1,216 research outputs found
Le mazze rettorali
No full textAnalisi delle cinquecentesche mazze in argento legate alla rifondazione dello Studio Universitario Pisano voluta nel 1546 da Cosimo de' Medici
In traccia di orafi e committenti senesi
No full textUn percorso tra le presenze di arte orafa nel patrimonio dell'antico Ospedale di Santa Maria della Scala, che grazie al rilevamento dei marchi di garanzia impressi permette di individuare anche alcune nuove identità di argentieri locali
PH DEPENDENCE OF THE VARIOUS PHASES OF THE PROTON PUMP OF CYTOCHROME C OXIDASE
No full textCytochrome c oxidase(COX)catalyses the reduction of dioxygen to water by ferrocytochrome c.This reaction is coupled to the translocation of up to 1H+/e-
4H+/O2 across the coupling membrane from the inner to the outer aqueous phase (1,2).
The catalytic cycle of COX can be divided into two phases: a reductive phase and an oxidative phase.A study is presented on the pHdependence of proton transfer of COX reconstituted in vesicles,associated with the oxidation phase,the reduction phase and the oxidation-rereduction rapid transitio
Inhibition of proton pumping in membrane reconstituted bovine heart cytochrome c oxidase by zinc binding at the inner matrix side
No full textA study is presented on the effect of zinc binding at the matrix side, on the proton pump of purified liposome
reconstituted bovine heart cytochrome c oxidase (COV). Internally trapped Zn2+ resulted in 50% decoupling
of the proton pump at level flow. Analysis of the pH dependence of inhibition by internal Zn2+ of proton
release in the oxidative and reductive phases of the catalytic cycle of cytochrome c oxidase indicates that Zn2+
suppresses two of the four proton pumping steps in the cycle, those taking place when the 2 OH− produced in
the reduction of O2 at the binuclear center are protonated to 2 H2O. This decoupling effect could be associated
with Zn2+ induced conformational alteration of an acid/base cluster linked to heme a3
Redox Bohr effects and the role of heme a in the proton pump of bovine heart cytochrome c oxidase
No full textStructural and functional observations are reviewed which provide evidence for a central role of redox Bohr
effect linked to the low-spin heme a in the proton pump of bovine heart cytochrome c oxidase. Data on the
membrane sidedness of Bohr protons linked to anaerobic oxido-reduction of the individual metal centers in
the liposome reconstituted oxidase are analysed. Redox Bohr protons coupled to anaerobic oxido-reduction of
heme a (and CuA) and CuB exhibit membrane vectoriality, i.e. protons are taken up from the inner space upon
reduction of these centers and released in the outer space upon their oxidation. Redox Bohr protons coupled
to anaerobic oxido-reduction of heme a3 do not, on the contrary, exhibit vectorial nature: protons are
exchanged only with the outer space. A model of the proton pump of the oxidase, in which redox Bohr protons
linked to the low-spin heme a play a central role, is described. This article is part of a Special Issue entitled:
Allosteric cooperativity in respiratory proteins
Protonmotive cooperativity in cytochrome c oxidase
No full textCooperative linkage of solute binding at separate binding sites in allosteric proteins is an important functional attribute of soluble and membrane bound hemoproteins. Analysis of proton/electron coupling at the four redox centers, i.e. CuA, heme a, heme a3 and CuB, in the purified bovine cytochrome c oxidase in the unliganded, CO-liganded and CN-liganded states is presented. These studies are based on direct measurement of scalar proton translocation associated with oxido-reduction of the metal centers and pH dependence of the midpoint potential of the redox centers. Heme a (and CuA) exhibits a cooperative proton/electron linkage (Bohr effect). Bohr effect seems also to be associated with the oxygenreduction chemistry at the heme a3–CuB binuclear center. Data on electron transfer in cytochrome c oxidase are also presented, which, together with structural data, provide evidence showing the occurrence of direct electron transfer from CuA to the binuclear center in addition to electron transfer via heme a. A survey of structural and functional data showing the essential role of cooperative proton/electron linkage at heme a in the proton pump of cytochrome c oxidase is presented. On the basis of this and related functional and structural information, variants for cooperative mechanisms in the proton pump of the oxidase are examined
G. Accarisi e nipote: souvenir del passato nella Firenze del secondo Ottocento
No full textL'attività di una bottega orafa fiorentina del secondo Ottocento, presente con successo all'Esposizione Universale di Parigi del 1889
Coupling of electron transfer with proton transfer at heme a and Cu(A) (redox Bohr effects) in cytochrome c oxidase. Studies with the carbon monoxide inhibited enzyme
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