Horseradish peroxidase , scanning

The enzyme horseradish peroxidase is a hemoprotein and the region of the Soret band exhibits large differences between the position and extinction coefficients of the uncombined and combined forms. Both forms were first studied by spectrophotometry, but the E—S complexes were 0 labile that they could not be examined extensively by any other spectroscopic method. Using rapid-scanning spectrophotometry and rapid mixing, Chance was able to distinguish the spectra of compound I and II and determine the various rate constants of the multistep reaction with rather poor precision. 

H Zhou, S Kasai, T Yasukawa, T Matsue. Imging the activity of immobilized horseradish peroxidase with scanning electrochemical/chemiluminescence microscopy. Electrochemistry 67 1135-1137, 1999. 

FIGURE 11.13. Cyclic voltammogram of 4-mM DMFc on a horseradish peroxidase (HRP)/Eastman AQ 55-modified glassy carbon electrode (GCE) in acetonitrile containing 1.5% v/v water at 20 C. (A) Response of the biosensor in the absence (I) and presence (II) of 1 mM butanone peroxide (BTP). (B) Response of the biosensor to 1 mM BTP (I) and on addition of 1 mM of the inhibitor, thiourea (II). A 20 1 drop of mixed polymer-enzyme solution containing 1.4% Eastman AQ55 polymer and 0.05 mg HRP was evaporated on a 3 mm diameter GCE scan rate 5 mV s support electrolyte 0.1 M tetraethylammonium p-toluenesulphonate. 

Fig. 4. Repeated scan UV-spectra in lAA-Asp (A) and lAA (B) oxidase reactions by horseradish peroxidase. A spectrum was scanned every 5 min. Room temperature was 23 C. 0.4 jiiM peroxidase, 50 mM sodium acetate (pH 4). A, 0.1 mM IAA-Asp + 0.1 mM H,0.>. B, 0.1 mM lAA...

Figure 3. Dependence of current on potential for a NaI04 oxidized horseradish peroxidase immobilized in a 3-dimensional epoxy hydrogel free of electron relaying osmium redox centers. (A) noH2C (B) 0.1mMH2O2 Conditions aerated pH 7 physiological phosphate buffer solution scan rate 2.5 mV s l 500 RPM.

FIGURE 11.5 Approach curve of a HjOj-selective amperometric tip electrode toward a polymer layer loaded with GOx. The tip was produced by immobilizing horseradish peroxidase onto the cross section of an insulated carbon fiber of 7 pm diameter. Solution composition 1 mM glucose in air-saturated 0.2 M phosphate buffer, pH 7. (Reprinted with permission from Horrocks, B.R., Schmidtke, D., Heller, A., and Bard, A.J., Scanning electrochemical microscopy. 24. Enzyme ultramicroelectrodes for the measurement of hydrogen peroxide at surfaces, Anal. Chem., 65, 3605-3614, 1993. Copyright 1993 American Chemical Society.)... 

Zhou, H., Kasai, S., Matsue, T., Imaging localized horseradish peroxidase on a glass surface with scanning electrochemical/ chemiluminescence microscopy. AwaZ. Biochem. 2001, 290, 83-88. 

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