Cytochrome electrodes modified

Figure 3.89 Cyclic voltammograms of 500 pm cytochrome c at a gold electrode modified by (a) 2-mercaptopyridine, (b> 2-mercaptosuccinic acid, 4,4 -dithiobis(butanoic acid), (d) 4-mercaploaniline. pH 7.0 phosphate buffer +0.1 M NaC104. Scan rale 50mVs . From Allen...

F. Lisdat, B. Ge, E. Ehrentreich-Forster, R. Reszka, and F.W. Scheller, Superoxide dismutase activity measurement using cytochrome c-modified electrode. Anal. Chem. 71,1359—1365 (1999). 

K.V. Gobi and F. Mizutani, Efficient mediatorless superoxide sensors using cytochrome c-modified electrodes. Surface nano-organization for selectivity and controlled peroxidase activity. J. Electroanal. Chem. 484, 172-181 (2000). 

J. Wang, M. Li, Z. Shi, N. Li, and Z. Gu, Direct electrochemistry of cytochrome c at a glassy carbon electrode modified with single-wall carbon nanotubes. Anal. Chem. 74, 1993-1997 (2002). 

Y. Sato and F. Mizutani, Electrochemical responses of cytochrome c on gold electrodes modified with nucleic acid base derivatives - electrochemical and quartz crystal microbalance studies. Electrochim. Acta 45, 2869-2875 (2000). 

J.M. Sevilla, T. Pineda, A.J. Roman, R. Madueno, and M. Blazquez, The direct electrochemistry of cytochrome c at a hanging mercury drop electrode modified with 6-mercaptopurine. J. Electroanal. Chem. 451, 89-93 (1998). 

K.V. Gobi, Y. Sato, and F. Mizutani, Mediatorless superoxide dismutase sensors using cytochrome c-modified electrodes xanthine oxidase incorporated polyion complex membrane for enhanced activity and in-vivo analysis. Electroanalysis 13, 397-403 (2001). 

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...

Let us pass to other cytochromes. Cytochrome f (or cytochrome C552) (FW = 15 000), the crystal structure of which is known,11 is an electron carrier present in the photosynthetic chain and also possesses a positive overall charge. It exhibits a reversible Fe(III)/Fe(II) reduction at a gold electrode modified with 4,4/-dithiopyridine,12 Figure 10. 

Before leaving our discussion of cytochromes, it is instructive to examine the voltammetric response of cytochrome c at a gold electrode modified by hydroxoalkanethiol carbon chains of variable length, Figure 14.28... 

Cyclic voltammograms recorded in an aqueous solution of cytochrome c (pH 7.1) at gold electrodes modified by (a) 3-hydroxo-l-propanthiol (b) 11-hydroxo-l-undecanthiol. Scan rate 0.5 V s . T = 0°C... 

Direct electrical communication between enzyme aetive sites and electrodes may also be facilitated by the nanoscale morphology of the electrode. The modification of electrodes with metal nanoparticles allows the tailoring of surfaees with features that can penetrate close enough to the enzyme aetive site to make non-mediated electron transfer possible. Electrodes modified by unaggregated 12 nm diameter gold nanoparticles have been found to have the eorrect morphology to allow direct electron transfer between the cytochrome c active site and the eleetrode [41]. Elec-... 

Reduction of horse cytochrome C with [Colsepll ", [Co(diAMsar)]2+, and [Co(NOcapten)]2+ cations was reported in Refs. 316-320. The intrinsic reactivity of these complexes with proteins make it possible the use of clathrochelates as potential protein redox titrants, electrochemical mediators, and electrode modifiers. 

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. 2.3. (a) Illustration of cytochrome c interaction with MUA-modified electrode and (b) cyclic voltammogTEims of a thick-film array gold electrode with immobilized cjdochrome c. Electrode modifier mercaptoundecanoic acid (MUA). 

Electrode/Modifier Cytochrome c coupling Sensor parameter, detection range... 

DNA adsorbed on a glassy carbon electrode was also used as an effective electron promoter enabling electron transfer via hopping conduction through electrode/base pair/cytochrome c by Ikeda et al. [128]. Gold electrodes modified with short oligonucleotides inunohilized via thiol chemisorption were described hy Lisdat et al. [129] to study the promotion of electron transfer to cytochrome c. 

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