared to the value of 0.35 eV in pristine SnTe. As a result, a high power factor of ca. 24.8 μW cm^?1 K^?2 at 816 K in Sn_0.83Ag_0.03Mn_0.17Te was attained. The lattice thermal conductivity of Sn_0.83Ag_0.03Mn_0.17Te reached to an ultralow value (ca. 0.3 W m^?1 K^?1) at 865 K, owing to the formation of Ag₇Te₄ nanoprecipitates in SnTe matrix. A high thermoelectric figure of merit (z T≈1.45 at 865 K) was obtained in Sn_0.83Ag_0.03Mn_0.17Te.     

ABSORPTION CHANGES IN BACTERIAL CHROMATOPHORES-II. A NEW CHLOROPHYLL-LIKE PIGMENT FROM THE OXIDATION OF CHROMATQPHORES FROM RHODOSPIRILLUM RUBRUM

Abstract— Evidence is presented which points to (at least) two bound forms of bacteriochlor-ophyll present in chromatophores of Rhodospirillum rubrum , both of them readily converted to unbound bacteriochlorophyll (abs. max 770 mμ) when the chromatophores are extracted with acetone or ethanol. Controlled oxidation of the chromatophores with Ir(IV) or with Zn (II) and ferricyanide preferentially destroys the more strongly absorbing pigment (abs. max 880 mμ) but brings about only a slight decrease in the magnitude of the photoinduced absorption changes at 810 and 792 mμ. Such oxidations yield a new pigment, absorbing at 715 mμ in the aqueous preparation and, more strongly, at 680–684 mu when the pigment is extracted into organic solvents. This pigment is formed irreversibly and is therefore different from the material formed by photooxidation of chromatophores. Its visible spectrum and the spectrum of the material formed from it by acidification suggest that it is a chlorophyll-like substance, possibly derived from bacteriochlorophyll by (two-electron) oxidation of one of the dihydropyrrole rings to a pyrrole ring. Directions are given for separation of this pigment from other colored compounds present in the oxidation mixtures.     

DEVELOPMENT OF THERMOLUMINESCENCE BANDS DURING GREENING OF WHEAT LEAVES UNDER CONTINUOUS AND INTERMITTENT ILLUMINATION

Abstract— Mature wheat leaves excited by 1-min illumination at a low temperature of -60° C showed five thermoluminescence bands at -45, -10, +25, +40 and +55° C (denoted as Z_u, A, B₁ B₂ and C bands, respectively). The development of these bands during greening of etiolated wheat leaves under continuous and intermittent illumination was investigated, and the following results were obtained. (1) Etiolated leaves showed only the C band. When these leaves were greened under continuous light, the B₁ and B₂ bands appeared at 3 h and the Z_u band appeared at 10 h. The B₁ and B₂ bands were intensified during prolonged greening under continuous illumination to be the strong bands observed for mature leaves. The A band and the group of B₁ and B₂ bands were alternative: Similar experiments by excitation of thermoluminescence at -20° C showed the development of the A band instead of these B₁ and B₁ bands. (2) When the etiolated leaves were greened under intermittent illumination (1-ms light + 5-min dark), the Z_u band first appeared after 5 h of illumination (60 flashes) and was gradually intensified during further illumination with 340 flashes but, interestingly, neither the B₁ nor the B₂ band appeared even after 24–28 h of illumination with 280–340 flashes. (3) On exposure of such leaves greened under intermittent illumination to continuous light, the B₁ and B₂ bands were rapidly developed. The appearance of these bands was accompanied by the generation of the Hill activity (DCIP photoreduction with water as electron donor). (4) These results were discussed in relation to the previous study on photoactivation of the latent water-splitting system accumulated in the leaves greened under intermittent illumination. It was deduced that the structure responsible for the A band or the group of B₁ and B₂ bands is involved in the evolution of oxygen in chloroplasts, and probably involves cations of the Mn²⁺ catalyst generated by the action of light.     

Light-dependent Oxygen Consumption in Bacteriochlorophyll-Serine-treated Melanoma Tumors: On-line Determination Using a Tissue-inserted Oxygen Microsensor

Successful application of anticancer therapy, and especially photodynamic therapy (PDT) mediated by type II (PDTII) processes, depends on the oxygen content within the tumor before, during and after treatment. The high consumption of oxygen during type II PDT imposes constraints on therapy strategies. Although rates of oxygen consumption and repletion during PDTII were suggested by theoretical studies, direct measurements have not been reported. Application of a novel oxygen sensor allowed continuous and direct in situ measurements (up to a depth of 8–9 mm from the tumor surface and for several hours) of temporal variations in the oxygen partial pressure (pO₂) during PDT. Highly pigmented M2R mouse melanoma tumors implanted in CD1 nude mice were treated with bacteriochlorophyll-serine (Bchl-Ser; a new photodynamic reagent) and were subjected to fractionated illumination (700 < λ. < 900 nm) at a fluence rate of 12 mW cm^-2. This illumination led to total oxygen depletion with an average consumption rate of 7.2 uAf(O₂) s^-1. Spontaneous reoxygenation (at an average rate of 2.5 µM(O₂)/s) was observed during the following dark period. These rates are in good agreement with theoretical considerations (Foster et al., Radiat. Res. 126, 296,1991 and Henning et al, Radiat. Res. 142, 221, 1995). The observed patterns of oxygen consumption and recovery during prolonged periods of light/dark cycles were interpreted in terms of vasculature damage and sensitizer clearance. The presented data support the previously suggested advantages of fractionated illumination for type II photodynamic processes.     

THE EFFECT OF PHOSPHORYLATION UNCOUPLERS AND ELECTRON TRANSPORT INHIBITORS UPON SPECTRAL SHIFTS AND DELAYED LIGHT EMISSION OF PHOTOSYNTHETIC BACTERIA

Abstract— Delayed light emission (measured 4 msec after excitation) and the light-induced red shifts of the bacteriochlorophyll and carotenoid absorption bands of chromatophores of Rhodopseudomonas spheroides were inhibited by a variety of reagents. These included anti-mycin A, NQNO, CCCP, desaspidin, quinacrine, chlorpromazine, 2,4-dinitrophenol, gramicidin D, Triton X-100 and valinomycin in the presence of potassium, cesium or ammonium ions. Delayed light emission was enhanced by orthophenanthroline, ethanol, succinate and glutathione.
Delayed light emission from chromatophores of Rhodospirillum rubrum was attenuated during photophosphorylation but restored approximately to its initial value in the presence of oligomycin. Since the delayed light and band shifts are inhibited under conditions which tend to deplete or block the formation of high energy phosphorylation intermediate, it is suggested that the presence of a high energy intermediate is a prerequisite for the appearance of each of the three phenomena.