Multivalency is an important effect in biological processes and supramolecular assemblies. Multiple noncovalent interactions of two partners may occur with an affinity greater than the sum of the corresponding monovalent interactions. The mechanical stability of multivalent interactions is important for the understanding of numerous biological processes. However due to their complexity, the binding enhancement in such systems is not yet fully understood. [1]

We developed a simple model system using coordinative bonds between pyridine nanorods. SFM based single molecule force spectroscopy (SMFS) [2] in aqueous solutions of CuSO4, combined with DFT calculations of bond dissociation under force, revealed details of the bond opening that are usually not accessible by ensemble methods. The bivalent system rather opens successively than simultaneously, which leads to lower rupture forces than for the monovalent system, over a broad range of loading rates. Our model system can be varied to study structural effects influencing the mechanical stability of multivalent interactions.

[1] J.D. Badjic et al. Acc. Chem. Res. 2005, 38, 723-732.

[2] M.I. Gianotti and G.J. Vancso ChemPhysChem 2007, 8, 2290-2307.