Adsorbed Monolayers of Macromolecules on Atomically Flat Surfaces

B. Cortecka, C. Lippert, X. Ni, W. Tröger, T. Butz

The adsorption of two-dimensional arrays of macromolecules on substrates plays an important role in the fabrication of model membranes, optoelectronic devices (light induced conformational changes), sensors and so on. Surfaces of mica, gold, or 1T-TaS₂ serve as atomically flat  substrates for the deposition of macromolecules. Of special interest  are self-assembly macromolecules which form highly correlated two-dimensional  monolayers.

The degree of orientation of these monolayers, especially of globular proteins like the electron transfer proteins azurin, plastocyanin, and stellacyanin, can be determined by the specific labelling of the macromolecules with radioisotopes which allow the detection of the orientation of the electric field gradient (EFG)  by time differential perturbed angular correlation  (TDPAC) of g-rays.

The possibility of changing the properties of proteins intentionally via site directed mutagenesis offers unprecedented possibilities of creating optimized protein layers for various purposes. For example, protein mutants with a "surface histidine" or "surface cysteine" can stimulate the formation of a nitrogen-sulfur- or a disulfide-bridge to  the surface of 1T-TaS₂ inducing a preferential orientation of the  protein monolayers.

We intend to use oriented monolayers of small blue copper proteins which act as electron transfer proteines for future investigations of the elctron tranfer process in these systems.

Collaborations:

• G. Karlsson, K. Sigfridsson, Ö. Hansson
  Lundberg Laboratory, Department of Biochemistry and Biophysics,
  Göteborg University and Chalmers University of Technology, Göteborg, Sweden