|S. Schwan1, M. Fritzsche1, Dirk Prüfer2, Andreas Heilmann1, and Uwe Spohn1
1Biological Materials and Interfaces, Fraunhofer Institute for Mechanics of Materials Halle, Heideallee 19, D-06120 Halle, Germany
Small P-protein aggregates, the so-called Forisomes  were investigated micromechanically. After the addition of Ca(II) ions the Forisom transforms chemical energy into mechanical work. The dependencies of both the geometric parameters and the generated forces on the calcium(II) concentration and the pH value were measured. After their reaction with calcium ion the Forisoms contract by 10 to 40% of its original length. The reversible switching mechanism is discussed also on the basis of the apparent dissociation constant of the Ca(II)-Foriosme-complex and the Hill coefficient. The thermodynamic cycle process can be completed by extraction of the calcium ions from the protein aggregate, e.g. by EDTA. In the presence of 50 µM - 10 mM Ca(II) the Forisoms generate forces between 10 and 100 nN. The forces were measured by microscopic observation of the bending of thin glass fibres. More precise methods were developed based on bending of a laser light guiding glass fibre and a position sensitive 2D detector. The results open up a new way to miniaturized bioactuators, which could be controlled by the Ca(II) concentration or the pH value.