@article{KappBeissenhirtzGeyeretal.2006,
  author    = {Kapp, A. and Beissenhirtz, Moritz Karl and Geyer, F. and Scheller, F. and Viezzoli, Maria Silvia and Lisdat, Fred},
  title     = {Electrochemical and sensorial behavior of SOD mutants immobilized on gold electrodes in aqueous/organic solvent mixtures},
  series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis},
  volume    = {18},
  journal   = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis},
  publisher = {Wiley},
  address   = {Weinheim},
  issn      = {1040-0397},
  doi       = {10.1002/elan.200603620},
  pages     = {1909 -- 1915},
  year      = {2006},
  abstract  = {A cysteine mutant of a monomeric human Cu, Zn-SOD (Glycine 61, Serine 142) has been immobilized directly on gold electrodes using the thiol groups introduced. The electrochemical behavior of the surface confined protein was studied in mixtures of aqueous buffer and DMSO up to an organic solvent content of 60\%. The formal potential was found to be rather independent of the DMSO content. However, half peak width increased and the redoxactive amount clearly decreased with raising DMSO content. In addition, the kinetics of the heterogeneous electron transfer became slower; but still a quasireversible electrochemical conversion of the mutant SOD was feasible. Thus, the electrodes were applied for sensorial superoxide detection. At a potential of +220 mV vs. Ag/AgCl advantage was taken of the partial oxidation reaction of the enzyme. A defined superoxide signal was obtained in solutions up to 40\% DMSO. The sensitivity of the mutant electrodes decreased linearly with the organic solvent content in solution but was still higher compared to conventional cyt.c based sensors. At DMSO concentrations higher than 40\% no sensor response was detected.},
  language  = {en}
}
@article{KappBeissenhirtzGeyeretal.2006,
  author    = {Kapp, Andreas and Beissenhirtz, Moritz Karl and Geyer, F. and Scheller, Frieder W. and Viezzoli, Maria Silvia and Lisdat, Fred},
  title     = {Electrochemical and sensorial behaviour of SOD mutants immobilized on gold electrodes in aqueous / organic solvent mixtures},
  issn      = {1040-0397},
  doi       = {10.1002/elan.200603620},
  year      = {2006},
  language  = {en}
}
@article{BeissenhirtzSchellerViezzolietal.2006,
  author    = {Beissenhirtz, Moritz Karl and Scheller, Frieder W. and Viezzoli, Maria Silvia and Lisdat, Fred},
  title     = {Engineered superoxide dismutase monomers for superoxide biosensor applications},
  issn      = {0003-2700},
  doi       = {10.1021/Ac051465g},
  year      = {2006},
  abstract  = {Because of its high reaction rate and specificity, the enzyme superoxide dismutase (SOD) offers great potential for the sensitive quantification of superoxide radicals in electrochemical biosensors. In this work, monomeric mutants of human Cu,Zn-SOD were engineered to contain one or two additional cysteine residues, which could be used to bind the protein to gold surfaces, thus making the use of promotor molecules unnecessary. Six mutants were successfully designed, expressed, and purified. All mutants bound directly to unmodified gold surfaces via the sulfur of the cysteine residues and showed a quasireversible, direct electron transfer to the electrode. Thermodynamic and kinetic parameters of the electron transfer were characterized and showed only slight variations between the individual mutants. For one of the mutants, the interaction with the superoxide radical was studied in more detail. For both partial reactions of the dismutation, an interaction between protein and radical could be shown. In an amperometric biosensorial approach, the SOD-mutant electrode was successfully applied for the detection of superoxide radicals. In the oxidation region, the electrode surpassed the sensitivity of the commonly used cytochrome c electrodes by similar to 1 order of magnitude while not being limited by interferences, but the electrode did not fully reach the sensitivity of dimeric Cu,Zn-SOD immobilized on MPA-modified gold},
  language  = {en}
}