Photoaffinity labeling of the azidoatrazine receptor site in reaction centers of Rhodopseudomonas sphaeroides

AbstractPhotoaffinity labeling of photosynthetic reaction centers of Rhodopseudomonas sphaeroides by the herbicide inhibitor, azido[14C]atrazine, occurs principally on the L-subunit. The specificity of labeling is greater at 77 than at 295 K. Kinetic studies of charge recombination in reaction centers indicate competition between azidoatrazine and ubiquinone-1 (Q-1) for binding to the reaction center. This competition occurs through the L-subunit binding site, as increasing concentrations of Q-1 decrease azido[14C]atrazine labeling of this site. It is proposed that the inhibitor binding site, predominantly on the L-subunit, and the secondary quinone binding site on the M-subunit, are adjacent so that there is partial overlap by one molecule of the domain occupied by the other

Le poète contemporain face à ses « frères »

Dans le contexte d’un retour massif de la notion de « fraternité » dans le discours contemporain, cet article examine deux ouvrages récents relevant d’une nouvelle « littérature fraternitaire » : Le Mot frère, de Stéphane Bouquet (2005) et Frères migrants, de Patrick Chamoiseau (2017). Nous analysons d’abord la façon dont ces textes mettent en place un dispositif d’accueil du plus vulnérable, par leur système poétique et énonciatif. Ensuite, nous observons la façon dont le vocabulaire spécifique de la fraternité, avec ses ambiguïtés, est déployé dans chacun de ces textes, avant d’évoquer les limites de cette fraternité par l’écriture, aussi bien dans le rapport de ces textes à l’action politique proprement dite que dans les apories énonciatives qu’on y rencontre.In the context of a massive return of the concept of "fraternity" in contemporary discourse, this article examines two recent works pertaining to a new "fraternitarian literature" : Le Mot frère, by Stéphane Bouquet (2005) and Frères migrants, by Patrick Chamoiseau (2017). We first analyze how these texts set up a welcoming mechanism for the most vulnerable, by their poetic and enunciative system. Then, we observe the way in which the specific vocabulary of fraternity, with its ambiguities, is deployed in each of these texts, before evoking the limits of this fraternity by writing, in its relation to the political action per se as well as in the enunciative aporias that one meets in these texts

AUGMENTATION DES RÉSERVES DE CAPACITÉ DU MÉTRO M1 DES TL

Le métro m1 des Transports lausannois (tl) est l’axe principal de transports publics de l’Ouest-Lausannois desservant notamment les Hautes Écoles depuis le centre de Lausanne et depuis la Gare de Renens. Construit en 1991, il a contribué à la transformation de ce district limitrophe, industriel en un territoire dynamique qui monte aujourd’hui en puissance. Le parc de matériel roulant datant de 1991 et 1995 achève cet été de 2018 sa maintenance de mi-vie. Si l’on peut escompter une quinzaine d’années supplémentaires de service, il est temps de mener une réflexion sur l’avenir du m1 afin d’aboutir à un projet rationnel, défendable et exécutable à l’horizon charnière 2035. Si cet horizon présente une opportunité de changer complètement de paradigme et si des idées fusent pour une métamorphose de la ligne en un autre moyen de transport, cette étude recherche des leviers d’absorption de la demande afin de pérenniser le système actuel. En effet, la demande sur le m1 ne cesse d’augmenter avec une progression attendue de vingt à quarante pourcents à l’horizon 2035. Ce rapport analyse et combine trois leviers différents pour évaluer les réserves de capacité supplémentaires réalisables jusqu’à cet horizon mais aussi à long-terme. L’implémentation de ces moyens d’action ainsi que les conséquences contingentes ont également été étudiées

A dedicated haem lyase is required for the maturation of a novel bacterial cytochrome c with unconventional covalent haem binding

In bacterial c-type cytochromes, the haem cofactor is covalently attached via two cysteine residues organized in a haem c-binding motif. Here, a novel octa-haem c protein, MccA, is described that contains only seven conventional haem c-binding motifs (CXXCH), in addition to several single cysteine residues and a conserved CH signature. Mass spectrometric analysis of purified MccA from Wolinella succinogenes suggests that two of the single cysteine residues are actually part of an unprecedented CX15CH sequence involved in haem c binding. Spectroscopic characterization of MccA identified an unusual high-potential haem c with a red-shifted absorption maximum, not unlike that of certain eukaryotic cytochromes c that exceptionally bind haem via only one thioether bridge. A haem lyase gene was found to be specifically required for the maturation of MccA in W. succinogenes. Equivalent haem lyase-encoding genes belonging to either the bacterial cytochrome c biogenesis system I or II are present in the vicinity of every known mccA gene suggesting a dedicated cytochrome c maturation pathway. The results necessitate reconsideration of computer-based prediction of putative haem c-binding motifs in bacterial proteomes

Biogenesis of cytochrome b6 in photosynthetic membranes

In chloroplasts, binding of a c′-heme to cytochrome b6 on the stromal side of the thylakoid membranes requires a specific mechanism distinct from the one at work for c-heme binding to cytochromes f and c6 on the lumenal side of membranes. Here, we show that the major protein components of this pathway, the CCBs, are bona fide transmembrane proteins. We demonstrate their association in a series of hetero-oligomeric complexes, some of which interact transiently with cytochrome b6 in the process of heme delivery to the apoprotein. In addition, we provide preliminary evidence for functional assembly of cytochrome b6f complexes even in the absence of c′-heme binding to cytochrome b6. Finally, we present a sequential model for apo- to holo-cytochrome b6 maturation integrated within the assembly pathway of b6f complexes in the thylakoid membranes

Formation of Flavanol-aldehyde Adducts in Barrel-aged White Wine – Possible Contribution of These Products to Colour

This paper describes the formation and diversity of new compounds resulting from the polymerisation of furanic andphenolic flavanol-aldehydes with HPLC‑DAD and LC‑ES/MS analysis. Polymerisation, resulting from nucleophilicreactions, formed dimers, trimers, soluble and insoluble polymers. Reactions in hydroalcoholic solution with purealdehydes (phenolic and furanic) and flavanols (catechin) were studied. The study was repeated with differentaldehydes in white wine. This research focused particularly on the colour properties of the released products and theirpotential impact on the colour of white wine. Some products were purified and isolated; these were mainly catechinfurfuraldehyde,catechin-methyl-5-furfuraldehyde, catechin-hydroxymethyl-furfuraldehyde,catechin-vanillin, andcatechin-syringaldehyde dimers. The most powerful coloured products resulted from furanic aldehydes. Over thecourse of the experiment, the reaction produced dimers, trimers and oligomers. After 50 to 60 days, the colour of thesolution was mainly due to soluble polymeric forms. In addition, the role of SO2, generally used during vinificationand ageing, was studied. The influence of SO2 on the kinetics of the reaction was limited