Micromechanical Investigation of Chemomechanical P-Proteine Aggregates (Forisomes) from Vicia Faba

Small P-protein aggregates, the so-called Forisomes [1] were investigated microm echnically. After the addition of Ca(II)ions the Forisom transforms chemical ene rgy into mechanical work. The dependencies of both the geometric prarameters and the generated forces on the calcium(II) concentration and the pH value were mea sured. After their reaction with calcium 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)-Forisome-complex and the Hill coefficient. The thermodynamic cycle process can be completed extractio n of these calcium ions from the protein aggregate, e.g. by EDTA. In the presen ce of 50 µM - 10 mM Ca(II) the Forisoms generate forces between 10 and 100 nN. T he 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 gu iding glass fibre. The results open up a new way to miniaturized bioactuators, w hich could be controlled by the Ca(II) concentration or the pH value. [1] M. Knoblauch; G. Noll; T. Müller; D. Prüfer; I. Schneider-Hüther; D. Scharner; A. J.E. van Bel; W. Peters: Nautre Materials 2 (2003), 600-603