Use of magnetic particles for determining binding between bioactive molecules

An assay as well as tools and app. therefore are disclosed for detg. interaction between microbiol. entities such as bioactive mols. using at least a first particle or microcarrier e.g. a bead, and a second particle which may also be a microcarrier, e.g. a second bead. At least the first microcarrier is magnetic. When two beads are used and both beads are magnetic, the beads preferably differ in the size of their magnetic moment. A means is provided for placing a binding between bioactive mols. under a mech. stress to thereby distinguish between bindings of different strengths. In one aspect, the second bead, (with a larger magnetic moment) is used to magnetically remove target mols. linked to beads with smaller magnetic moment which are weakly bound to a capture mol. (itself generally coupled to a mobile or immobile surface). Alternatively, fluid frictional forces can be applied to one of the particles to disrupt weak bindings. Depending upon the embodiment, the first bead and/or second particle can be used for detection purposes. [on SciFinder (R)]