Peptide interfacial adsorption is kinetically limited by the thermodynamic stability of self association

摘要

We present a study of the adsorption of two peptides at the octane-water interface. The first peptide. Lac21, exists in mixed monomertetramer equilibrium in bulk solution with an apprecia- ble monomer concentration. The second peptide, L8c28, exists as a tetramer in solution. with minimal exposed hydrophobic surface. A kinetic limitation to interfacial adsorption exists for Lac28 at moderate to high surface coverage that is not observed for Lac21. We estimate the potential energy barrier for Lac28 adsorption to be 42 kJ/mol and show that this is comparable to the expected free energy barrier for tetramer dissociation. This finding suggests that. at moderate to high surface coverage. adsorption is kinetically limited by the availability of inter facially active monomeric "do- mains" in the subinterfacial region. We also show how the com- monly used empirical equation for protein adsorption dynamics can be used to estimate the potential energy barrier for adsorption. Such an approach is shown to be consistent with a formal descrip- tion of diffusion-adsorption, provided a large potential energy barrier exists. This work demonstrates that the dynamics of inter- facial adsorption depend on protein thermodynamic stability and hence structure. in a quantifiable way.