Conclusions and Perspectives - Dynamic Force Spectroscopy and Biomolecular Recognition - page 243

7 Conclusions and

Perspectives

Anna Rita Bizzarri and Salvatore Cannistraro

The achievement of a complete and unified picture of biorecognition processes in
living organisms requires a large effort based on the combination of standard exper-
imental approaches with highly innovative techniques, with the support of adequate
theoretical models (see Chapter 1). The traditional concepts of specificity, affinity,
and rate constants, widely used to describe biorecognition, have to be updated also to
take into account additional aspects, such as the distance and the orientation between
the biomolecules, the eventual immobilization on the cell surface, the molecular den-
sity, and so on. In this context, single molecule techniques emerged as extremely use-
ful tools to elucidate even subtle details of the biorecognition mechanisms. Dynamic
force spectroscopy (DFS) has gained a prominent position among these techniques
due to its ability to capture molecular events at the basis of the molecular interaction,
well-complementing information coming from standard biomolecular and spectro-
scopic techniques operating in bulk. This essentially stems from the capability of
DFS to measure unbinding forces with picoNewton sensitivity between single cou-
ples of biomolecules immobilized on suitable surfaces, under physiological condi-
tions, without labeling and in real time.
The progressively higher relevance of DFS is witnessed by the continuous
increase in the number of both scientific publications and atomic force microscopy
(AFM) equipments devoted to DFS experiments in the worldwide scientific commu-
nity. Indeed, DFS has been applied to investigate a variety of biomolecular systems
playing many different biological functions (see Chapter 6), allowing also to eluci-
date the influence on the kinetic and thermodynamical properties of some important
factors that are usually hidden when bulk techniques are used, such as punctual muta-
tions within the partners, molecular heterogeneity, conformational changes, local
environmental changes, molecular crowding, and so on. These investigations hold
a remarkable interest since they offer also the possibility of tailoring the molecular
structure and dynamics of biomolecules, ligands, drugs, and so on to optimize the
function in which they are involved. DFS has made accessible the investigation of
the energy landscape of interacting biomolecules evidencing the presence of many
nearly isoenergetic local minima, whose exploration should be considered in order
to achieve a consistent description of the kinetic response of biomolecular systems
during the biorecognition process; this could also explain the “history” dependence
of the unbinding data of the system. These results have moreover given new impetus
to the development of theoretical models to interpret the mechanisms that govern the

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