Protein electrochemically active

Because process mixtures are complex, specialized detectors may substitute for separation efficiency. One specialized detector is the array amperometric detector, which allows selective detection of electrochemically active compounds.23 Electrochemical array detectors are discussed in greater detail in Chapter 5. Many pharmaceutical compounds are chiral, so a detector capable of determining optical purity would be extremely useful in monitoring synthetic reactions. A double-beam circular dichroism detector using a laser as the source was used for the selective detection of chiral cobalt compounds.24 The double-beam, single-source construction reduces the limitations of flicker noise. Chemiluminescence of an ozonized mixture was used as the principle for a sulfur-selective detector used to analyze pesticides, proteins, and blood thiols from rat plasma.25 Chemiluminescence using bis (2,4, 6-trichlorophenyl) oxalate was used for the selective detection of catalytically reduced nitrated polycyclic aromatic hydrocarbons from diesel exhaust.26... 

There are, however, various types of active transport systems, involving protein carriers and known as uniports, symports, and antiports as indicated in Figure 3.7. Thus, symports and antiports involve the transport of two different molecules in either the same or a different direction. Uniports are carrier proteins, which actively or passively (see section "Facilitated Diffusion") transport one molecule through the membrane. Active transport requires a source of energy, usually ATP, which is hydrolyzed by the carrier protein, or the cotransport of ions such as Na+ or H+ down their electrochemical gradients. The transport proteins usually seem to traverse the lipid bilayer and appear to function like membrane-bound enzymes. Thus, the protein carrier has a specific binding site for the solute or solutes to be transferred. For example, with the Na+/K+ ATPase antiport, the solute (Na+) binds to the carrier on one side of... 

The ubiquitous electrochemical behavior of ferrocene and its relative chemical stability have made this organometallic complex a useful group for the preparation of redox-active devices. The incorporation of ferrocene-modified amino acids into larger polypeptide structures can therefore lead to electrochemically active de novo designed proteins. In addition, the attachment of ferrocene derivatives to peptides make them electroactive and eligible to electrochemical detection. Hence, it is not surprising that the first synthesis of a ferrocene-modified amino acid dates back to the 1950s. 

Protein phosphatase inhibition is usually detected by colorimetric methods, but the development of a biosensor requires the search of other transduction techniques. Electrochemistry has been widely used in biosensors because of the simplicity, easy to use, portability, disposability and cost-effectiveness of the devices. As protein phosphatase is not an oxidoreductase enzyme, our work has been devoted to the investigation of novel enzymatic substrates, electrochemically active only after their dephosphorylation by the protein phosphatase. Nevertheless, colorimetric assays have been used for the optimisation of several experimental parameters. 

Electrochemical Activation of Enzymes by the Attachment of Redox Relays to the Protein Backbone... 

HPLC, high performance (or pressure) liquid chromatography, is particularly suited for small water-soluble molecules and proteins. Most used for analysis of DNA fragments is the reverse phase HPLC. Detection with electrochemical detectors are preferred. There are many different brands of ECD detectors and electrodes/cells. In our laboratory we have found that the ESA Coulochem is working excellent for our purposes and provides excellent sensitivity. Similar experience with other detectors can be found. We have found that for HPLC-ECD analysis of urine, separation is critical due to electrochemically active peaks eluting close to that of 8-oxodG. Ways to detect a false peak is given in details elsewhere [3]. 

The involvement of lysine amino acid residues on cytochrome c in the heterogeneous reactions with functionalized electrodes seems to have been established. Importantly, it is now thought that the proposed protein-promoter complex is more likely to be dynamic, as revealed by the results of a recent investigation (28) of site-specific 4-chloro-3,5-dinitrophenyl (CDNP)-substituted cytochrome c. It was found that monosubstitution of either Lys 13 or Lys 72 did not result in any significant change in its electrochemical response, whereas two modifications greatly decreased the heterogeneous rate constant, and complete loss of electrochemical activity was observed upon modification of more lysines. It was proposed that the electrode reaction occurred in numerous rotational conformations. Therefore, for the mono-... 

As has been shown, this kind of reaction does take place on the mercury electrode in the presence of cystine. The i-E curves measured on an amalgamated electrode in the presence of peroxidase apoenzyme in the solution also have anodic and cathodic maxima, similar to those obtained in the peroxidase solution. Thus, in the potential region investigated, the S—S groups of the protein globule of peroxidase are electrochemically active. Heme iron in the active center does not take part in the observed redox process. 

Conductivity Detection. The use of a conductivity detector is the basic configuration scheme of any ion-chromatography system. The sensitivity is high and it needs practically no maintenance, an important cispect in routine analysis. The detector is so simple to use that it is — cf. above the case of the Karl Fischer determination — not recognized as an electrochemical detector. Latest developments with membrane suppressor systems allow the use of the gradient elution technique. Using this procedure it is possible to analyse in the same run ions of extremely different characteristics (cf. Fig.4) as demonstrated for the analysis of a protein based active principle. 

Several strategies to increase the production of electron shuttles have been developed to improve the MFC performance in the model exoeleetrogens. For Shewanella species, flavins (riboflavin and flavin mononucleotide) are the most well-known self-secreted electron shuttles. Using deletion mutants lacking various Mtr-associated proteins, the significance of the Mtr extracellular respiratory pathway for the reduction of flavins has been demonstrated. The decaheme cytochromes found on the outer surface of the cell (MtrC and OmcA) are required for the majority of Mtr-associated proteins activity. Weakly acidic pH resulted in poor performance of the MFC and low riboflavin concentrations in the bacterial cultures, while enhanced electrochemical activity of riboflavin was reported at alkaline pH. The increase of riboflavin biosynthesis by Shewanella at the alkaline condition underlies the improvement in the electricity output in MFCs. ... 

For high-performance separation methods suffering of insufficient detectability in determination of MC in environmental samples for routine applications the most effective is preconcentration on immunosorbents. The new advantageous competitors in this field might be enzymatic assays and biosensors based on inhibition of protein phosphatase activity by MC. Some successful attempts in this field have been reported recently as colorimetric assays or electrochemical biosensors. 

---