TY - THES A1 - Bistolas, Nikitas T1 - Investigation of the direct heterogenous electron transfer of hemoglobin and cytochrome P450 enzymes and bioanalytical application Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Bistolas, Nikitas A1 - Christenson, A. A1 - Ruzgas, T. A1 - Jung, Christiane A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula T1 - Spectroelectrochemistry of cytochrome P450cam N2 - The spectroelectrochemistry of camphor-bound cytochrome P450cam (P450cam) using gold electrodes is described. The electrodes were modified with either 4,4'-dithiodipyridin or sodium dithionite. Electrolysis of P450cam was carried out when the enzyme was in solution, while at the same time UV visible absorption spectra were recorded. Reversible oxidation and reduction could be observed with both 4,4'-dithiodipyridin and dithionite modified electrodes. A formal potential (E-0') of -373 mV vs Ag/AgCl 1 M KCl was determined. The spectra of P450cam complexed with either carbon monoxide or metyrapone, both being inhibitors of P450 catalysis, clearly indicated that the protein retained its native state in the electrochemical cell during electrolysis. (C) 2003 Elsevier Inc. All rights reserved Y1 - 2004 ER - TY - JOUR A1 - Bistolas, Nikitas A1 - Wollenberger, Ursula A1 - Jung, Christiane A1 - Scheller, Frieder W. T1 - Cytochrome P450 biosensors : a review N2 - Cytochrome P450 (CYP) is a large family of enzymes containing heme as the active site. Since their discovery and the elucidation of their structure, they have attracted the interest of scientist for many years, particularly due to their catalytic abilities. Since the late 1970s attempts have concentrated on the construction and development of electrochemical sensors. Although sensors based on mediated electron transfer have also been constructed, the direct electron transfer approach has attracted most of the interest. This has enabled the investigation of the electrochemical properties of the various isoforms of CYP. Furthermore, CYP utilized to construct biosensors for the determination of substrates important in environmental monitoring, pharmaceutical industry and clinical practice. (c) 2004 Elsevier B. V. All rights reserved Y1 - 2005 ER - TY - JOUR A1 - Colas, Helene A1 - Ewen, Kerstin M. A1 - Hannemann, Frank A1 - Bistolas, Nikitas A1 - Wollenberger, Ursula A1 - Bernhardt, Rita A1 - de Oliveira, Pedro T1 - Direct and mediated electrochemical response of the cytochrome P450 106A2 from Bacillus megaterium ATCC 13368 JF - Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society N2 - CYP106A2 is one of only a few known steroid hydroxylases of bacterial origin, which might be interesting for biotechnological applications. Despite the enzyme having been studied for more than 30 years, its physiological function remains elusive. To date, there have been no reports of the redox potential of CYP106A2, which was supposed to be unusually low for a cytochrome P450. In this work we show that cyclic voltammetry is not only suitable to determine the redox potential of challenging proteins such as CYP106A2, measured at - 128 mV vs. NHE, but also to study molecular interactions of the enzyme with different interaction partners via the respective electrochemical responses. The effect of small ligands, such as carbon monoxide and cyanide, was observed on the cyclic voltammograms of CYP106A2. Furthermore, we found that Tween 80 caused a positive shift of the redox potential of immobilised CYP106A2 indicative for water expulsion from the haem environment. Moreover, electron transfer mediation phenomena with biological redox partners (e.g. ferredoxins) were studied. Finally, the influence of two different kinds of substrates on the electrochemical response of CYP106A2 was assessed, aligning observations from spectral and electrochemical studies. KW - Cytochrome P450 KW - Cyclic voltammetry KW - Modified electrode KW - Protein interaction KW - Substrate binding Y1 - 2012 U6 - https://doi.org/10.1016/j.bioelechem.2012.01.006 SN - 1567-5394 VL - 87 IS - 5 SP - 71 EP - 77 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Lei, Chenghong A1 - Wollenberger, Ursula A1 - Bistolas, Nikitas A1 - Guiseppi-Eli, A. A1 - Scheller, Frieder W. T1 - Electron transfer of hemoglobin at electrodes modified with colloidal clay nanoparticles Y1 - 2002 ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Bistolas, Nikitas A1 - Liu, Songqin A1 - Jänchen, Michael A1 - Katterle, Martin A1 - Wollenberger, Ursula T1 - Thirty years of haemoglobin electrochemistry N2 - Electrochemical investigations of the blood oxygen carrier protein include both mediated and direct electron transfer. The reaction of haemoglobin (Hb) with typical mediators, e.g., ferricyanide, can be quantified by measuring the produced ferrocyanide which is equivalent to the Hb concentration. Immobilization of the mediator within the electrode body allows reagentless electrochemical measuring of Hb. On the other hand, entrapment of the protein within layers of polyclectrolytes, lipids, nanoparticles of clay or gold leads to a fast heterogeneous electron exchange of the partially denatured Hb. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 ER - TY - JOUR A1 - Shumyantseva, V. V. A1 - Ivanov, Y. D. A1 - Bistolas, Nikitas A1 - Scheller, Frieder W. A1 - Archakov, Alexander I. A1 - Wollenberger, Ursula T1 - Direct electron transfer of cytochrome P450 2B4 at electrodes modified with non-ionic detergent and colloidal clay nanoparticles N2 - A method for construction of biosensors with membranous cytochrome P450 isoenzymes was developed based on clay/ detergent/protein mixed films. Thin films of sodium montmorillonite colloid with incorporated cytochrome P450 2134 (CYP2B4) with nonionic detergent were prepared on glassy carbon electrodes. The modified electrodes were electrochemically characterized, and bio-electrocatalytic reactions were followed. CYP2B4 can be reduced fast on clay- modified glassy carbon electrodes in the presence of the nonionic detergent Tween 80. In anaerobic solutions, reversible oxidation and reduction is obtained with a formal potential between -0.292 and - 0.305 V vs Ag/AgCl 1 M KCl depending on the preparation of the biosensor. In air-saturated solution, bio-electrocatalytic reduction currents can be obtained with the CYP2B4-modified electrode on addition of typical substrates such as aminopyrine and benzphetamine. This reaction was suppressed when methyrapone, an inhibitor of P450 reactions, was present. Measurement of product formation also indicates the bioelectrocatialysis by CYP2B4 Y1 - 2004 ER - TY - JOUR A1 - Wollenberger, Ursula A1 - Bistolas, Nikitas A1 - Jung, Christiane A1 - Shumyantseva, V. V. A1 - Ruzgas, T. A1 - Scheller, Frieder W. T1 - Elektroden-Design für elektronische Wechselwirkung mit Monooxygenasen Y1 - 2004 SN - 3-8047-2132-x ER -