Horseradish catalase electrode

Figure 5.11. Reactive oxidant production by human neutrophils. In (a), neutrophils (5 x lOVml) were suspended in buffer containing 10 pM luminol in the presence and absence of a mixture of the extracellular oxidants scavengers SOD (1 /ig/ml), catalase (2 pg/ml) and methionine (0.25 mg/ml, to scavenge HOC1). In (b), neutrophils (1 x 106/ml) were suspended in buffer containing 75 jUM cytochrome c (to measure Of production) or 4 jUM scopoletin plus 5 /ig/ml horseradish peroxidase (to measure H202 production). In (c), neutrophils (2 x lOfyml) were placed in the chamber of a Clark-type 02 electrode. All measurements were made at 37 °C cell suspensions were stimulated by the addition of 1 /

Direct electron transfer has also been achieved with many metalloproteins such as cytochrome C, horseradish peroxidase, microperoxidase (MP-11), myoglobin, hemoglobin, catalase, azurin, and so on, immobilized on different CNT-modified electrodes [45, 61, 144—153]. 

Acetylcholineesterase and choline oxidase A glassy C electrode surface was modified with osmium poly (vinyl-pyridine) redox polymer containing horseradish peroxidase (Os-gel-HRP) and then coated with a co-immobilized layer of AChE and ChO. A 22 pL pre-reactor, in which ChO and catalase were immobilized on beads in series, was used to remove choline. The variation in extracellular concentration of ACh released from rat hippocampal tissue culture by electrical stimulation was observed continuously with the online biosensor combined with a microcapillary sampling probe. Measurement of ACh and Ch was carried out by using a split disc C film dual electrode. 

There have been few direct electrochemical studies of peroxidase and catalase due to the highly irreversible nature of these electrode reactions. Horseradish peroxidase was found to be electroinactive at the dropping mercury electrode. Tarasevich and co-workers observed a cyclic voltam-metric response for the electron transfer of horseradish peroxidase at an amalgamated gold electrode. However, this response was ascribed to the disulfide bonds of the protein at neutral pH and not to the heme group. No response was detected at pyrolytic graphite electrodes. ... 

In an earlier study Brown" reported that both horseradish peroxidase and beef liver catalase were electroinactive polarographically under anaerobic conditions. However, under conditions which gave rise to the primary hydrogen peroxide complexes of these proteins, a reductive response was observed. Brown attributed these responses to the direct reduction of the respective hydrogen peroxide complexes of peroxidase and catalase." In one other report catalase was reported to be electroinactive at the dropping mercury electrode. ... 

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