TY - JOUR A1 - Fandrich, Artur A1 - Buller, Jens A1 - Schäfer, Daniel A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Lisdat, Fred T1 - Electrochemical characterization of a responsive macromolecular interface on gold JF - Physica status solidi : A, Applications and materials science N2 - This study reports on the investigation of a thermoresponsive polymer as a thin film on electrodes and the influence of coupling a peptide and an antibody to the film. The utilized polymer from the class of poly(oligoethylene glycol)-methacrylate polymers (poly(OEGMA)) with carboxy functions containing side chains was synthesized and properly characterized in aqueous solutions. The dependence of the cloud point on the pH of the surrounding media is discussed. The responsive polymer was immobilized on gold electrodes as shown by electrochemical, quartz crystal microbalance (QCM), and atomic force microscopy (AFM) techniques. The temperature dependent behavior of the polymer covalently grafted to gold substrates is investigated using cyclic voltammetry (CV) in ferro-/ferricyanide solution. Significant changes in the slope of the temperature-dependence of the voltammetric peak current and the peak separation values clearly indicate the thermally induced conformational change on the surface. Finally, a biorecognition reaction between a short FLAG peptide (N-Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys-C) covalently immobilized on the polymer interface and the corresponding IgG antibody was performed. The study shows that the responsiveness of the electrode is retained after peptide coupling and antibody binding, although the response is diminished. KW - biorecognition reactions KW - cyclic voltammetry KW - electrodes KW - gold KW - interfaces KW - responsive polymers Y1 - 2015 U6 - https://doi.org/10.1002/pssa.201431698 SN - 1862-6300 SN - 1862-6319 VL - 212 IS - 6 SP - 1359 EP - 1367 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Fandrich, Artur A1 - Buller, Jens A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Lisdat, Fred T1 - Electrochemical detection of the thermally induced phase transition of a thin stimuli-responsive polymer film JF - ChemPhysChem : a European journal of chemical physics and physical chemistry KW - cyclic voltammetry KW - electrochemical impedance spectroscopy KW - polymers KW - surface chemistry KW - surface plasmon resonance Y1 - 2012 U6 - https://doi.org/10.1002/cphc.201100924 SN - 1439-4235 VL - 13 IS - 8 SP - 2020 EP - 2023 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Fandrich, Artur A1 - Buller, Jens A1 - Memczak, Henry A1 - Stoecklein, W. A1 - Hinrichs, K. A1 - Wischerhoff, E. A1 - Schulz, B. A1 - Laschewsky, André A1 - Lisdat, Fred T1 - Responsive Polymer-Electrode Interface-Study of its Thermo- and pH-Sensitivity and the Influence of Peptide Coupling JF - Electrochimica acta : the journal of the International Society of Electrochemistry (ISE) N2 - 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. KW - Stimuli-responsive materials KW - electroanalysis KW - modified electrode KW - bioreceptors KW - peptides KW - surface modification KW - cyclic voltammetry KW - IR ellipsometry KW - quartz crystal microbalance Y1 - 2017 U6 - https://doi.org/10.1016/j.electacta.2017.01.080 SN - 0013-4686 SN - 1873-3859 VL - 229 SP - 325 EP - 333 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Yan, Jiawei A1 - Frøkjær, Emil Egede A1 - Engelbrekt, Christian A1 - Leimkühler, Silke A1 - Ulstrup, Jens A1 - Wollenberger, Ulla A1 - Xiao, Xinxin A1 - Zhang, Jingdong T1 - Voltammetry and single-molecule in situ scanning tunnelling microscopy of the redox metalloenzyme human sulfite oxidase JF - ChemElectroChem N2 - Human sulfite oxidase (hSO) is a homodimeric two-domain enzyme central in the biological sulfur cycle. A pyranopterin molybdenum cofactor (Moco) is the catalytic site and a heme b(5) group located in the N-terminal domain. The two domains are connected by a flexible linker region. Electrons produced at the Moco in sulfite oxidation, are relayed via heme b(5) to electron acceptors or an electrode surface. Inter-domain conformational changes between an open and a closed enzyme conformation, allowing "gated" electron transfer has been suggested. We first recorded cyclic voltammetry (CV) of hSO on single-crystal Au(111)-electrode surfaces modified by self-assembled monolayers (SAMs) both of a short rigid thiol, cysteamine and of a longer structurally flexible thiol, omega-amino-octanethiol (AOT). hSO on cysteamine SAMs displays a well-defined pair of voltammetric peaks around -0.207 V vs. SCE in the absence of sulfite substrate, but no electrocatalysis. hSO on AOT SAMs displays well-defined electrocatalysis, but only "fair" quality voltammetry in the absence of sulfite. We recorded next in situ scanning tunnelling spectroscopy (STS) of hSO on AOT modified Au(111)-electrodes, disclosing, a 2-5 % surface coverage of strong molecular scale contrasts, assigned to single hSO molecules, notably with no contrast difference in the absence and presence of sulfite. In situ STS corroborated this observation with a sigmoidal tunnelling current/overpotential correlation. KW - cyclic voltammetry KW - human sulfite oxidase KW - in  situ scanning KW - tunnelling spectroscopy KW - self-assembled molecular monolayers KW - single-crystal gold electrodes Y1 - 2021 U6 - https://doi.org/10.1002/celc.202001258 SN - 2196-0216 VL - 8 IS - 1 SP - 164 EP - 171 PB - Wiley-VCH CY - Weinheim ER -