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. Furthermore, the present invention relates to a method for determining whether a compound is an activator of (poly)peptide function, comprising the steps of (a) immobilizing a (poly)peptide on a carrier; (b) attaching the (poly)peptide 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 separate measurements are carried out in the presence of a test and a reference buffer, wherein the test buffer comprises a compound suspected of being an activator of the function of said (poly)peptide and wherein the reference buffer comprises (i) a compound known to have no effect on the activity of said (poly)peptide or (ii) a compound known to be an activator of said (poly)peptide; (d) comparing the force spectra of the (poly)peptide measured in the presence of the test and the reference buffer; and (e) concluding from a difference of the force spectra of step (d) whether the compound suspected of being an activator of said (poly)peptide is an activator of the (poly)peptide. Finally the present invention relates to a method for determining whether a compound is an inhibitor of (poly)peptide function.