Redox differential

In both the reactive groundwater and reactive conductor models, the impetus for electronic current flow in mineralisation comes from the redox differential between the oxidised groundwater environment surrounding the upper part of the conductor and reducing agents in contact with its lower part. The upward movement of electrons consumes oxidising agents in basal overburden and results in the development of a... 

The peak-shaped response of differential-pulse measurements results in unproved resolution between two species with similar redox potentials, hi various situations, peaks separated by 50 mV may be measured. Such quantitation depends not only upon the corresponding peak potentials but also on the widths of the peak. The width of the peak (at half-height) is related to the electron stoichiometry ... 

This corresponds with MacDiarmid s observations which show that the second redox step is strongly pH-dependent. MacDiarmid further differentiated his redox model to take account of the fact that pure leucoemaraldine with its amine-N is already protonated at pH values 2, and that the totally oxidized pemigraniline with its less basic imine-N can also be protonated. This gives the following (simplified) reaction scheme ... 

The redox potentials of the ITO electrodes modified with CgoN -MePH clusters were measured by cyclic voltammetry and differential pulse voltammetry in the absence and presence of magnetic processing. 

The slope of the tangent to the curve at the inflection point where oc = is thus inversely proportional to the number of electrons n. The E-oc curves are similar to the titration curves of weak acids or bases (pH-or). For neutralization curves, the slope dpH/doc characterizes the buffering capacity of the solution for redox potential curves, the differential dE/da characterizes the redox capacity of the system. If oc — for a buffer, then changes in pH produced by changes in a are the smallest possible. If a = in a redox system, then the potential changes produced by changes in oc are also minimal (the system is well poised ). 

In many investigations of CT, pendant redox probes interact with both bases of abase pair. However, studies of base-base charge transfer can differentiate between discrete intra- and interstrand reactions (Fig. 7). These investigations further attest to the critical role of base stacking in DNA-mediated CT. In B-DNA duplexes, stacking interactions are largely restricted to... 

However, recently, several other non-redox mechanisms have been implicated in the modulation of cell growth by carotenoids, which include the direct modulation of the expression of proteins and transcription factors involved in cell proliferation, differentiation and apoptosis. 

Palozza, P., Serini, S., Torsello, A. et al. 2002b. Regulation of cell cycle progression and apoptosis by beta-carotene in undifferentiated and differentiated HL-60 leukemia cells possible involvement of a redox mechanism. Int J Cancer 97 593-600. 

Phase-sensitive detection is not at all specihc for EPR spectroscopy but is used in many different types of experiments. Some readers may be familiar with the electrochemical technique of differential-pulse voltammetry. Here, the potential over the working and reference electrode, E, is varied slowly enough to be considered as essentially static on a short time scale. The disturbance is a pulse of small potential difference, AE, and the in-phase, in-frequency detection of the current affords a very low noise differential of the i-E characteristic of a redox couple. 

Trotti, D., Nussberger, S., Volterra, A., and Hediger, M. A. (1997) Differential modulation of the uptake currents by redox interconversion of cysteine residues in the human neuronal glutamate transporter EAAC1. Eur. J. Neurosci. 9,2207-2212. 

Electrochemical communication between electrode-bound enzyme and an electrode was confirmed by such electrochemical characterizations as differential pulse voltammetxy. As shown in Fig. 11, reversible electron transfer of molecularly interfaced FDH was confirmed by differential pulse voltammetry. The electrochemical characteristics of the polypyrrole interfaced FDH electrode were compared with those of the FDH electrode. The important difference between the electrochemical activities of these two electrodes is as follows by the employment of a conductive PP interface, the redox potential of FDH shifted slightly as compared to the redox potential of PQQ, which prosthetic group of FDH and the electrode shuttling between the prosthetic group of FDH and the electrode through the PP interface. In addition, the anodic and cathodic peak shapes and peak currents of PP/FDH/Pt electrode were identical, which suggests reversibility of the electron transport process. 

We conventionally cite the oxidized form first within each symbol, which is why the general form is o,r> so pb4+ Pb + is correct, but 2+ 4+ is not. Some people experience difficulty in deciding which redox state is oxidized and which is the reduced. A simple way to differentiate between them is to write the balanced redox reaction as a reduction. For example, consider the oxidation reaction in Equation (7.1). On rewriting this as a reduction, i.e. Al3+(aq) + 3e = A Em, the oxidized redox form will automatically precede the reduced form as we read the equation from left to right, i.e. are written in the correct order. For example, o,r for the couple in Equation (7.1) is Ai3+,ai-... 

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