Fig. 4.

Small molecule detection. The oscillation amplitude (a) and phase shift (b) of a c-Abl modified fiber during the binding of imatinib onto c-Abl. The black arrow marks the addition of 10 μl buffer, the red arrows mark the additions of 10 μl 500 μM imatinib (final concentration of 15 μM), and the blue arrow indicates the change of the solution back to buffer. Fiber diameter: 11 μm, length: 7 mm. (c) Negative control. Two successive additions of 10 μl 500 μM suberoylanilide hydroxamic acid (red arrows) to the c-Abl modified fiber. Fiber diameter: 12 μm, length: 7.5 mm. (d) Negative control. Response of a fiber modified with myelin basic protein to the addition of 10 μl 500 μM imatinib (marked by a red arrow). Fiber diameter: 10.4 μm, length: 7 mm. (e) Inhibition of c-Abl with AMP-PNP (green arrows), exposure of the inhibited c-Abl to imatinib (red arrow), and replacement of the solution with PBS buffer (blue arrow). Red line is the average of the raw data (black line). Fiber diameter: 10 μm, length: 7.5 mm. (f) Positive control. The fiber was modified with c-kit kinase, which interacts with imatinib. Additions of 10 μl buffer and 10 μl 500 μM imatinib (final concentration: 15 μM), and change of the solution back to buffer are marked with black, red and blue arrows, respectively. Fiber diameter: 16 μm, length: 8 mm. Buffer for above experiments: 2.5 mM Tris-HCl buffer (pH = 7.5) with 1 mM MgCl₂.