Macroscopic oxidation-reduction potentials

Table II. Cytochrome c3 Macroscopic Oxidation-Reduction Potentials...

There are 32 microscopic formal potentials for the redox process of the tetra-heme protein, cytochrome C3, and the deconvolution of these microscopic states distributed over 110 mV is impossible using electrochemical techniques. Many heme-methyl signals are observed separately, e.g. each heme of cytochrome C3 has four methyl groups so that 80 three-proton intensity signals originating from the 16 heme-methyl groups would be expected in the course of a four-electron reduction process. The microscopic formal potentials of the 32 redox processes can be calculated from the chemical shifts of each heme-methyl group at the five macroscopic oxidation states [125, 127]. The results are shown in Table 6 and the macroscopic formal potential can be deduced from these results. 

A chemomechanical system can be defined as one that is used to obtain macroscopic mechanical energy caused by microscopic deformation in response to changes in an external environment it is also considered to be a system for obtaining large deformations effectively by using microscopic mechanical energy. Polymer gels can be functional polymers that possess complex system functions similar to those of biomaterials. Thus, they are potentially useful chemomechanical materials and various studies are underway today. Chemomechanical systems actuate by phase transition, oxidation-reduction, chelation, and formation of complexes between polymers. They are classified as follows ... 

Although the microscopic mechanism of pit initiation and oxide breakdown is still not fully understood (40, 41), the macroscopic behavior of enhanced local dissolution and diffusion of dissolved metal ions can be described using current-potential (i-E) curves (Figure 3). The solution conditions in a pit create two distinct electrochemical cells. At the bottom of the pit, the oxidation half-reaction is acidic dissolution of Fe (equation 1), which is balanced primarily by reduction of water to hydrogen gas (equation 3). The second cell is at the mouth of the pit, where the halfreactions are dissolution at a passivated iron metal surface (alkaline conditions) and reduction of water or stronger oxidants such as O2 or RX. 

Various techniques have been used to create a macroscopic analogy to the crack tip bare surfaces on which the oxidation and reduction rates can be measured. These include mechanical methods to rupture the surface oxide that involve slowly [87-91] or rapidly [92,93] straining the alloy, complete fracturing of the specimen to create a bare fracture surface [94,95] cyclic straining [88,96], scratching the alloy surface [97-102], and grinding [103]. Electrochemical methods have also been used to cathodically reduce the oxide [1,104-106] and then pulse to the potential of interest. Copyright 2002 Marcel Dekker, Inc. 

SECM was employed not only to induce the deposition of Ag particles at the ITIES but also to monitor their nucleation and growth dynamics at the nanoscale. In this approach, a 25 pm-diameter Ag tip was oxidized to generate Ag , which was reduced by decamethylferrocene at the DCE/ water interface (Fig. 16a). The tip current based on Ag oxidation depends on the rate of Ag" reduction at the ITIES, thereby enabling the kinetic study of Ag deposition. The phase boundary potential of the macroscopic ITIES was controlled by changing the aqueous and organic concentrations of a common ion, CIO4, to enable the modulation of the driving force. 

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