Interaction forces of bacterial adhesin XadA1 on silicon and cellulose surfaces.

<p>Schematics of the force spectroscopy (<b>A</b>) measurements at five different positions on the surface where force curves were acquired. The force histograms (<b>B</b>-<b>D</b>) for bare silicon (Si, B) ethyl cellulose (EC, <b>C</b>) and cellulose acetate (CA, <b>D</b>), show the total number of events (please notice the different scales for the number of events); multiple rupture events were observed for EC and CA. Typical retraction force-distance curves for AFM tips coated with XadA1 adhesion protein (<b>E</b>) for Si (i), EC (ii) and CA (iii). The inset shows the fluorescence image of the functionalized AFM tip and cantilever visualized using fluorophore labeled second antibodies (scale bar = 40µm). Measured interaction forces (<b>F</b>-<b>H</b>) between XadA1 coated AFM tip and bare Si (<b>F</b>), EC (<b>G</b>) and CA (<b>H</b>) substrates in PBS buffer shown in sequential acquisition order. The colors indicate a different region of the sample probed in each set of force curves. The bin sizes for (<b>B</b>), (<b>C</b>) were adjusted to 22pN and (<b>D</b>) to 5pN to allow accurate visualization of the molecular interaction characteristics.