TY - JOUR A1 - Beissenhirtz, Moritz Karl A1 - Scheller, Frieder W. A1 - Stöcklein, Walter F. M. A1 - Kurth, D. A1 - Möhwald, Helmuth A1 - Lisdat, Fred T1 - Electroactive cytochrome c multilayers within a polyelectrolyte assembly Y1 - 2004 ER - TY - JOUR A1 - Lettau, Kristian A1 - Gajovic-Eichelmann, N. A1 - Kwak, Young-Keun A1 - Scheller, Frieder W. A1 - Warsinke, Axel T1 - Hydroxylasen und katalytische Polymere für Biochips Y1 - 2004 ER - TY - JOUR A1 - Kröning, Steffen A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula A1 - Lisdat, Fred T1 - Myoglobin-Clay Electrode for Nitric Oxide (NO) Detection in Solution Y1 - 2004 ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Tiepner, K. A1 - Warsinke, Axel T1 - Anwendung von Biosensoren in der Lebensmittelanalytik Y1 - 2004 SN - 3-89947-120-2 ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Wagener, C. T1 - From gene to life Y1 - 2004 ER - TY - JOUR A1 - Kleuser, U. A1 - Stöcklein, Walter F. M. A1 - Pieper-Fürst, U. A1 - Scheller, Frieder W. T1 - Partikelverstärkte Oberflächenplasmonresonanz für die Quantifizierung von Matrix Metalloproteinase-2 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 - TY - JOUR A1 - Scheller, Frieder W. A1 - Warsinke, Axel A1 - Pfeiffer, Dorothea A1 - Czeponik, J. T1 - Biosensorik / Bioanalytik Y1 - 2004 SN - 3-87081-372-5 ER - TY - JOUR A1 - Krylov, Andrey V. A1 - Beissenhirtz, Moritz Karl A1 - Adamzig, Holger A1 - Scheller, Frieder W. A1 - Lisdat, Fred T1 - Thick-film electrodes for measurement of superoxide and hydrogen peroxide based on direct protein-electrode contacts N2 - Cytochrome c was immobilized on screen-printed thick-film gold electrodes by a self-assembly approach using mixed monolayers of mercaptoundecanoic acid and mercaptoundecanol. Cyclic voltammetry revealed quasi-reversible electrochemical behavior of the covalently fixed protein with a formal potential of +10 mV vs. Ag/AgCl. Polarized at +150 mV vs. Ag/AgCl the electrode was found to be sensitive to superoxide radicals in the range 300-1200 nmol L-1. Compared with metal needle electrodes sensitivity and reproducibility could be improved and combined with the easiness of preparation. This allows the fabrication of disposable sensors for nanomolar superoxide concentrations. By changing the electrode potential the sensor can be switched from response to superoxide radicals to hydrogen peroxide-another reactive oxygen species. H2O2 sensitivity can be provided in the range 10-1000 mumol L-1 which makes the electrode suitable for oxidative stress studies Y1 - 2004 ER - TY - JOUR A1 - Beissenhirtz, Moritz Karl A1 - Kwan, R. C. H. A1 - Ko, K. M. A1 - Renneberg, Reinhard A1 - Scheller, Frieder W. A1 - Lisdat, Fred T1 - Comparing in vitro electrochemical measurement of superoxide scavenging activity with an in vivo assessment of antioxidant potential in Chinese tonifying herbs N2 - The in vitro superoxide scavenging activity (as determined by electrochemical measurement) and the in vivo antioxidant potential (as determined by a mouse model of carbon tetrachloride (CCl4) hepatotoxicity) of methanolic extracts prepared from 10 Chinese tonifying herbs were compared. Electrochemical measurement using a cytochrome c (Cyt. c) sensor showed that all of the tested herbal extracts exhibited a medium superoxide scavenging activity of different potency, as indicated by their IC50 values. The in vivo measurement demonstrated that 80% of the herbal extracts displayed in vivo antioxidant potential, as assessed by the percentage of protection of the activity of plasma alanine aminotransferases and the hepatic glutathione regeneration capacity under CCl4-intoxicated condition. Although the in vitro antioxidant activity did not correlate quantitatively with the in vivo antioxidant potential, for 8 out of 10 samples a similar tendency was found. The rapid amperometric assessment of antioxidant potential by Cyt. c sensor may offer a convenient and direct method for screening as well as the quality control of herbal products. Copyright (C) 2004 John Wiley Sons, Ltd Y1 - 2004 ER - TY - JOUR A1 - Beissenhirtz, Moritz Karl A1 - Scheller, Frieder W. A1 - Lisdat, Fred T1 - A superoxide sensor based on a multilayer cytochrome c electrode N2 - A novel multilayer cytochrome c electrode for the quantification of superoxide radical concentrations is introduced. The electrode consists of alternating layers of cytochrome c and poly(aniline(sulfonic acid)) on a gold wire electrode. The formation of multilayer structures was proven by SPR experiments. Assemblies with 2-15 protein layers showed electrochemical communication with the gold electrode. For every additional layer, a substantial increase in electrochemically active cytochrome c (cyt. c) was found. For electrodes of more than 10 layers, the increase was more than 1 order of magnitude as compared to monolayer electrode systems. Thermodynamic and kinetic parameters of the electrodes were characterized. The mechanism of electron transfer within the multilayer assembly was studied, with results suggesting a protein-protein electron-transfer model. Electrodes of 2-15 layers were applied to the in vitro quantification of enzymatically generated superoxide, showing superior sensitivity as compared to a monolayer-based sensor. An electrode with 6 cyt. c/PASA layers showed the highest sensitivity of the systems studied, giving an increase in sensitivity of half an order of magnitude versus the that of the monolayer electrode. The stability of the system was optimized using thermal treatment, resulting in no loss in sensor signal or protein loading after 10 successive measurements or 2 days of storage Y1 - 2004 SN - 0003-2700 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 - Kulys, J. A1 - Krikstopaitis, K. A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula T1 - Electrochemical parameters of phenoxazine derivatives in solution and at monolayer-modified gold electrodes N2 - Electrochemical properties of beta-(10-phenoxazinyl) propylamine (APPX) and beta-(10-phenoxazinyl) propionic acid (PPX) have been studied in solution, and in immobilized state on gold electrodes modified with monolayers of cystamine and mercaptoundecanoic acid. A reversible diffusion-controlled process of APPX and PPX was observed at a bare gold electrode. The electrochemical conversion of both compounds at modified gold electrodes was a quasireversible diffusion-controlled process. The redox potential of immobilized APPX (443 mV) was similar to the potential in solution, while the value of the immobilized PPX was 131 mV higher than in solution. The immobilized mediators were electrocatalytically active in the fungal peroxidase-catalyzed hydrogen peroxide reduction Y1 - 2004 ER - TY - JOUR A1 - Lettau, Kristian A1 - Warsinke, Axel A1 - Laschewsky, André A1 - Mosbach, K. A1 - Yilmaz, E. A1 - Scheller, Frieder W. T1 - An esterolytic imprinted polymer prepared via a silica-supported transition state analogue N2 - In this work we describe a new preparation method for an esterolytic imprinted polymer with catalytic sites on the surface. A template was prepared by immobilizing a transition state analogue (phosphoramidic acid derivative) of an esterolytic reaction within porous silica particles. Polymerization within the pores was carried out using 4- vinylimidazole as a functional monomer and divinylbenzene as a cross-linker. The polymer was released by dissolution of the silica support with hydrofluoric acid and catalytic properties were studied by incubation with three different 4- nitrophenylesters and spectrophotometric determination of the released 4-nitrophenol. For 4-nitrophenyl acetate an activity of 211 nmol min(-1) mg(-1) and a K-m value of 2.2 mmol L-1 was obtained Y1 - 2004 ER - TY - JOUR A1 - Pieper-Fürst, U. A1 - Kleuser, U. A1 - Stöcklein, Walter F. M. A1 - Warsinke, Axel A1 - Scheller, Frieder W. T1 - Detection of subicomolar concentrations of human matrix metalloproteinase-2 by an optical biosensor N2 - We describe in this paper the development of a one-step sandwich assay for the highly sensitive and fast detection of human matrix metalloproteinase (MMP)-2 (EC 3.4.24.24), using surface plasmon resonance (SPR). For the assay, two ligands were selected: monoclonal anti-MMP-2 antibody Ab-2 and the tissue inhibitor of metalloproteinases (TIMP)-2. They were chosen on the basis of (1) their affinities to MMP-2, (2) the efficiency of immobilization to the sensor chip, (3) the efficiency of adsorption to colloidal gold, and (4) the stability of these protein-coated gold particles. The assay included mixing of MMP-2 with antibody Ab-2 adsorbed to colloidal gold with a diameter of about 20 rim and injection into the flowcell of the SPR instrument containing immobilized TIMP-2. By using colloidal gold particles an amplification factor of 114 and a detection limit of 0.5 pM for MMP-2 were obtained. The precision of the assay was high even at low analyte concentrations, the standard deviation being 8.3% for five determinations of 1 pM MMP- 2. No significant binding was observed with the structurally related MMP-9. The assay is far more sensitive and faster than commonly used methods for MMP-2 detection. As TIMP-bound MMP-2 is not detected by this method, the assay can be applied for measuring free MMP-2, reflecting the imbalance of free and inhibitor-bound enzyme in various pathological situations. (C) 2004 Elsevier Inc. All rights reserved Y1 - 2004 ER - TY - JOUR A1 - Loew, Noya A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula T1 - Characterization of self-assembling of glucose dehydrogenase in mono- and multilayers on gold electrodes N2 - Glucose dehydrogenase (GDH) was assembled electrostatically onto QCM-gold electrodes by their sequential deposition with anionic polyelectrolytes such as PSS and PASA. For the layer-by-layer arrangements both the microgravimetric and the electrochemical sensor signal were followed. Increasing amounts of GDH were deposited by stepwise formation of alternating layers of GDH and PSS or PASA. The mass increase was about 1.88 mug/cm(2) for one GDH/ PASA bilayer and 2.4 mug/cm(2) for a GDH/PSS bilayer. The addition of phenolic compounds resulted in an oxidation current, which could be catalytically increased by the GDH catalysed reaction in the presence of glucose. The system functions as glucose sensor when quinones are present in nonlimiting amount. The amperometric response was already diffusion limited when a single layer of GDH was adsorbed. The sensor sensitivity increased by a factor of 10 when MSA was used instead of MUA as initial electrode modifier Y1 - 2004 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 - Scheller, Frieder W. A1 - Bier, Frank Fabian T1 - Analytical Biochemistry (Editorial) Y1 - 2004 ER -