The number of ruptured bonds
Very often, during the measurements on the surface of living cells, force histograms show multiple maxima (like for example in Fig. 5.20b) that correspond to the simultaneous rupture of subsequent complexes. To quantify this case, the area under each
peak can be used as an indicator of the probability of simultaneous rupture of n bonds.
Figure 5.24 Probability of the simultaneous rupture of n bonds obtained for (a) N-cadherin-antibody complex in cancerous T24 and reference HCV29 cells, (b) for the lectin concanavalin A (ConA) and glycans either attached to isolated protein (carboxypeptidase Y, CaY) or present in a plasma membrane of prostate cells (cell line: PC-3). The distributions were normalized to the total number of events.
The probability of the simultaneous rupture of n-bonds, obtained for the same interaction occurring between N-cadherin and its monoclonal antibody in cancerous T24 and reference HCV29 cells, is shown in Fig. 5.24a. One can observe that the
simultaneous rupture of 2-3 bonds was the most probable for the cancerous cells (T24) as compared to the reference cells (HCV29) where the rupture of a single bond was most prominent. When lectin was used as a probe for mannose bearing glycans, simultaneous rupture was observed when these glycans were attached to the isolated protein where they were better accessible (Fig. 5.24b). Such situation indicates larger number of active, isolated and single protein molecules on the investigated surface.