@article{KrylovPfeilLisdat2004, author = {Krylov, Andrey V. and Pfeil, Wolfgang and Lisdat, Fred}, title = {Denaturation and renaturation of cytochrome c immobilized on gold electrodes in DMSO-containing buffers}, year = {2004}, abstract = {Cytochrome c (cyt c) was immobilized on surface-modified gold electrodes using a self-assembling approach. The resulting cyt c electrode was studied using cyclic voltammetry. Compared to pure phosphate buffer, cyt c electrodes exhibited in DMSO-containing solutions lower oxidation and reduction peak currents, which originated from a decrease in the addressable electro-active amount of the surface-immobilized protein. This is associated with the process of protein denaturation. The denaturation kinetics can be described by a sum of two processes with time constants differing by more than one order of magnitude. The subsequent change of the aqueous/organic medium back to a pure aqueous buffer resulted in a shift of the formal potential to its initial value and a partial recovery of the peak current. This can be attributed to the renaturation of the cyt c. The extent of renaturation depended on the organic solvent/water ratio of the mixture used. The kinetics of protein renaturation were similar to those of the denaturation process. (C) 2004 Elsevier B.V. All rights reserved}, language = {en} } @article{GeSchellerLisdat2003, author = {Ge, Bixia and Scheller, Frieder W. and Lisdat, Fred}, title = {Electrochemistry of immobilized CuZnSOD and FeSOD and their interaction with superoxide radicals}, year = {2003}, abstract = {Copper, zinc superoxide dismutase (CuZnSOD) from bovine erythrocytes and iron superoxide dismutase from Escherichia coli (FeSOD) were immobilized on 3-mercaptopropionic acid (MPA)-modified gold electrodes, respectively. The characterization of the SOD electrodes showed a quasi-reversible, electrochemical redox behavior with a formal potential of 47 {\~n} 4 mV and -154 {\~n} 5 mV (vs. Ag/AgCl, 1 M KCl) for surface adsorbed CuZnSOD and FeSOD, respectively. The heterogeneous electron transfer rate constants were determined to be about 65 and 35/s, respectively. Covalent fixation of both SODs was also feasible with only slight changes in the formal potential. The interaction of superoxide radicals (O2-) with the SOD electrode was investigated. No catalytic current could be observed. However, due to the fast cyclic reaction of SOD with superoxide, the communication of the protein with the electrode was strongly influenced. The amperometric detection of superoxide radicals is discussed.}, language = {en} } @article{BeissenhirtzSchellerLisdat2003, author = {Beissenhirtz, Moritz Karl and Scheller, Frieder W. and Lisdat, Fred}, title = {Immobilized cytochrome c sensor in organic / aqueous media for the characterization of hydrophilic and hydrophobic antioxidants}, year = {2003}, language = {en} } @article{BuettemeyerPhilippSchlenzkaetal.2003, author = {B{\"u}ttemeyer, R. and Philipp, A. W and Schlenzka, L. and Mall, J. W. and Beissenhirtz, Moritz Karl and Lisdat, Fred}, title = {Epigallocatechin gallate can significantly decrease free oxygen radicals in the reperfusion insury in vivo}, year = {2003}, language = {en} } @article{IgnatovShishniashviliGeetal.2002, author = {Ignatov, S. and Shishniashvili, D. and Ge, Bixia and Scheller, Frieder W. and Lisdat, Fred}, title = {Amperometric biosensor based on a functionalized gold electrode for the detection of antioxidants}, year = {2002}, language = {en} } @article{ButtermeyerPhilippMalletal.2002, author = {Buttermeyer, R. and Philipp, A. W. and Mall, J. W. and Ge, Bixia and Scheller, Frieder W. and Lisdat, Fred}, title = {In vivo measurement of oxygen derived free radicals during reperfusion injury}, year = {2002}, language = {en} } @article{GeLisdat2002, author = {Ge, Bixia and Lisdat, Fred}, title = {Superoxide sensor based on cytochrome c immobilized on mixed-thiol SAM with a new calibration method}, year = {2002}, language = {en} } @article{SchellerWollenbergerLeietal.2002, author = {Scheller, Frieder W. and Wollenberger, Ursula and Lei, Chenghong and Jin, Wen and Ge, Bixia and Lehmann, Claudia and Lisdat, Fred and Fridman, Vadim}, title = {Bioelectrocatalysis by redox enzymes at modified electrodes}, year = {2002}, language = {en} } @article{FandrichBullerMemczaketal.2017, author = {Fandrich, Artur and Buller, Jens and Memczak, Henry and Stoecklein, W. and Hinrichs, K. and Wischerhoff, E. and Schulz, B. and Laschewsky, Andr{\´e} and Lisdat, Fred}, title = {Responsive Polymer-Electrode Interface-Study of its Thermo- and pH-Sensitivity and the Influence of Peptide Coupling}, series = {Electrochimica acta : the journal of the International Society of Electrochemistry (ISE)}, volume = {229}, journal = {Electrochimica acta : the journal of the International Society of Electrochemistry (ISE)}, publisher = {Elsevier}, address = {Oxford}, issn = {0013-4686}, doi = {10.1016/j.electacta.2017.01.080}, pages = {325 -- 333}, year = {2017}, abstract = {This study introduces a thermally responsive, polymer-based electrode system. The key component is a surface-attached, temperature-responsive poly(oligoethylene glycol) methacrylate (poly(OEGMA)) type polymer bearing photoreactive benzophenone and carboxy groups containing side chains. The responsive behavior of the polymer in aqueous media has been investigated by turbidimetry measurements. Polymer films are formed on gold substrates by means of the photoreactive 2(dicyclohexylphosphino)benzophenone (DPBP) through photocrosslinking. The electrochemical behavior of the resulting polymer-substrate interface has been investigated in buffered [Fe(CN)6](3-)/[Fe (CN)6](4-)solutions at room temperature and under temperature variation by cyclic voltammetry (CV). The CV experiments show that with increasing temperature structural changes of the polymer layer occur, which alter the output of the electrochemical measurement. Repeated heating/cooling cycles analyzed by CV measurements and pH changes analyzed by quartz crystal microbalance with dissipation monitoring (QCM-D) reveal the reversible nature of the restructuring process. The immobilized films are further modified by covalent coupling of two small biomolecules - a hydrophobic peptide and a more hydrophilic one. These attached components influence the hydrophobicity of the layer in a different way the resulting change of the temperature-caused behavior has been studied by CV indicating a different state of the polymer after coupling of the hydrophobic peptide.}, language = {en} } @article{RiedelSabirSchelleretal.2017, author = {Riedel, M. and Sabir, N. and Scheller, Frieder W. and Parak, Wolfgang J. and Lisdat, Fred}, title = {Connecting quantum dots with enzymes}, series = {Nanoscale}, volume = {9}, journal = {Nanoscale}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2040-3364}, doi = {10.1039/c7nr00091j}, pages = {2814 -- 2823}, year = {2017}, abstract = {The combination of the biocatalytic features of enzymes with the unique physical properties of nanoparticles in a biohybrid system provides a promising approach for the development of advanced bioelectrocatalytic devices. This study describes the construction of photoelectrochemical signal chains based on CdSe/ZnS quantum dot (QD) modified gold electrodes as light switchable elements, and low molecular weight redox molecules for the combination with different biocatalysts. Photoelectrochemical and photoluminescence experiments verify that electron transfer can be achieved between the redox molecules hexacyanoferrate and ferrocene, and the QDs under illumination. Since for both redox mediators a concentration dependent photocurrent change has been found, light switchable enzymatic signal chains are built up with fructose dehydrogenase (FDH) and pyrroloquinoline quinone-dependent glucose dehydrogenase ((PQQ) GDH) for the detection of sugars. After immobilization of the enzymes at the QD electrode the biocatalytic oxidation of the substrates can be followed by conversion of the redox mediator in solution and subsequent detection at the QD electrode. Furthermore, (PQQ) GDH has been assembled together with ferrocenecarboxylic acid on top of the QD electrode for the construction of a funtional biohybrid architecture, showing that electron transfer can be realized from the enzyme over the redox mediator to the QDs and subsequently to the electrode in a completely immobilized fashion. The results obtained here do not only provide the basis for light-switchable biosensing and bioelectrocatalytic applications, but may also open the way for self-driven point-of-care systems by combination with solar cell approaches (power generation at the QD electrode by enzymatic substrate consumption).}, language = {en} }