Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Adsorbed protein, redox state

Voltammetry of Adsorbed Proteins, Fig. 2 Non-tumover behavior during cyclic voltammetry at scan rates where the protein oxidation state is in equilihrimn with the electrode potential at all times in the experiment, (a) Cyclic voltammogram of a surface confined redox center undergoing redox transformation with a midpoint potential of 0.1 V and n =. The peak potentials of the reductive, Ep and oxidative, Ep , peaks are indicated. [Pg.2105]

One of the main advantages of the optically transparent thin-layer spectroelectrochemical technique (OTTLSET) is that the oxidized and reduced forms of the analyte adsorbed on the electrode and in the bulk solution can be quickly adjusted to an equilibrium state when the appropriate potential is applied to the thin-layer cell, thereby providing a simple method for measuring the kinetics of a redox system. The formal potential E° and the electron transfer number n can be obtained from the Nernst equation by monitoring the absorbance changes in situ as a function of potential. Other thermodynamic parameters, such as AH, AS, and AG, can also be obtained. Most redox proteins do not undergo direct redox reactions on a bare metal electrode surface. However, they can undergo indirect electron transfer processes in the presence of a mediator or a promoter the determination of their thermodynamic parameters can then... [Pg.702]

As discussed before in the case of nucleic acids the authors have also considered the incidence of the interfacial conformation of the hemoproteins on the appearance of the SERRS signals from the chromophores. Although under their Raman conditions no protein vibration can be observed, the possibility of heme loss or protein denatura-tion are envisaged to explain a direct interaction of the heme chromophores with the electrode surface in the case of the adsorl Mb. extensive denaturation of Cytc at the electrode appears unlikely to the authors on the basis of the close correspondence of the surface and solution spectra. Furthermore, the sluggish electron transfer kinetics measured by cyclic voltammetry in the case of Cytc is also an argument in favour of some structural hindrance for the accessibility to the heme chromophore in the adsorbed state of Cytc. This electrochemical aspect of the behaviour of Cytc has very recently incited Cotton et al. and Tanigushi et al. to modify the silver and gold electrode surface in order to accelerate the electron transfer. The authors show that in the presence of 4,4-bipyridine bis (4-pyridyl)disulfide and purine an enhancement of the quasi-reversible redox process is possible. The SERRS spectroscopy has also permitted the characterization of the surface of the modified silver electrode. It has teen thus shown, that in presence of both pyridine derivates the direct adsorption of the heme chromophore is not detected while in presence of purine a coadsorption of Cytc and purine occurs In the case of the Ag-bipyridyl modified electrode the cyclicvoltammetric and SERRS data indicate that the bipyridyl forms an Ag(I) complex on Ag electrodes with the appropriate redox potential to mediate electron transfer between the electrode and cytochrome c. [Pg.49]

Thus, it can be seen that the study of the electrochemical behavior of protein macromolecules in the adsorbed state can provide highly important information on their redox transformations. It is necessary, however, to take into account the possibility of significant conformational restructuring of proteins in the adsorbed state. To elucidate the role of conformational changes it is necessary to undertake investigations combining electrochemical and spectral methods. [Pg.259]

By contrast with cytochrome c, the properties of cytochrome C3 adsorbed at Ag as determined by SERS or voltammetry are very similar [35] to those of the native state. Voltammograms observed for three types of cytochrome C3 show resolution of the non-equivalence of redox sites. Also, apparently by contrast to the situation found at Hg electrodes, cyclic voltammetry shows that the reduced form remains electroactive. It is important to note here that the cytochromes C3 are very stable proteins that survive extended periods at high temperature and extreme pH [64]. [Pg.154]

If the presence of a soluble mediator shuttling the electrons between the electrode and the enzyme is to be avoided, other modes of wiring [15] the enzyme to the electrode ought to be sought after. One may think of direct electron transfer between the electrode and the enzyme at the adsorbed state. It has indeed been shown that small redox proteins, such as cytochrome c or ferredoxins may show an unmediated reversible electrochemical response when the electrode surface is adequately prepared [16-19]. There have been few reports of direct electron transfer with redox enzymes [20,21]. With flavoen-zymes, the observed signals are likely to be those of the free flavin deriving from the denaturation of the enzyme [21]. The high probability of denaturation of the adsorbed enzyme prevents the viability of this mode of electron transport in most cases. [Pg.5977]


See other pages where Adsorbed protein, redox state is mentioned: [Pg.106]    [Pg.477]    [Pg.256]    [Pg.88]    [Pg.274]    [Pg.2108]    [Pg.152]    [Pg.82]    [Pg.375]    [Pg.181]    [Pg.390]    [Pg.457]    [Pg.166]    [Pg.133]    [Pg.50]    [Pg.34]    [Pg.106]    [Pg.250]    [Pg.321]    [Pg.188]    [Pg.5643]    [Pg.2105]    [Pg.350]    [Pg.73]    [Pg.326]    [Pg.698]    [Pg.247]    [Pg.130]   
See also in sourсe #XX -- [ Pg.482 ]




SEARCH



Adsorbate states

Adsorbed proteins

Adsorbed states

Adsorbent proteins

Redox state

© 2024 chempedia.info