Intracellular redox potential

Recent work at Diversa has provided some insights into the host effects on desulfurization. It was reported that in addition to the obvious substrate transport and growth differences between various strains of same genus, the intracellular redox potential can potentially influence the rate as well as extent of desulfurization [219], Additionally,... 

The introduction of redox-sensitive linkages, such as the disulphide group, has been used to prepare liposomes that are susceptible to the lower intracellular redox potential relative to the extracellular environment. Symmetrical disulphides are synthesised by oxidation of thiol-containing structures [64, 130, 131] (see Fig. 7),... 

A platinized nanotip served also as an excellent potentiometric probe to enable the measurement of intracellular redox potentials [69],... 

Park M, Lee S, Lee S, Ho W, Earm Y. Different modulation of Ca-activated K channels by the intracellular redox potential in pulmonary and ear arterial smooth muscle cells of the rabbit. Eur J Physiol 1995 430 308-314. 

This enzyme [EC 2.7.1.23] catalyzes the reaction of ATP with NAD+ to produce ADP and NADP+. This reaction has the potential for altering the intracellular [NADP+]/ [NADPH] redox potential by converting NAD+ to NADP+, but details on the regulation of this enzyme have not been worked out. 

Besides the use of amino acids as a nitrogen source, flor yeast may use these compounds to balance the oxidation-reduction potential under conditions of restricted oxygen availability. This can be achieved by releasing amino acids into the medium to restore the intracellular redox balance by oxidation of excess NADH (Mauricio et ah, 2001a,b Moreno-Arribas and Polo, 2005 Valero et ah, 2003). 

NMR can help to monitor energization, see, e.g. [121, 273], especially the levels of 31P-containing metabolites, e.g. [45, 366], enzyme kinetics, compartmentalized intracellular ion activities, the fate of 3H-, 2H-, 13C-, 15N-, or 19F-labeled tracers, e.g. [108,109], 02 tension, compartmentalized redox potential, membrane potential, cell number or cell volume, see [133], and even pH. Major drawbacks are the cost of the equipment, the low intrinsic sensitivity and the interpretation of spectra [430]. 

High concentrations of heavy metals that affect, directly or indirectly, the redox potential in the reducing intracellular milieu, particularly copper, induce the formation of reactive oxygen species. These, in turn, can trigger the chain reaction causing lipid peroxidation, which affects membrane integrity and induces structural changes to proteins and nucleic acids that can result in cell death. 

In order to more directly investigate the regulation of metabolism by the redox potential of the cell, we have recently labeled the intracellular pools of pyridine nucleotides in the liver, using the C-labeled vitamins, nicotinic acid and nicotinamide ... 

Although we have demonstrated a method for intracellular Raman investigations, the actual information which can be acquired is rather nonspecific. For a useful intracellular sensor high specificity to either certain cellular conditions, like pH or redox potential, or for the detection of marker molecules for different cellular processes is desirable. 

The redox potential within the cells is substantially lower than in the plasma (May and Williams, 1980), and may vary depending upon particular cellular biochemical activities and a myriad of potential redox couples such as reduced and oxidized glutathione species. In general, greater levels of reduced glutathione in the intracellular fluids than in the plasma may provide an indication of an overall lower oxidation condition within the cells. However, it is interesting to note that intracellular fluids have relatively high concentrations of dissolved sulfate (Table 4), in spite of the more reduced conditions inferred to be present. 

There are many specific methods available that are suitable for a certain set of conditions or for a particular experimental aim (Patterson, 1979 Griffiths, 1985). These include radiochromium labelling (radiochromium binds to viable protein and is released on cell damage/death), cellular ATP, intracellular volume (by ratios of radiochemicals), specific stains (e.g. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), triphenyltetrazolium chloride, neutral red), redox potential, turbidity, calorimetry (Griffiths, 1985) and biomass monitors. 

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