Abstract: The present invention relates to a method for determining the state of activation of a (poly)peptide, comprising the steps of: (a) immobilizing a (poly)peptide on a carrier; (b) attaching the (poly)peptide immobilized on the carrier to a force measuring device of a force spectroscope; (c) applying a pulling force to the (poly)peptide and measuring the force required for stretching and/or unfolding of the (poly)peptide attached to the carrier, wherein the measurements are carried out (i) prior to and (ii) after treatment with a known modulator of said (poly)peptide; (d) comparing the force spectra of the (poly)peptide prior to and after treatment with the modulator; and (e) concluding from a difference of the force spectra of step (d) on the state of activation of the (poly)peptide.