BIOLOGICAL APPLICATION OF THE ATOMIC FORCE MICROSCOPE

In the last years wonderful results have been published in the field of single molecule visualization and manipulation techniques. The atomic force microscope is increasingly used in biological research. The instrument was developed in the 20th century. A small tip at the end of a µm-size cantilever scans the studied surface. During the scan the deflection of the cantilever is proportional to the force acting between the tip and the surface. The spatial resolution of the instrument is determined by the sharpness of the tip. On the highest resolution images even atoms can be distinguished. Compared with the electron microscope a great advantage of the instrument is that biological samples can be studied in fluids, in their natural environment. This makes possible to observe proteins or cells during function.

With the aid of atomic force microscope results impossible to attain by other techniques have been achieved in biological systems.

Here we present several results from our atomic force microscopy research:

• By studying oligonucleotides we observed that short sequences of nucleic acids self-assemble on mica surface in a long chain-like formation. This self-assembly could have a role in the origin of life, by forming DNA or RNA, the information carrying molecules.
• On protein level we studied the interaction of the photosynthetic reaction center with carbon nanotubes. The complex formed is a promising material for biotechnological applications.
• Studying the proton pumping protein bacteriorhodopsin, we measured the size change during its function, which was direct detection of the conformational change of the protein.
• During the study of endothelial cells we observed that mannitol treatment influences their volume and elasticity. Upon prolonged calcium treatment a change in cell shape could be detected.
• We demonstrated a difference in shape and elasticity between wild-type and mutant bacteria.

Further developments

The accumulated knowledge helps develop new nanotechnological materials and contributes to understanding the action mechanism of drugs during medical treatments.