Multivalency: influence of the residence time and the retraction rate on rupture forces measured by AFM

Abstract

International audienceThe Bell-Evans theory relative to rupture forces between non-covalently interacting molecules predicts that the rupture force increases linearly with the logarithm of the force loading rate. Here we investigate by force spectroscopy performed with an atomic force microscope (AFM) the rupture forces between surfaces covered by beta-cyclodextrin (beta-CD) molecules and AFM tips coated with adamantane (AD) groups. The beta-CD molecules are either deposited through a self-assembled monolayer (SAM) or grafted on poly(allylamine hydrochloride) chains (PAH-CD) that are adsorbed on the substrate. The AD groups are fixed covalently on the AFM tip through either a one-AD or a four-AD platform linked to the tip though a PEO chain. It is found that while the rupture forces between AFM tips covered with tetravalent AD molecules and SAM-CD surfaces do not exceed twice those found with tips covered by monovalent AD molecules, the rupture forces increase by a factor of 20 on PAH-CD substrates for a tetravalent AD covered tip compared to a monovalent one. Thus, there seems to exist a synergistic effect between the molecule multivalence and the polymeric nature of the CD-covered substrate. As found in the literature, we observe an increase of the intensity of the rupture forces between the AD-covered AFM tip and the beta-CD covered substrate with the contact time over timescales up to several seconds. Finally, we find that when the host-guest system involves the multivalency of the AD guest and/or the polymeric nature of the host the mean rupture force decreases with the loading rate in contrast to what is predicted by the Bell-Evans theory. We tentatively explain this ``anti-Bell-Evans'' behavior by the possibility of rebinding during the rupture process. This effect should have important implications in the understanding of forces at the cellular level

Controlling Multivalent Binding through Surface Chemistry: Model Study on Streptavidin

“…Among the different surface chemistry approaches, supported lipid bilayers (SLBs) and self-assembled monolayers (SAMs) ,− are the most commonly used to study − and to realize , multivalent binding to surfaces. They can be formed on various solid supports (metal/metal oxide, transparent/opaque, conducting/insulating, planar macroscopic surface/curved particle surface, etc.…”

Impact of Multimeric Ferrocene‐containing Cyclodecapeptide Scaffold on Host‐Guest Interactions at a β‐Cyclodextrin Covered Surface

“…-CD thiol was synthesized according to previously reported procedure. [35] The synthesis was carried out by condensation of 6-monodeoxy-6-monoamino--cyclodextrin on commercially available HS-C11H22-EG6-COONHS in the presence of DIPEA (pH 8-9) in DMF.…”

Influence of Surface Chemistry on Host/Guest Interactions: A Model Study on Redox-Sensitive β-Cyclodextrin/Ferrocene Complexes

“…Despite the wide use of host/guest interactions, our understanding of the parameters determining their efficiency at interfaces, and in particular of the role of surface chemistry, remains limited. Previous studies highlighted the importance of the parameters related to the host/guest moieties (surface density, ,– concentration in solution, , affinity, valency, ,– and lateral mobility), the surrounding liquid medium (presence of competing guests , or anions), and the underlying substrate (Au, Si, and doping level) . In particular, it has been shown that the affinity of host/guest complexes is altered at the surface compared to that in solution, with both higher and lower association constants being reported. ,,, There are studies suggesting that these effects are related to different chemical structures of guest derivatives, resulting in different combinations of binding forces during the formation of host/guest complexes (hydrophobic, electrostatic, and hydrogen bonding). , Other studies showed that electrolyte anions interact with host cavities with different affinities and, in some cases, interfere with host/guest binding. , One can expect that the parameters of the interface, including the arrangement of host/guest groups, the linkers connecting them to the surface, and the nature of diluting molecules, can also affect the efficiency of host/guest complexation and on-demand dissociation, an aspect that has not yet been studied thoroughly.…”