Microperoxidase-11 Monolayers

Cobalt(I I )-protoporphyrin IX-reconstitu-ted Mb has also been found to form an affinity complex with MP-11 mono-layer electrodes [338, 339]. The association constant of the affinity complex between the reconstituted Mb and MP-11 corresponds to = 1.6 x 10 M , and the electron-transfer rate constant in 

Fe(III)-de novo protein/NR, or Fe(III)-de novo protein/Co(II)-reconstituted Mb were cross-linked with glutaric dialdehyde to yield electrically contacted electrocatalytic electrodes. The Fe(III)-de novo protein/NR-electrode assembly was applied for the electrocatalyzed reduction of N03 to N02 and acted as an amperometric NOs sensor (Fig. 26b), and the Fe(III)-de novo protein/Co(II)-reconstituted Mb integrated electrode stimulated the electrocatalyzed hydrogenation of acetylene dicarboxyhc acid to malic acid. 

---

Microperoxidase-11 monolayers mediate electron transfer to hemoproteins [e.g., Cyt c, myoglobin (Mb) and hemoglobin (Hb)] by the formation of affinity complexes at the interface [81]. Microgravimetric analysis of these assemblies has determined the association constant of myoglobin to the MP-11 monolayer to be Ka = 3.9 X 10 M . The MP-11-hemoprotein affinity complexes permit the mediated reduction of protein heme sites. Figure 4 shows the electrocatalytic cathodic currents originating from the MP-11 MET to the heme centers of Cyt c, Mb and Hb. The heme-containing monolayer can also stimulate MET to cytochrome-... 

Figure 4. The electron-transfer process from an Au electrode to soluble heme proteins as mediated by a monolayer of microperoxidase-11. Cyclic voltammograms of a microperoxidase-11 monolayer-electrode in the absence (a) and presence of added hemoproteins (b) with hemoglobin, 6 X 10 M (c) with myoglobin, 2 x 10 M (d) with cytochrome c, 2 x 10 M. Measurements recorded in 0.1 M phosphate buffer, pH 7.0, under Ar potential scan rate, 5 mV s. ...

Katz E, Filanovsky B, WiUner I. A biofuel cell based on two immiscible solvents and glucose oxidase and microperoxidase-11 monolayer-functionalized electrodes. New J... 

Figure 21. (A) The assembly of an integrated nitrate sensor electrode by the cross-linking of a microperoxidase-11-nitrate reductase (cytochrome-dependent, EC 1.9.6.1) affinity complex on an Au electrode. (B) Cyclic voltammograms of the integrated MP-ll-NR monolayer-modified Au electrode (roughness factor ca. 15). (a) 0.1 M phosphate buffer, pH 7.0 (b) in the presence of KNO3, 20 mM. Potential scan rate, 5 mV s . Inset electrocatalytic cathodic currents [E = —0.6 V vs. SCE) transduced by the modified electrode at different concentrations of KNO3. Measurements were performed under argon.

A. N. J. Moore, E. Katz, I. Willner, Electrocatalytic Reduction of Organic Peroxides in Organic Solvents by Microperoxidase-11 Immobilized as a Monolayer on a Gold Electrode. J. Electroanal. Chem., 417 (1996) 189-192. 

The electrochemical contacting of solution-state enzymes with siuTace-immobilized redox-mediators is of interest for studying the interfacial association affinity interactions between enzymes and mediators. The electrochemical kinetics of electrodes functionalized with layers of various mediators (e.g. viologens [59], Ceo-derivatives [60], microperoxidase-11 [61]) have been studied upon their interaction with diffusionally free enzymes. Some relay-functionalized interfaces demonstrate MET without a significant amount of association of the enzyme molecules with the relay-modified surfaces. For example, a Ceo monolayer-functionalized Au-electrode has been applied to contact soluble GOx (Fig. 3a) [60]. CV revealed an efficient electrocatalytic current developed by the Ceo-modified electrode in the presence of GOx and glucose (Fig. 3b) [60], dependent on the glucose concentration (Fig. 3b, inset). However, kinetic analysis... 

The lanthaninn teehnique was used to study the epithelial permeability in the rat small intestine (Madara and Trier 1982). Dense lanthanum precipitates in TJ and paracellular spaces were restricted to a subpopulation of villous goblet cells and were not found between villous absorptive cells. These TJ were also permeable to barium, but not to macromolecular tracers such as microperoxidase, eytochrome c and horseradish peroxidase. It was also shown that palmitoylcamitine (PCC) opens TJ in a monolayer of Caco-2 colon carcinoma cells this phenomenon appears to be responsible for the significant enhancement of the absorption of hydrophilic drugs across intestinal mucosa caused by PCC and other long-chain acylcamitines (Hochman, Fix et al. 1994).In an experiment on rats, it was demonstrated that immobilisation stress induced a significant (but reversible) increase in epithelial permeability to the lanthanum tracer (Mazzon, Stumiolo et al. 2002). 

---