CD Laboratory for Nanoscopic Methods in Biophysics

A new atomic force microscope is being developed that allows simultaneous measurement of the topography of biochemical reactions (biospecific recognition), the material contrast and the fluorescence of a sample.

In atomic force microscopy, a nanoscopic needle at the end of a leaf spring (cantilever) is guided over the surface of a sample. The surface structure changes the position of the leaf spring. This deflection is measured and provides information about the atomic forces acting between the tip and the surface. Until now, this has been used almost exclusively for mechanical scanning of surfaces in the nanometre range. Research is now being carried out into utilising this measuring principle for other types of measurement.

Chemical methods are being developed that allow the cantilever tip to be functionally adapted. Special molecules are to be deposited in high density on the cantilever tip, which interact with some molecules on the surface and influence the cantilever. In this way, the type of molecules in the surface - and not just their structure - can be recognised; this is referred to as biochemical and molecular recognition.

Research is also being carried out on the oscillation of the cantilever in MAC mode. In this mode, the needle touches the surface point by point and the cantilever oscillates at a high frequency. Forces on the surface that act on the needle change the amplitude and frequency - an effect that can be measured. Here, the amplitude, phase and frequency of the oscillation are analysed with the following objectives: firstly, to determine their effects on the resolution of the measurement and, secondly, to determine the material contrast and the distribution of certain proteins. New methods of signal processing and simulations are used to gain insights into the imaging process and thus create opportunities to improve the contrast and resolution of the image.

Work is also underway to combine the possibilities of atomic force microscopy with those of fluorescence measurements. To do this, the mechanical decoupling of the two measurement principles must be resolved. If this succeeds, such a combination will allow the study of complex cellular processes.