Observation of the destruction of biomolecules under compression force

The atomic force microscope (AFM) has been eagerly employed in biology and various biomolecules have been measured by single molecule level. However, a biosample is generally flexible and weak against environmental change. Thus, the perturbation induced by an AFM probe should be observed and controlled to apply an AFM measurement to the biological study. In this study, we tried to observe the destruction of biosample under compression force. By using a force curve mode confocal laser scanning microscope/AFM (CLSM/AFM) system, the denaturation of green fluorescent protein (GFP) induced by the compression force was observed by the simultaneous measurement of the fluorescence change. Consequently, it is clarified that GFP molecule exhibited the reversible denaturation by the compression force of averaged 5 nN and that the fluorescence was quenched.