The interaction between biomolecules is a key aspect to examine and characterise biological systems. Common interactions are e.g. antibody-antigen interactions [27,66,110] or protein-protein interactions. A very versatile biosensor that can detect different kinds of biomolecules (DNA, Proteins, ...) and also examine different interactions between them would be most desirable, therefore. This is quite difficult, because the size of the biomolecules, the bond-type and with it the bond-force differ a lot, from a small antibody to a big protein-complex. For all marker based biosensors, this means that many versatile markers have to be available. The magnetic markers that are used in this thesis are available in many different sizes and configurations (see section 1.2).
A new technique to measure the bond-force between two biomolecules with magnetic markers is presented in chapter 4. To show the general applicability of this method, the well known streptavidin-biotin and the avidin-biotin bonds were examined. In order to understand the processes during the bond-force measurements, the following sections describe the major properties of all three participating biomolecules and the bond properties.