Bridging redox-responsive

The redox processes responsible for the switching of the bridging redox polymer can also be brought about by redox processes induced by molecular species in solution Alternatively, the switching processes can be designed so that a solution component is essential for, or mediates the redox process. The array electrode can then be used as a sensor for those solution constituents. 

MPA-bridged SOD-electrode complex could be formed via a variety of interactions between MPA and the SODs, such as electrostatic, hydrophobic, and/or hydrogen bonding interactions, which is believed to be responsible for the observed direct electron transfer properties of the SODs. Besides, such interactions substantially enable the SODs to be stably confined at the MPA-modilied Au electrode, which can be further evident from the re-observation of the redox responses of SODs in a pure electrolyte solution containing no SOD with the MPA-modified electrode previously used in SOD solutions. 

Spontaneously adsorbed monolayers of the dimeric complex (Figure 5.11) [(pOp) Os(bpy)2 (4-tet) Os(bpy)2 Cl]3+, where pOp is 4,4 -bipyridyl, bpy is 2,2/-bipyridyl and 4-tet is 3,6-bis(4-pyridyl)-l,2,4,5-tetrazine, have been assembled on platinum microelectrodes in an attempt to address these issues [33]. Significantly, as illustrated in Figure 5.11, the voltammetric response associated with the Osn/m reaction is unusually ideal for both metal centers. Studies using mononuclear model compounds reveal that the redox responses centered at approximately 0.620 and 0.300 V correspond to the inner [(pOp) Os(bpy)2 (4-tet)]2+ and outer [(4-tet) Os(bpy)2 Cl]+ moieties, respectively. The observation of two well-defined voltammetric waves indicates that electron transfer can occur across the [(pOp) Os(bpy)2 (4-tet)]2+ bridge to the outer [Os(bpy)2 Cl]+ moiety, i.e. charge trapping does not occur. 

Schematic illustration of (a) the chemical structure of disulfide-bridged PCL-SS-PEEP block copolymer and (b) of the activity of redox-responsive nanocarriers upon cellular uptake and release in the reductive environment of the cytosol. 

Metallothioneins (MT) are unique 7-kDa proteins containing 20 cysteine molecules bounded to seven zinc atoms, which form two clusters with bridging or terminal cysteine thiolates. A main function of MT is to serve as a source for the distribution of zinc in cells, and this function is connected with the MT redox activity, which is responsible for the regulation of binding and release of zinc. It has been shown that the release of zinc is stimulated by MT oxidation in the reaction with glutathione disulfide or other biological disulfides [334]. MT redox properties led to a suggestion that MT may possesses antioxidant activity. The mechanism of MT antioxidant activity is of a special interest in connection with the possible antioxidant effects of zinc. (Zinc can be substituted in MT by some other metals such as copper or cadmium, but Ca MT and Cu MT exhibit manly prooxidant activity.)... 

Potentiometric redox measurements are often performed in nonaqueous or mixed-solvent media. For such solvents various potentiometric sensors have been developed, which, under rigorously controlled conditions, give a Nemstian response over a wide ranges of activities, particularly in buffered solutions. There are some experimental limitations, such as with solvent purification and handling or use of a reference electrode without salt bridges, but there also ate important advantages. Solutes may be more soluble in such media, and redox... 

The structure and enzyme kinetics of bovine erythrocyte superoxide dismutase are reviewed. The protein has a novel imidazolate-bridged copper(II)-zinc(II) catalytic center in each of two identical subunits. Since a C /Cu1 redox couple is responsible for the dismutase activity of the enzyme, the role of zinc is of interest. Both 220-MHz NMR measurements of the exchangeable histidine protons and chemical modifications using diethylpyrocarbonate demonstrate that zinc alone can fold the protein chain in the region of the active site into a conformation resembling that of the native enzyme. Other possible roles for zinc are discussed. Synthetic, magnetic, and structural studies of soluble, imidazolate-bridged copper complexes of relevance to the 4 Cu(II) form of the enzyme have been made. 

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