Ferricyanide reduction

Fig. 3. (a) Typical galvanostatic limiting-current curve for copper deposition at a copper disk in acidified CuS04 solution. The circles indicate the experimental curve. The solid curves were calculated using kinetic parameters as indicated, (b) Typical galvanostatic limiting current curve for ferricyanide reduction at a nickel electrode in equimolar ferri ferrocyanide solution with excess NaOH. [From Selman (S8).]... 

Experimental results obtained at a rotating-disk electrode by Selman and Tobias (S10) indicate that this order-of-magnitude difference in the time of approach to the limiting current, between linear current increases, on the one hand, and the concentration-step method, on the other, is a general feature of forced-convection mass transfer. In these experiments the limiting current of ferricyanide reduction was generated by current ramps, as well as by potential scans. The apparent limiting current was taken to be the current value at the inflection point in the current-potential curve. 

The reaction may be characterized by slow surface kinetics, leading to shortening of the plateau. Compare, for example, ferricyanide reduction and copper deposition at a rotating disk (shown in Fig. 3a and b). 

Fouad and Ibl (F6) have suggested that the transfer rate in free-convective turbulent flow should follow a Ra1/3 dependence. Experimentally they found a slightly lower dependence, probably due to the partly laminar regime on such plates. Because the exponent is not determined by theoretical considerations, there is considerable variation in the coefficients of turbulent, free convection correlations. Among other factors, inaccuracies in the calculation of the density-driving force may be responsible for discrepancies. This is particularly likely for the case of the ferricyanide reduction reaction. 

C. Osmotically Ruptured Intact Plastids (Ferricyanide Reduction)... 

These data are from Coulson and Heath (10) The 0 doses were delivered for short times (5 min in Part A, and 1 min in Parts B S C) to prevent breakage of the plastids. In Part C, the intact plastids were treated as in B and then osmotically checked by resuspension in a solution containing no osmoticium, before assaying as in Part A. Ferricyanide reduction was measured spectrophotometrically. 

Note A problem in the interpretation of the amiloride inhibition of proton release is the amiloride inhibition of di-ferric transferrin and ferricyanide reduction (Sun et al., 1987). The question arises does inhibition of the exchanger inhibit electron transport or does inhibition of electron transport inhibit a H release not dependent on the exchanger Exchanger inhibition is most likely because of the Na+ dependence for part of the H release (Sun et al., 1988). As an alternative, proton transport may be necessary for electron transport (Stahl and Anst, 1993). 

Table 3. Comparison of H+ Release Rates and Ferricyanide Reduction Rates of C3H10T1/2 and C3H10T1/2 Ha-ras Transfected Cells...

Ferricyanide Reduction Rate (nmole/min/gww) Proton Release Rate with Fe(CN)6 (nmoles min 1 gww ) Ratio (FT/e)... 

Note Ferricyanide reduction rate calculation based on 400 x 106 cells per gram. 

The oxidation of the enamine on El in PDHc by nonlipoic acid acceptors has also been explored for many years. For example, ferricyanide reduction monitored by visible spectroscopy has become a standard test to assay El activity, notwithstanding the attendant problems, including the instability of the thiazolium ring to such conditions. 2,6-Dichlorophenolindophenol (DCPIP) has also been used as an alternative electron acceptor in mechanistic studies of PDHcs75. 

Steady-state kinetic experiments indicate that the rate of ferricyanide reduction by the enzyme is essentially independent of ferricyanide concentration in the range 0.2-3.0 mM. This is another reason... 

Figure 15.6 Phase shift of the EHD impedance corresponding to the ferricyanide reduction on a platinum electrode (area 0.38 cm ) coated with a photoresist on which an array of circular sites of diameter dact was patterned, dact = 649 fim, Ci — 96 rpm ( ) and 375 rpm (A). Theoretical curve for a single microelectrode (dashed line), or for the active disk electrode (solid line). (Taken from Deslouis and Tribollet. )...

Yang etal. report an experimental and computational study of mass transfer to a channel wall downstream of a cylinder. The rate of mass transfer was recorded at various locations. Ferricyanide reduction at a mass-transfer-controlled rate from an electrolyte containing a large amount of KCl was used for the experimental measurements. A diagram of the cell is shown in Fig. 7. A cylinder of diameter d is placed a distance b from the bottom wall, and a working electrode of length 2L is placed at a distance x downstream of the center of the cylinder. The fluid flow can be characterized with a Reynolds number defined as... 

These observations are readily explained in terms of reactions of the aquo salts and it would appear that the usually accepted rapid oxidation of ferrocyanide by hydrogen peroxide is misleading. The fact that this is a very slow reaction means that although the ferricyanide reduction is fairly rapid there is no possibility of appreciable catalytic decomposition of the peroxide by the compensating reactions mechanism. 

Of the four catalytic activities stimulated by CaM, two activities (cytochrome c and ferricyanide reductions) were similarly stimulated in apo-NOS when compared to native NOS (Table I). This indicated that CaM s activation of these processes occurred through a mechanism not involving the flavin-to-heme electron transfer. Further analysis showed that CaM binding increased the rate of electron transfer from NADPH into the flavin centers by a factor of 20, revealing a direct activation of the reductase domain by CaM. 

Liposomes. Liposomes were prepared by sonication from egg yolk phosphatidyl choline (Sigma type X-E) according to the method of Hinkle (18). The assay medium used to determine effects of herbicides and FCCP contained 0.2 ml liposomes in 1.8 ml of 0.3 M NaCl, 20 mM tris-HCl (pH 7.5), 5 mM Na-ascorbate, 80 yM ferrocene, and 80 yM tetraphenylboron. Ferricyanide reduction was measured spectrophotometrically at 420 nm and 25 C. 

Shown in Table II are I q values for inhibition of electron transport in spinach thylakoids (water to ferricyanide) and the associated phosphorylation reaction by the test compounds. Also included are I5Q values for inhibition of the light-dependent quenching of atebrin fluorescence and the ratio obtained by dividing the Icq for the atebrin response by the I q for inhibition of photophosphorylation. The relative order of inhibitory potency for some of the compounds for inhibition of ferricyanide reduction has been reported previously (12). For the herbicides,... 

Dose/response curves were developed from traces such as shown in Figure 3B for dinoseb. For comparative purposes, the concentration of compound required to increase the rate of ferricyanide reduction to twice that of the no-herbicide control rate are shown in the last column of Table VI. Uncouplers such as FCCP accelerate the rate of ferricyanide reduction, presumably by shuttling protons across the membrane in response to the electrical potential generated by the reduction of ferricyanide by ferrocene (28). In this study, FCCP was the most effective compound. The two phenolic herbicides (dinoseb and ioxynil) were more active than propanil and chlorpropham. Among the carbanilates, 3-CHPC and... 

Herbicide inhibition of ferricyanide reduction by the Hill reaction in isolated chloroplasts (1). 

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