Changes in supramolecular structure of lipid bilayers induced by protein-lipid interactions
Final Report Abstract
The most important results originating from realization of this research project may be summarized as follow: 1) descritption of the structure of model lipid membrane adsorbed on metal and oxide surfaces, modelling implant materials; 2) characterization of structural changes in unsymmetric lipid bilayers exposed to physiological electric fields and impact of a protein binding on the structure of model lipid membranes. IR transmitting or absorbing substances such as silicates, titanium or titanium oxide, the most common implant materials, are not suitable for IRRAS analysis. Within this project it was demonstrated that despite the fact that silica and titanium are transparent and silicate at wavelengths below 1300 cm-1 absorptive to IR radiation, when deposited in the form of ultra thin films on IR reflecting material such as gold, the enhancement of the electric field at the interface is comparable to that of Au alone, fulfilling the surface selection rule. Within this project the PM IRRAS was successfully used for the first time to characterize thin silicate oxide and titanium/titania films. Moreover structure and stability of model lipid bilayers formed on the silica, titania (preferred implant materials) and gold surface was presented. Studies of unsymmetric lipid bilayers containing gangliosides, modelling cell membranes of neurones, showed unexpected electrochemical characterization. The potential induced adsorption-desorption process was found to be irreversible. This unusual electrochemical behavior has never been observed in symmetric ganglioside-free model lipid bilayers. In situ PM IRRAS experiment combined to electrochemistry was used to clarify differences in electochemcial behaviour of symmetric and unsymmetric ganglisoide containing bilayers. Spectroelectrochemical experiments have shown that negative potentials facilitate formation of pores in the model membrane with simultaneous rearrangement of ganglioside molecules. Thus, breaking of the asymmetry of the model lipid bilayer is the irreversible step observed during the potential driven adsorption-desorption process. From biological point of view the formation of defects and breaking of the asymmetry of the bilayer may affect signalling events and carbohydrate based recognition phenomena, which belong to main functions of glycolipids on surfaces of neuronal cell membranes. Challenging experimentally remains the analysis of structural changes accompanying a lipid membrane due to interaction with proteins. In this project the vast impact of the in situ PM IRRAS under electrochemical control on analysis of strong and weak lipid – protein interactions was demonstrated. Small, hoverer very important changes in the structure of a single lipid bilayer due to a weak interaction with a protein has been presented in the literature for the first time. The successful description at the sub-molecular level of a weak lipid-protein interaction opens-up new research opportunities.
Publications
- Langmuir, 23,2007,9303-9309. „PM IRRAS investigations of thin silica films deposited on gold: Part 1 Theory and proff of concept”
Zawisza, I.; Wittstock, G.; Boukherroub, R.; Szunertis, S.
- Langmuir, 24,2008,7378-7387. „Application of thin titanium/titanium oxide layers deposited on gold for infrared reflection absorption spectroscopy: structural studies of lipid bilayers”
Zawisza, I.; Nullmeier, M.; Pust, S.E.; Boukherroub, R.; Szunertis, S.; G. Wittstock
- Physical Chemistry Chemical Physics, 11,2009,10140-109151. “Orientation of the GM1 ganglioside in Langmuir-Blodgett monolayers: a PM IRRAS and computational study”
M. Röefzaad, T. Kluner, I. Brand
- Journal of Electroanalytical Chemistry, 624,2010,177-188, special issue dedicated to J. Lipkowski. “Interaction of siglec protein with glycolipids in a lipid bilayer deposited on a gold electrode surface”
M. Nullmeier, H. Koliwer-Brandl, S. Kelm, I. Brand
- Langmuir, 26,2010,362-370. ”Structural analysis of HS(CD2)12(O-CH2-CH2)6OCH3 monolayers on gold by means of polarization modulation infrared reflection absorption spectroscopy. Progress of the reaction with bromine”
I. Brand, M. Nullmeier, T. Klüner, R. Jogireddy, J. Christoffers, G. Wittstock
- “Thin films on titania and their applications in life sciences” IN: “Nanotechnologies for the Life Sciences” Vol.V “Nanostructured Thin Films for Life Sciences”, Ed. Ch. Kumar, Willey, Heidelberg, 2010, pp 203-250
Brand. I.; Nullmeier, M.
- 2011. ”Supramoleculare Strukturveränderungen in asymmetrischen Lipiddoppelschichten”, Doctorate thesis
M. Nullmeier
