Figure 3.

(A) Addition of different ATP concentrations to a functionalized AFM tip scanning mica in fluid is followed by dose-dependent deflection signals. The different concentrations are given in different colors and patterns. The corresponding deflection signals are given in the so-called mean roughness, a feature provided by the software package of the BioScope. The values expressed in nanometers represent the mean deviation of the data points in the plus and minus z direction in relation to a reference area set as zero (40). Mean roughness represents the mean value of the surface relative to the center plane (see also B and C). (B and C) After addition of the vehicle ATP-γS, which is unable to undergo hydrolysis, or ADP (C), we observe almost no change of the deflection signal illustrated by the lack of change in the mean roughness value. However, after addition of ATP (relative concentration to ATP-γS of 1:1 and to ADP of 1:10), an increase of the mean roughness can be detected. (D) Autoradiographs of a thin-layer chromatogram from a time course of [α-³²P]ATP hydrolysis in the presence of S1 myosin-coated and uncoated cantilevers. Note a time-dependent ATP hydrolysis in the presence of S1 myosin-coated cantilevers, which is not detected in the presence of uncoated cantilevers.