Enzyme redox

Topaquinone-containing enzymes, REDOX-ACTIVE AMINO ACIDS... 

Surface-enhanced resonance Raman spectra were observed from dye molecules spaced as distant as six spacer increments (ca. 16 nm = 16 A) from the silver surface. These studies suggested that an electromagnetic mechanism is operative in this assembly in contradistinction to a chemical mechanism that would require direct contact between the Raman-active species and the metal surface. These studies are of relevance in the study of chromophoric species in biological membranes (e.g., enzymes, redox proteins, and chlorophylls). 

Enzyme Redox stale Donor atoms (bond length. A) Ref. 

C. Loechel, A. Basran, J. Basran, N. S. Scrutton and E. A. Hall, Using trimethylamine dehydrogenase in an enzyme linked amperometric electrode. Part 1. Wild-type enzyme redox mediation, Analyst, 128(2) (2003) 166-172 Part 2. Rational design engineering of a wired mutant, Analyst, 128(7) (2003) 889-898. 

Heller A. Electrical connection of enzyme redox centers to electrodes. Journal of Physical Chemistry 1992, 96, 3579-3587. 

The redox mediator 2,6-dichlorophenol indophenol, can mediate electron transfer from and to the redox enzyme, cytochrome c. The mediator was switched between the oxidized and reduced forms by the application of a potential using optically transparent electrodes in a thin-layer cell. From the absorbances of the oxidized and reduced form of the enzyme, the ratio of their concentrations at various potentials was obtained. Calculate the formal potential E° of the enzyme from the data given in Table E.l. Confirm that the enzyme redox process involves one electron transfer. (Contractor)... 

One of the models proposed for a possible enzyme redox reaction mechanistic pathway suggests (Fig. 17.8) that the enzyme contains simultaneously a part that acts as a solution cathode containing a so-called cathodic system where reduction occurs, and another that acts as a solution anode where there is oxidation35. The total charge transfer for the whole chemical reaction is therefore zero. This model is not completely correct, but the concept of a total chemical reaction without electron transfer to the exterior of the enzyme, although controlled by electron transfer, is interesting. 

Enzyme Redox couple Redox potential (mV) References ... 

In spite of their catalytic versatility and their capacity to transform a variety of pollutant compounds, peroxidases are not applied at large scale yet. The challenges that should be solved to use peroxidases for environmental purposes have been recently reviewed [146], Three main protein engineering challenges have been identified (a) the enhancement of operational stability, specifically hydrogen peroxide stability (see Chap. 11) (b) the increase of the enzyme redox potential in order to widen the substrate range (see Chap. 4) (c) the development of heterologous expression and industrial production (see Chap. 12). 

Enzyme Redox State Ni K-Edge Energy 0.2 (eV) Area 0.005 eV (relative to NiCl42 )a %NiEPR Detectable % of EPR Active Ni Poisedc... 

A major advance in the construction of electrically contacted enzyme electrodes involves the structural alignment of the enzyme redox center with respect to the electrode interface in conjunction with the site-specific positioning of a redox relay component between the enzyme redox center and the electrode. The design of such electrodes promotes a new level of molecular architecture of biomolecules on surfaces, enabling us to optimize the electrical contact of the resulting enzyme elec-... 

Figure 39. Electrical communication between an enzyme redox center and a photoexcited species attaining light-induced biocatalyzed transformations (A) direct electrical wiring of the protein by its chemical modification with tethered electron-relay units (B) electrical communication by the immobilization of the protein into a redox-functionalized polymer matrix.

By the second approach, the enzyme is immobilized in a redox polymer assembly (Figure 39B). Electron-transfer quenching of the photosensitizer by the polymer matrix generates an electron pool for the activation of the enzyme. Photoreduction of nitrate to nitrite was accomplished by the physical encapsulation of NitraR in a redox-functionalized 4,4 -bipyridinium acrylamide copolymer [234]. In this photosystem, Ru(bpy)3 + was used as a photosensitizer and EDTA as a sacrificial electron donor. Oxidation of the excited photosensitizer results in electron transfer to the redox polymer, and the redox sites on the polymer mediate further electron transfer to the enzyme redox center, where the biocatalyzed transformation occurs. The rate constant for the MET from the redox polymer functionalities to the enzyme active site is — (9 + 3) x 10 s. Similarly, the enzyme glutathione reductase was electrically wired by interacting the enzyme with a redox polymer composed of polylysine modified with A-methyl-A -carboxyalkyl-4,4 -bipyridinium. The photosensitized reduction of oxidized glutathione (GSSG) (Eq. 21) ... 

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