Antifouling bastadin congeners target blue mussel phenoloxidase and complex copper(II) ions

Synthetically prepared congeners of spongederived bastadin derivatives such as 5,5'-dibromohemibastadin- 1 (DBHB) that suppress the settling of barnacle larvae were identified in this study as strong inhibitors of blue mussel phenoloxidase that is involved in the firm attachment of mussels to a given substrate. The IC50 value of DBHB as the most active enzyme inhibitor encountered in this study amounts to 0.84 mu M. Inhibition of phenoloxidase by DBHB is likely due to complexation of copper(II) ions from the catalytic centre of the enzyme by the a-oxo-oxime moiety of the compound as shown here for the first time by structure activity studies and by X-ray structure determination of a copper(II) complex of DBHB.Biotechnology & Applied MicrobiologyMarine & Freshwater BiologySCI(E)EI0ARTICLE61148-11581

Dipolar atomic spin ensembles in a double-well potential

We experimentally study the spin dynamics of mesoscopic ensembles of ultracold magnetic spin-3 atoms located in two separated wells of an optical dipole trap. We use a radio-frequency sweep to selectively flip the spin of the atoms in one of the wells, which produces two separated spin domains of opposite polarization. We observe that these engineered spin domains are metastable with respect to the long-range magnetic dipolar interactions between the two ensembles. The absence of inter-cloud dipolar spin-exchange processes reveals a classical behavior, in contrast to previous results with atoms loaded in an optical lattice. When we merge the two subsystems, we observe spin-exchange dynamics due to contact interactions which enable the first determination of the s-wave scattering length of 52Cr atoms in the S=0 molecular channel a_0=13.5^{+11}_{-10.5}a_B (where a_B is the Bohr radius).Comment: 9 pages, 7 figure

Proton-transfer pathways in the mitochondrial S. cerevisiae cytochrome c oxidase

In cytochrome c oxidase (CytcO) reduction of O2 to water is linked to uptake of eight protons from the negative side of the membrane: four are substrate protons used to form water and four are pumped across the membrane. In bacterial oxidases, the substrate protons are taken up through the K and the D proton pathways, while the pumped protons are transferred through the D pathway. On the basis of studies with CytcO isolated from bovine heart mitochondria, it was suggested that in mitochondrial CytcOs the pumped protons are transferred though a third proton pathway, the H pathway, rather than through the D pathway. Here, we studied these reactions in S. cerevisiae CytcO, which serves as a model of the mammalian counterpart. We analyzed the effect of mutations in the D (Asn99Asp and Ile67Asn) and H pathways (Ser382Ala and Ser458Ala) and investigated the kinetics of electron and proton transfer during the reaction of the reduced CytcO with O2. No effects were observed with the H pathway variants while in the D pathway variants the functional effects were similar to those observed with the R. sphaeroides CytcO. The data indicate that the S. cerevisiae CytcO uses the D pathway for proton uptake and presumably also for proton pumping

A common coupling mechanism for A-type heme-copper oxidases from bacteria to mitochondria

Mitochondria metabolise almost all of the oxygen that we consume, reducing it to water by cytochrome c oxidase (CcO). CcO maximises energy capture into the protonmotive force by pumping protons across the mitochondrial inner membrane. Forty years after the H+/e- stoichiometry was established, a consensus has yet to be reached on the route taken by pumped protons to traverse CcO’s hydrophobic core and on whether bacterial and mitochondrial CcOs operate via the same coupling mechanism. To resolve this, we exploited the unique amenability to mitochondrial DNA mutagenesis of the yeast S. cerevisiae to introduce single point mutations in the hydrophilic pathways of CcO to test function. From ADP/O ratio measurements on preparations of intact mitochondria, we definitely established that the D-channel, and not the H-channel, is the proton pump of the yeast mitochondrial enzyme, supporting an identical coupling mechanism in all forms of the enzyme

Ecological monitoring of coral reefs in IFRECOR survey sites in Martinique between 2001 and 2006

Monitoring of coral reefs in Martinique started in 2001, after the first permanent IFRECOR survey site was created in the island. Four permanent transects of 60 m long are sampled twice a year during the dry and the wet season in the area. Benthic community cover and fish assemblages are assessed using scuba diving techniques. The benthic communities composition remained stable, while already degraded, until end 2005 with average coral cover values of 38.7 % over the Southern reef sites and 22.9 % on the Atlantic coast. The major bleaching event during the second semester of the year 2005 killed about 14 % of the coral colonies in Martinique. Beginning 2006, a disease outbreak also killed another 15 % of the corals, with signifi cant differences between species. Globally, although coral reef decline had started before these events, an average of 30 % of the coral reefs of Martinique disappeared during the past 2 years. Thereby, there was a decrease in the average coral cover down to 32.9 % (South Caribbean) and 14.8 % (Atlantic). No effect has been recorded yet on coral reef fi sh assemblages in terms of total biodiversity, individuals and biomass. Global climate change and anthropogenic pressures are principally involved in the coral reef ecological status in Martinique. Regional MPAs projects are under review and could be an environmental issue for coral reef protection and preservation in the futureLes récifs coralliens de Martinique font l'objet d'un suivi scientifique depuis 2001, date de création de la première station de référence IFRECOR dans le département. Progressivement 4 stations ont été mises en place sous la forme de transects permanents d'une longueur de 60 m et sont échantillonnées chaque année au cours des saisons sèche et humide. Le recouvrement par les communautés benthiques ainsi que la structure des peuplements ichtyologiques sont évalués à partir d'un protocole d'observation en plongée. Les communautés, bien que déjà dégradées, présentaient une stabilité relative jusque fin 2005, avec un taux de couverture moyen de 38,7 % du fond pour les sites coralliens du sud Caraïbe à 22,9 % sur la côte atlantique. L'épisode de blanchissement qui a touché l'ensemble de la Caraïbe au second semestre 2005 a entraîné une mortalité des colonies coralliennes évaluée à 14 %. Début 2006, le développement de maladies spécifiques des coraux a fait à nouveau chuter le taux de corail vivant de 15 %, avec des différences significatives selon les espèces. Globalement, bien que le déclin des récifs ait été amorcé bien avant ces événements majeurs, la perte en corail vivant sur les récifs de Martinique est évaluée à 30 % en moyenne au cours des deux dernières années. Ainsi les taux de couverture moyens en corail évalués au cours des deux suivis de l'année 2006 n'étaient plus que de 32,9 % à 14,8 % sur les mêmes sites respectifs. Aucun changement significatif dans la structure des peuplements de poissons (biodiversité totale, effectifs et biomasse) pris dans leur ensemble n'a été mis en évidence suite à ces changements écologiques. Le réchauffement climatique et les nombreuses pressions anthropiques qui s'exercent sur les côtes de l'île sont majoritairement responsables de cet état écologique. Des projets de réserves marines régionales sont en cours d'étude et devraient permettre de prendre des mesures efficaces de préservation des écosystèmes coralliens de la Martinique dans les années à venir

Nuclear Skins and Halos in the Mean-Field Theory

Nuclei with large neutron-to-proton ratios have neutron skins, which manifest themselves in an excess of neutrons at distances greater than the radius of the proton distribution. In addition, some drip-line nuclei develop very extended halo structures. The neutron halo is a threshold effect; it appears when the valence neutrons occupy weakly bound orbits. In this study, nuclear skins and halos are analyzed within the self-consistent Skyrme-Hartree-Fock-Bogoliubov and relativistic Hartree-Bogoliubov theories for spherical shapes. It is demonstrated that skins, halos, and surface thickness can be analyzed in a model-independent way in terms of nucleonic density form factors. Such an analysis allows for defining a quantitative measure of the halo size. The systematic behavior of skins, halos, and surface thickness in even-even nuclei is discussed.Comment: 22 RevTeX pages, 22 EPS figures included, submitted to Physical Review

Determination of the b quark mass at the M_Z scale with the DELPHI detector at LEP

An experimental study of the normalized three-jet rate of b quark events with respect to light quarks events (light= \ell \equiv u,d,s) has been performed using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are found to agree with theoretical predictions treating mass corrections at next-to-leading order. Measurements of the b quark mass have also been performed for both the b pole mass: M_b and the b running mass: m_b(M_Z). Data are found to be better described when using the running mass. The measurement yields: m_b(M_Z) = 2.85 +/- 0.18 (stat) +/- 0.13 (exp) +/- 0.19 (had) +/- 0.12 (theo) GeV/c^2 for the CAMBRIDGE algorithm. This result is the most precise measurement of the b mass derived from a high energy process. When compared to other b mass determinations by experiments at lower energy scales, this value agrees with the prediction of Quantum Chromodynamics for the energy evolution of the running mass. The mass measurement is equivalent to a test of the flavour independence of the strong coupling constant with an accuracy of 7 permil.Comment: 24 pages, 10 figures, Accepted by Eur. Phys. J.