| 1. |
- Brusova, Z, et al.
(författare)
-
Bioelectrocatalysis of plant peroxidases immobilized on graphite in aqueous and mixed solvent media
- 2005
-
Ingår i: Electroanalysis. - : Wiley. - 1040-0397 .- 1521-4109. ; 17:5-6, s. 460-468
-
Tidskriftsartikel (refereegranskat)abstract
- The bioelectrocatalytic function of two plant peroxidases, horseradish peroxidase (HRP) and a newly purified royal palm tree-leaf peroxidase (RPTP), was studied on graphite electrodes in aqueous buffer solutions, over the pH range 7.0 - 3.0, and in aqueous buffer solutions, at pH 6.0, containing different amounts of a polar organic cosolvent, i.e., ethanol and acetonitrile. The kinetics of direct and of mediated (using catechol as mediator) reduction of H2O2 at the HRP- and RPTP-modified graphite electrodes were analyzed amperometrically at - 50 mV(vs. Ag broken vertical bar AgCl broken vertical bar 0.1 M KCl) in a flow-through wall-jet electrochemical system. Values of the apparent rate constant of the heterogeneous electron transfer between the enzyme and graphite, k(s) the rate constant for enzymatic reduction of H2O2, k(1), and the rate constant of mediated reduction of H2O2, k(3), were determined using the modified Koutecky-Levich approach. Analysis of the variation of the rate constants and the response of the peroxidase-modified electrodes to H2O2 with pH and content of the organic cosolvent demonstrated that maximal peroxidase bioelectrocatalytic activity occurred at pH 5.0 - 6.0 and at concentrations of ethanol of 10 - 20% v/v. At a lower pH, higher concentrations of ethanol, and in aqueous solutions of acetonitrile, the bioelectrocatalytic activity of the peroxidase-modified electrodes drastically decreased. However, contrary to the data for homogeneous catalysis, both peroxidases were bioelectrocatalytically active even in 95% organic co-solvents, thus demonstrating a stabilizing effect of the enzyme immobilization on the bioelectrocatalytic performance of the peroxidases. RPTP immobilized on graphite demonstrated lower overall activity but a higher pH- and organic cosolvent-stability than HRP.
|
|
| 2. |
- Fapyane, Deby, et al.
(författare)
-
Gated electron transfer reactions of truncated hemoglobin from Bacillus subtilis differently orientated on SAM-modified electrodes
- 2015
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:23, s. 15365-15374
-
Tidskriftsartikel (refereegranskat)abstract
- Electron transfer (ET) reactions of truncated hemoglobin from Bacillus subtilis (trHb-Bs) are suggested to be implicated in biological redox signalling and actuating processes that may be used in artificial environment-sensing bioelectronic devices. Here, kinetics of ET in trHb-Bs covalently attached via its surface amino acid residues either to COOH- or NH2-terminated (CH2)(2-16) alkanethiol SAM assembled on gold are shown to depend on the alkanethiol length and functionalization, not being limited by electron tunnelling through the SAMs but gated by ET preceding reactions due to conformational changes in the heme active site/at the interface. ET gating was sensitive to the properties of SAMs that trHb-Bs interacted with. The ET rate constant k(s) for a 1e(-)/H+ reaction between the SAM-modified electrode and heme of trHb-Bs was 789 and 110 s(-1) after extrapolation to a zero length SAM, while the formal redox potential shifted 142 and 31 mV, for NH2- and COOH-terminated SAMs, respectively. Such domain-specific sensitivity and responsivity of redox reactions in trHb-Bs may be of immediate biological relevance and suggest the existence of bioelectronic regulative mechanisms of ET proceeding in vivo at the protein-protein charged interfaces that modulate the protein reactivity in biological redox signalling and actuating events.
|
|
| 3. |
- Ferapontova, Elena, et al.
(författare)
-
Direct electrochemical oxidation of DNA on polycrystalline gold electrodes
- 2003
-
Ingår i: Electroanalysis. - : Wiley. - 1040-0397 .- 1521-4109. ; 15:7, s. 629-634
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochemical CV and SWV studies were performed with double stranded DNA from salmon testes (dsDNA) and single stranded DNAs, containing 25 nucleotides (ssDNA) directly adsorbed at polycrystalline An electrodes. A distinct oxidation peak at + 730 mV (SWV, scan rate 0.248 V s(-1)) or at + 730 - + 780 mV (CV, scan rate from 0.3 to 1 V s(-1)) was obtained with DNA-modified Au electrodes after a time-dependent prepolarization step at a positive potential value, i.e., at + 500 mV (vs. Ag AgCl), performed with the DNA-modified Au electrodes dipped in a blank buffer solution. No electrochemical activity was detected when ssDNA, containing no guanines, was used for adsorptive modification of the Au electrodes. Electrochemical impedance measurements registered a possible reorganization of the adsorbed DNA layer in the course of the prepolarization, accompanied by decreasing in-phase impedance. ne results enable us to relate the oxidation process observed at the DNA-modified Au electrodes with the oxidation of guanine residues in DNA.
|
|
| 4. |
- Ferapontova, Elena, et al.
(författare)
-
Direct electrochemistry of proteins and enzymes
- 2005
-
Ingår i: Electrochemistry of nucleic acids and proteins : towards electrochemical sensors for genomic and proteomics. - 044452150X
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
|
|
| 5. |
- Ferapontova, Elena E., et al.
(författare)
-
Bioelectrocatalytic detection of theophylline at theophylline oxidase electrodes
- 2007
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 22:11, s. 2508-2515
-
Tidskriftsartikel (refereegranskat)abstract
- Bioelectrocatalytic oxidation of theophylline was studied at gold and graphite electrodes modified with microbial theophylline oxidase (ThOx), a multi-cofactor redox enzyme capable of selective oxidation of theophylline. Gold electrodes were additionally modified with self-assembled monolayers (SAMs) of (-OH)- and (-NH2)-terminated alkanethiols of different chain lengths, to achieve compatibility between ThOx and the electrode surface. On graphite, ThOx was either physically co-adsorbed with a surfactant didodecyldimethylammonium bromide (DDAB), or entrapped within an Os-redox-polymer film. At all electrodes, ThOx was bioelectrocatalytically active; direct electrochemistry of ThOx in the absence of theophylline was followed only at the SAM-modified gold electrodes. Direct electrochemistry of ThOx correlated with redox transformations of the heme domain of ThOx, with a E-o/ of - 110 +/- 2 mV versus Ag vertical bar AgCl, at pH 7. Bioelectrocatalytic oxidation of theophylline was optimal at mixed (-OH)/(-NH2)-terminated SAMs; co-adsorption of ThOx with DDAB improved the bioelectrocatalytic performance of the ThOx-electrode. In both cases, the response to theophylline was within the mM range. Alternatively, a reagentless ThOx-electrode based on ThOx cross-linked within the Os-redox-polymer matrix demonstrated a linear response to theophylline within the physiologically important 0.02-0.6 mM (3.6-72 mg I-1) concentration range with a sensitivity of 52.1 +/- 7.8 mA cm(-2) m(-1). (c) 2006 Elsevier B.V. All rights reserved.
|
|
| 6. |
- Fernandez, Esther, et al.
(författare)
-
Electron transfer reactions, cyanide and O-2 binding of truncated hemoglobin from Bacillus subtilis
- 2013
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 110, s. 86-93
-
Tidskriftsartikel (refereegranskat)abstract
- The truncated hemoglobin from Bacillus subtilis (trHb-Bs) possesses a surprisingly high affinity for oxygen and resistance to (auto)oxidation; its physiological role in the bacterium is not understood and may be connected with its very special redox and ligand binding reactions. Electron transfer reactions of trHb-Bs were electrochemically studied in solution and at graphite electrodes. Spectrophotometrical potentiometric titration and direct electrochemical measurements gave a heme iron redox potential of -103 +/- 4 mV and -108 +/- 2 mV vs. NHE, at pH 7, respectively. The redox potential of the heme in trHb-Bs shifted -59 mV per pH unit at pH higher than 7, consistently with a 1e(-)/1H(+) - transfer reaction. The heterogeneous rate constant k(s), for a quasi-reversible 1e(-)-1H(+) - transfer reaction between graphite and trHb-Bs was 10.1 +/- 2.3 s(-1). Upon reversible cyanide binding the ks doubled, while the redox potential of heme shifted 21 mV negatively, presumably reflecting changes in redox activity and in vivo signaling functions of trHb-Bs associated with ligand binding Bioelectrocatalytic reduction of O-2 catalyzed by trHb-Bs was one of the most efficient hitherto reported for Hbs, with an apparent catalytic rate constant, k(cat), of 56 +/- 6s(-1). The results obtained are of particular interest for applications of trHb in environmental biosensing and toxicity screening. (C) 2013 Elsevier Ltd. All rights reserved.
|
|
| 7. |
- Shipovskov, Stepan, et al.
(författare)
-
Spraying enzymes in microemulsions of AOT in nonpolar organic solvents for fabrication of enzyme electrodes
- 2005
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 77:21, s. 7074-7079
-
Tidskriftsartikel (refereegranskat)abstract
- A new technique suitable for automated, large-scale fabrication of enzyme electrodes by air-spraying enzymes in organic inks is presented. Model oxidoreductases, tyrosinase (Tyr) and glucose oxidase (GOx), were adapted to octane-based ink by entrapment in a system of reverse micelles (RM) of surfactant AOT in octane to separate and stabilize the catalytically active forms of the enzymes in nonpolar organic media. Nonpolar caoutchouk polymer was also used to create a kind of "dry micelles" at the electrode/solution interface. Enzyme/RM/polymer-containing organic inks were air-brushed onto conductive supports and were subsequently covered by sprayed Nafion membranes. The air-brushed enzyme electrodes exhibited relevant bioelectrocatalytic activity toward catechol and glucose, with a linear detection range of 0.1-100 mu M catechol and 0.5-7 mM glucose; the sensitivities were 2.41 A M-1 cm(-2) and 2.98 mA M-1 cm(-2) for Tyr and GOx electrodes, respectively. The proposed technique of air-brushing enzymes in organic inks enables automated construction of disposable enzyme electrodes of various designs on a mass-production scale.
|
|
| 8. |
- Sosna, Maciej, et al.
(författare)
-
Direct electrochemistry and Os-polymer-mediated bioelectrocatalysis of NADH oxidation by Escherichia coil flavohemoglobin at graphite electrodes
- 2013
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 42, s. 219-224
-
Tidskriftsartikel (refereegranskat)abstract
- Escherichia coli flavohemoglobin (HMP), which contains one heme and one FAD as prosthetic groups and is capable of reducing O-2 by its heme at the expense of NADH oxidized at its FAD site, was electrochemically studied at graphite (Gr) electrodes. Two signals were observed in voltammograms of HMP adsorbed on Gr, at -477 and -171 mV vs. Ag vertical bar AgCl, at pH 7.4, correlating with electrochemical responses from the FAD and heme domains, respectively. The electron transfer rate constant for ET reaction between FAD of HMP and the electrode was estimated to be 83 s(-1). Direct bioelectrocatalytic oxidation of NADH by HMP was not observed, presumably due to impeded substrate access to HMP orientated on Gr through the FAD-domain and/or partial denaturation of HMP. Bioelectrocatalysis was achieved when HMP was wired to Gr by the Os redox polymers, with the onset of NADH oxidation at the formal potential of the particular Os complex (+140 mV or -195 mV). Apparent Michaelis constants K-M(app) and j(max) were determined, showing bioelectrocatalytic efficiency of NADH oxidation by HMP exceeding the one earlier shown with diaphorase, which makes HMP very attractive as a component of bioanalytical and bioenergetic devices. (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 9. |
- Sosna, Maciej, et al.
(författare)
-
Electrochemical Characterization and Bioelectrocatalytic H2O2 Sensing of Non-Symbiotic Hexa-Coordinated Sugar Beet Hemoglobins
- 2020
-
Ingår i: ChemElectroChem. - : Wiley. - 2196-0216. ; 7:9, s. 2114-2122
-
Tidskriftsartikel (refereegranskat)abstract
- The biological role of non-symbiotic plant hemoglobins (Hbs) is not well understood. It may involve sensing and signaling of reactive nitrogen and oxygen species–a property that can be used in electrochemical sensing. Here, we electrochemically studied two novel non-symbiotic Beta vulgaris Hbs: BvHb1.2 and BvHb2 expressed in E. coli. At pH 7, we observed close potentials of their Fe2+/3+ hemes, −349 mV for BvHb1.2 and −345/−457 mV vs. Ag/AgCl for the “open” penta-/“closed” hexa-coordinated states of BvHb2. BvHbs bound and bioelectrocatalytically reduced O2 and H2O2 at potentials significantly exceeding their Fe2+/3+ heme potentials. BvHb2, with the onset of H2O2 reduction at 370 mV, enabled O2-interference-free 10 μM H2O2 detection at 0 mV, with a 87 nA μM−1 cm−2 sensitivity comparable to some peroxidases. The results underpin broad electrochemical applications of BvHbs in the electroanalysis of reactive species and in electrochemical biotransformations.
|
|
