|Frank Leisten, Matthias Wiechmann, Oliver Enders, and Hans-Albert Kolb
Institute of Biophysics, University of Hannover, Herrenhäuser St. 2, D-30419 Hannover, Germany
Nanostructures of lysozyme molecules adsorbed to mica are generated by atomic force microscopy in contact-,tapping-and force-distance-mode in aqueous solution. It is shown that in contact mode at high ionic strength and adjusted lysozyme concentration a monolayer of defined structure and orientation can be formed by the scan process of the tip. A lateral resolution of the monolayer of about 80 nm could be achieved. At larger loading forces besides a lysozyme monolayer also 3D-aggregates could be generated in parallel. In force-distance mode the volume of 3D-aggregates grows with increasing lysozyme concentration,loading force and number or frequency of up-and down-movement of the tip. Also in tapping mode 3D-aggregates could be generated at the selected incubation conditions. It is postulated that screening of electrostatic interaction between lysozyme and substrate at high ionic strength is critical for monolayer formation.Different to the known dip-pen nanolithography (DPN) for DTN adsorption of lysozyme to the tip and thereafter the flow to the mica surface at contact is discussed.