Figure 5. Dimerization of MMP-9 Renders the Enzyme Immobile Both on Gelatin Layers and Collagen Fibril surfaces.

A. FPR curve for fluorescently labeled gelatin-adsorbed MMP-9 homodimer was obtained as described above in Figure 3. No detectable increase of fluorescence (open circles) occurs after the photobleaching pulse indicating the immobility of the MMP-9 homodimer. Monitoring beam photobleaching alone, indicated by the solid curves (Eq. 3.2 [12] with mobile fraction = 0), accounts for the decay of fluorescence before and after the photobleaching pulse. B (upper panel). A primary fluorescence record, rebinned to 40 ms (upper curve), was obtained from an individual fibril decorated with fluorescently labeled MMP-9 homodimer. The background noise in the primary record was suppressed by applying the spatial background filter described earlier [13] to reveal a flat baseline (lower curve) indicating the absence of single molecule spikes. B (lower panel). A primary fluoresence record, rebinned to 40 ms (upper curve), was obtained from an individual fibril decorated with fluorescently labeled MMP-9 monomer. The background noise in the primary record was suppressed by applying the same spatial background filter to reveal significant fluctuations in fluoresence (lower curve) indicating the presence of single molecule spikes.