Redox molecules

Receptor molecules, redox-active, electrochemical recognition of charged and neutral guest species... 

In order to probe these effects, a number of studies on the kinetics of electron transfer between small molecule redox reagents and proteins, as well as protein-protein electron transfer reactions, have been carried out (38-41). The studies on reactions of small molecules with electron transfer proteins have pointed to some specificity in the electron transfer process as a function of the nature of the ligands around the small molecule redox reagents, especially the hydrophobicity of these... 

The most important structure changes for indicator dyes are (1) Reversible transition between acid and base form of a molecule (pH indicator), (2) Reversible transition between reduced and oxidized forms of a molecule (redox indicator), and (3) Reversible transition between the free molecule and its complex with a cation (metal indicator) [1],... 

In addition to catalyzing the oxidative or reductive transformation of small molecules, redox metalloenzymes can also effect the translocation of protons against a chemical gradient across a membrane. Conceptually, this movement can be understood from the point of view of the fundamental coordination chemistry of metal-oxo complexes (46, 47). Reversible reduction of metal-oxo complexes often occurs concomitantly with protonation, as shown in equations 7 and 8. 

Lor LA, Schneck J, McNulty DE et al (2007) A simple assay for detection of small-molecule redox activity. J Biomol Screen 12 881-890... 

Since the first report of the application of mediated ottle to the study of the redox properties of biological molecules, the technique has been widely used for this purpose. Table 1 summarizes this body of work. A number of novel applications of ottle described in this table have served to provide new insights into the thermodynamics of biological molecule redox reactions. One of these applications is described in some detail in the following discussion. 

Mechanism Vcr, fcapp vs. Co Redox molecule Redox reaction Kinetic parameters (25 °C) Ref. 

Strong pH dependencies of the rates of reduction of a number of cytochromes c and the blue copper protein azurin by ascorbic acid are interpreted in terms of reaction of the ascorbate anion rather than highly reactive deprotonated forms of the proteins since it is unlikely that all the proteins would act in a similar fashion. The second-order rate constants for the ascorbate " anion increase with increasing positive charge on the protein consistent with an outer-sphere mechanism. This is confirmed by cyt c(iii) where the rate of reduction by ascorbate exceeds the limiting rate of substitution of methionine-80 by imidazole at pH 9.0 (7=0.1 M, 21 °C), 8 s" Activation parameters are similar to those of other outer-sphere reactions between proteins and small-molecule redox agents. 

A method that has been extensively used is the reference ion/molecule redox couple using (mainly) polarographic measurements. A reference ion I" that can be reduced to lyand is complexed by a sufficiently large ligand L that shields it from interaction with the solvent is used in both the oxidized and reduced forms as a reference electrode in a cell such as ... 

Isopropanol as a Probe Molecule Redox versus Acid Properties of... 

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