Fig. 7

AFM imaging of SWO1 action on CNCs. CNCs on a single silicon wafer (~1 cm²) were incubated with either 0.4 µM BSA (A, B) or SWO1 (C, D) in 50 mM sodium acetate buffer, pH 5.0, at 40 °C with mild agitation. Incubation was done over 24 h in a total reaction volume of 2 mL. AFM imaging was done on dried silicon wafers at room temperature. No evidence for BSA- or SWO1-induced structural changes were found by visual examination. However, the presence of molecules attached to either CNCs or the silicon wafer can be observed (A–D). Most of the BSA molecules are positioned randomly on the silicon wafer (A). An exemplary amplified section is shown in B. Multiple BSA molecules are visible (green circles), and only one BSA molecule seems to be associated with a crystallite (red circle). Contrary, SWO1 showed a clear trend to become attached to CNCs (C). An exemplary amplified CNC confirmed that the ratio of molecules attached to crystals (red circles) and particles on the surface (green circles) has significantly increased (D). Note that for an easier viewing, not all BSA/SWO1 molecules are highlighted (D). E Statistical analysis of the size distribution showed an apparent increase in the width of CNCs upon incubation with SWO1. However, this effect is attributed to the size of the adsorbed protein and the presence of a hydration shell (see Fig. 8). Scale bars 100 nm