Biomolecular Recognition: Analysis of DFS Data - Dynamic Force Spectroscopy and Biomolecular Recognition - page 186

in DFS was to ascertain the level of bond attachment (single or multiple) since the
difficulty in data analysis increased with the presence of multiple bonds. However,
we also described methods and tools that allow the adequate treatment of multiple
bonds. This is important since the most important recognition processes in tissues
often require multiple binding. The second take home message from this chapter is
that, despite all its approximations, the Bell-Evans' model is well adapted to ana-
lyzing the energy landscape of a ligand-receptor bond rupture. The Bell-Evans' for-
malism allows the treatment of single and multiple parallel bond ruptures and that of
multiple energy barriers.
It is clear that DFS is a relatively young technique and improvements will con-
tinue to occur. Central to the DFS technique is the analysis of FD curves. Most of
the laboratories involved in DFS experiments developed their own set of tools for
interpreting the retract trace from the FD curve. Unfortunately, no software compar-
ison has been performed to assess the performance of each method. Undoubtedly,
this is a tedious work. Nevertheless, it is an important step for strengthening the per-
tinence of DFS in single molecule interactions. A central point to such assessment
is the availability of well-characterized test sets of FD curves. Rules will have to
be defined to characterize what is an adequate FD curve? For instance, a data file
format should be defined; units will need to be homogenized; negative and positive
controls will need to be present; nonspecific FD curves should also be included. The
availability of DFS test sets will allow in-depth study of several tasks in data analy-
sis. For instance, the shape of rupture events or the position of rupture events along
the dissociation can be assessed and their effects on the energy landscape quantified.
In addition, effects of experimental parameters such as the contact time, the trigger
threshold, or the time delay between two consecutive measures could be evaluated.
It is the purpose of the European COST Action TD1002 (AFM4NanoMed&Bio) to
tackle some of these challenges so that the field of DFS will continue to grow and
application of DFS to biologically relevant system will flourish.

ACKNOWLEDGMENTS
This work has been supported by the program for environmental nuclear toxicology
of the Commissariat l'energie atomique et aux energies alternatives (CEA), France.

ABBREVIATIONS
AFM Atomic force microscopy

AFS Atomic force spectroscopy

CPD Cumulative probability distribution

DFS Dynamic force spectroscopy

F* Most probable rupture force

FD Force-displacement

F rupt Rupture force

k cant Spring constant of the cantilever

k eq Slope of the retract curve before the unbinding event