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Conjugated polyelectrolytes: conformation sensitive optical probes for the recording of biological processes
Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-5582-140X
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: urn:nbn:se:liu:diva-30214Local ID: 15709ISBN: 91-85457-01-9 (print)OAI: oai:DiVA.org:liu-30214DiVA: diva2:251036
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
List of papers
1. Conformational transitions of a free amino-acid-functionalized polythiophene induced by different buffer systems
Open this publication in new window or tab >>Conformational transitions of a free amino-acid-functionalized polythiophene induced by different buffer systems
2002 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 14, no 42, 10011-10020 p.Article in journal (Refereed) Published
Abstract [en]

A chiral, 3-substituted polythiophene with an amino-acid function shows pH-dependent visible, emission and circular dichroism spectra in buffered aqueous solution. At pH equal to the pI of the amino-acid, the backbone adopts a nonplanar right-handed helical conformation and the polymer chains are separated from each other. Increasing pH leads to a more planar conformation of the backbone and an aggregation of the polymer chains occurs. A lower pH will also lead to a more planar conformation of the backbone, but aggregation of the polymer chains appears to be absent. The aggregates are disrupted by increasing ionic strength in alkaline buffer systems, indicating hydrogen bonding is important for aggregation. On the other hand, ions containing an amino group and one or more hydroxyl groups induce a more planar conformation of the polymer backbone.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-46886 (URN)10.1088/0953-8984/14/42/313 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
2. Chip and solution detection of DNA hybridization using a luminescent zwitterionic polythiophene derivative
Open this publication in new window or tab >>Chip and solution detection of DNA hybridization using a luminescent zwitterionic polythiophene derivative
2003 (English)In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 2, no 6, 419-424 p.Article in journal (Refereed) Published
Abstract [en]

Electronic polymers in aqueous media may offer bioelectronic detection of biospecific interactions. Here we report a fluorometric DNA hybridization detection method based on non-covalent coupling of DNA to a water-soluble zwitterionic polythiophene derivative. Introduction of a single-stranded oligonucleotide will induce a planar polymer and aggregation of the polymer chains, detected as a decrease of the intensity and a red-shift of the fluorescence. On addition of a complementary oligonucleotide, the intensity of the emitted light is increased and blue-shifted. The detection limit of this method is at present ~10−11 moles. The method is highly sequence specific, and a single-nucleotide mismatch can be detected within five minutes without using any denaturation steps. The interaction with DNA and the optical phenomena persists when the polymer is deposited and patterned on a surface. This offers a novel way to create DNA chips without using covalent attachment of the receptor or labelling of the analyte.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-46558 (URN)10.1038/nmat899 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
3. Self-assembly of synthetic peptides control conformation and optical properties of a zwitterionic polythiophene derivative
Open this publication in new window or tab >>Self-assembly of synthetic peptides control conformation and optical properties of a zwitterionic polythiophene derivative
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.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-14039 (URN)10.1073/pnas.1834422100 (DOI)
Available from: 2006-09-28 Created: 2006-09-28 Last updated: 2017-12-13
4. Twisting macromolecular chains: self-assembly of a chiral supermolecule from nonchiral polythiophene polyanions and random-coil synthetic peptides
Open this publication in new window or tab >>Twisting macromolecular chains: self-assembly of a chiral supermolecule from nonchiral polythiophene polyanions and random-coil synthetic peptides
2004 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 101, no 31, 11197-11202 p.Article in journal (Refereed) Published
Abstract [en]

The self-assembly of a negatively charged conjugated polythiophene derivative and a positively charged synthetic peptide will create a chiral, well ordered supermolecule. This supermolecule has the three-dimensional ordered structure of a biomolecule and the electronic properties of a conjugated polymer. The molecular complex being formed clearly affects the conformation of the polymer backbone. A main-chain chirality, such as a predominantly one-handed helical structure induced by the acid–base complexation between the conjugated polymer and the synthetic peptide, is seen. The alteration of the polymer backbone influences the optical properties of the polymer, seen as changes in the absorption, emission, and Raman spectra of the polymer. The complexation of the polythiophene and the synthetic peptide also induce a change from random-coil to helical structure of the synthetic peptide. The supermolecule described in this article may be used in a wide range of applications such as biomolecular devices, artificial enzymes, and biosensors.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-45666 (URN)10.1073/pnas.0401853101 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
5. Enantiomeric substituents determine the chirality of luminescent conjugated polythiophenes
Open this publication in new window or tab >>Enantiomeric substituents determine the chirality of luminescent conjugated polythiophenes
2004 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 37, no 17, 6316-6321 p.Article in journal (Refereed) Published
Abstract [en]

Chiral isomers of 3-substituted polythiophenes with amino acid functiontionalized side chains are compared. The polymers show pH-dependent absorption, emission, and circular dichroism spectra in buffered aqueous solution. At pH equal to pI of the amino acid, the backbones adopt nonplanar helical conformations, and the polymer chains are separated from each other. Increasing pH leads to more planar conformations of the backbones and an aggregation of the polymer chains occurs. A lower pH will also lead to more planar conformation of the backbones, but aggregation of the polymer chains appears to be absent. The nonplanar to planar transition of the polymer backbone and the separation/aggregation of different polymer chains is not affected by stereochemistry of the zwitterionic side chain. The two isomers have almost identical pH-dependent absorption and emission spectra. However, the chirality of the zwitterionic side chain is reflected in the conformation of the polymer backbone, giving rise to a right-handed and left-handed helical form of polythiophene chains since the induced circular dichroism patterns of the two polymers are mirror images.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-45660 (URN)10.1021/ma048859e (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
6. Optical emission of a conjugated polyelectrolyte: calcium-induced conformational changes in calmodulin and calmodulin-calcineurin interactions
Open this publication in new window or tab >>Optical emission of a conjugated polyelectrolyte: calcium-induced conformational changes in calmodulin and calmodulin-calcineurin interactions
2004 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 37, no 24, 9109-9113 p.Article in journal (Refereed) Published
Abstract [en]

Electronic polymers in aqueous media offer bioelectronic detection of biomolecular processes. Here we report fluorometric detection of calcium-induced conformational changes in calmodulin based on noncovalent assembly of calmodulin to a water-soluble zwitterionic polythiophene derivative. Assembly with calmodulin will induce a planar geometry and aggregation of the polymer chains, detected as a decrease of the intensity and a red shift of the fluorescence. Upon addition of Ca2+ the intensity of the emitted light is increased and blue-shifted. The geometrical alteration of the polymer chains can further be utilized for recording of the binding of calcineurin to the calcium-activated POWT−calmodulin complex. This novel methodology, using a conformation-sensitive probe, allows fluorometric detection of conformational changes in biomolecules and protein−protein interactions without any covalent modifications of the biomolecules. The rapid and selective method is based on noncovalent interactions between a zwitterionic polythiophene derivative and the biomolecule of interest. This offers a novel way to create microarrays without using covalent attachment of the receptor or labeling of the analyte.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-45577 (URN)10.1021/ma048605t (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
7. Conjugated polyelectrolytes: conformation-sensitive optical probes for detection of amyloid fibril formation
Open this publication in new window or tab >>Conjugated polyelectrolytes: conformation-sensitive optical probes for detection of amyloid fibril formation
2005 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 44, no 10, 3718-3724 p.Article in journal (Refereed) Published
Abstract [en]

The in vivo deposition of amyloid fibrils is a hallmark of many devastating diseases known as the amyloidoses. Amyloid formation in vitro may also complicate production of proteins in the biotechnology industry. Simple, sensitive, and versatile tools that detect the fibrillar conformation of amyloidogenic proteins are thus of great importance. We have developed a negatively charged conjugated polyelectrolyte that displays different characteristic optical changes, detected visually or by absorption and emission, depending on whether the protein with which it forms a complex is in its native state or amyloid fibril conformation. This simple, rapid, and novel methodology was applied here to two amyloidogenic proteins, insulin and lysozyme, and its validity for detection of their fibrillar conformation was verified by currently used methods such as circular dichroism, transmission electron microscopy, and Congo red absorption.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14599 (URN)10.1021/bi047402u (DOI)
Available from: 2007-10-12 Created: 2007-10-12 Last updated: 2017-12-13

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