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Mimicking the properties of antifreeze glycoproteins: synthesis and characterization of a model system for ice nucleation and antifreeze studies
Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
2005 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 33, 15849-15859 p.Article in journal (Refereed) Published
Abstract [en]

Synthesis of β-D-Gal-(1 → 3)-β-D-GalNAc coupled to HOC2H4NHCOC15H30SH is described. This compound was coadsorbed at various proportions with C2H5OC2H4NHCOC15H30SH to form statistically mixed self-assembled monolayers (SAMs) on gold in an attempt to mimic the properties of the active domain in antifreeze glycoproteins (AFGPs). The monolayers were characterized by null ellipsometry, contact angle goniometry, X-ray photoelectron spectroscopy, and infrared reflection−absorption spectroscopy. The disaccharide compound adsorbed preferentially, and SAMs prepared at a solution molar ratio >0.3 displayed total wetting. The mixed SAMs showed well-organized alkyl chains up to a disaccharide surface fraction of 0.8. The amount of gauche conformers in the alkyls increased rapidly above this point, and the monolayers became disordered and less densely packed. Furthermore, the generated mixed SAMs were subjected to water vapor at constant relative humidity and the subsequent ice crystallization on a cooled substrate was monitored via an optical microscope. Interestingly, rapid crystallization occurred within a narrow range of temperatures on mixed SAMs with a high disaccharide content, surface fraction >0.3. The reported crystallization temperatures and the ice layer topography were compared with results obtained for a much simpler reference system composed of −OH/−CH3 terminated n-alkanethiols in order to account for changes in topography of the water/ice layer with surface energy. Although preliminary, the obtained results can be useful in the search for the molecular mechanism behind the antifreeze activity of AFGPs.

Place, publisher, year, edition, pages
2005. Vol. 109, no 33, 15849-15859 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-14337DOI: 10.1021/jp050752lOAI: oai:DiVA.org:liu-14337DiVA: diva2:23266
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2017-12-13
In thesis
1. Biomimetic surfaces: Preparation, characterization and application
Open this publication in new window or tab >>Biomimetic surfaces: Preparation, characterization and application
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [sv]

I denna avhandling beskrivs tillverkning, karaktärisering och tillämpning av ett antal biomimetiska ytor. Biomimetik är att härma naturen och grundtanken är att titta på hur naturen löst liknande problemställningar. Två olika typer av modellsystem med inspiration från naturen har tagits fram för framtida tillämpningar inom bioanalys, biosensorer samt antifrysmaterial. Det ena typen av modellsystem innefattar fosforylerade ytor och det andra består av ytor som härmar antifrys(glyko)proteiner. Ytorna tillverkades av monolager av självorganiserande svavelorganiska molekyler och karaktäriserades före tillämpning med hjälp av ellipsometri, IR-spektroskopi, kontaktvinkelmätning och röntgenfotoelektronspektroskopi.

Modellsystemen för att studera vattenfrysning på ytor inspirerades av antifrys(glyko)proteiner som bl.a. kan hittas i polarfiskar. Två modellsystem utvecklades och studerades med avseende på frysning av kondenserat vatten. Det ena designades att härma den aktiva domänen hos ett antifrysglykoproteiner (AFGP) och det andra härmade typ I antifrysproteiner (AFP I). Frysstudierna visade på signifi-kanta skillnader för AFGP-modellen jämfört med ett (OH/CH3) referenssystem med jämförbar vätbarhet, men inte för AFP Imodellen. Vattnet frös vid högre temperatur för AFGPmodellen.

Modellsystemen med fosforylerade ytor inspirerades av fosforylering och biomineralisering. Två system utvecklades, ett med långa och ett med korta alkylkedjor på aminosyraanalogerna, både med och utan fosfatgrupp. En ny metod användes med skyddsgrupper på fosfaterna hos de långa analogerna innan bildandet av monolager. Skyddsgrupperna togs bort efter bildandet av monolager. Dessa monolager undersöktes också med elektrokemiska metoder och signifikant högre kapacitans observerades för de fosforylerade monolageren jämfört med de icke fosforylerade.

Abstract [en]

This thesis describes the preparation, characterization and application of a few biomimetic surfaces. Biomimetics is a modern development of the ancient Greek concept of mimesis, i.e. man-made imitation of nature. The emphasis has been on the preparation and characterization of two types of model systems with properties inspired by nature with future applications in bioanalysis, biosensors and antifreeze materials. One type of model system involves phosphorylated surfaces; the other consists of surfaces mimicking antifreeze (glyco)proteins. The surfaces were made by chemisorbing organosulfur substances to a gold surface into monomolecular layers, so called self-assembled monolayers (SAMs). The physicochemical properties of the SAMs were thoroughly characterized with null ellipsometry, contact angle goniometry, x-ray photoelectron spectroscopy and infrared spectroscopy prior to application.

The work on antifreeze surfaces was inspired by the structural properties of antifreeze (glyco)proteins, which can be found in polar fish. Two model systems were developed and studied with respect to ice nucleation of condensed water layers. One was designed to mimic the active domain of antifreeze glycoproteins (AFGP) and the other mimicked type I antifreeze proteins (AFP I). Subsequent ice nucleation studies showed a significant difference between the AFGP model and a (OH/CH3) reference system displaying identical wetting properties, whereas the AFP I model was indistinguishable from the reference system.

The model systems with phosphorylated surfaces were inspired from phosphorylations and biomineralization. Two systems were developed, short- and long-chained amino acid analogues, with and without a phosphate group. A novel approach with protected groups before attachment to gold were developed for the long-chained analogues. The protective groups could be removed successfully after assembly. The long-chained SAMs were evaluated with electrochemical methods and significantly higher capacitance values were observed for the phosphorylated SAMs compared to the non-phosphorylated.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2007. 84 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1069
Keyword
Self-assembled monolayers, biomimetic surfaces, phosphates, antifreeze, surface spectroscopy
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-8492 (URN)978-91-85715-99-2 (ISBN)
Public defence
2007-03-30, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2009-04-23
2. Synthesis of inositolphosphoglycans found in Trypanosoma cruzi and development of novel carbohydrate monomolecular layers
Open this publication in new window or tab >>Synthesis of inositolphosphoglycans found in Trypanosoma cruzi and development of novel carbohydrate monomolecular layers
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, synthetic carbohydrate chemistry has been utilized to contribute to the fundamental understanding of three biological relevant areas. These include parasite cell-membrane glycoconjugates, protein-resistant surfaces and antifreeze glycoproteins.

The synthesis of inositolphosphoglycans found in Trypanosoma cruzi, the pathogen of Chagas´ disease, is described. A protected derivative of 6-(2-aminoethyl phosphonic acid)-2-amino-2-deoxy-α-D-glucopyranosyl-(1→6)-D-myo-inositol-1-phosphate was identified as an appropriate acceptor to give a synthetic route to the core oligosaccharide of T. cruzi glycoinositolphospholipids. The assembly of three building blocks accomplished the synthesis of the heptasaccharyl myo-inositol Galf(β1→3)-Manp(α1→2)-[Galf(β1→3)]-Manp(α1→2)-Manp(α1→6)-Manp(α1→4)-6-(2 -aminoethyl phosphonic acid)-GlcNp-(α1→6)-myo-Ins-1-PO4, the glycan of the T. cruzi lipopeptidophosphoglycan.

Carbohydrate self-assembled monolayers (SAMs) on gold were designed, synthesized and characterized to investigate their protein rejecting properties. Synthesis of methylated and non-methylated galactose-terminated alkanethiols provided mixed carbohydrate monomolecular layers. The physiochemical properties of the mixed SAMs were elucidated with ellipsometry, infrared reflection-absorption spectroscopy and contact angle goniometry. The irreversible adsorption of the model proteins fibrinogen and lysozyme was determined with ex-situ ellipsometry. Neither of the proteins adsorbed within a mixed regime corresponding to contact angles of water between 24° and 45°.

A carbohydrate model system mimicking the properties of antifreeze glycoproteins was developed. A Gal(β1→3)-GalNAc terminated 16-mercapto-hexadecanoic acid derivative was synthesized and co-adsorbed with an ethyl-terminated thiol in various proportions to form mixed SAMs on gold. The monolayers were characterized and the antifreeze model system was evaluated by initial ice nucleation studies.

Synthetic routes to protected ethyl 2-deoxy-2-phthalimido-1-β-D-thio-galactosamine derivatives via epimerization of corresponding glucosamine compounds were explored to provide methods in future synthesis of antifreeze glycoproteins and analogues.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2005. 63 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 980
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-29937 (URN)15363 (Local ID)91-85457-56-6 (ISBN)15363 (Archive number)15363 (OAI)
Public defence
2005-12-02, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-12-04Bibliographically approved

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Hederos, MarkusKonradsson, PeterBorgh, AnnikaLiedberg, Bo

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