Nanomechanical microcantilevers have played a vital role in detecting biomolecular interactions. The ability of microcantilevers to detect biomolecular interactions is ascribed to the principle that the surface stress, caused by biomolecular interactions, dominates the dynamical response of the microcantilever. Here we have experimentally studied the correlation between biomolecular interactions and the dynamical response of microcantilevers. Moreover, the authors employed a mechanical beam model to calculate the surface stress, representing the biomolecular interactions, through measuring the resonant frequency shift. The quantitative analysis of surface stress, driven by the specific protein-protein interactions, demonstrated that microcantilevers enable the quantitative study of biomolecular interactions. (c) 2006 American Institute of Physics.