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ATR-FTIR Biosensors for Antibody Detection and Analysis. Int J Mol Sci 2022; 23:ijms231911895. [PMID: 36233197 PMCID: PMC9570191 DOI: 10.3390/ijms231911895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 09/29/2022] [Accepted: 10/04/2022] [Indexed: 11/17/2022] Open
Abstract
Quality control of drug products is of paramount importance in the pharmaceutical world. It ensures product safety, efficiency, and consistency. In the case of complex biomolecules such as therapeutic proteins, small variations in bioprocess parameters can induce substantial variations in terms of structure, impacting the drug product quality. Conditions for obtaining highly reproducible grafting of 11-mercaptoundecanoic acid were determined. On that basis, we developed an easy-to-use, cost effective, and timesaving biosensor based on ATR-FTIR spectroscopy able to detect immunoglobulins during their production. A germanium crystal, used as an internal reflection element (IRE) for FTIR spectroscopy, was covalently coated with immunoglobulin-binding proteins. This thereby functionalized surface could bind only immunoglobulins present in complex media such as culture media or biopharmaceutical products. The potential subsequent analysis of their structure by ATR-FTIR spectroscopy makes this biosensor a powerful tool to monitor the production of biotherapeutics and assess important critical quality attributes (CQAs) such as high-order structure and aggregation level.
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Blond P, Bevernaegie R, Troian-Gautier L, Lagrost C, Hubert J, Reniers F, Raussens V, Jabin I. Ready-to-Use Germanium Surfaces for the Development of FTIR-Based Biosensors for Proteins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:12068-12076. [PMID: 33007158 DOI: 10.1021/acs.langmuir.0c02681] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Germanium is particularly suitable for the design of FTIR-based biosensors for proteins. The grafting of stable and thin organic layers on germanium surfaces remains, however, challenging. To tackle this problem, we developed a calix[4]arene-tetradiazonium salt decorated with four oligo(ethylene glycol) chains and a terminal reactive carboxyl group. This versatile molecular platform was covalently grafted on germanium surfaces to yield robust ready-to-use surfaces for biosensing applications. The grafted calixarene monolayer prevents nonspecific adsorption of proteins while allowing bioconjugation with biomolecules such as bovine serum albumin (BSA) or biotin. It is shown that the native form of the investigated proteins was maintained upon immobilization. As a proof of concept, the resulting calix[4]arene-based germanium biosensors were used through a combination of ATR-FTIR spectroscopy and fluorescence microscopy for the selective detection of streptavidin from a complex medium. This study opens real possibilities for the development of sensitive and selective FTIR-based biosensors devoted to the detection of proteins.
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Affiliation(s)
- Pascale Blond
- Laboratoire de Chimie Organique, Université libre de Bruxelles (ULB), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium
- Laboratory for the Structure and Function of Biological Membranes, Centre for Structural Biology and Bioinformatics, Université libre de Bruxelles (ULB), Boulevard du Triomphe, CP206/02, B-1050 Brussels, Belgium
| | - Robin Bevernaegie
- Laboratoire de Chimie Organique, Université libre de Bruxelles (ULB), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium
| | - Ludovic Troian-Gautier
- Laboratoire de Chimie Organique, Université libre de Bruxelles (ULB), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium
| | | | - Julie Hubert
- Chemistry of Surfaces, Interfaces and Nanomaterials, Université libre de Bruxelles (ULB), Boulevard du Triomphe, CP 255, B-1050 Brussels, Belgium
| | - François Reniers
- Chemistry of Surfaces, Interfaces and Nanomaterials, Université libre de Bruxelles (ULB), Boulevard du Triomphe, CP 255, B-1050 Brussels, Belgium
| | - Vincent Raussens
- Laboratory for the Structure and Function of Biological Membranes, Centre for Structural Biology and Bioinformatics, Université libre de Bruxelles (ULB), Boulevard du Triomphe, CP206/02, B-1050 Brussels, Belgium
| | - Ivan Jabin
- Laboratoire de Chimie Organique, Université libre de Bruxelles (ULB), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium
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Abstract
Infrared difference spectroscopy probes vibrational changes of proteins upon their perturbation. Compared with other spectroscopic methods, it stands out by its sensitivity to the protonation state, H-bonding, and the conformation of different groups in proteins, including the peptide backbone, amino acid side chains, internal water molecules, or cofactors. In particular, the detection of protonation and H-bonding changes in a time-resolved manner, not easily obtained by other techniques, is one of the most successful applications of IR difference spectroscopy. The present review deals with the use of perturbations designed to specifically change the protein between two (or more) functionally relevant states, a strategy often referred to as reaction-induced IR difference spectroscopy. In the first half of this contribution, I review the technique of reaction-induced IR difference spectroscopy of proteins, with special emphasis given to the preparation of suitable samples and their characterization, strategies for the perturbation of proteins, and methodologies for time-resolved measurements (from nanoseconds to minutes). The second half of this contribution focuses on the spectral interpretation. It starts by reviewing how changes in H-bonding, medium polarity, and vibrational coupling affect vibrational frequencies, intensities, and bandwidths. It is followed by band assignments, a crucial aspect mostly performed with the help of isotopic labeling and site-directed mutagenesis, and complemented by integration and interpretation of the results in the context of the studied protein, an aspect increasingly supported by spectral calculations. Selected examples from the literature, predominately but not exclusively from retinal proteins, are used to illustrate the topics covered in this review.
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Güldenhaupt J, Amaral M, Kötting C, Schartner J, Musil D, Frech M, Gerwert K. Zeitaufgelöst und markerfrei gemessene ligandeninduzierte Konformationsänderungen von HSP90 - hin zu einem Konformationsaktivitätsscreening für die Wirkstoffentwicklung. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201802603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jörn Güldenhaupt
- Lehrstuhl für Biophysik; Ruhr-Universität Bochum; 44780 Bochum Deutschland
| | - Marta Amaral
- Molecular Interactions and Biophysics; Merck KGaA; Frankfurter Straße 250 64293 Darmstadt Deutschland
- Derzeitige Adresse: Sanofi-Aventis (Deutschland) GmbH; Biologics Research/ Protein Therapeutics; Frankfurt am Main Deutschland
| | - Carsten Kötting
- Lehrstuhl für Biophysik; Ruhr-Universität Bochum; 44780 Bochum Deutschland
| | - Jonas Schartner
- Lehrstuhl für Biophysik; Ruhr-Universität Bochum; 44780 Bochum Deutschland
| | - Djordje Musil
- Molecular Interactions and Biophysics; Merck KGaA; Frankfurter Straße 250 64293 Darmstadt Deutschland
| | - Matthias Frech
- Molecular Interactions and Biophysics; Merck KGaA; Frankfurter Straße 250 64293 Darmstadt Deutschland
| | - Klaus Gerwert
- Lehrstuhl für Biophysik; Ruhr-Universität Bochum; 44780 Bochum Deutschland
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Güldenhaupt J, Amaral M, Kötting C, Schartner J, Musil D, Frech M, Gerwert K. Ligand-Induced Conformational Changes in HSP90 Monitored Time Resolved and Label Free-Towards a Conformational Activity Screening for Drug Discovery. Angew Chem Int Ed Engl 2018; 57:9955-9960. [PMID: 29772085 PMCID: PMC6099472 DOI: 10.1002/anie.201802603] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Indexed: 11/25/2022]
Abstract
Investigation of protein–ligand interactions is crucial during early drug‐discovery processes. ATR‐FTIR spectroscopy can detect label‐free protein–ligand interactions with high spatiotemporal resolution. Here we immobilized, as an example, the heat shock protein HSP90 on an ATR crystal. This protein is an important molecular target for drugs against several diseases including cancer. With our novel approach we investigated a ligand‐induced secondary structural change. Two specific binding modes of 19 drug‐like compounds were analyzed. Different binding modes can lead to different efficacy and specificity of different drugs. In addition, the kobs values of ligand dissociation were obtained. The results were validated by X‐ray crystallography for the structural change and by SPR experiments for the dissociation kinetics, but our method yields all data in a single and simple experiment.
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Affiliation(s)
- Jörn Güldenhaupt
- Lehrstuhl für Biophysik, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Marta Amaral
- Molecular Interactions and Biophysics, Merck KGaA, Frankfurter Strasse 250, 64293, Darmstadt, Germany.,Current address: Sanofi-Aventis (Deutschland) GmbH, Biologics Research/Protein Therapeutics, Frankfurt am Main, Germany
| | - Carsten Kötting
- Lehrstuhl für Biophysik, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Jonas Schartner
- Lehrstuhl für Biophysik, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Djordje Musil
- Molecular Interactions and Biophysics, Merck KGaA, Frankfurter Strasse 250, 64293, Darmstadt, Germany
| | - Matthias Frech
- Molecular Interactions and Biophysics, Merck KGaA, Frankfurter Strasse 250, 64293, Darmstadt, Germany
| | - Klaus Gerwert
- Lehrstuhl für Biophysik, Ruhr-Universität Bochum, 44780, Bochum, Germany
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Sigurdardóttir SB, Lehmann J, Ovtar S, Grivel J, Negra MD, Kaiser A, Pinelo M. Enzyme Immobilization on Inorganic Surfaces for Membrane Reactor Applications: Mass Transfer Challenges, Enzyme Leakage and Reuse of Materials. Adv Synth Catal 2018. [DOI: 10.1002/adsc.201800307] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Sigyn Björk Sigurdardóttir
- Technical University of DenmarkDTU Chemical Engineering Søltofts Plads, Building 229 2800 Kgs. Lyngby Denmark
| | - Jonas Lehmann
- Technical University of DenmarkDTU Energy Frederiksborgvej 399 4000 Roskilde Denmark
| | - Simona Ovtar
- Technical University of DenmarkDTU Energy Frederiksborgvej 399 4000 Roskilde Denmark
| | - Jean‐Claude Grivel
- Technical University of DenmarkDTU Energy Frederiksborgvej 399 4000 Roskilde Denmark
| | - Michela Della Negra
- Technical University of DenmarkDTU Energy Frederiksborgvej 399 4000 Roskilde Denmark
| | - Andreas Kaiser
- Technical University of DenmarkDTU Energy Frederiksborgvej 399 4000 Roskilde Denmark
| | - Manuel Pinelo
- Technical University of DenmarkDTU Chemical Engineering Søltofts Plads, Building 229 2800 Kgs. Lyngby Denmark
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7
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Blond P, Mattiuzzi A, Valkenier H, Troian-Gautier L, Bergamini JF, Doneux T, Goormaghtigh E, Raussens V, Jabin I. Grafting of Oligo(ethylene glycol)-Functionalized Calix[4]arene-Tetradiazonium Salts for Antifouling Germanium and Gold Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:6021-6027. [PMID: 29724105 DOI: 10.1021/acs.langmuir.8b00464] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Biosensors that can determine protein concentration and structure are highly desired for biomedical applications. For the development of such biosensors, the use of Fourier transform infrared (FTIR) spectroscopy with the attenuated internal total reflection (ATR) configuration is particularly attractive, but it requires appropriate surface functionalization of the ATR optical element. Indeed, the surface has to specifically interact with a target protein in close contact with the optical element and must display antifouling properties to prevent nonspecific adsorption of other proteins. Here, we report robust monolayers of calix[4]arenes bearing oligo(ethylene glycol) (oEG) chains, which were grafted on germanium and gold surfaces via their tetradiazonium salts. The formation of monolayers of oEGylated calix[4]arenes was confirmed by AFM, IR, and contact angle measurements. The antifouling properties of these modified surfaces were studied by ATR-FTIR spectroscopy and fluorescence microscopy, and the nonspecific absorption of bovine serum albumin was found to be reduced by 85% compared to that of unmodified germanium. In other words, the organic coating by oEGylated calix[4]arenes provides remarkable antifouling properties, opening the way for the design of germanium- or gold-based biosensors.
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Affiliation(s)
- Pascale Blond
- Laboratoire de Chimie Organique , Université Libre de Bruxelles (ULB) , avenue F. D. Roosevelt 50 , CP160/06, B-1050 Brussels , Belgium
- Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics , Université Libre de Bruxelles (ULB) , avenue F. D. Roosevelt 50 , CP206/02, B-1050 Brussels , Belgium
| | - Alice Mattiuzzi
- Laboratoire de Chimie Organique , Université Libre de Bruxelles (ULB) , avenue F. D. Roosevelt 50 , CP160/06, B-1050 Brussels , Belgium
- X4C , Rue Chêne Bonnet 128 , 6110 Montigny-le-Tilleul , Belgium
| | - Hennie Valkenier
- Engineering of Molecular NanoSystems , Ecole Polytechnique de Bruxelles, Université Libre de Bruxelles (ULB) , avenue F. D. Roosevelt 50 , CP165/64, B-1050 Brussels , Belgium
| | - Ludovic Troian-Gautier
- Laboratoire de Chimie Organique , Université Libre de Bruxelles (ULB) , avenue F. D. Roosevelt 50 , CP160/06, B-1050 Brussels , Belgium
| | - Jean-François Bergamini
- Institut des Sciences Chimiques de Rennes (Equipe MaCSE), CNRS, UMR 6226 , Université de Rennes 1 , Campus de Beaulieu, Bat 10C, 35042 Cedex Rennes , France
| | - Thomas Doneux
- Chimie Analytique et Chimie des Interfaces , Université Libre de Bruxelles (ULB) , Campus de la Plaine, boulevard du Triomphe , CP255, B-1050 Brussels , Belgium
| | - Erik Goormaghtigh
- Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics , Université Libre de Bruxelles (ULB) , avenue F. D. Roosevelt 50 , CP206/02, B-1050 Brussels , Belgium
| | - Vincent Raussens
- Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics , Université Libre de Bruxelles (ULB) , avenue F. D. Roosevelt 50 , CP206/02, B-1050 Brussels , Belgium
| | - Ivan Jabin
- Laboratoire de Chimie Organique , Université Libre de Bruxelles (ULB) , avenue F. D. Roosevelt 50 , CP160/06, B-1050 Brussels , Belgium
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8
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Schartner J, Güldenhaupt J, Katharina Gaßmeyer S, Rosga K, Kourist R, Gerwert K, Kötting C. Highly stable protein immobilizationviamaleimido-thiol chemistry to monitor enzymatic activity. Analyst 2018; 143:2276-2284. [DOI: 10.1039/c8an00301g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Combining a novel protein immobilisation method with multivariate curve resolution enables the direct observation of biocatalysis by ATR-FTIR spectroscopy.
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Affiliation(s)
- Jonas Schartner
- Department of Biophysics
- Ruhr-Universität Bochum
- 44801 Bochum
- Germany
| | - Jörn Güldenhaupt
- Department of Biophysics
- Ruhr-Universität Bochum
- 44801 Bochum
- Germany
| | | | - Katharina Rosga
- Department of Biophysics
- Ruhr-Universität Bochum
- 44801 Bochum
- Germany
| | - Robert Kourist
- Junior Research Group for Microbial Biotechnology
- Ruhr-Universität Bochum
- 44801 Bochum
- Germany
| | - Klaus Gerwert
- Department of Biophysics
- Ruhr-Universität Bochum
- 44801 Bochum
- Germany
| | - Carsten Kötting
- Department of Biophysics
- Ruhr-Universität Bochum
- 44801 Bochum
- Germany
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Haas J, Mizaikoff B. Advances in Mid-Infrared Spectroscopy for Chemical Analysis. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2016; 9:45-68. [PMID: 27070183 DOI: 10.1146/annurev-anchem-071015-041507] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Infrared spectroscopy in the 3-20 μm spectral window has evolved from a routine laboratory technique into a state-of-the-art spectroscopy and sensing tool by benefitting from recent progress in increasingly sophisticated spectra acquisition techniques and advanced materials for generating, guiding, and detecting mid-infrared (MIR) radiation. Today, MIR spectroscopy provides molecular information with trace to ultratrace sensitivity, fast data acquisition rates, and high spectral resolution catering to demanding applications in bioanalytics, for example, and to improved routine analysis. In addition to advances in miniaturized device technology without sacrificing analytical performance, selected innovative applications for MIR spectroscopy ranging from process analysis to biotechnology and medical diagnostics are highlighted in this review.
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Affiliation(s)
- Julian Haas
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, 89069 Ulm, Germany;
| | - Boris Mizaikoff
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, 89069 Ulm, Germany;
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Nabers A, Ollesch J, Schartner J, Kötting C, Genius J, Haußmann U, Klafki H, Wiltfang J, Gerwert K. An infrared sensor analysing label-free the secondary structure of the Abeta peptide in presence of complex fluids. JOURNAL OF BIOPHOTONICS 2016; 9:224-234. [PMID: 25808829 DOI: 10.1002/jbio.201400145] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 02/19/2015] [Accepted: 03/01/2015] [Indexed: 06/04/2023]
Abstract
The secondary structure change of the Abeta peptide to beta-sheet was proposed as an early event in Alzheimer's disease. The transition may be used for diagnostics of this disease in an early state. We present an Attenuated Total Reflection (ATR) sensor modified with a specific antibody to extract minute amounts of Abeta peptide out of a complex fluid. Thereby, the Abeta peptide secondary structure was determined in its physiological aqueous environment by FTIR-difference-spectroscopy. The presented results open the door for label-free Alzheimer diagnostics in cerebrospinal fluid or blood. It can be extended to further neurodegenerative diseases. An immunologic ATR-FTIR sensor for Abeta peptide secondary structure analysis in complex fluids is presented.
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Affiliation(s)
- Andreas Nabers
- Protein Research Unit Ruhr within Europe (PURE), Ruhr-University Bochum, Department of Biophysics ND04-596, Universitätsstraße 150, 44780, Bochum, Germany
| | - Julian Ollesch
- Protein Research Unit Ruhr within Europe (PURE), Ruhr-University Bochum, Department of Biophysics ND04-596, Universitätsstraße 150, 44780, Bochum, Germany
| | - Jonas Schartner
- Protein Research Unit Ruhr within Europe (PURE), Ruhr-University Bochum, Department of Biophysics ND04-596, Universitätsstraße 150, 44780, Bochum, Germany
| | - Carsten Kötting
- Protein Research Unit Ruhr within Europe (PURE), Ruhr-University Bochum, Department of Biophysics ND04-596, Universitätsstraße 150, 44780, Bochum, Germany
| | - Just Genius
- Protein Research Unit Ruhr within Europe (PURE), LVR-Hospital Essen, Department of Psychiatry and Psychotherapy, Medical Faculty University of Duisburg-Essen, 45147, Essen, Germany
| | - Ute Haußmann
- Protein Research Unit Ruhr within Europe (PURE), LVR-Hospital Essen, Department of Psychiatry and Psychotherapy, Medical Faculty University of Duisburg-Essen, 45147, Essen, Germany
| | - Hans Klafki
- Protein Research Unit Ruhr within Europe (PURE), LVR-Hospital Essen, Department of Psychiatry and Psychotherapy, Medical Faculty University of Duisburg-Essen, 45147, Essen, Germany
| | - Jens Wiltfang
- Protein Research Unit Ruhr within Europe (PURE), LVR-Hospital Essen, Department of Psychiatry and Psychotherapy, Medical Faculty University of Duisburg-Essen, 45147, Essen, Germany
- University Medical Center, Department of Psychiatry and Psychotherapy, Georg-August-University, 37073, Göttingen, Germany
| | - Klaus Gerwert
- Protein Research Unit Ruhr within Europe (PURE), Ruhr-University Bochum, Department of Biophysics ND04-596, Universitätsstraße 150, 44780, Bochum, Germany.
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11
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Bolivar JM, Eisl I, Nidetzky B. Advanced characterization of immobilized enzymes as heterogeneous biocatalysts. Catal Today 2016. [DOI: 10.1016/j.cattod.2015.05.004] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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12
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Schartner J, Hoeck N, Güldenhaupt J, Mavarani L, Nabers A, Gerwert K, Kötting C. Chemical Functionalization of Germanium with Dextran Brushes for Immobilization of Proteins Revealed by Attenuated Total Reflection Fourier Transform Infrared Difference Spectroscopy. Anal Chem 2015; 87:7467-75. [PMID: 26102158 DOI: 10.1021/acs.analchem.5b01823] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Protein immobilization studied by attenuated total reflection Fourier transform infrared (ATR-FT-IR) difference spectroscopy is an emerging field enabling the study of proteins at atomic detail. Gold or glass surfaces are frequently used for protein immobilization. Here, we present an alternative method for protein immobilization on germanium. Because of its high refractive index and broad spectral window germanium is the best material for ATR-FT-IR spectroscopy of thin layers. So far, this technique was mainly used for protein monolayers, which lead to a limited signal-to-noise ratio. Further, undesired protein-protein interactions can occur in a dense layer. Here, the germanium surface was functionalized with thiols and stepwise a dextran brush was generated. Each step was monitored by ATR-FT-IR spectroscopy. We compared a 70 kDa dextran with a 500 kDa dextran regarding the binding properties. All surfaces were characterized by atomic force microscopy, revealing thicknesses between 40 and 110 nm. To analyze the capability of our system we utilized N-Ras on mono-NTA (nitrilotriacetic acid) functionalized dextran, and the amount of immobilized Ras corresponded to several monolayers. The protein stability and loading capacity was further improved by means of tris-NTA for immobilization. Small-molecule-induced changes were revealed with an over 3 times higher signal-to-noise ratio compared to monolayers. This improvement may allow the observation of very small and so far hidden changes in proteins upon stimulus. Furthermore, we immobilized green fluorescent protein (GFP) and mCherry simultaneously enabling an analysis of the surface by fluorescence microscopy. The absence of a Förster resonance energy transfer (FRET) signal demonstrated a large protein-protein distance, indicating an even distribution of the protein within the dextran.
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Affiliation(s)
- Jonas Schartner
- Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr-University, 44801 Bochum, Germany
| | - Nina Hoeck
- Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr-University, 44801 Bochum, Germany
| | - Jörn Güldenhaupt
- Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr-University, 44801 Bochum, Germany
| | - Laven Mavarani
- Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr-University, 44801 Bochum, Germany
| | - Andreas Nabers
- Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr-University, 44801 Bochum, Germany
| | - Klaus Gerwert
- Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr-University, 44801 Bochum, Germany
| | - Carsten Kötting
- Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr-University, 44801 Bochum, Germany
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