Thesis-PDF - IAP/TU Wien
Thesis-PDF - IAP/TU Wien
Thesis-PDF - IAP/TU Wien
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Figure 3.11: The cantilever deflection (bending). For a hard surface it<br />
amounts to the same effect if either the cantilever is pushed against the<br />
surface or a surface feature pushes against the cantilever. This fact can<br />
be used in order to calibrate the reading from the photodiode measuring<br />
cantilever bending.<br />
Figure 3.12: Force extension profile of a single titin molecule. The titin<br />
protein is folded in several subunits that unfold in sequential order when the<br />
protein is stretched. Each unfolding event is recorded as a sharp drop of the<br />
pulling force that acts on the cantilever. Image adapted from [8].<br />
titin molecule is show in Fig. 3.12. The periodic sawtooth-like pattern reflects<br />
domain unfolding in the peptide chain consistent with its modular construction<br />
and can be explained as a stepwise increase of the molecule’s length upon each<br />
unfolding event. ([70])<br />
3.4 AFM Manipulation Techniques<br />
Besides information collection the AFM can be used to manipulate matter on the<br />
small scale. Although this can be a time consuming process, only having one<br />
cantilever to do the work, the sample can be altered in a very precise way. The<br />
techniques can be classified into three categories, adding matter to, rearranging or<br />
removing matter from the substrate. Some of the methods, of course, may overlap<br />
in those categories as more effects apply at the same time.<br />
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