Redox schematic representation

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

Fig. 5. Schematic representation of a Pt electrode coated with succesive layers of redox polymers A and B a bilayer transistor electrode. Arrows indicate directions in which communication of the electrode and the outer layer is possible (from ref. ).

Fig. 6. Schematic representation of the midpoint redox potentials and electron and protron balances relating the various active site states as detected by FTIR (65).

Fig. 7. Schematic representation of the redox and spin states attained by center 1 and center 2 of D. desulfuricans Fuscoredoxin as indicated by EPR and Mossbauer spectroscopies. The fully reduced state indicated in the figure remains to be completely understood. In particular, the numbers of electrons accepted are still under debate. Filled circles represent Fe(II).

FIG. 25 (a) Schematic representation for a photocatalytic mechanism based on shuttle photosensitizers at liquid-liquid interfaces. (Reprinted with permission from Ref. 182. Cop5right 1999 American Chemical Society.) (b) This mechanism is compared to the photo-oxidation of 1-octanol by the heterodimer ZnTPPS-ZnTMPyP in the presence of the redox mediator ZnTPP. (From Ref. 185.)... 

Fig. 8 Schematic representation of dihydropyridine-pyridinium redox delivery system. (From Ref. 66)...

Figure 4.12 Schematic representation of the proposed reaction mechanism for overall photocatalytic water splitting using 03 - redox mediator and a mixture of Pt-Ti02-anatase and Ti02-rutile photocatalysts. Adapted from [161] (2001) with permission from Elsevier.

Figure 19 Schematic representation of LB films composed of charge generating AMP and charge transporting redox monolayers sandwiched between two electrodes.

Fig. 6. Schematic representation for the ADH-catalyzed electroenzymatic oxidation of 2-hexene-l-ol and 2-butanol with indirect electrochemical NAD+ regeneration using (3,4,7,8-tetramethyl-l.lO-phenanthroline) iron(II/III) [Fe(tmphen)3] as redox catalyst...

Figure 14.9 Schematic representation of the redox metals of beef heart CcOX with their relative distances. (From Brunori et al., 2005. Copyright 2005, with permission from Elsevier.)...

Figure 18.6 Schematic representation of the physiological role of prion protein (Prpc) in copper homeostasis and redox signalling. (From Crichton and Ward, 2006. Reproduced with permission from John Wiley Sons., Inc.)...

Schematic representation of the aquatic (photo)redox cycling of iron. = denotes the lattice surface of an iron(III)(hydr)oxide.

Figure 37 Schematic representation of the redox sequences occurring in photosynthesis...

Figure 6.31 Schematic representation of a glucose sensor operating with ferrocene to mediate the redox chemistry of glucose oxidase (GOD).

Figure 2.5 Schematic representation of the Au/MPS/PAH-Os/solution interface modeled in Refs. [118-120] using the molecular theory for modified polyelectrolyte electrodes described in Section 2.5. The red arrows indicate the chemical equilibria considered by the theory. The redox polymer, PAH-Os (see Figure 2.4), is divided into the poly(allyl-amine) backbone (depicted as blue and light blue solid lines) and the pyridine-bipyridine osmium complexes. Each osmium complex is in redox equilibrium with the gold substrate and, dependingon its potential, can be in an oxidized Os(lll) (red spheres) or in a reduced Os(ll) (blue sphere) state. The allyl-amine units can be in a positively charged protonated state (plus signs on the polymer...

Figure 42. Schematic representation of the shuttling occurring in an overcharged cell that is based on electrolytes containing redox additive as protection.

Figure 9.2. Mechanisms of aminoglycoside toxicity. This schematic representation summarizes the principles of aminoglycoside toxicity discussed in the text. Treatment with the drugs leads to the formation of reactive oxygen species through a redox-active complex with iron and unsaturated fatty acid or by triggering superoxide production by way of NADPH oxidase. An excess of reactive oxygen species, not balanced by intracellular antioxidant systems, will cause an oxidative imbalance potentially severe enough to initiate cell death pathways. Augmenting cellular defenses by antioxidant therapy can reverse the imbalance and restore homeostasis to protect the cell.

Fig. 3.6 A schematic representation of semiconductor energy band levels and energy distribution of the electrolyte redox system.

Figure 7.7 Schematic representation of a liquid-junction photovoltaic cell using an n-type semiconductor. R/O is the redox couple in the electrolyte.

Figure 7.9 Schematic representation of visible light-induced decomposition of water using RuOj and Pt as redox catalysts codeposited on colloidal Ti02-(Following Gratzel, 1981.)...

Figure 5.3 Schematic representation of the light-harvesting redox-active dendrimers and...

Figure 12 Schematic representation of thermodynamic and kinetic parameters influencing interfacial electron-transfer processes between the semiconductor and an adsorbed redox specie.

Figure 1 Schematic representation of a Gratzel solar cell. Sub-band-gap light absorption leads to the formation of the sensitizer excited state, followed by electron injection into the conduction band of the high-area nanocrystalline semiconductor. The electrons can be drawn into a circuit to do useful work and returned to the system through the redox mediator, the I/Ij" couple, at the counterelectrode.

Fig. 1. Schematic representation of the metal—electrolyte interface and reaction sites for outer-sphere (a, c) and inner-sphere (b) redox reaction paths at electrodes [12].

Fig. 13. (a) Schematic representation of the formation of mixed potential, M, at an inert electrode with two simultaneous redox processes (I) and (II) with formal equilibrium potentials E j and E2. Observed current density—potential curve is shown by the broken line, (b) Representation of the formation of corrosion potential, Econ, by simultaneous occurrence of metal dissolution (I), hydrogen evolution, and oxygen reduction. Dissolution of metal M takes place at far too noble potentials and hence does not contribute to EC0Ir and the oxygen evolution reaction. The broken line shows the observed current density—potential curve for the system. 

Figure 22.1 Schematic representation of an indirect electrochemical process (given for an oxidation Med0Jt, Medred oxidized and reduced forms of the redox catalyst = mediator Sox, Sred oxidized and reduced forms of the substrate).

Fig. 30. Schematic representation of a photo-electroswitch where the emission properties of a photosensitive centre are modulated by the electrochemical interconversion of a redox centre inducing luminescence quenching by energy or electron transfer.

Figure 58 Schematic representation of the arrangement of the redox centres in cytochrome oxidase...

Figure 3.27 Schematic representation of a redox couple in a speherical cavity of radius a, separated from a film of width L by a distance d. The point charge Aq at the center of the sphere is the change of the charge in the ET process, z and p are cylindrical coordinates, and ek (7c = /, 11, III) denote the dielectric constants eoakf eok for the three zones (Reprinted from Y. -P. Liu and M. D. Newton, J. Phys. Chemv 98, 7162-7169. Copyright (1994) with permission from American Chemical Society).

Fig. 7.5. Schematic representation of some of the redox mediator processes at a whole cell biosensor. Lipohilic mediators may be reduced at redox active sites in the plasma membrane or at sites within the cytoplasm or both processes may occur—depending on the cell type and the mediator. Lipophobic mediators can only be reduced at sites on the outside edge of the plasma membrane. The oxidized form of the mediator. O, may be present in excess, but much of the reduced form. R, may need to diffuse between packed cells (dotted arrows) or through the cytoplasm (squiggly arrows). The subscripts aq, cyt, elec, and surf represent mediator in the aqueous phase, within the cytoplasm, at the electrode surface, and at the plasma membrane-aqueous interface, respectively.

Fig. 18. Redox-coupled conformational change in a loop between helices I and II of subunit I. A stereoview (A, see color insert) and a schematic representation of the hydrogen bond network connecting Asp-51 with the matrix space (B). (A) The molecular surface on the intermembrane side is shown by small dots. Maroon and green sticks represent the structures in the fully oxidized and reduced states. (B) Dotted lines show hydrogen bonds. The rectangle represents a cavity near heme a. The two dotted lines connecting the matrix surface and the cavity represent the water path. The dark balls show the positions of the fixed water molecules.

FIGURE 6. Schematic representation of the catalytic reaction cycle in flavocytochrome b2. Five redox intermediates of FCB2 during the oxidation of one molecule of lactate at a steady-state turnover rate of 100 sec and the reduction of two molecules of cytochrome c at the rate of 200sec° are shown. Step 4 is the rate limiting step in the steady state and the maximal rates of some of the other electron transfer steps are indicated. Reproduced from Daff et al., 1996 with permission. 

Figure 4 Schematic representation of the range of redox potentials covered by iron(II)/(III) complexes in aqueous media...

Figure 23. Schematic representation of the cathodic and anodic partial current densities at a metal electrode in contact with a simple redox system as a function of the over potential U - The bars on the vertical axis indicate one decade of current, the bars on the horizontal axis indicate 0.1 V (or 0.1 eV for the electrochemical potential scale).

Figure 5. Schematic representation of the roles of electrostatic and hydrophobic interactions in the formation of ET complexes between redox proteins. Asymmetric placement of charged residues with respect to the prosthetic groups results in the electrostatically stabilized complex (left) being less optimal for ET than the complex stabilized by interactions between uncharged surfaces (right). This is a consequence of the larger distance between cofactors in the former complex than in the latter.

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