Iron-sulfur centers in the photosynthetic reaction center complex fromChlorobium vibrioforme. Differences from and similarities to the iron-sulfur centers in Photosystem I

The photosynthetic reaction center complex from the green sulfur bacteriumChlorobium vibrioforme has been isolated under anaerobic conditions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveals polypeptides with apparent molecular masses of 80, 40, 30, 18, 15, and 9 kDa. The 80- and 18-kDa polypeptides are identified as the reaction center polypeptide and the secondary donor cytochromec ₅₅₁ encoded by thepscA andpscC genes, respectively. N-terminal amino acid sequences identify the 40-kDa polypeptide as the bacteriochlorophylla-protein of the baseplate (the Fenna-Matthews-Olson protein) and the 30-kDa polypeptide as the putative 2[4Fe-4S] protein encoded bypscB. Electron paramagnetic resonance (EPR) analysis shows the presence of an iron-sulfur cluster which is irreversibly photoreduced at 9K. Photoaccumulation at higher temperature shows the presence of an additional photoreduced cluster. The EPR spectra of the two iron-sulfur clusters resemble those of F_A and F_B of Photosystem I, but also show significantly differentg-values, lineshapes, and temperature and power dependencies. We suggest that the two centers are designated Center I (with calculatedg-values of 2.085, 1.898, 1.841), and Center II (with calculatedg-values of 2.083, 1.941, 1.878). The data suggest that Centers I and II are bound to thepscB polypeptide.     

Expression of pH-sensitive green fluorescent protein in Arabidopsis thaliana

This is the first report on using green fluorescent protein (GFP) as a pH reporter in plants. Proton fluxes and pH regulation play important roles in plant cellular activity and therefore, it would be extremely helpful to have a plant gene reporter system for rapid, non‐invasive visualization of intracellular pH changes. In order to develop such a system, we constructed three vectors for transient and stable transformation of plant cells with a pH‐sensitive derivative of green fluorescent protein. Using these vectors, transgenic Arabidopsis thaliana and tobacco plants were produced. Here the application of pH‐sensitive GFP technology in plants is described and, for the first time, the visualization of pH gradients between different developmental compartments in intact whole‐root tissues of A. thaliana is reported. The utility of pH‐sensitive GFP in revealing rapid, environmentally induced changes in cytoplasmic pH in roots is also demonstrated.     

Cartography and Clandestinité in Leïla Sebbar’s Shérazade: 17 ans, brune, frisée, les yeux verts

In this paper, I read Leïla Sebbar’s staging in her novel Shérazade: 17 ans, brune, frisée, les yeux verts of the resistance by children of North African and other immigrants in the early 1980s to the French state’s cartographic modes and documents of control. The paper will consider the many uses to which the map was put by the French state in its colonization of North Africa and particularly Algeria, and later in its attempts to control the banlieues its policies of citizenship and cartographic control yielded on the margins of Paris. In this context, I will explore the ways in which the novel’s characters, living clandestinely in a squatt, simultaneously resist, put to use, and even supercede state documents of control as they disrupt everyday life and conduct heists across the city of Paris. The paper will explore unofficial cartographies of Paris, from those afforded by the radios libres and alternative publications such as Libération and Sans Frontièrez, to oral and almost proverbial networks of knowledge criss-crossing the city of Paris, while also tracing the uses to which supplemental cartographic sketches and counterfeit identity cards are put in the pages of the novel. The paper will be in dialogue with theoretical and critical formulations of space, cartography, and state control put forward by Michel de Certeau, Henri Lefebvre, Michel Foucault, and Tom Conley. The paper will conclude with a consideration of the means and limits of resistance by the novel’s characters in the context of this body of theory and criticism.     

Algal Population Growth Model Integrated with Toxicokinetics for Ecological Risk Assessment under Time-Varying Pesticide Exposure

An algal population growth model integrated with toxicokinetics was developed for assessing the effect of pesticides on population dynamics. This model is a simple one-compartment, first-order kinetic model in which toxicity (growth inhibition and mortality) depends on the intracellular effective concentration of a pesticide at a target site. The model's parameters were derived using an experimental study that investigated the effects of pretilachlor, bensulfuron-methyl, pentoxazone, and quinoclamine on the growth, mortality, and subsequent population recovery of the green alga Pseudokirchneriella subcapitata. Modeled and measured trajectories of algal population dynamics agreed well. The effect on population recovery was underestimated by the model that ignored the toxicokinetics. The four tested herbicides had a variety of toxicity characteristics and physicochemical properties, indicating the wide range of the model's applicability. Moreover, the developed model and the obtained model's parameters were extrapolated to predict long-term algal population dynamics under time-varying herbicide exposure. The calculated integral biomass lost compared with the control was considered a quantitative index of the population-level ecological risk. The model's prediction showed that the same exposure level (peak concentration is equivalent to EC50) indicated much different population-level effect depending on the herbicide.     

Visualization of viral DNA assembly using nonfluorescent staining

ABSTRACT

We present an easy test for rapid visualization of viral DNA assemblies in infected cell cytoplasm. We selected the best stains for nuclear staining: Nile blue A, Bismarck brown, gallocyanin chrome alum, methyl green pyronin and azure II. None of the staining techniques is fluorescent, which facilitates their use in everyday experiments. Methyl green is most promising for routine detection of viral DNA assemblies in the cytoplasm; the procedure enables ready detection of viral DNA accumulation in the cytoplasm.     

Application of muonic X-rays for elemental analysis

Because of the large μ mass compared to the electron mass, the muonic X-rays have energies very suitable for standard γ-ray spectroscopy (Ge detectors), so every element is easily recognized. By selecting the primary μ energies appropriately any part of the specimen, also well inside, can be nondestructively investigated. On the other hand, surface layers may be analyzed. Accuracies of quantitative analyses are 1% of the atomic abundance of the element in question in favorite cases. Results on applications in nuclear medicine and surface physics are presented, and ways of improving the muon flux density are discussed.     

Uptake and metabolism of taurine in the green alga Chlorella fusca

Taurine entered the alga Chlorella fusca Shihira et Krauss strain 21l-8b via a pH and energy-dependent system ("permease"). Transport followed triphasic kinetics from 10⁻⁶ to 10⁻² M with K_m values for taurine of 5.4 × 10⁻⁵, 4.1 × l0⁻⁴ and l.5 × 10⁻³ M. This uptake system was specific for sulfonic acids and showed no affinity for α- and β -amino acids or Na⁺; thus the permease of C. fusca is different from all known taurine transport systems with respect to structural specificity and lack of Na⁺ -dependence. Uptake was not observed in sulfate-grown algae but developed as a response to sulfate limitation within 2 h. Sulfate addition caused a rapid decline in taurine transport capacity. Labeled taurine was rapidly metabolized in C. fusca to sulfate and ethanolamine, suggesting oxidative hydrolysis as the mechanism of C-S bond cleavage. Further incorporation of these catabolic products in C - and S -metabolism was demonstrated. Taurine catabolism was also detected in other green algae and some cyanobacteria.