Redox-dependent effects

Palmer LA, Gaston B, Johns RA. Normoxic stabilization of hypoxia-inducible factor-1 expression and activity redox-dependent effect of nitrogen oxides. Mol Pharmacol 2000 58 1197-1203. 

Zhao, W, Mackenzie, G.G., Murray, O.T., Zhang, Z., and Rigas, B. (2009). Phosphoaspirin (Mdc-43), a novel benzyl ester of aspirin, inhibits the growth of human cancer cell lines more potently than aspirin A redox-dependent effect. Carcinogenesis 30, 512-519. 

The most commonly used physical method for long-term eutrophication control in lakes is that of artificial destratification. This method is well tried and understood and uses either jetted water or compressed air bubbles to break down the lake stratification in the summer months. Algal growth is also affected by an increase in circulation. This is due to the artificial shading effect which results from the algae spending less time near the surface and consequently less time in the light. This technique also reduces the redox-dependent phosphorus release from sediments because the sediment surface remains aerobic. 

In order to investigate the structural requirements for the strong redox dependence, AEia values were also measured for anthraquinone, 12, and benzyl, 13, in the presence of 5 equivalents of diphenylurea in DMF. Under these conditions, phenan-threnequinone gives a shift of 61 mV, whereas anthraquinone gives a shift of only 8 mV and benzil 5 mV. Unlike phenanthrenequinone, the urea can only H-bond to one carbonyl oxygen at a time with anthraquinone. Two bifurcated H-bonds are possible, but these together would be much weaker than the two close to linear H-bonds possible with oquinones. A similar situation arises with benzil, since rotation about the central —C bond will be hindered in the radical anion and the favored conformation will have the oxygens trans due to electrostatic repulsion and steric effects. 

Indirect evidence for small redox-dependent differences has been presented based on titration studies of the S -phosphate for NMN and NMNH IT). Such determinations, however, are highly suspect because the effects of titration of the 5 -phosphate are not limited to through-space interactions. Chemical shifts also depend on orbital overlap ofdie intervening bonds and localized bond polarization, neither of which is a direct function of the interatomic distances 4). 

The side chain at C-3 undergoes profound redox-dependent alterations in its chemical properties. The electron orbitals of the carboxamide in NAD are not delocalized into the pyridine ring. On reduction, however, the side chain becomes effectively a vinylogous urea. It shows strong resonance delocalization into the double bonds, with the carbonyl coplanar [although skewed conformations at 150° also represent local minima in the torsional conformation space... 

Since colloidal particles of silver and gold also give large SERS effects, it is useful to consider these as disconnected microelectrodes. Controlled variations in the potential at the interface between silver sol particles and electrolyte solution have been achieved by adding the Eu3+/Eu2+ redox system and varying the concentration ratio [22]. From measurements of SER spectra of pyridine adsorbed on the silver sol, the potential-dependent effects have been found to be identical with those given by bulk silver electrodes. These experiments also demonstrated that the intensity ratio of the pyridine Raman bands at ca. 1010 and 1040 cm-1 may be used as a simple but effective measure of sin-face potential for colloidal metals. 

The numerical model CoTReM was applied to investigate the depth dependent effects of respiration and redox processes related to CaCO dissolntion (Pfeifer et al. 2002 cf. Fig. 15.16 in chapter 15). Interestingly, if calculated until a steady-state situation is reached, the model-derived calcite dissolution and precipitation rates produce an almost perfect fit to the measured CaC03 profile in the sediment (Fig. 9.8), which suggests that 90 % of the CaC03 flux to the sea floor is redissolved in the sediment. 

There are two caveats to such an argument. Firstly, analysis of the radiosensitization data for different levels of effect showed that the slope of equation (16) varied with effect. This implies two (or more) mechanisms, with different redox dependencies, are involved. Secondly, the experimental... 

Salas VM, Corcoran GB (1997) Calcium-dependent DNA damage and adenosine 3 5 -cyclic monophosphate- independent glycogen phosphorylase activation in an in vitro model of acetaminophen-induced liver injury. Hepatology 25 1432-1438 Salminen WF Jr, Voellmy R, Roberts SM (1998) Effect of N-acetylcysteine on heat shock protein induction by acetaminophen in mouse liver. J Pharmacol Exp Ther 286 519-524 Schiodt FV, Ott P, Christensen E, Bondesen S (2002) The value of plasma acetaminophen half-life in antidote-treated acetaminophen overdosage. Clin Pharmacol Ther 71 221-225 Schnellmann JG, Pumford NR, Kusewitt DF, Bucci TJ, Hinson JA (1999) Deferoxamine delays the development of the hepatotoxicity of acetaminophen in mice. Toxicol Lett 106 79-88 Shen HM, Pervaiz S (2006) TNF receptor superfamily-induced cell death redox-dependent execution. FASEB J 20 1589-1598... 

A hydroxyl functionalized ionic liquid (IL) l-(3-chloro-2-hydroxy-propyl)-3-methylimidazolium tetrafluoroborate (PMIMBF4) was used for the preparation of bulky-modified carbon paste electrode (IL-CPE) by Guo et al. [31] and it was applied to the sensitive detection of adenosine-5 -diphosphate (ADP). Due to the specific characteristics of IL such as high ionic conductivity and strong adsorption ability, IL-CPE showed remarkable redox catalysis effect on the oxidation of ADP. By using (DPV) the oxidation peak current was linearly dependent on the ADP concentration in the range from 10.0 to 1000.0 pmol L with the detection limit as 3.23 pmol L (3o). 

Another problem is that the Nernst equation is a function of activities, not concentrations. As a result, cell potentials may show significant matrix effects. This problem is compounded when the analyte participates in additional equilibria. For example, the standard-state potential for the Fe "/Fe " redox couple is +0.767 V in 1 M 1TC104, H-0.70 V in 1 M ITCl, and -H0.53 in 10 M ITCl. The shift toward more negative potentials with an increasing concentration of ITCl is due to chloride s ability to form stronger complexes with Fe " than with Fe ". This problem can be minimized by replacing the standard-state potential with a matrix-dependent formal potential. Most tables of standard-state potentials also include a list of selected formal potentials (see Appendix 3D). 

L/(mol-s) (39,40). QDI is also attacked by hydroxide ion (eq. 4) to produce a quinone monoimine (QMI), itself an oxidized developer derived from /)-aminopheno1. Such compounds can further react with coupler, albeit at a slower rate than QDI, to form a dye and were cited in the seminal patent as color developers (32). However, the dyes derived from this deaminated developer have different hues from the QDI dyes, and these hues are pH-dependent as a consequence of the phenoHc group contributed by the developer. Although the deamination reaction to produce QMI is fast, the rate constant is 10 to 10 L/(mol-s) (40—42), its effect is somewhat offset by the redox reaction of the QMI with the reduced developer, present in large excess, to regenerate the desired QDI. The primary net effect of the deamination reaction is to enlarge the resulting dye cloud (43). 

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