Redox potential basic value

The redox potential values of all metal atoms, except alkaline and earth-alkaline metals [60], are higher than that of °(H20/eaq) = —2.87 V he- However, some complexed ions are not reducible by alcohol radicals under basic conditions and thus ii°(M L/ M°L)< —2.1 Vnhe (Table 2). The results were confirmed by SCF calculations of Ag L and Ag L structures associated with the solvation effect given by the cavity model for L = CN [61] or NH3 [47], respectively. 

The relatively low value is attributed to the absorption of the ferrocene fragment at 280 nm. The isoelectrofocusing of Fc-HPR confirmed its homogeneity with the expectedly shifted isoelectric point to a more basic pH (cf. 8.1 and 8.5 for HRP and Fc-HRP, respectively). Cyclic voltammetry experiments indicated the ferrocene moiety in Fc-HRP (Fig. 12). New anodic and cathodic peaks are around 360 and 300 mV, respectively (Fig. 12b). The redox potential of 327 mV for Fc-HRP is shifted anodically compared with that for Fc-Hemin in water (264 mV). This may indicate that the ferrocene unit is shielded by amino acid residues located in the vicinity of the active site. 

As a result of the high ionic charge to radius ratio of titanium(IV), normal salts of titanium(IV) are difficult to prepare from aqueous solutions these often yield basic, hydrolyzed species. A tris-catechol species, [Ti(cat)3], prepared by Raymond etal. is one exception it is stable in aqueous solution up to pH 12. The catechol ligand is so stabilizing to Ti that the Ti ATi reduction potential is shifted from the value of -1-0.1V cited as the standard potential in acid in Scheme 1 to a value for [Ti(cat)3] of -1.14 V vs. NHE, affording a powerful example of ligand tuning of metal redox potential. 

Redox potentials for the different copper centers in the blue oxidases have been determined for all members of the group but in each case only for a limited number of species. The available data are summarized in Table VI 120, 121). The redox potentials for the type-1 copper of tree laccase and ascorbate oxidase are in the range of 330-400 mV and comparable to the values determined for the small blue copper proteins plastocyanin, azurin, and cucumber basic protein (for redox potentials of small blue copper proteins, see the review of Sykes 122)). The high potential for the fungal Polyporus laccase is probably due to a leucine or phenylalanine residue at the fourth coordination position, which has been observed in the amino-acid sequences of fungal laccases from other species (see Table IV and Section V.B). Two different redox potentials for the type-1 copper were observed for human ceruloplasmin 105). The 490-mV potential can be assigned to the two type-1 copper sites with methionine ligand and the 580-mV potential to the type-1 center with the isosteric leucine at this position (see Section V.B). The... 

The type I copper sites function as electron transfer centers in the blue copper proteins and in multicopper enzymes, particularly oxidases (33). They are characterized by their intense blue color, their unusually small A values, and their very positive redox potentials (Table II). X-ray crystal structures of several blue copper proteins have been determined, notably plastocyanin (34), azurin (35), cucumber basic blue protein (36), and pseudoazurin (37). The active site structures show marked similarities but also distinct differences (Fig. 8). 

Basic characterisation tests include tests designed to assess the effect of a single variable on the leaching behaviour of a material. Such tests commonly comprise tests to establish the effect of leaching at different pH values and at different redox potentials. 

The choice of solvents has considerable impact on the reduction and oxidation potentials measured. The values vary up to 400 mV depending on the solution medium. Obviously factors like donor/acceptor properties, Lewis basicity, or the ability to form hydrogen bonds have large influence on the redox potential. 

In the present scenario of protection of product development rights, it is expected that a large number of new products, based on the basic anthracycline structure, will be developed for anti-tumom trials. While basic radiation chemistry may not differ significantly fi om what we already know, it will be very interesting to know how the redox properties change with new structures [88], The most important characteristics for either anti-tumom action or toxicity is the redox potential values. We should be able to put substituents at will to have a desired redox potential of the substrate. This is extremely important from the research point of view. However, no concerted efforts have been made in this direction. 

Similar observations on the oxidation of the thallium atom or on the reduction of T1+ have been made by pulse radiolysis. They are in agreement, as for silver, with the value determined from the electrode potential and the sublimation energy of the bulk metal into atoms, i.e. °(T1 /T1 ) = —1.9 Vnhe-Silver ions complexed by cyanide, ammonia, or EDTA, Ag L, are not reduced by the radical (CH3)2C OH, even under basic conditions, and the redox potential of these complexed forms must be more negative than —2.1 According... 

By abbreviating the first term (the basic value of the redox potential) to , we obtain the corresponding Nemst equation ... 

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