Paper BI+AS+BA+NS+SS-ThA9
Exploring the Formation, Lifetime and Dissociation Statistics of Acid-Amine Bonds

Thursday, October 31, 2013, 4:40 pm, Room 102 B

Acid-amine interactions are non-covalent, long-range interactions, contributing to the structural integrity in manmade adhesives and to serve complex life functions in several biological systems. Understanding how these interactions develop and alter over time in an aqueous environment, especially when presented across an interface, is vital when it comes to designing functional surfaces for biomedical applications. We use single molecule force spectroscopy to investigate the contact dynamics of molecular bonds under near-physiological conditions. We explore the interactions of NH₂/COOH bonds that are presented across the atomic force microscopy (AFM) tip-surface interface, with much focus on the dissociation of these bonds by studying specific signatures obtained during the force measurements^#. Since the approach permits us to have an exquisite of control over the interface, a number of experimental parameters are varied such as the number density of the molecules, ionic strength of the surrounding medium and extension/retract speed of the tip to vary the loading rate. A statistical evaluation of the interactions and contact dynamics is discussed to assess the influence of the experimental parameters on the bond dissociation. The transition rate under zero-load conditions is calculated combining the detachment statistics and Kramer Evans theory. Our results provide new insights into the binding regime and dissociation behavior of acid-amine bonds from non-equilibrium to near-equilibrium conditions as a function of the loading rate on a logarithmic scale in aqueous environments of varying ionic concentration.

^# M Valtiner, SH Donaldson , MA Gebbie, JN Israelachvili, J. Am. Chem. Soc., 2012, 134, pp 1746–1753.