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Monitoring the interfacial capacitance at self-assembled phosphate monolayers on gold electrodes upon interaction with calcium and magnesium
Linköping University, Department of Physics, Chemistry and Biology, 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, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
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2002 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 74, no 9, p. 1979-1985Article in journal (Refereed) Published
Abstract [en]

Electrochemical impedance spectroscopy has been used to evaluate the change in interracial capacitance upon calcium and magnesium coordination to a phosphate-modified electrode. The phosphate electrode was prepared via immobilization of phosphorylated, thiol-containing, serine analogues onto gold. Upon subjection to calcium and magnesium, a substantial drop in capacitance was observed. Magnesium displayed the largest influence on the capacitance: a 27% capacitance drop was observed upon introduction of a 1 mM solution of magnesium ions. The lowered capacitance is a result of a change in the potential and charge distribution at the film/electrolyte interface as the cations coordinate to the phosphate groups. Moreover, the relationship between electrode potential and capacitance has been investigated and reveals a significant difference between monovalent and divalent cations. As complementary information, infrared reflection absorption spectra of the phosphorylated monolayer having different counterions are presented. The results reported in this paper indicate that the phosphorylated amino acid analogue monolayers could be used in investigations of the biochemically important coordination of calcium and magnesium to phosphates and phosphorylated amino acids.

Place, publisher, year, edition, pages
Washington,DC, USA: American Chemical Society (ACS), 2002. Vol. 74, no 9, p. 1979-1985
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-47026DOI: 10.1021/ac015635aISI: 000175358800032OAI: oai:DiVA.org:liu-47026DiVA, id: diva2:267922
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2021-09-24Bibliographically approved
In thesis
1. Phosphorylated Monomolecular Layers: Design, Synthesis, Characterization and Application
Open this publication in new window or tab >>Phosphorylated Monomolecular Layers: Design, Synthesis, Characterization and Application
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the design, synthesis and characterization of organo-phosphatemonomolecular layers, so called self-assembled monolayers, using the strategy of linking organosulfur substances to a gold surface. Moreover there is also a paper included, which describes the development of synthetic pathways to various phospholipids, for which I have developed an interest in later projects.

For the first study of the properties of phosphates, and also for concomitant application of developed systems, analogues of the amino acids serine, threonine and tyrosine, phosphorylated and non-phosphorylated, were synthesized. 16-Mercaptohexadecanamide based analogues were characterized as monolayers and large polar and charge effects were observed, introduced by the phosphate. Problems were, however, encountered as a post modification of phosphates was applied and a disordering of the monolayers observed. Moreover there were no expected effects observable upon interaction with Ca2+ and Mg2+.

Based on the conclusions from the first study 3-mercaptopropionamide based analogues were used instead. Characterization of the analogues including counter ion exchange (H+,Na+, Ca2+ and Mg2+) revealed large electronic and possible structural differences depending on the counter ion.

Again the charge and polar effects induced by the phosphate were investigated, and the study was also extended to interaction of the phosphate with Ca2+ and Mg2+. Strong effects were observed, which were also dependent on the ion concentration within a significant range. The polarity and charge properties of the phosphate layer were thus found to be variable.

In the fourth study an additional Ca2+ and Mg2+ sensitive system was applied in combination with the phosphate surface. Phosphate surface/phospholipid vesicle interactions were studied under different conditions of Mg2+ (Ca2+) treatment. For comparison, the corresponding hydroxyl and sulphate surfaces were included and also the most well characterized surface concerning phospholipid vesicle interaction, SiO2. Most importantly, supported phospholipid bilayer (SPB) formation was found to be inducible on both the phosphate and sulphate surfaces, however at defined conditions of Mg2+ (Ca2+) treatment and concentration. The conclusion is that the processes of phospholipid vesicle adsorption and SPB formation are largely dependent on vesicle/surface interaction and vesicle stability.

The last paper included in this thesis is a synthetic method development aimed at easy preparations of various phospholipid derivatives. In the future these methods could be used for synthesis of functionalized lipids and aid in the development of models mimicking biological systems such as artificial cell membranes.

Place, publisher, year, edition, pages
Linköping: Linköping University, 2002. p. 51
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 764
National Category
Physical Chemistry
Identifiers
urn:nbn:se:liu:diva-179557 (URN)9173733954 (ISBN)
Public defence
2002-09-27, hörsal Planck, Fysikhuset,, Linköpings Universitet, Linköping, 13:00
Opponent
Available from: 2021-09-24 Created: 2021-09-24 Last updated: 2023-03-07Bibliographically approved

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Ekeroth, JohanKonradsson, PeterBjörefors, FredrikLundström, IngemarLiedberg, Bo

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