TY - GEN A1 - Scheller, Frieder W. A1 - Sakar Dasdan, Dolunay T1 - Selected papers presented on the 2nd International Conference on the New Trends in Chemistry, Zagreb, Croatia, April 19-22, 2016 Preface T2 - Bulgarian chemical communications : journal of the Chemical Institutes of the Bulgarian Academy of Sciences and of the Bulgarian Chemical Society = Izvestija po chimija Y1 - 2016 SN - 0324-1130 VL - 48 SP - 4 EP - 4 PB - Bulgarian Academy of Sciences CY - Sofia ER - TY - JOUR A1 - Peng, Lei A1 - Yarman, Aysu A1 - Jetzschmann, Katharina J. A1 - Jeoung, Jae-Hun A1 - Schad, Daniel A1 - Dobbek, Holger A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Molecularly Imprinted Electropolymer for a Hexameric Heme Protein with Direct Electron Transfer and Peroxide Electrocatalysis JF - SENSORS N2 - For the first time a molecularly imprinted polymer (MIP) with direct electron transfer (DET) and bioelectrocatalytic activity of the target protein is presented. Thin films of MIPs for the recognition of a hexameric tyrosine-coordinated heme protein (HTHP) have been prepared by electropolymerization of scopoletin after oriented assembly of HTHP on a self-assembled monolayer (SAM) of mercaptoundecanoic acid (MUA) on gold electrodes. Cavities which should resemble the shape and size of HTHP were formed by template removal. Rebinding of the target protein sums up the recognition by non-covalent interactions between the protein and the MIP with the electrostatic attraction of the protein by the SAM. HTHP bound to the MIP exhibits quasi-reversible DET which is reflected by a pair of well pronounced redox peaks in the cyclic voltammograms (CVs) with a formal potential of -184.4 +/- 13.7 mV vs. Ag/AgCl (1 M KCl) at pH 8.0 and it was able to catalyze the cathodic reduction of peroxide. At saturation the MIP films show a 12-fold higher electroactive surface concentration of HTHP than the non-imprinted polymer (NIP). KW - hydrogen peroxide KW - bioelectrocatalysis KW - molecularly imprinted polymers KW - direct electron transfer KW - self-assembled monolayer Y1 - 2016 U6 - https://doi.org/10.3390/s16030272 SN - 1424-8220 VL - 16 SP - 1343 EP - 1364 PB - MDPI CY - Basel ER - TY - JOUR A1 - Erdossy, Julia A1 - Horvath, Viola A1 - Yarman, Aysu A1 - Scheller, Frieder W. A1 - Gyurcsanyi, Robert E. T1 - Electrosynthesized molecularly imprinted polymers for protein recognition JF - Trends in Analytical Chemistry N2 - Molecularly imprinted polymers (MIPs) for the recognition of proteins are expected to possess high affinity through the establishment of multiple interactions between the polymer matrix and the large number of functional groups of the target. However, while highly affine recognition sites need building blocks rich in complementary functionalities to their target, such units are likely to generate high levels of nonspecific binding. This paradox, that nature solved by evolution for biological receptors, needs to be addressed by the implementation of new concepts in molecular imprinting of proteins. Additionally, the structural variability, large size and incompatibility with a range of monomers made the development of protein MIPs to take a slow start. While the majority of MIP preparation methods are variants of chemical polymerization, the polymerization of electroactive functional monomers emerged as a particularly advantageous approach for chemical sensing application. Electropolymerization can be performed from aqueous solutions to preserve the natural conformation of the protein templates, with high spatial resolution and electrochemical control of the polymerization process. This review compiles the latest results, identifying major trends and providing an outlook on the perspectives of electrosynthesised protein-imprinted MIPs for chemical sensing. (C) 2016 Elsevier B.V. All rights reserved. KW - Molecularly imprinted polymers KW - Proteins KW - Surface imprinting KW - Electropolymerization KW - Nanostructuring KW - Hybrid nanofilms Y1 - 2016 U6 - https://doi.org/10.1016/j.trac.2015.12.018 SN - 0165-9936 SN - 1879-3142 VL - 79 SP - 179 EP - 190 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Menger, Marcus A1 - Yarman, Aysu A1 - Erdössy, Júlia A1 - Yildiz, Huseyin Bekir A1 - Gyurcsányi, Róbert E. A1 - Scheller, Frieder W. T1 - MIPs and Aptamers for Recognition of Proteins in Biomimetic Sensing JF - Biosensors : open access journal N2 - Biomimetic binders and catalysts have been generated in order to substitute the biological pendants in separation techniques and bioanalysis. The two major approaches use either "evolution in the test tube" of nucleotides for the preparation of aptamers or total chemical synthesis for molecularly imprinted polymers (MIPs). The reproducible production of aptamers is a clear advantage, whilst the preparation of MIPs typically leads to a population of polymers with different binding sites. The realization of binding sites in the total bulk of the MIPs results in a higher binding capacity, however, on the expense of the accessibility and exchange rate. Furthermore, the readout of the bound analyte is easier for aptamers since the integration of signal generating labels is well established. On the other hand, the overall negative charge of the nucleotides makes aptamers prone to non-specific adsorption of positively charged constituents of the sample and the "biological" degradation of non-modified aptamers and ionic strength-dependent changes of conformation may be challenging in some application. KW - biomimetic recognition elements KW - aptamers KW - molecularly imprinted polymers KW - chemical sensors KW - aptasensors KW - in vitro selection KW - SELEX Y1 - 2016 U6 - https://doi.org/10.3390/bios6030035 SN - 2079-6374 VL - 6 SP - 4399 EP - 4413 PB - MDPI CY - Basel ER - TY - JOUR A1 - Yarman, Aysu A1 - Scheller, Frieder W. T1 - MIP-esterase/Tyrosinase Combinations for Paracetamol and Phenacetin JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - A new electrochemical MIP sensor for the most frequently used drug paracetamol (PAR) was prepared by electropolymerization of mixtures containing the template molecule and the functional monomers ophenylenediamine, resorcinol and aniline. The imprinting factor of 12 reflects the effective target binding to the MIP as compared with the non-imprinted electropolymer. Combination of the MIP with a nonspecific esterase allows the measurement of phenacetin - another analgesic drug. In the second approach the PAR containing sample solution was pretreated with tyrosinase in order to prevent electrochemical interferences by ascorbic acid and uric acid. Interference-free indication at a very low electrode potential without fouling of the electrode surface was achieved with the o-phenylenediamine: resorcinol-based MIP. KW - Paracetamol KW - Molecularly imprinted polymers KW - Electropolymerization KW - Tyrosinase KW - Esterase KW - Phenacetin Y1 - 2016 U6 - https://doi.org/10.1002/elan.201600042 SN - 1040-0397 SN - 1521-4109 VL - 28 SP - 2222 EP - 2227 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Yarman, Aysu A1 - Dechtrirat, Decha A1 - Bosserdt, Maria A1 - Jetzschmann, Katharina J. A1 - Gajovic-Eichelmann, Nenad A1 - Scheller, Frieder W. T1 - Cytochrome c-derived hybrid systems based on moleculary imprinted polymers JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - Hybrid architectures which combine a MIP with an immobilized affinity ligand or a biocatalyst sum up the advantages of both components. In this paper, hybrid architectures combining a layer of a molecularly imprinted electropolymer with a mini-enzyme or a self-assembled monolayer will be presented. (i) Microperoxidase-11 (MP-11) catalyzed oxidation of the drug aminopyrine on a product-imprinted sublayer: The peroxide dependent conversion of the analyte aminopyrine takes place in the MP-11 containing layer on top of a product-imprinted electropolymer on the indicator electrode. The hierarchical architecture resulted in the elimination of interfering signals for ascorbic acid and uric acid. An advantage of the new hierarchical structure is the separation of MIP formation by electropolymerization and immobilization of the catalyst. In this way it was for the first time possible to integrate an enzyme with a MIP layer in a sensor configuration. This combination has the potential to be transferred to other enzymes, e.g. P450, opening the way to clinically important analytes. (ii) Epitope-imprinted poly-scopoletin layer for binding of the C-terminal peptide and cytochrome c (Cyt c): The MIP binds both the target peptide and the parent protein almost eight times stronger than the non-imprinted polymer with affinities in the lower micromolar range. Exchange of only one amino acid in the peptide decreases the binding by a factor of five. (iii) MUA-poly-scopoletin MIP for cytochrome c: Cyt c bound to the MIP covered gold electrode exhibits direct electron transfer with a redox potential and rate constant typical for the native protein. The MIP cover layer suppresses the displacement of the target protein by BSA or myoglobin. The combination of protein imprinted polymers with an efficient electron transfer is a new concept for characterizing electroactive proteins such as Cyt c. The competition with other proteins shows that the MIP binds its target Cyt c preferentially and that molecular shape and the charge of protein determine the binding of interfering proteins. KW - Molecularly imprinted polymers KW - Microperoxidase-11 KW - Cytochrome c KW - Catalytically active MIPs KW - Epitope imprinting KW - Monoclonal MIPs Y1 - 2015 U6 - https://doi.org/10.1002/elan.201400592 SN - 1040-0397 SN - 1521-4109 VL - 27 IS - 3 SP - 573 EP - 586 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Peng, Lei A1 - Utesch, Tillmann A1 - Yarman, Aysu A1 - Jeoung, Jae-Hun A1 - Steinborn, Silke A1 - Dobbek, Holger A1 - Mroginski, Maria Andrea A1 - Tanne, Johannes A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Surface-Tuned Electron Transfer and Electrocatalysis of Hexameric Tyrosine-Coordinated Heme Protein JF - Chemistry - a European journal N2 - Molecular modeling, electrochemical methods, and quartz crystal microbalance were used to characterize immobilized hexameric tyrosine-coordinated heme protein (HTHP) on bare carbon or on gold electrodes modified with positively and negatively charged self-assembled monolayers (SAMs), respectively. HTHP binds to the positively charged surface but no direct electron transfer (DET) is found due to the long distance of the active sites from the electrode surfaces. At carboxyl-terminated surfaces, the neutrally charged bottom of HTHP can bind to the SAM. For this "disc" orientation all six hemes are close to the electrode and their direct electron transfer should be efficient. HTHP on all negatively charged SAMs showed a quasi-reversible redox behavior with rate constant k(s) values between 0.93 and 2.86 s(-1) and apparent formal potentials E-app(0)' between -131.1 and -249.1 mV. On the MUA/MU-modified electrode, the maximum surface concentration corresponds to a complete monolayer of the hexameric HTHP in the disc orientation. HTHP electrostatically immobilized on negatively charged SAMs shows electrocatalysis of peroxide reduction and enzymatic oxidation of NADH. KW - electrochemistry KW - electron transfer KW - heme proteins KW - molecular modeling KW - monolayers Y1 - 2015 U6 - https://doi.org/10.1002/chem.201405932 SN - 0947-6539 SN - 1521-3765 VL - 21 IS - 20 SP - 7596 EP - 7602 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Spricigo, Roberto A1 - Leimkühler, Silke A1 - Gorton, Lo A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula T1 - The Electrically Wired Molybdenum Domain of Human Sulfite Oxidase is Bioelectrocatalytically Active JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - We report electron transfer between the catalytic molybdenum cofactor (Moco) domain of human sulfite oxidase (hSO) and electrodes through a poly(vinylpyridine)-bound [osmium(N,N'-methyl-2,2'-biimidazole)(3)](2+/3+) complex as the electron-transfer mediator. The biocatalyst was immobilized in this low-potential redox polymer on a carbon electrode. Upon the addition of sulfite to the immobilized separate Moco domain, the generation of a significant catalytic current demonstrated that the catalytic center is effectively wired and active. The bioelectrocatalytic current of the wired separate catalytic domain reached 25% of the signal of the wired full molybdoheme enzyme hSO, in which the heme b(5) is involved in the electron-transfer pathway. This is the first report on a catalytically active wired molybdenum cofactor domain. The formal potential of this electrochemical mediator is between the potentials of the two cofactors of hSO, and as hSO can occupy several conformations in the polymer matrix, it is imaginable that electron transfer from the catalytic site to the electrode through the osmium center occurs for the hSO molecules in which the Moco domain is sufficiently accessible. The observation of catalytic oxidation currents at low potentials is favorable for applications in bioelectronic devices. KW - Metalloenzymes KW - Enzyme catalysis KW - Immobilization KW - Osmium Y1 - 2015 U6 - https://doi.org/10.1002/ejic.201500034 SN - 1434-1948 SN - 1099-0682 IS - 21 SP - 3526 EP - 3531 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Jetzschmann, Katharina J. A1 - Jagerszki, Gyula A1 - Dechtrirat, Decha A1 - Yarman, Aysu A1 - Gajovic-Eichelmann, Nenad A1 - Gilsing, Hans-Detlev A1 - Schulz, Burkhard A1 - Gyurcsanyi, Robert E. A1 - Scheller, Frieder W. T1 - Vectorially Imprinted Hybrid Nanofilm for Acetylcholinesterase Recognition JF - Advanced functional materials N2 - Effective recognition of enzymatically active tetrameric acetylcholinesterase (AChE) is accomplished by a hybrid nanofilm composed of a propidium-terminated self-assembled monolayer (Prop-SAM) which binds AChE via its peripheral anionic site (PAS) and an ultrathin electrosynthesized molecularly imprinted polymer (MIP) cover layer of a novel carboxylate-modified derivative of 3,4-propylenedioxythiophene. The rebinding of the AChE to the MIP/Prop-SAM nanofilm covered electrode is detected by measuring in situ the enzymatic activity. The oxidative current of the released thiocholine is dependent on the AChE concentration from approximate to 0.04 x 10(-6) to 0.4 x 10(-6)m. An imprinting factor of 9.9 is obtained for the hybrid MIP, which is among the best values reported for protein imprinting. The dissociation constant characterizing the strength of the MIP-AChE binding is 4.2 x 10(-7)m indicating the dominant role of the PAS-Prop-SAM interaction, while the benefit of the MIP nanofilm covering the Prop-SAM layer is the effective suppression of the cross-reactivity toward competing proteins as compared with the Prop-SAM. The threefold selectivity gain provided by i) the shape-specific MIP filter, ii) the propidium-SAM, iii) signal generation only by the AChE bound to the nanofilm shows promise for assessing AChE activity levels in cerebrospinal fluid. KW - acetylcholinesterase KW - biomimetic sensors KW - molecularly imprinted electropolymers KW - peripheral anionic site KW - propidium Y1 - 2015 U6 - https://doi.org/10.1002/adfm.201501900 SN - 1616-301X SN - 1616-3028 VL - 25 IS - 32 SP - 5178 EP - 5183 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Tanne, Johannes A1 - Jeoung, Jae-Hun A1 - Peng, Lei A1 - Yarman, Aysu A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Schad, Daniel A1 - Dobbek, Holger A1 - Wollenberger, Ursula A1 - Bier, Frank Fabian A1 - Scheller, Frieder W. T1 - Direct Electron Transfer and Bioelectrocatalysis by a Hexameric, Heme Protein at Nanostructured Electrodes JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - A nanohybrid consisting of poly(3-aminobenzenesulfonic acid-co-aniline) and multiwalled carbon nanotubes [MWCNT-P(ABS-A)]) on a gold electrode was used to immobilize the hexameric tyrosine-coordinated heme protein (HTHP). The enzyme showed direct electron transfer between the heme group of the protein and the nanostructured surface. Desorption of the noncovalently bound heme from the protein could be excluded by control measurements with adsorbed hemin on aminohexanthiol-modified electrodes. The nanostructuring and the optimised charge characteristics resulted in a higher protein coverage as compared with MUA/MU modified electrodes. The adsorbed enzyme shows catalytic activity for the cathodic H2O2 reduction and oxidation of NADH. KW - HTHP KW - Nanohybrid KW - Poylaniline KW - Multiwalled carbon nanotube Y1 - 2015 U6 - https://doi.org/10.1002/elan.201500231 SN - 1040-0397 SN - 1521-4109 VL - 27 IS - 10 SP - 2262 EP - 2267 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Yarman, Aysu A1 - Bachmann, Till A1 - Hirsch, Thomas A1 - Kubick, Stefan A1 - Renneberg, Reinhard A1 - Schumacher, Soeren A1 - Wollenberger, Ursula A1 - Teller, Carsten A1 - Bier, Frank Fabian ED - Gu, MB ED - Kim, HS T1 - Future of biosensors: a personal view JF - Advances in biochemical engineering, biotechnology JF - Advances in Biochemical Engineering-Biotechnology N2 - Biosensors representing the technological counterpart of living senses have found routine application in amperometric enzyme electrodes for decentralized blood glucose measurement, interaction analysis by surface plasmon resonance in drug development, and to some extent DNA chips for expression analysis and enzyme polymorphisms. These technologies have already reached a highly advanced level and need minor improvement at most. The dream of the "100-dollar' personal genome may come true in the next few years provided that the technological hurdles of nanopore technology or of polymerase-based single molecule sequencing can be overcome. Tailor-made recognition elements for biosensors including membrane-bound enzymes and receptors will be prepared by cell-free protein synthesis. As alternatives for biological recognition elements, molecularly imprinted polymers (MIPs) have been created. They have the potential to substitute antibodies in biosensors and biochips for the measurement of low-molecular-weight substances, proteins, viruses, and living cells. They are more stable than proteins and can be produced in large amounts by chemical synthesis. Integration of nanomaterials, especially of graphene, could lead to new miniaturized biosensors with high sensitivity and ultrafast response. In the future individual therapy will include genetic profiling of isoenzymes and polymorphic forms of drug-metabolizing enzymes especially of the cytochrome P450 family. For defining the pharmacokinetics including the clearance of a given genotype enzyme electrodes will be a useful tool. For decentralized online patient control or the integration into everyday "consumables' such as drinking water, foods, hygienic articles, clothing, or for control of air conditioners in buildings and cars and swimming pools, a new generation of "autonomous' biosensors will emerge. KW - Biosensors KW - Molecularly imprinted polymers KW - Personalized medicine Y1 - 2014 SN - 978-3-642-54143-8; 978-3-642-54142-1 U6 - https://doi.org/10.1007/10_2013_251 SN - 0724-6145 VL - 140 SP - 1 EP - 28 PB - Springer CY - Berlin ER - TY - JOUR A1 - Neumann, Bettina A1 - Yarman, Aysu A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Characterization of the enhanced peroxidatic activity of amyloid beta peptide-hemin complexes towards neurotransmitters JF - Analytical & bioanalytical chemistry N2 - Binding of heme to the amyloid peptides A beta 40/42 is thought to be an initial step in the development of symptoms in the early stages of Alzheimer's disease by enhancing the intrinsic peroxidatic activity of heme. We found considerably higher acceleration of the reaction for the physiologically relevant neurotransmitters dopamine and serotonin than reported earlier for the artificial substrate 3,3',5,5'-tetramethylbenzidine (TMB). Thus, the binding of hemin to A beta peptides might play an even more crucial role in the early stages of Alzheimer's disease than deduced from these earlier results. To mimic complex formation, a new surface architecture has been developed: The interaction between the truncated amyloid peptide A beta 1-16 and hemin immobilized on an aminohexanethiol spacer on a gold electrode has been analyzed by cyclic voltammetry. The resulting complex has a redox pair with a 25 mV more cathodic formal potential than hemin alone. KW - Peroxidatic activity Y1 - 2014 U6 - https://doi.org/10.1007/s00216-014-7822-8 SN - 1618-2642 SN - 1618-2650 VL - 406 IS - 14 SP - 3359 EP - 3364 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Yarman, Aysu A1 - Scheller, Frieder W. T1 - The first electrochemical MIP sensor for tamoxifen JF - Sensors N2 - We present an electrochemical MIP sensor for tamoxifen (TAM)-a nonsteroidal anti-estrogen-which is based on the electropolymerisation of an O-phenylenediamine. resorcinol mixture directly on the electrode surface in the presence of the template molecule. Up to now only. bulk. MIPs for TAM have been described in literature, which are applied for separation in chromatography columns. Electro-polymerisation of the monomers in the presence of TAM generated a film which completely suppressed the reduction of ferricyanide. Removal of the template gave a markedly increased ferricyanide signal, which was again suppressed after rebinding as expected for filling of the cavities by target binding. The decrease of the ferricyanide peak of the MIP electrode depended linearly on the TAM concentration between 1 and 100 nM. The TAM-imprinted electrode showed a 2.3 times higher recognition of the template molecule itself as compared to its metabolite 4-hydroxytamoxifen and no cross-reactivity with the anticancer drug doxorubucin was found. Measurements at + 1.1 V caused a fouling of the electrode surface, whilst pretreatment of TAM with peroxide in presence of HRP generated an oxidation product which was reducible at 0 mV, thus circumventing the polymer formation and electrochemical interferences. KW - molecularly imprinted polymers KW - anticancer drug KW - tamoxifen KW - electropolymerisation Y1 - 2014 U6 - https://doi.org/10.3390/s140507647 SN - 1424-8220 VL - 14 IS - 5 SP - 7647 EP - 7654 PB - MDPI CY - Basel ER - TY - JOUR A1 - Dechtrirat, Decha A1 - Gajovic-Eichelmann, Nenad A1 - Wojcik, Felix A1 - Hartmann, Laura A1 - Bier, Frank Fabian A1 - Scheller, Frieder W. T1 - Electrochemical displacement sensor based on ferrocene boronic acid tracer and immobilized glycan for saccharide binding proteins and E. coli JF - Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics N2 - Pathogens such as viruses and bacteria use their envelope proteins and their adhesin lectins to recognize the glycan residues presented on the cell surface of the target tissues. This principle of recognition is used in a new electrochemical displacement sensor for the protein concanavalin A (ConA). A gold electrode was first modified with a self-assembled monolayer of a thiolated mannose/OEG conjugate and a ferrocene boroxol derivative was pre-assembled as reporter molecule onto the mannose surface. The novel tracer molecule based on a 2-hydroxymethyl phenyl boronic acid derivative binds even at neutral pH to the saccharides which could expand the application towards biological samples (i.e., urine and feces). Upon the binding of ConA, the tracer was displaced and washed away from the sensor surface leading to a decrease in the electrochemical signal. Using square wave voltammetry (SWV), the concentration of ConA in the sample solution could be determined in the dynamic concentration range established from 38 nmol L-1 to 5.76 mu mol L-1 with a reproducible detection limit of 1 mu g mL(-1) (38 nmol L-1) based on the signal-to-noise ratio (S/N=3) with fast response of 15 min. The new reporter molecule showed a reduced non-specific displacement by BSA and ribonuclease A. The sensor was also successfully transferred to the first proof of principle for the detection of Escherichia coli exhibiting a detection limit of approximately 6 x 102 cells/mL Specificity of the displacement by target protein ConA and E. coli was demonstrated since the control proteins (i.e., BSA and RNaseA) and the control E. coli strain, which lack of type 1 fimbriae, were ineffective. (C) 2014 Elsevier B.V. All rights reserved. KW - Ferrocene benzoboroxol biosensor KW - Concanavalin A KW - Displacement KW - Escherichia coli KW - Ferrocene boronic acid KW - Self-assembled monolayer Y1 - 2014 U6 - https://doi.org/10.1016/j.bios.2014.02.028 SN - 0956-5663 SN - 1873-4235 VL - 58 SP - 1 EP - 8 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Yarman, Aysu A1 - Schulz, Christopher A1 - Sygmund, Cristoph A1 - Ludwig, Roland A1 - Gorton, Lo A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Third generation ATP sensor with enzymatic analyte recycling JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - For the first time the direct electron transfer of an enzyme - cellobiose dehydrogenase, CDH - has been coupled with the hexokinase catalyzed competition for glucose in a sensor for ATP. To enhance the signal output for ATP, pyruvate kinase was coimmobilized to recycle ADP by the phosphoenolpyruvate driven reaction. The new sensor overcomes the limit of 1:1 stoichiometry of the sequential or competitive conversion of ATP by effective enzymatic recycling of the analyte. The anodic oxidation of the glucose converting CDH proceeds at electrode potentials below 0 mV vs. Ag vertical bar AgCl thus potentially interfering substances like ascorbic acid or catecholamines do not influence the measuring signal. The combination of direct electron transfer of CDH with the enzymatic recycling results in an interference-free and oxygen-independent measurement of ATP in the lower mu molar concentration range with a lower limit of detection of 63.3 nM (S/N=3). KW - ATP KW - Third generation sensor KW - Enzymatic recycling KW - Cellobiose dehydrogenase KW - Hexokinase KW - Pyruvate kinase Y1 - 2014 U6 - https://doi.org/10.1002/elan.201400231 SN - 1040-0397 SN - 1521-4109 VL - 26 IS - 9 SP - 2043 EP - 2048 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Yarman, Aysu A1 - Nagel, Thomas A1 - Gajovic-Eichelmann, Nenad A1 - Fischer, Anna A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Bioelectrocatalysis by Microperoxidase-11 in a Multilayer Architecture of Chitosan Embedded Gold Nanoparticles JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - We report on the redox behaviour of the microperoxidase-11 (MP-11) which has been electrostatically immobilized in a matrix of chitosan-embedded gold nanoparticles on the surface of a glassy carbon electrode. MP-11 contains a covalently bound heme c as the redox active group that exchanges electrons with the electrode via the gold nanoparticles. Electroactive surface concentration of MP-11 at high scan rate is between 350+/-50 pmol cm(-2), which reflects a multilayer process. The formal potential (E degrees') of MP-11 in the gold nanoparticles-chitosan film was estimated to be -(267.7+/-2.9) mV at pH 7.0. The heterogeneous electron transfer rate constant (k(s)) starts at 1.21 s(-1) and levels off at 6.45 s(-1) in the scan rate range from 0.1 to 2.0 V s(-1). Oxidation and reduction of MP-11 by hydrogen peroxide and superoxide, respectively have been coupled to the direct electron transfer of MP-11. KW - Microperoxidase KW - Direct electron transfer KW - Nanoparticles KW - Hydrogen peroxide KW - Superoxide KW - Bioelectrocatalysis Y1 - 2011 U6 - https://doi.org/10.1002/elan.201000535 SN - 1040-0397 VL - 23 IS - 3 SP - 611 EP - 618 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Yarman, Aysu A1 - Badalyan, Artavazd A1 - Gajovic-Eichelmann, Nenad A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Enzyme electrode for aromatic compounds exploiting the catalytic activities of microperoxidase-11 JF - Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics N2 - Microperoxidase-11 (MR-11) which has been immobilised in a matrix of chitosan-embedded gold nanoparticles on the surface of a glassy carbon electrode catalyzes the conversion of aromatic substances. This peroxide-dependent catalysis of microperoxidase has been applied in an enzyme electrode for the first time to indicate aromatic compounds such as aniline. 4-fluoroaniline, catechol and p-aminophenol. The electrode signal is generated by the cathodic reduction of the quinone or quinoneimine which is formed in the presence of both MP-II and peroxide from the substrate. The same sensor principle will be extended to aromatic drugs. KW - Microperoxidase-11 KW - Nanoparticles KW - p-Aminophenol KW - Aniline KW - Catechol KW - 4-Fluoroaniline KW - Biosensors Y1 - 2011 U6 - https://doi.org/10.1016/j.bios.2011.09.004 SN - 0956-5663 VL - 30 IS - 1 SP - 320 EP - 323 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Wu, Yunhua A1 - Wollenberger, Ursula A1 - Hofrichter, Martin A1 - Ullrich, Rene A1 - Scheibner, Katrin A1 - Scheller, Frieder W. T1 - Direct electron transfer of Agrocybe aegerita peroxygenase at electrodes modified with chitosan-capped Au nanoparticles and its bioelectrocatalysis to aniline JF - Sensors and actuators : B, Chemical N2 - Three different sizes of chitosan-capped Au nanoparticles were synthesized and were used to incorporate Agrocybe aegerita peroxygenase (AaeAPO) onto the surface of glassy carbon electrode. The direct electron transfer of AaeAPO was achieved in all films. The highest amount of electroactive enzyme and highest electron transfer rate constant k(s) of AaeAPO were obtained in the film with the smallest size of chitosan-capped Au nanoparticles. In anaerobic solutions, quasi-reversible oxidation and reduction are obtained with a formal potential of -0.280V vs. Ag/AgCl 1 M KCl in 100 mM (pH 7.0) PBS at scan rate of 1 V s(-1). Bioelectrocatalytic reduction currents can be obtained with the AaeAPO-modified electrode on addition of hydrogen peroxide. This reaction was suppressed when sodium azide, an inhibitor of AaeAPO, was present. Furthermore, the peroxide-dependent conversion of aniline was characterized and it was found that a polymer product via p-aminophenol is formed. And the AaeAPO biosensor was applied to determine aniline and p-aminophenol. KW - Agrocybe aegerita peroxygenase KW - Au nanoparticles KW - Direct electron transfer KW - Aniline biosensor KW - Bioelectrocatalysis Y1 - 2011 U6 - https://doi.org/10.1016/j.snb.2011.09.090 SN - 0925-4005 VL - 160 IS - 1 SP - 1419 EP - 1426 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Yarman, Aysu A1 - Gröbe, Glenn A1 - Neumann, Bettina A1 - Kinne, Mathias A1 - Gajovic-Eichelmann, Nenad A1 - Wollenberger, Ursula A1 - Hofrichter, Martin A1 - Ullrich, Rene A1 - Scheibner, Katrin A1 - Scheller, Frieder W. T1 - The aromatic peroxygenase from Marasmius rutola-a new enzyme for biosensor applications JF - Analytical & bioanalytical chemistry N2 - The aromatic peroxygenase (APO; EC 1.11.2.1) from the agraric basidomycete Marasmius rotula (MroAPO) immobilized at the chitosan-capped gold-nanoparticle-modified glassy carbon electrode displayed a pair of redox peaks with a midpoint potential of -278.5 mV vs. AgCl/AgCl (1 M KCl) for the Fe(2+)/Fe(3+) redox couple of the heme-thiolate-containing protein. MroAPO oxidizes aromatic substrates such as aniline, p-aminophenol, hydroquinone, resorcinol, catechol, and paracetamol by means of hydrogen peroxide. The substrate spectrum overlaps with those of cytochrome P450s and plant peroxidases which are relevant in environmental analysis and drug monitoring. In M. rotula peroxygenase-based enzyme electrodes, the signal is generated by the reduction of electrode-active reaction products (e.g., p-benzoquinone and p-quinoneimine) with electro-enzymatic recycling of the analyte. In these enzyme electrodes, the signal reflects the conversion of all substrates thus representing an overall parameter in complex media. The performance of these sensors and their further development are discussed. KW - Unspecific peroxygenase KW - Cytochrome P450 KW - Biosensors KW - Phenolic substances Y1 - 2012 U6 - https://doi.org/10.1007/s00216-011-5497-y SN - 1618-2642 VL - 402 IS - 1 SP - 405 EP - 412 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Bosserdt, Maria A1 - Gajovic-Eichelman, Nenad A1 - Scheller, Frieder W. T1 - Modulation of direct electron transfer of cytochrome c by use of a molecularly imprinted thin film JF - Analytical & bioanalytical chemistry N2 - We describe the preparation of a molecularly imprinted polymer film (MIP) on top of a self-assembled monolayer (SAM) of mercaptoundecanoic acid (MUA) on gold, where the template cytochrome c (cyt c) participates in direct electron transfer (DET) with the underlying electrode. To enable DET, a non-conductive polymer film is electrodeposited from an aqueous solution of scopoletin and cyt c on to the surface of a gold electrode previously modified with MUA. The electroactive surface concentration of cyt c was 0.5 pmol cm(-2). In the absence of the MUA layer, no cyt c DET was observed and the pseudo-peroxidatic activity of the scopoletin-entrapped protein, assessed via oxidation of Ampliflu red in the presence of hydrogen peroxide, was only 30 % of that for the MIP on MUA. This result indicates that electrostatic adsorption of cyt c by the MUA-SAM substantially increases the surface concentration of cyt c during the electrodeposition step, and is a prerequisite for the productive orientation required for DET. After template removal by treatment with sulfuric acid, rebinding of cyt c to the MUA-MIP-modified electrode occurred with an affinity constant of 100,000 mol(-1) L, a value three times higher than that determined by use of fluorescence titration for the interaction between scopoletin and cyt c in solution. The DET of cyt c in the presence of myoglobin, lysozyme, and bovine serum albumin (BSA) reveals that the MIP layer suppresses the effect of competing proteins. KW - Cytochrome c KW - Molecularly imprinted polymer film KW - Mercaptoundecanoic acid KW - Direct electron transfer KW - Scopoletin (7-hydroxy-6-methoxycoumarin) Y1 - 2013 U6 - https://doi.org/10.1007/s00216-013-7009-8 SN - 1618-2642 VL - 405 IS - 20 SP - 6437 EP - 6444 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Yarman, Aysu A1 - Scheller, Frieder W. T1 - Coupling biocatalysis with molecular imprinting in a biomimetic sensor JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition KW - biomimetic sensors KW - electropolymers KW - enzymes KW - hierarchical structures KW - molecularly imprinted polymers Y1 - 2013 U6 - https://doi.org/10.1002/anie.201305368 SN - 1433-7851 SN - 1521-3773 VL - 52 IS - 44 SP - 11521 EP - 11525 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Yarman, Aysu A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Sensors based on cytochrome P450 and CYP mimicking systems JF - ELECTROCHIMICA ACTA N2 - Cytochrome P450 enzymes (CYPs) act on more than 90 percent of all drugs currently on the market. The catalytic cycle requires electron supply to the heme iron in the presence of oxygen. Electrochemistry allows to characterise the reaction mechanism of these redox enzymes by observing the electron transfer in real time. According to the number of publications on protein electrochemistry CYP has the third position after glucose oxidase and cytochrome c. CYP based enzyme electrodes for the quantification of drugs, metabolites or pesticides have been developed using different iso-enzymes. A crucial step in the sensor development is the efficiency of coupling the biocatalytic systems with the electrode is. In the 1970s the direct electron transfer of heme and heme peptides called microperoxidases (MPs) was used as model of oxidoreductases. They exhibit a broad substrate spectrum including hydroxylation of selected aromatic substrates, demethylation and epoxidation by means of hydrogen peroxide. It overlaps with that of P450 making heme and MPs to alternate recognition elements in biosensors for the detection of typical CYP substrates. In these enzyme electrodes the signal is generated by the conversion of all substrates thus representing in complex media an overall parameter. By combining the biocatalytic substrate conversion with selective binding to a molecularly imprinted polymer layer the specificity has been improved. Here we discuss different approaches of biosensors based on CYP, microperoxidases and catalytically active MIPs and discuss their potential as recognition elements in biosensors. The performance of these sensors and their further development are discussed. (C) 2013 Elsevier Ltd. All rights reserved. KW - Cytochrome P450 KW - Microperoxidases KW - Catalytically active molecularly imprinted polymers KW - Biosensors KW - Personalised medicine Y1 - 2013 U6 - https://doi.org/10.1016/j.electacta.2013.03.154 SN - 0013-4686 SN - 1873-3859 VL - 110 SP - 63 EP - 72 PB - PERGAMON-ELSEVIER SCIENCE LTD CY - OXFORD ER - TY - JOUR A1 - Frasca, Stefano A1 - von Graberg, Till A1 - Feng, Jiu-Ju A1 - Thomas, Arne A1 - Smarsly, Bernd M. A1 - Weidinger, Inez M. A1 - Scheller, Frieder W. A1 - Hildebrandt, Peter A1 - Wollenberger, Ursula T1 - Mesoporous indium tin oxide as a novel platform for bioelectronics N2 - Stable immobilization and reversible electrochemistry of cytochrome c in a tranparent indium tin oxide film with a well-defined mesoporosity (mpITO) is demonstrated. the transparency and good conductivity, in combination with the large surface area of mpITO, allow the incorporation of a high amount of elelctroactive biomolecules and their electrochemical and spectroscopic investigation. UV/Vis and resonance Raman spectroscopy, in combination with direct protein voltammetry are employed for the characterization of cytochrome c immobilized in the mpITO and reveal no perturbant of the structural of the integrity of the redox protein. The potential of this modified material as a biosensor detection of superoxide anions is also demonstrated. Y1 - 2010 UR - http://www3.interscience.wiley.com/journal/122208635/home U6 - https://doi.org/10.1002/cctc.201000047 SN - 1867-3880 ER - TY - JOUR A1 - Baeumner, Antje J. A1 - Gauglitz, Guenter A1 - Scheller, Frieder W. T1 - Focus on bioanalysis N2 - Editoria Y1 - 2010 UR - http://www.springerlink.com/content/100417 U6 - https://doi.org/10.1007/s00216-010-4203-9 SN - 1618-2642 ER - TY - JOUR A1 - Spricigo, Roberto A1 - Dronov, Roman A1 - Lisdat, Fred A1 - Leimkühler, Silke A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula T1 - Electrocatalytic sulfite biosensor with human sulfite oxidase co-immobilized with cytochrome c in a polyelectrolyte-containing multilayer N2 - An efficient electrocatalytic biosensor for sulfite detection was developed by co-immobilizing sulfite oxidase and cytochrome c with polyaniline sulfonic acid in a layer-by-layer assembly. QCM, UV-Vis spectroscopy and cyclic voltammetry revealed increasing loading of electrochemically active protein with the formation of multilayers. The sensor operates reagentless at low working potential. A catalytic oxidation current was detected in the presence of sulfite at the modified gold electrode, polarized at +0.1 V ( vs. Ag/AgCl 1 M KCl). The stability of the biosensor performance was characterized and optimized. A 17-bilayer electrode has a linear range between 1 and 60 mu M sulfite with a sensitivity of 2.19 mA M-1 sulfite and a response time of 2 min. The electrode retained a stable response for 3 days with a serial reproducibility of 3.8% and lost 20% of sensitivity after 5 days of operation. It is possible to store the sensor in a dry state for more than 2 months. The multilayer electrode was used for determination of sulfite in unspiked and spiked samples of red and white wine. The recovery and the specificity of the signals were evaluated for each sample. Y1 - 2009 UR - http://www.springerlink.com/content/100417 U6 - https://doi.org/10.1007/s00216-008-2432-y SN - 1618-2642 ER - TY - JOUR A1 - Scheller, Frieder W. T1 - Tribute to Guenter Gauglitz (Editorial) Y1 - 2009 UR - http://www.springerlink.com/content/100417 U6 - https://doi.org/10.1007/s00216-008-2548-0 SN - 1618-2642 ER - TY - JOUR A1 - Loew, Noya A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. A1 - Katterle, Martin T1 - Direct electrochemistry and spectroelectrochemistry of osmium substituted horseradish peroxidase N2 - In this contribution the substitution of the central protoporphyrin IX iron complex of horseradish peroxidase by the respective osmium porphyrin complex is described. The direct electrochemical reduction of the Os containing horseradish peroxidase (OsHRP) was achieved at ITO and modified glassy carbon electrodes and in combination with spectroscopy revealed the three redox couples (OsHRP)-H-III/(OsHRP)-H-IV, (OsHRP)-H-IV/(OsHRP)-H-V and (OsHRP)-H-V/ (OsHRP)-H-VI. The midpoint potentials differ dependent on the electrode material used with E-1/2 (Os-III/IV) of -0.4 V (ITO) and -0.25 V (GC), E-1/2 (Os-IV/V) of -0.16 V (ITO) and +0.10 V (GC), and E-1/2 (Os-V/VI)of +018 V (ITO), respectively Moreover, with immobilised OsHRP the direct electrocatalytic reduction of hydrogen peroxide and tert-butyl hydroperoxide was observed. In comparison to electrodes modified with native HRP the sensitivity of the OsHRP-electrode for tert-butyl hydroperoxide is higher. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/15675394 U6 - https://doi.org/10.1016/j.bioelechem.2009.03.015 SN - 1567-5394 ER - TY - JOUR A1 - Lisdat, Fred A1 - Dronov, Roman A1 - Möhwald, Helmuth A1 - Scheller, Frieder W. A1 - Kurth, Dirk G. T1 - Self-assembly of electro-active protein architectures on electrodes for the construction of biomimetic signal chains N2 - The layer-by-layer adsorption technique based on the consecutive deposition of oppositely charged species is for the preparation of protein multilayers with fully electro-active protein molecules. The methodology was established with cytochrome c and the polyelectrolyte sulfonated polyaniline (PASA). The technique is also useful for the construction of bi-protein architectures confining protein-protein communication to an electrode. Following natural examples of protein complexes with defined signal transfer, cytochrome c was arranged with enzymes such as xanthine oxidase, bilirubin oxidase, laccase, and sulfite oxidase in self-assembled multilayer architectures. Thus, biomimetic signal chains from the enzyme substrate via the enzyme and cytochrome c towards the electrode can be established. Communication between proteins immobilised in multiple layers on the electrode can be achieved by in situ generation of small shuttle molecules or more advantageously by direct interprotein electron transfer. This allows the construction of new sensing electrodes, the properties of which can be tuned by the number of deposited protein layers. The mechanism of electron transfer within such protein assemblies on gold electrodes will be discussed. Y1 - 2009 UR - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CC U6 - https://doi.org/10.1039/B813559b SN - 1359-7345 ER - TY - JOUR A1 - Spricigo, Roberto A1 - Richter, Claudia A1 - Leimkühler, Silke A1 - Gorton, Lo A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula T1 - Sulfite biosensor based on osmium redox polymer wired sulfite oxidase N2 - A biosensor, based on a redoxactive osmium polymer and sulfite oxidase on screen-printed electrodes, is presented here as a promising method for the detection of sulfite. A catalytic oxidative current was generated when a sample containing sulfite was pumped over the carbon screen-printed electrode modified with osmium redox polymer wired sulfite oxidase. A stationary value was reached after approximately 50 s and a complete measurement lasted no more than 3 min. The electrode polarized at -0.1 V (vs. Ag vertical bar AgCl 1M KCl) permits minimizing the influence of interfering substances, since these compounds can be unspecific oxidized at higher potentials. Because of the good stability of the protein film on the electrode surface, a well functioning biosensor-flow system was possible to construct. The working stability and reproducibility were further enhanced by the addition of bovine serum albumin generating a more long-term stable and biocompatible protein environment. The optimized biosensor showed a stable signal for more than a week of operation and a coefficient of variation of 4.8% for 12 successive measurements. The lower limit of detection of the sensor was 0.5 mu M sulfite and the response was linear until 100 mu M. The high sensitivity permitted a 1:500 dilution of wine samples. The immobilization procedure and the operational conditions granted minimized interferences. Additionally, repeating the immobilization procedure to form several layers of wired SO further increased the sensitivity of such a sensor. Finally. the applicability of the developed sulfite biosensor was tested on real samples, such as white and red wines. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/09277757 U6 - https://doi.org/10.1016/j.colsurfa.2009.09.001 SN - 0927-7757 ER - TY - JOUR A1 - Halámek, Jan A1 - Wollenberger, Ursula A1 - Stöcklein, Walter F. M. A1 - Warsinke, Axel A1 - Scheller, Frieder W. T1 - Signal amplification in immunoassays using labeling via boronic acid binding to the sugar moiety of immunoglobulin G : proof of concept for glycated hemoglobin N2 - A novel electrochemical immunoassay based on the multiple affinity labeling of the indicator antibody with an electro-active tag is presented. The concept is illustrated for the determination of the glycated hemoglobin HbA1c in hemoglobin samples. Hemoglobin is adsorbed to the surfactant-modified surface of a piezoelectric quartz crystal. Whereas the quartz crystal nanobalance is used to validate the total Hb binding, the HbA1c on the sensor surface is recognized by an antibody and quantified electrochemically after the sugar moieties of the antibody have been labeled in-situ with ferroceneboronic acid. The sensitivity of this sensor is about threefold higher than the sensitivity of a hemoglobin sensor, where the ferroceneboronic acid is bound directly to HbA1c. Y1 - 2007 UR - http://www.informaworld.com/openurl?genre=journal&issn=0003-2719 U6 - https://doi.org/10.1080/00032710701327096 SN - 0003-2719 ER - TY - JOUR A1 - Halámek, Jan A1 - Wollenberger, Ursula A1 - Stöcklein, Walter F. M. A1 - Scheller, Frieder W. T1 - Development of a biosensor for glycated hemoglobin N2 - The development of an electrochemical piezoelectric sensor for the detection of glycated hemoglobin is presented. The total hemoglobin (Hb) content is monitored with a mass-sensitive quartz crystal modified with surfactants, and the glycated fraction of the immobilized Hb is determined by subsequent voltarnmetric measurement of the coupled ferroceneboronic acid. Different modifications of the sensor were tested for their hemoglobin binding ability. Deoxycholate (DOCA) was found to be the most suitable among the examined modifiers. Piezoelectric quartz crystals with gold electrodes were modified with DOCA by covalent binding to a pre-formatted 4-aminothiophenol monolayer. The properties of the Hb binding to DOCA and the pH effect on this interaction were studied. In the proposed assay for glycated hemoglobin at first an Hb sample is incubated with ferroceneboronic acid (FcBA), which binds to the fructosyl residue of the glycated Hb. Then this preincubated Hb sample is allowed to interact with the DOCA-modified piezoelectric quartz crystal. The binding is monitored by quartz crystal nanobalance QCN). The amount of FcBA present on the sensor surface is determined by square wave voltammetry. The binding of FcBA results in well-defined peaks with an EO' of +200 mV versus Ag/AgC1 (1 M KC1). The peak height depends on the degree of glycated Hb in the sample ranging from 0% to 20% of total Hb. The regeneration of the sensing surface is achieved by pepsin digestion of the deposited Hb. Thus the sensor can be re-used more than 30 times. Y1 - 2007 UR - http://www.sciencedirect.com/science/journal/00134686 U6 - https://doi.org/10.1016/j.electacta.2007.03.059 SN - 0013-4686 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 - Neumann, B. A1 - Scheller, Frieder W. T1 - Enzyme and microbial sensors for environmental Monitoring Y1 - 1993 ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Kirstein, Dieter A1 - Schubert, Florian A1 - Pfeiffer, Dorothea A1 - McNeil, C. J. T1 - Enzymes in electrochemical biosensors Y1 - 1993 ER - TY - JOUR A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Enzyme activation for activator and enzyme activity measurement Y1 - 1993 ER - TY - JOUR A1 - Wollenberger, Ursula A1 - Schubert, Florian A1 - Pfeiffer, Dorothea A1 - Scheller, Frieder W. T1 - Enhancing biosensor performance using multienzyme systems Y1 - 1993 ER - TY - JOUR A1 - Pfeiffer, Dorothea A1 - Scheller, Frieder W. A1 - Schubert, Florian A1 - Setz, K. T1 - Amperometric enzyme electrodes for lactate and glucose determinations in highly diluted and undiluted media Y1 - 1993 ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula A1 - Schubert, Florian A1 - Pfeiffer, Dorothea A1 - Markower, Alexander A1 - McNeil, C. J. T1 - Multienzyme biosensors : coupled enzyme reactions and enzyme activation Y1 - 1993 ER - TY - JOUR A1 - Bogdanovskaya, V. A. A1 - Fridman, Vadim A1 - Tarasevich, M. R. A1 - Scheller, Frieder W. T1 - Bioelectrocatalysis by immobilized peroxidase : the reaction mechanism and the possibility of electroanalytical detection of both inhibitors and activators of enzyme Y1 - 1994 ER - TY - JOUR A1 - Wollenberger, Ursula A1 - Neumann, B. A1 - Riedel, K. A1 - Scheller, Frieder W. T1 - Enzyme and microbial sensors for phosphate, phenols, pesticides and peroxides Y1 - 1994 ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Heiduschka, P. T1 - Preparation of an electrode surface with a high density of binding sites by an electrochemical reduction of a poly (nitrophenol) film Y1 - 1994 ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Makower, Alexander A1 - Ghindilis, A. L. A1 - Bier, Frank Fabian A1 - Ehrentreich-Förster, Eva A1 - Wollenberger, Ursula A1 - Bauer, Christian G. A1 - Micheel, Burkhard A1 - Pfeiffer, Dorothea A1 - Szeponik, Jan A1 - Michael, N. A1 - Kaden, H. T1 - Enzyme sensors for subnanomolar concentrations Y1 - 1995 ER - TY - JOUR A1 - Stancík, L. A1 - Macholán, L. A1 - Pluhacek, I. A1 - Scheller, Frieder W. T1 - Biosensing of rapeseed glucosinolates using amperometric enzyme electrodes based on membrane-bound glucose oxidase or tyrosinase Y1 - 1995 ER - TY - JOUR A1 - Riedel, K. A1 - Beyersdorf-Radeck, Baerbel A1 - Neumann, B. A1 - Scheller, Frieder W. A1 - Schmid, Rolf D. T1 - Microbial sensors for determination of aromatics and their chloro derivatives. Part III: Determination of chlorinated phenols using a biosensor containing Trichosporon beigelii (cutaneum) Y1 - 1995 ER - TY - JOUR A1 - Iliev, I. A1 - Kaisheva, A. A1 - Scheller, Frieder W. A1 - Pfeiffer, Dorothea T1 - Amperometric gas-diffusion / enzyme electrode Y1 - 1995 ER - TY - JOUR A1 - Jin, Wen A1 - Wollenberger, Ursula A1 - Bier, Frank Fabian A1 - Scheller, Frieder W. T1 - Construction and characterization of multi-layer-enzyme electrode : covalent binding of quinoprotein glucose dehydrogenase onto gold electrodes Y1 - 1995 ER - TY - JOUR A1 - Ghindilis, A. L. A1 - Makower, Alexander A1 - Bauer, Christian G. A1 - Bier, Frank Fabian A1 - Scheller, Frieder W. T1 - Determination of p-aminophenol and catecholamines at picomolar concentrations based on recycling enzyme amplification Y1 - 1995 ER - TY - JOUR A1 - Eremenko, A. V. A1 - Makower, Alexander A1 - Jin, Wen A1 - Rüger, P. A1 - Scheller, Frieder W. T1 - Biosensor based on an enzyme modified electrode for highly - sensitive measurement of polyphenols Y1 - 1995 ER - TY - JOUR A1 - Scheller, Frieder W. A1 - Pfeiffer, Dorothea A1 - Schubert, Florian A1 - Wollenberger, Ursula T1 - Enzyme - based electrodes Y1 - 1995 ER - TY - JOUR A1 - Pfeiffer, Dorothea A1 - Scheller, Frieder W. A1 - McNeil, C. J. A1 - Schulmeister, Thomas T1 - Cascade-like exponential substrate amplification in enzyme sensors Y1 - 1995 ER -