Surface anchoring reduces the lifetime of single specific bonds

¹ Technische Universität München, Physik Department E22 85747 Garching, Germany
² Institute of Biological Information Processing, Research Centre Jülich 52425 Jülich, Germany
³ Institute of Thin Films and Interfaces, Research Centre Jülich 52425 Jülich, Germany

Received: 6 September 2002
Accepted: 13 January 2003

Abstract

We investigated the force-induced dissociation of single specific bonds between protein A and immunoglobulin G. In these experiments both proteins were tethered to microbeads. Piconewton forces were applied by means of an ultrasoft spring. Upon bond formation the thermal fluctuations of this soft spring were reduced. This resulted in a sizeable contribution to the free enthalpy of bonding. Including this effect we calculated the relation between the lifetime of bonds connecting both microbeads and the lifetime of the bond between free molecules. We found that in the first case the lifetime depended on the stiffness of the force probe. Moreover, the lifetime was reduced by almost two orders of magnitude. Both predictions were verified in our experiments.