hexacyanoferrate-iii and catechol

The present paper reports on the diffusion characteristics and electron transfer properties of a membrane obtained from polyazetidine prepolymer (PAP) consisting of repeating units of 1-(aminomethyl)-1-{2-[(6-oxyhexane)amino]ethyl}-3-hydroxyazetidinium chloride studied in the presence of seven simple redox electroactive molecules: ABTS, catechol, dopamine, ferrocenecarboxylic acid, ferricyanide, ferrocyanide, and the osmium complex bis(2,2-bipyridyl)-4-aminomethylpyridine chloride hexafluorophosphate (Os[(bpy)(2) 4-AMP Cl](+)). Using water as medium, the apparent diffusion coefficients (D(app)), the concentrations of the compounds in the membrane, and the heterogeneous rate constants (k(s)) were calculated as a function of temperature, and the influence thereof on these parameters was evaluated. Even if D(app) and k(s) values in the presence of PAP are smaller than in solution, this decrease is small enough to indicate that the PAP membrane shows excellent diffusion and electron-exchange properties with respect to other commonly used membranes reported in the literature.

Topics: Azetidines; Benzothiazoles; Catechols; Diffusion; Dopamine; Electrochemical Techniques; Electron Transport; Ferricyanides; Ferrocyanides; Microelectrodes; Oxidation-Reduction; Polymers; Sulfonic Acids; Temperature

Equations are presented by which potential-volume data from redox titrations can be analyzed. Mixtures of analytes as well as of titrants may be analyzed, yielding for each component its concentration, number of electrons, and reduction potential. A novel weighting function ensures endpoint accuracy in fitting. Standard deviation of each parameter is obtained. The equations can be readily implemented in Microsoft Excel. Agreement with true values and good precision of fit parameters is demonstrated for a number of test cases. Use of these exact equations enables analysis of analyte mixtures without prior separation using single titrant or titrant mixtures. The equations were used to demonstrate that N-bromosuccinimide, a useful oxidant for organic analytes, undergoes hydrolysis.

Topics: Algorithms; Amines; Antioxidants; Ascorbic Acid; Bromosuccinimide; Catechols; Cerium; Electrochemistry; Ferricyanides; Hydrolysis; Least-Squares Analysis; Oxidation-Reduction; Titrimetry

Membrane-permeable electron donors, duroquinol, diphenylcarbazide, pyrocatechol and tert-octylcatechol, promoted both reduction of an impermeant electron acceptor and proton transport with cultured carrot cells. These cells were preloaded with electron donors for 15, 30, 45 and 60 min. Aliquots of cells were removed at various times, washed free of excess electron donors and assayed for their effect on transplasma membrane redox with impermeable hexacyanoferrate (HCF III) as the electron acceptor and for simultaneous H+ excretion in the presence of hexacyanoferrate. All four electron donors stimulated HCF III reduction and associated H+ excretion. Below a rate of hexacyanoferrate reduction of 6 mumol/g dry wt. per min, the ratios of H+/e- were between 0.3 and 1 with low concentrations (0.1 mM) of the added electron donors. When hexacyanoferrate reduction exceeded 6 mumol/g dry wt. per min, proton release began to cascade to give ratios of 1 to 3, suggesting activation of an H(+)-ATPase or a proton transporter. This behavior by cultured carrot cells indicates that a certain threshold of proton concentration in a limited membrane domain must be reached in order for the proton channel to be opened.

Topics: Biological Transport, Active; Catechols; Cell Membrane; Cells, Cultured; Diphenylcarbazide; Electrons; Ferricyanides; Hydrogen; Hydroquinones; Ion Channels; Oxidation-Reduction; Plant Cells; Plants; Protons

Catechol(o-dihydroxybenzene) at low concentrations (20-100 microM) stimulates FeCN-dependent O2 evolution of spheroplasts isolated from the cyanobacterium Synechococcus both in the presence and absence of DBMIB, an inhibitor of electron flow from PSII to PSI, the stimulation being two-fold with saturating concentration of (60 microM) catechol. Catechol thus appears to mediate the acceptance of electrons at the reducing side of PSII. Similarly it may act on the component of electron donor to PSII and caused the photoreduction of FeCN when O2 evolution capacity of spheroplasts is damaged by heat treatment. Analysis of the temperature effect on FeCN-supported O2 evolution by spheroplasts suggests that catechol shifts the temperature maxima to a lower temperature and thereby hastens the decay of O2 evolution capacity by heat as compared to the normal spheroplasts. Catechol also induces a change in the magnitude of activation energy for ferricyanide Hill activity of spheroplasts and lowers the transition temperature. These results suggest that lipophilic catechol brings about an alteration in membrane fluidity in cyanobacterial spheroplasts. Catechol is involved in a thermotropic destabilization of the membrane of the cyanobacterium. However, Al3+ was found to stabilize the membrane and raise the phase transition temperature. Further increase in temperature caused a gradual decline in the rate of O2 evolution.

Topics: Catechols; Chlorophyll; Cyanobacteria; Electron Transport; Ferricyanides; Light-Harvesting Protein Complexes; Oxygen; Photosynthetic Reaction Center Complex Proteins; Plant Proteins; Spheroplasts; Temperature