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J. Preiner, N. Kodera, J. Tang, A. Ebner, M. Brameshuber, D. Blaas, N. Gelbmann, H. Gruber, T. Ando, P. Hinterdorfer:
"IgGs are made for walking on bacterial and viral surfaces";
Nature Communications, 5 (2014), 43941 - 43948.

Binding of antibodies to their cognate antigens is fundamental for adaptive immunity.
Molecular engineering of antibodies for therapeutic and diagnostic purposes emerges to be
one of the major technologies in combating many human diseases. Despite its importance, a
detailed description of the nanomechanical process of antibody-antigen binding and dissociation
on the molecular level is lacking. Here we utilize high-speed atomic force microscopy
to examine the dynamics of antibody recognition and uncover a principle; antibodies do
not remain stationary on surfaces of regularly spaced epitopes; they rather exhibit `bipedal´
stochastic walking. As monovalent Fab fragments do not move, steric strain is identified as
the origin of short-lived bivalent binding. Walking antibodies gather in transient clusters that
might serve as docking sites for the complement system and/or phagocytes. Our findings
could inspire the rational design of antibodies and multivalent receptors to exploit/inhibit
steric strain-induced dynamic effects.