Regensburg 2004 – scientific programme

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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.127: Poster

Friday, March 12, 2004, 10:30–13:00, B

Induced changes in comformation and charge density of thin polymer films at the interface - a neutron and x-ray reflectivity study towards controlled protein-surface interaction — •Florian Rehfeldt¹, Roland Steitz², Regine v. Klitzing², and Motomu Tanaka¹ — ¹Lehrstuhl für Biophysik E22, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany — ²Stranski-Laboratorium, TU Berlin, Straße d. 17. Juni 112, D-10623 Berlin, Germany

The switching of physical properties of thin polymer films (charge density, conformation, etc.) under physiological conditions draws increasing attention to control cell-surface/protein-surface interaction by means of external stimulation. For this purpose, one of the attractive candidates is a relatively No-dqweakNo-dq polyelectrolyte, whose degree of ionisation (D.I.) can be controlled by pH titration. We chose a diblock-copolymer that possesses a hydrophobic MMA block and a hydrophilic DMAEMA block. The D.I. of DMAEMA block is 0.6 at pH = 5.5, and 0.2 at pH=8.5, respectively. When the block ratio is 1:1, this type of diblock forms an insoluble monolayer at air/water interface. Recently, we demonstrated the adsorption and desorption of weakly charged DMAEMA chains at air/water interface by pH titration. Such insoluble monolayers can be transferred from air/water interface onto hydrophobized silicon blocks, where distinct changes in the layer thickness as well as in the scattering length density were monitored with neutron reflectivity. Furthermore, adsorption of water-soluble proteins on charged- and uncharged brushes can be detected by ex-situ x-ray reflectivity and fluorescence microscopy.