TY - JOUR A1 - Liu, Songqin A1 - Wollenberger, Ursula A1 - Halamek, Jan A1 - Leupold, Eik A1 - Stöcklein, Walter F. M. A1 - Warsinke, Axel A1 - Scheller, Frieder W. T1 - Affinity interaction betwen phenylboronic acid-carrying self-assembled monolayers and FAD or HRP N2 - A method is provided for the recognition of glycated molecules based on their binding affinities to boronate- carrying monolayers. The affinity interaction of flavin adenine dinucleotide (FAD) and horseradish peroxidase (HRP) with phenylboronic acid monolayers on gold was investigated by using voltammetric and microgravimetric methods. Conjugates of 3-aminopherrylboronic acid and 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) or 11-mercaptoundecanoic acid were prepared and self-assembled on gold surfaces to generate monolayers. FAD is bound to this modified sur-face and recognized by a pair of redox peaks with a formal potential of -0.433 V in a 0.1 m phosphate buffer solution, pH 6.5. Upon addition of a sugar to the buffer, the bound FAD could be replaced, indicating that the binding is reversible. Voltammetric, mass measurements, and photometric activity assays show that the HRP can also be bound to the interface. This binding is reversible, and HRP can be replaced by sorbitol or removed in acidic solution. The effects of pH, incubation time, and concentration of H2O2 were studied by comparing the catalytic reduction of H2O2 in the presence of the electron-donor thionine. The catalytic current of the HRP-loaded electrode was proportional to HRP concentrations in the incubation solution in the range between 5 mu g mL(-1) and 0.4 mg mL(-1) with a linear slope of 3.34 mu A mL mg(-1) and a correlation coefficient of 0.9945 Y1 - 2005 ER - TY - JOUR A1 - Xu, Xuan A1 - Wollenberger, Ursula A1 - Qian, Jing A1 - Lettau, Katrin A1 - Jung, Christiane A1 - Liu, Songqin T1 - Electrochemically driven biocatalysis of the oxygenase domain of neuronal nitric oxide synthase in indium tin oxide nanoparticles/polyvinyl alcohol nanocomposite JF - Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society N2 - Nitric oxide synthase (NOS) plays a critical role in a number of key physiological and pathological processes. Investigation of electron-transfer reactions in NOS would contribute to a better understanding of the nitric oxide (NO) synthesis mechanism. Herein, we describe an electrochemically driven catalytic strategy, using a nanocomposite that consisted of the oxygenase domain of neuronal NOS (D290nNOSoxy), indium tin oxide (ITO) nanopartides and polyvinyl alcohol (PVA). Fast direct electron transfer between electrodes and D290nNOSoxy was observed with the heterogeneous electron transfer rate constant (k(er)) of 154.8 +/- 0.1 s(-1) at the scan rate of 5 V s(-1). Moreover, the substrate IV-hydroxy-L-arginine (NHA) was used to prove the concept of electrochemically driven biocatalysis of D290nNOSoxy. In the presence of the oxygen cosubstrate and tetrahydrobiopterin (BH4) cofactor, the addition of NHA caused the decreases of both oxidation current at + 0.1 V and reduction current at potentials ranging from -0.149 V to -0.549 V vs Ag/AgCl. Thereafter, a series of control experiments such as in the absence of BH4 or D290nNOSoxy were performed. All the results demonstrated that D290nNOSoxy biocatalysis was successfully driven by electrodes in the presence of BH4 and oxygen. This novel bioelectronic system showed potential for further investigation of NOS and biosensor applications. (C) 2013 Elsevier B.V. All rights reserved. KW - Nitric oxide synthase KW - Tetrahydrobiopterin KW - N-omega-hydroxy-L-arginine KW - Indium tin oxide nanoparticles KW - Biocatalysis Y1 - 2013 U6 - https://doi.org/10.1016/j.bioelechem.2013.04.005 SN - 1567-5394 SN - 1521-186X VL - 94 IS - 47 SP - 7 EP - 12 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Ju, Huangxian A1 - Liu, Songqin A1 - Ge, Bixia A1 - Lisdat, Fred A1 - Scheller, Frieder W. T1 - Electrochemistry of cytochrome c immobilized on colloidal gold modified carbon paste electrodes and its electrocatalytic activity Y1 - 2000 ER - TY - JOUR A1 - Liu, Songqin A1 - Wollenberger, Ursula A1 - Katterle, Martin A1 - Scheller, Frieder W. T1 - Ferroceneboronic acid-based amperometric biosensor for glycated hemoglobin N2 - An amperometric biosensor for the determination of glycated hemoglobin in human whole blood is proposed. The principle is based on the electrochemical measurement of ferroceneboronic acid (FcBA) that has been specifically bound to the glycated N-terminus. Hemoglobin is immobilized on a zirconium dioxide nanoparticle modified pyrolytic graphite electrode (PGE) in the presence of didodecyldimethylammonium bromide (DDAB). The incubation of this sensor in FcBA solution leads to the formation of an FcBA-modified surface due to the affinity interaction between boronate and the glycated sites of the hemoglobin. The binding of FcBA results in well-defined redox peaks with an E-0' of 0.299 V versus Ag/AgCl (1 M KCl). The square wave voltammetric response of the bound FcBA reflects the amount of glycated hemoglobin at the surface. This signal increases linearily with the degree of glycated hemoglobin from 6.8 to 14.0% of total immobilized hemoglobin. The scheme was applied to the determination of the fraction of glycated hemoglobin in whole blood samples. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/09254005 U6 - https://doi.org/10.1016/j.snb.2005.07.011 SN - 0925-4005 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 -