Cytochrome cyclic voltammograms with

FIG. 26 Cyclic voltammograms of 40 monolayers of Langmuir-Schaefer films of cytochrome P450SCC on indium-tin oxide glass plate (ITO) in 10 mM phosphate buffer at a scan rate of 20 mV/s between 0.4 and —0.4 V vs. Ag/AgCl. LS films on ITO worked as the working electrode, platinum as the counter, and Ag/AgCl as the reference electrode. Cholesterol dissolved in X-triton 100 was added 50 p.1 at a time (1) with cholesterol, (2) 50 p.1 of cholesterol, (3) 100 p.1 cholesterol, and (4) 150 p.1 of cholesterol. 

Figure 3 Cyclic voltammograms recorded at different scan rates in aqueous solution (pH 7) of cytochrome c, under the following experimental conditions (a) protein adsorbed on the Sn02 electrode surface (b) Au electrode pretreated with bipyridyl protein in solution...

Within the promoter there can be subtle structural differences that influence the polar interaction with the protein. For example, Figure 5 illustrates the cyclic voltammograms of cytochrome c obtained at a gold electrode modified with isomers of pyridine-carboxylaldehyde-thiosemi-carbazone (PATS). 

Figure 5 Cyclic voltammograms of cytochrome c recorded at gold electrodes modified with different isomers of PATS...

Figure 11 Cyclic voltammogram of cytochrome b5 recorded at a gold electrode pretreated with Cys-Lys-Cys. Aqueous solution at pH 7.0 (KCl 0.1 mol dm 3). Scan rate 0.005 Vs 1...

Fig. 14.28. Cyclic voltammograms of 100 n/W horse heart cytochrome cat an Au(110) surface modified with 4,4 -PySSPy, 2,2 -PySSPy, and diphenyl disulfide (PhSSPh) in a 0.1 M phosphate buffer solution containing 0.1 M NaCI04 (pH 7) at 25 °C. Scan rate 50 mV/s. (Reprinted from I. Taniguchi, Probing Metalloproteins and Bioelec-trochemical Systems, Interfacial 6(4) 34-37, Fig. 3, 1997. Reproduced by permission of the Electrochemical Society, Inc.)...

Figure 4. The electron-transfer process from an Au electrode to soluble heme proteins as mediated by a monolayer of microperoxidase-11. Cyclic voltammograms of a microperoxidase-11 monolayer-electrode in the absence (a) and presence of added hemoproteins (b) with hemoglobin, 6 X 10 M (c) with myoglobin, 2 x 10 M (d) with cytochrome c, 2 x 10 M. Measurements recorded in 0.1 M phosphate buffer, pH 7.0, under Ar potential scan rate, 5 mV s. ...

Fig. 1.1. (a) SPR angle shifts (A pi) showing the electrostatical adsorption of cytochrome-c on gold electrode surfaces modified with a 3-mercaptopropionic acid SAM (I) after addition of cytochrome-c to a final concentration of ca. 2.5 x 10 M in 5 mM Na-phosphate pH 7.0 (full fine) or in 5 mM Na-phosphate, 100 mM KCl pH 7.0 (dotted line) (11) after rinsing the surface with clean buffer solution, (b) Cyclic voltammograms of a monolayer of cytochrome-c adsorbed on a gold electrode modified with a 3-mercaptopropionic add SAM recorded in 5 mM Na-phosphate, pH 7.0, at 50, 100 and 200 mV s. Reproduced fix)m [214] with permission. 

Fig 5. Cyclic voltammograms of (A) cytochrome c alone (95 ixM), (B) cytochrome 65 alone (95 nM), (C) cytochrome c with cytochrome 65 (95 ijlM each), (D) Zn(II)-cyto-chrome e alone (75 ixM), and (E) cytochrome with Zn(II)-cytochrome c (75 ijlM each) at an edge-plane graphite electrode 1 mM HEPES/20 raM KCl, pH 7.0. Scan rate 10 mV... 

B) Cyclic voltammogram of surface-immobilized cytochrome c oxidase in the absence and presence of the natural cytochrome c (cyt. c) electron donor, as indicated. The scan rate was 2 mVs f Adapted with permission from Ref. [151]. 

Mediated electrochemistry of human SO has been investigated using cytochrome c as the electroactive relay of electrons between SO and the electrode. A layer-by-layer arrangement of cytochrome c and human SO was assembled on a mixed-SAM modified Au electrode. Cyclic voltammograms of the assemblies containing different numbers of layers in the presence of 1 mM sulfite (Figure 5.14) show a linear increase of the catalytic current with layer number. 

Fig. 10. Cyclic voltammogram of horse cytochrome c at pH 9.30. Solution contained 0.35 mM oxidized cytochrome c in a medium consisting of 0.10 M sodium perchlorate, 0.02 M sodium borate and 0.01 M 4,4 -bipyridyl as promoter. An Au electrode, area 0.0079 cm was used. Scan rate 5mVs , temperature 25 °C. Two chemically non-reversible redox processes are observed. Wave 2c is associated with reduction of the State IV conformer which prevails at this pH. Note the virtual absence of wave Ic, which would be observed for reduction of the State III conformer. The corresponding return wave 2a is not observed because the Fe(II) product reverts immediately to the State IIj, conformer resembling State HI of the Feflll) form. Instead, re-oxidation (wave la) is observed at a potential appropriate for the native State III system. From Ref. 62, redrawn with kind permission of the authors...

Santucci and co-workers [146] studied microperoxidase , an Fe-porphyrin undecapeptide (MW 1900), pi = 4.7) obtained by hydrolysis of cytochrome c. Cyclic voltammograms, showing diffusion-controlled reduction and oxidation waves, were obtained with a PGE electrode at pH 7. At 25°, E was — 160 mV, i.e. considerably lower than for the intact native protein. This shift was attributed to the far greater solvent exposure for the microperoxidase heme group. By contrast with most electron-transfer proteins, and with behaviour now much more reminiscent of small redox molecules, well-defined electrochemistry was not critically dependent upon electrolyte conditions. There was merely some enhancement of the electrochemical rate (decrease in AEp) upon changing from O.IOM NaC104 to 0.025 M Mg(C104)2. 

Figure 7. The cyclic voltammogram of a solution containing cytochrome c and caibon monoxide (a) as in (a) but with the enzyme, carbon monoxide oxidoreductase added.

Figure 5 Cyclic voltammogram of cytochrome c at the Au-electrode functionalized with the primer S -ACGGATGCTCC-lCH ljSH that was hybridized with the complementary oligonucleotide. Electrochemical experiment recorded in Tris-buffer, pH 7.5 potential scan rate, 50 mV s. (Adapted from Ref. 36 with permission.)...

Using the silver-coated gold QCM electrodes functionalized with a controlled submonolayer surface coverage of octadecyl mercaptan and the dual chamber dialysis cell for bilayer deposition, over 95% of the electrodes work—i.e., they are successfully modified with functional cytochrome c oxidase [69]. Figure 11 shows cyclic voltammograms conducted at three different representative oxidase-modified electrodes and a control experiment for a lipid bilayer membrane containing no immobilized oxidase [69]. Some difference in peak current and wave... 

Figure 4. Linear sweep voltammograms (solid lines) at a PySSPy modified gold microelectrode array for the reduction of 44 pM cytochrome c in 0.2 M tris/cacodylic acid buffer at the scan rate of (a) 5 mVs , (b) 10 mVs i, (c) 20 mVs-, (d) 50 mVs i. cyclic voltammogram (dashed lines) at a PySSPy modified gold electrode with a large size (1.4 mm in diameter) was measured in the same solution for comparison.

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