Adhesion and Immobilization of functional Biopolymers

The adhesive properties of polymers onto solid supports govern the function of many biosensors and medical implants. Also the immobilisation of complex biopolymers (e.g. molecular machines) is a prerequisite to understand their function on the molecular level.
In our group we investigate the interaction between single polymer molecules and solid supports on the molecular level in aqueous environment. To this aim we covalently attach single polymer molecules (e.g. spider silk motives) onto the tip of an Atomic Force Microscope, bring the molecule in contact with the substrate and measure the desorption force while retracting the tip (Figure). These experiments did yield valuable information on the interaction between charged polymers and charged solid substrates in aqueous solution [1,2]. In the framework of CompInt we focus on hydrophobic interaction. Material is supported by the groups of Prof. Scheibel and Prof. Stutzmann (Jose Garrido), we work in close collaboration with the group of Prof. Netz, who performs MD-Simulations. In the last two years we already developed some basic understanding of hydrophobic interactions [3,4].
The second aim in our group is the immobilization of a functional protein translocation complex (TOC of mitochondria) onto a glass substrate to study protein import with single molecule fluorescence and magnetic tweezers [5]. For various reasons the immobilization of functional membrane proteins for single molecule investigations onto solid substrates could not be achieved yet. The understanding of hydrophobic interactions at surfaces will help towards this goal.

Relevant Publications:

1. T. Hugel, M. Seitz (2001). The Study of Molecular Interactions by AFM Force Spectroscopy. Macromol. Rapid Commun, 22:1.
2. M. Seitz, C. Friedsam, W. Jöstl, T. Hugel, H. E. Gaub (2003) Probing Surfaces with Single Polymers. ChemPhysChem 4: 986.
3. M. Geisler, T. Pirzer, C. Ackerschott, S. Lud, J. Garrido, T. Scheibel, T. Hugel (2008). Influence of Hofmeister Salts on the adhesion of spider silk proteins onto hydrophobic substrates: an AFM-base single molecule study. Langmuir, in press.
4. D. Horinek, A. Serr, M. Geisler, T. Pirzer, U. Slotta, S. Q. Lud, J. A. Garrido, T. Scheibel, T. Hugel, R. R. Netz (2008). Single molecule peptide hydrophobicity results from the interplay of water structure effects and dispersion interaction. PNAS, in press.
5. T. Hugel, J. Michaelis, C. Hetherington, P. Jardine, S. Grimes, J. Walter, W. Falk, D. Anderson, C. Bustamante (2007). Experimental Test of the Connector Rotation during DNA Packaging into the Bacteriophage phi29 Capsids. PLOS Biology 5:558.