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Self-assembly of synthetic peptides control conformation and optical properties of a zwitterionic polythiophene derivative
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-5582-140X
Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
2003 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 100, no 18, 10170-10174 p.Article in journal (Refereed) Published
Abstract [en]

The optical transitions of a chiral, three-substituted polythiophene with an amino acid function can be tuned by interactions with synthetic peptides. The addition of a positively charged peptide with a random-coil formation will force the polymer to adopt a nonplanar conformation, and the intensity of the emitted light is increased and blue-shifted. After the addition of a negatively charged peptide with a random-coil conformation, the backbone of the polymer adopts a planar conformation and an aggregation of the polymer chains occurs, seen as a red shift and a decrease of the intensity of the emitted light. By adding the positively charged peptide designed to form a four-helix bundle with the negatively charged peptide, the polymer aggregates are disrupted and the intensity of the emitted light is increased because of separation of the polymer chains. This technique could be used as a platform for making novel sensors and biomolecular switches.

Place, publisher, year, edition, pages
2003. Vol. 100, no 18, 10170-10174 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-14039DOI: 10.1073/pnas.1834422100OAI: oai:DiVA.org:liu-14039DiVA: diva2:22502
Available from: 2006-09-28 Created: 2006-09-28 Last updated: 2017-12-13
In thesis
1. Protein-protein interactions in model systems: design, control of catalytic activity and biosensor applications
Open this publication in new window or tab >>Protein-protein interactions in model systems: design, control of catalytic activity and biosensor applications
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the design of polypeptides, unordered in the monomeric state but capable of folding into helix-loop-helix motifs and dimerise to form four-helix bundles. The goal of the design was to encode them with the capacity to form dimers highly selectively and the ability to carry out molecular functions in the folded state but not in the unordered state, and thus to establish a molecular link between recognition and function. The 42-residue sequences JR2E and JR2K were both shown by CD spectroscopy to adopt unordered conformations under single solute conditions at pH 7 but to form helical conformations in a 1:1 mixture. Analytical ultracentrifugation showed that JR2E and JR2K formed a clean heterodimer and the dissociation constant Kd, measured by CD spectroscopy, was found to be 5 ± 1 μM. Discrimination was enabled by the incorporation of charged residues at the dimer interface in the helical segments of the helix-loop-helix motif. Glutamic acids were incorporated in JR2E and lysines in JR2K, and charge repulsion prevented the monomeric subunits from forming homodimers. In mixtures, however, highly helical heterodimers were formed. The cooperative transition from unordered conformation to heterodimeric four-helix bundle was exploited in the design of a signal response system by incorporating a reactive site, capable of catalysing the hydrolysis of a m-nitrophenyl ester, into the negatively charged polypeptide. In the unfolded state the functionalised polypeptide was virtually inactive but in the folded state, induced by the interaction with JR2K, the substrate was hydrolysed approximately an order of magnitude more efficiently.

Interactions between the designed polypeptides and a functionalised polythiophene polymer were studied and it was found that the conformation of the polymer was controlled by the polypeptides, largely by electrostatic interactions. The negatively charged JR2E forced the polymer to adopt a planar conformation while the positively charged JR2K induced a more twisted conformation of the polymer. The spectral changes coupled to the conformational transitions of the polymer were used to measure the binding of human Carbonic anhydrase II by JR2E functionalised with a benzenesulphonamide ligand, in demonstration of its use as a tool for high-throughput screening.

JR2E immobilised on gold nanoparticles was shown to form homodimers reversibly under pH control, with affinities large enough to determine the state of aggregation of the gold nanoparticles.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2006
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1037
Keyword
Chemistry, Protein interactions, design, catalysis, biosensors, hybride materials, nanoparticles, Kemi
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-7485 (URN)91-85523-19-4 (ISBN)
Public defence
2006-09-22, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 09:15 (English)
Opponent
Supervisors
Available from: 2006-09-28 Created: 2006-09-28 Last updated: 2009-04-01Bibliographically approved
2. Conjugated polyelectrolytes: conformation sensitive optical probes for the recording of biological processes
Open this publication in new window or tab >>Conjugated polyelectrolytes: conformation sensitive optical probes for the recording of biological processes
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The physical properties of conjugated polymers can be utilized for a wide range of biosensors. For instance, the conformational flexibility fouud in conjugated polyelectrolytes, allows direct connection between the geometry of chains and the resulting electronic structure and optical processes, since the extension of the π-conjugated system is distorted by conformational changes of the polyelectrolyte backbone. The biosensors presented in this thesis are utilizing conformational changes of conjugated polyelectrolytes for the detection of biomolecular processes, such as biospecific interactions and conformational changes of biomolecules. The methodology have been used for the detection of DNA-hybridization, single nucleotide polymorphism (SNP) in DNA, conformational alterations of synthetic peptides, conformational alterations of Calmodulin and binding of Ca2+-activated Calmodulin (CaM) to Calcineurin, and amyloid fibril formation of amyloidogenic proteins.

The method is based on non-covalent assembly of a conjugated polyelectrolyte and a biomolecule of interest. Upon exposure to a second biomolecule recognizing the first biomolecule or a conformational change of the first biomolecule, a conformational alteration of the polyelectrolyte backbone and a change in the electronic properties of the polyelectrolyte occurs, and these alterations can be detected by a change of the absorption or the fluorescence from the polyelectrolyte. Hence, conjugated polyelectrolytes can be used as novel conformation sensitive optical probes for the detection of several biological processes. The biomolecular interaction or the conformational changes of the biomolecule are reflected as an alteration of the geometry and the electronic structure of the bouud polyelectrolyte chains and are detected by absorption and emission. The present mechanism may be used for detection of a variety biomolecular processes, and the simplicity and the diversity of this methodology make it suitable for making inexpensive protein- and DNA-chips for rapid detection of biomolecular recognition.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2005. 61 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 961
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-30214 (URN)15709 (Local ID)91-85457-01-9 (ISBN)15709 (Archive number)15709 (OAI)
Public defence
2005-09-15, Planck, Fysikhuset, Linköpings universitet, Linköping, 13:15 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2014-04-08

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Nilsson, PeterRydberg, JohanBaltzer, LarsInganäs, Olle

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